xref: /dports/security/libzrtpcppcore/ZRTPCPP-4.6.6/zrtp/ZRtp.cpp

/*
  Copyright (C) 2006-2013 Werner Dittmann

  This program is free software: you can redistribute it and/or modify
  it under the terms of the GNU Lesser General Public License as published by
  the Free Software Foundation, either version 3 of the License, or
  (at your option) any later version.

  This program is distributed in the hope that it will be useful,
  but WITHOUT ANY WARRANTY; without even the implied warranty of
  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  GNU General Public License for more details.

  You should have received a copy of the GNU General Public License
  along with this program.  If not, see <http://www.gnu.org/licenses/>.
*/

/*
 * Authors: Werner Dittmann <Werner.Dittmann@t-online.de>
 */
#include <sstream>

#include <crypto/zrtpDH.h>
#include <crypto/hmac256.h>
#include <crypto/sha256.h>
#include <crypto/hmac384.h>
#include <crypto/sha384.h>

#include <crypto/skeinMac256.h>
#include <crypto/skein256.h>
#include <crypto/skeinMac384.h>
#include <crypto/skein384.h>

#include <crypto/aesCFB.h>
#include <crypto/twoCFB.h>

#include <libzrtpcpp/ZRtp.h>
#include <libzrtpcpp/ZrtpStateClass.h>
#include <libzrtpcpp/ZIDCache.h>
#include <libzrtpcpp/Base32.h>
#include <libzrtpcpp/EmojiBase32.h>

using namespace GnuZrtpCodes;

/* disabled...but used in testing and debugging, probably should have a
   controlling #define...
   *
static void hexdump(const char* title, const unsigned char *s, int l) {
    int n=0;

    if (s == NULL) return;

    fprintf(stderr, "%s",title);
    for( ; n < l ; ++n)
    {
        if((n%16) == 0)
            fprintf(stderr, "\n%04x",n);
        fprintf(stderr, " %02x",s[n]);
    }
    fprintf(stderr, "\n");
}
 * */

/*
 * This method simplifies detection of libzrtpcpp inside Automake, configure
 * and friends
 */
#ifdef __cplusplus
extern "C" {
#endif
    int ZrtpAvailable()
    {
        return 1;
    }
#ifdef __cplusplus
}
#endif

ZRtp::ZRtp(uint8_t *myZid, ZrtpCallback *cb, std::string id, ZrtpConfigure* config, bool mitmm, bool sasSignSupport):
        callback(cb), dhContext(NULL), DHss(NULL), auxSecret(NULL), auxSecretLength(0), rs1Valid(false),
        rs2Valid(false), msgShaContext(NULL), hash(NULL), cipher(NULL), pubKey(NULL), sasType(NULL), authLength(NULL),
        multiStream(false), multiStreamAvailable(false), peerIsEnrolled(false), mitmSeen(false), pbxSecretTmp(NULL),
        enrollmentMode(false), configureAlgos(*config), zidRec(NULL), saveZidRecord(true), signSasSeen(false),
        masterStream(NULL), peerDisclosureFlagSeen(false) {

#ifdef ZRTP_SAS_RELAY_SUPPORT
    enableMitmEnrollment = config->isTrustedMitM();
#pragma message "ZRTP SAS relay support is enabled."
#else
    enableMitmEnrollment = false;
#endif

    signatureData = NULL;
    paranoidMode = config->isParanoidMode();
    sasSignSupport = config->isSasSignature();

    // setup the implicit hash function pointers and length
    hashLengthImpl = SHA256_DIGEST_LENGTH;
    hashFunctionImpl = sha256;
    hashListFunctionImpl = sha256;

    hmacFunctionImpl = hmac_sha256;
    hmacListFunctionImpl = hmac_sha256;

    memcpy(ownZid, myZid, ZID_SIZE);        // save the ZID

    /*
     * Generate H0 as a random number (256 bits, 32 bytes) and then
     * the hash chain, refer to chapter 9. Use the implicit hash function.
     */
    randomZRTP(H0, HASH_IMAGE_SIZE);
    sha256(H0, HASH_IMAGE_SIZE, H1);        // hash H0 and generate H1
    sha256(H1, HASH_IMAGE_SIZE, H2);        // H2
    sha256(H2, HASH_IMAGE_SIZE, H3);        // H3

    // configure all supported Hello packet versions
    zrtpHello_11.configureHello(&configureAlgos);
    zrtpHello_11.setH3(H3);                    // set H3 in Hello, included in helloHash
    zrtpHello_11.setZid(ownZid);
    zrtpHello_11.setVersion((uint8_t*)zrtpVersion_11);


    zrtpHello_12.configureHello(&configureAlgos);
    zrtpHello_12.setH3(H3);                 // set H3 in Hello, included in helloHash
    zrtpHello_12.setZid(ownZid);
    zrtpHello_12.setVersion((uint8_t*)zrtpVersion_12);

    if (mitmm) {                            // this session acts for a trusted MitM (PBX)
        zrtpHello_11.setMitmMode();
        zrtpHello_12.setMitmMode();
    }
    if (sasSignSupport) {                   // the application supports SAS signing
        zrtpHello_11.setSasSign();
        zrtpHello_12.setSasSign();
    }

    // Keep array in ascending order (greater index -> greater version)
    helloPackets[0].packet = &zrtpHello_11;
    helloPackets[0].version = zrtpHello_11.getVersionInt();
    setClientId(id, &helloPackets[0]);      // set id, compute HMAC and final helloHash

    helloPackets[1].packet = &zrtpHello_12;
    helloPackets[1].version = zrtpHello_12.getVersionInt();
    setClientId(id, &helloPackets[1]);      // set id, compute HMAC and final helloHash

    currentHelloPacket = helloPackets[SUPPORTED_ZRTP_VERSIONS-1].packet;  // start with highest supported version
    helloPackets[SUPPORTED_ZRTP_VERSIONS].packet = NULL;
    peerHelloVersion[0] = 0;

    stateEngine = new ZrtpStateClass(this);
}

ZRtp::~ZRtp() {
    stopZrtp();
    if (DHss != NULL) {
        delete DHss;
        DHss = NULL;
    }
    if (stateEngine != NULL) {
        delete stateEngine;
        stateEngine = NULL;
    }
    if (dhContext != NULL) {
        delete dhContext;
        dhContext = NULL;
    }
    if (msgShaContext != NULL) {
        closeHashCtx(msgShaContext, NULL);
        msgShaContext = NULL;
    }
    if (auxSecret != NULL) {
        delete auxSecret;
        auxSecret = NULL;
        auxSecretLength = 0;
    }
    if (zidRec != NULL) {
        delete zidRec;
        zidRec = NULL;
    }
    memset(hmacKeyI, 0, MAX_DIGEST_LENGTH);
    memset(hmacKeyR, 0, MAX_DIGEST_LENGTH);

    memset(zrtpKeyI, 0, MAX_DIGEST_LENGTH);
    memset(zrtpKeyR, 0, MAX_DIGEST_LENGTH);
    /*
     * Clear the Initiator's srtp key and salt
     */
    memset(srtpKeyI, 0, MAX_DIGEST_LENGTH);
    memset(srtpSaltI, 0,  MAX_DIGEST_LENGTH);
    /*
     * Clear he Responder's srtp key and salt
     */
    memset(srtpKeyR, 0, MAX_DIGEST_LENGTH);
    memset(srtpSaltR, 0, MAX_DIGEST_LENGTH);

    memset(zrtpSession, 0, MAX_DIGEST_LENGTH);

    peerNonces.clear();
}

void ZRtp::processZrtpMessage(uint8_t *message, uint32_t pSSRC, size_t length) {
    Event_t ev;

    peerSSRC = pSSRC;
    ev.type = ZrtpPacket;
    ev.length = length;
    ev.packet = message;

    if (stateEngine != NULL) {
        stateEngine->processEvent(&ev);
    }
}

void ZRtp::processTimeout() {
    Event_t ev;

    ev.type = Timer;
    if (stateEngine != NULL) {
        stateEngine->processEvent(&ev);
    }
}

#ifdef oldgoclear
bool ZRtp::handleGoClear(uint8_t *message)
{
    char *msg, first, last;

    msg = (char *)message + 4;
    first = tolower(*msg);
    last = tolower(*(msg+6));

    if (first == 'g' && last == 'r') {
        Event_t ev;

        ev.type = ZrtpGoClear;
        ev.packet = message;
        if (stateEngine != NULL) {
            stateEngine->processEvent(&ev);
        }
        return true;
    }
    else {
        return false;
    }
}
#endif

void ZRtp::startZrtpEngine() {
    Event_t ev;

    if (stateEngine != NULL && stateEngine->inState(Initial)) {
        ev.type = ZrtpInitial;
        stateEngine->processEvent(&ev);
    }
}

void ZRtp::stopZrtp() {
    Event_t ev;

    if (stateEngine != NULL) {
        ev.type = ZrtpClose;
        stateEngine->processEvent(&ev);
    }
}

bool ZRtp::inState(int32_t state)
{
    if (stateEngine != NULL) {
        return stateEngine->inState(state);
    }
    else {
        return false;
    }
}

ZrtpPacketHello* ZRtp::prepareHello() {
    return currentHelloPacket;
}

ZrtpPacketHelloAck* ZRtp::prepareHelloAck() {
    return &zrtpHelloAck;
}

/*
 * At this point we will assume the role of Initiator. This role may change
 * in case we have a commit-clash. Refer to chapter 5.2 in the spec how
 * to break this tie.
 */
ZrtpPacketCommit* ZRtp::prepareCommit(ZrtpPacketHello *hello, uint32_t* errMsg) {

    myRole = Initiator;

    if (!hello->isLengthOk()) {
        *errMsg = CriticalSWError;
        return NULL;
    }
    // Save data before detailed checks - may aid in analysing problems
    peerClientId.assign((char*)hello->getClientId(), ZRTP_WORD_SIZE * 4);
    memcpy(peerHelloVersion, hello->getVersion(), ZRTP_WORD_SIZE);
    peerHelloVersion[ZRTP_WORD_SIZE] = 0;

    // Save our peer's (presumably the Responder) ZRTP id
    memcpy(peerZid, hello->getZid(), ZID_SIZE);
    if (memcmp(peerZid, ownZid, ZID_SIZE) == 0) {       // peers have same ZID????
        *errMsg = EqualZIDHello;
        return NULL;
    }
    memcpy(peerH3, hello->getH3(), HASH_IMAGE_SIZE);

    int32_t helloLen = hello->getLength() * ZRTP_WORD_SIZE;

    // calculate hash over the received Hello packet - is peer's hello hash.
    // Use implicit hash algorithm
    hashFunctionImpl((unsigned char*)hello->getHeaderBase(), helloLen, peerHelloHash);

    sendInfo(Info, InfoHelloReceived);

    /*
     * The Following section extracts the algorithm from the peer's Hello
     * packet. Always the preferend offered algorithms are
     * used. If the received Hello does not contain algo specifiers
     * or offers only unsupported optional algos then replace
     * these with mandatory algos and put them into the Commit packet.
     * Refer to the findBest*() functions.
     * If this is a MultiStream ZRTP object then do not get the cipher,
     * authentication from hello packet but use the pre-initialized values
     * as proposed by the standard. If we switch to responder mode the
     * commit packet may contain other algos - see function
     * prepareConfirm2MultiStream(...).
     */
    sasType = findBestSASType(hello);

    if (!multiStream) {
        pubKey = findBestPubkey(hello);                 // Check for public key algorithm first, must set 'hash' as well
        if (hash == NULL) {
            *errMsg = UnsuppHashType;
            return NULL;
        }
        if (cipher == NULL)                             // public key selection may have set the cipher already
            cipher = findBestCipher(hello, pubKey);
        if (authLength == NULL)                         // public key selection may have set the SRTP authLen already
            authLength = findBestAuthLen(hello);
        multiStreamAvailable = checkMultiStream(hello);
    }
    else {
        if (checkMultiStream(hello)) {
            return prepareCommitMultiStream(hello);
        }
        else {
            // we are in multi-stream but peer does not offer multi-stream
            // return error code to other party - unsupported PK, must be Mult
            *errMsg = UnsuppPKExchange;
            return NULL;
        }
    }
    setNegotiatedHash(hash);

    // Modify here when introducing new DH key agreement, for example
    // elliptic curves.
    dhContext = new ZrtpDH(pubKey->getName());
    dhContext->generatePublicKey();

    dhContext->getPubKeyBytes(pubKeyBytes);
    sendInfo(Info, InfoCommitDHGenerated);

    // Prepare IV data that we will use during confirm packet encryption.
    randomZRTP(randomIV, sizeof(randomIV));

    /*
     * Prepare our DHPart2 packet here. Required to compute HVI. If we stay
     * in Initiator role then we reuse this packet later in prepareDHPart2().
     * To create this DH packet we have to compute the retained secret ids,
     * thus get our peer's retained secret data first.
     */
    zidRec = getZidCacheInstance()->getRecord(peerZid);

    //Compute the Initator's and Responder's retained secret ids.
    computeSharedSecretSet(zidRec);

#ifdef ZRTP_SAS_RELAY_SUPPORT
    // Check if a PBX application set the MitM flag.
    mitmSeen = hello->isMitmMode();
#endif

    signSasSeen = hello->isSasSign();

    // Construct a DHPart2 message (Initiator's DH message). This packet
    // is required to compute the HVI (Hash Value Initiator), refer to
    // chapter 5.4.1.1.

    // Fill the values in the DHPart2 packet
    zrtpDH2.setPubKeyType(pubKey->getName());
    zrtpDH2.setMessageType((uint8_t*)DHPart2Msg);
    zrtpDH2.setRs1Id(rs1IDi);
    zrtpDH2.setRs2Id(rs2IDi);
    zrtpDH2.setAuxSecretId(auxSecretIDi);
    zrtpDH2.setPbxSecretId(pbxSecretIDi);
    zrtpDH2.setPv(pubKeyBytes);
    zrtpDH2.setH1(H1);

    int32_t len = zrtpDH2.getLength() * ZRTP_WORD_SIZE;

    // Compute HMAC over DH2, excluding the HMAC field (HMAC_SIZE)
    // and store in DH2. Key to HMAC is H0, use HASH_IMAGE_SIZE bytes only.
    // Must use implicit HMAC functions.
    uint8_t hmac[IMPL_MAX_DIGEST_LENGTH];
    uint32_t macLen;
    hmacFunctionImpl(H0, HASH_IMAGE_SIZE, (uint8_t*)zrtpDH2.getHeaderBase(), len-(HMAC_SIZE), hmac, &macLen);
    zrtpDH2.setHMAC(hmac);

    // Compute the HVI, refer to chapter 5.4.1.1 of the specification
    computeHvi(&zrtpDH2, hello);

    zrtpCommit.setZid(ownZid);
    zrtpCommit.setHashType((uint8_t*)hash->getName());
    zrtpCommit.setCipherType((uint8_t*)cipher->getName());
    zrtpCommit.setAuthLen((uint8_t*)authLength->getName());
    zrtpCommit.setPubKeyType((uint8_t*)pubKey->getName());
    zrtpCommit.setSasType((uint8_t*)sasType->getName());
    zrtpCommit.setHvi(hvi);
    zrtpCommit.setH2(H2);

    len = zrtpCommit.getLength() * ZRTP_WORD_SIZE;

    // Compute HMAC over Commit, excluding the HMAC field (HMAC_SIZE)
    // and store in Hello. Key to HMAC is H1, use HASH_IMAGE_SIZE bytes only.
    // Must use implicit HMAC functions.
    hmacFunctionImpl(H1, HASH_IMAGE_SIZE, (uint8_t*)zrtpCommit.getHeaderBase(), len-(HMAC_SIZE), hmac, &macLen);
    zrtpCommit.setHMAC(hmac);

    // hash first messages to produce overall message hash
    // First the Responder's Hello message, second the Commit (always Initator's).
    // Must use negotiated hash.
    msgShaContext = createHashCtx(msgShaContext);
    hashCtxFunction(msgShaContext, (unsigned char*)hello->getHeaderBase(), helloLen);
    hashCtxFunction(msgShaContext, (unsigned char*)zrtpCommit.getHeaderBase(), len);

    // store Hello data temporarily until we can check HMAC after receiving Commit as
    // Responder or DHPart1 as Initiator
    storeMsgTemp(hello);

    return &zrtpCommit;
}

ZrtpPacketCommit* ZRtp::prepareCommitMultiStream(ZrtpPacketHello *hello) {

    randomZRTP(hvi, ZRTP_WORD_SIZE*4);  // This is the Multi-Stream NONCE size

    zrtpCommit.setZid(ownZid);
    zrtpCommit.setHashType((uint8_t*)hash->getName());
    zrtpCommit.setCipherType((uint8_t*)cipher->getName());
    zrtpCommit.setAuthLen((uint8_t*)authLength->getName());
    zrtpCommit.setPubKeyType((uint8_t*)mult);  // this is fixed because of Multi Stream mode
    zrtpCommit.setSasType((uint8_t*)sasType->getName());
    zrtpCommit.setNonce(hvi);
    zrtpCommit.setH2(H2);

    int32_t len = zrtpCommit.getLength() * ZRTP_WORD_SIZE;

    // Compute HMAC over Commit, excluding the HMAC field (HMAC_SIZE)
    // and store in Hello. Key to HMAC is H1, use HASH_IMAGE_SIZE bytes only.
    // Must use the implicit HMAC function.
    uint8_t hmac[IMPL_MAX_DIGEST_LENGTH];
    uint32_t macLen;
    hmacFunctionImpl(H1, HASH_IMAGE_SIZE, (uint8_t*)zrtpCommit.getHeaderBase(), len-(HMAC_SIZE), hmac, &macLen);
    zrtpCommit.setHMACMulti(hmac);


    // hash first messages to produce overall message hash
    // First the Responder's Hello message, second the Commit
    // (always Initator's).
    // Must use the negotiated hash.
    msgShaContext = createHashCtx(msgShaContext);

    int32_t helloLen = hello->getLength() * ZRTP_WORD_SIZE;
    hashCtxFunction(msgShaContext, (unsigned char*)hello->getHeaderBase(), helloLen);
    hashCtxFunction(msgShaContext, (unsigned char*)zrtpCommit.getHeaderBase(), len);

    // store Hello data temporarily until we can check HMAC after receiving Commit as
    // Responder or DHPart1 as Initiator
    storeMsgTemp(hello);

    return &zrtpCommit;
}

/*
 * At this point we will take the role of the Responder. We have been in
 * the role of the Initiator before and already sent a commit packet that
 * clashed with a commit packet from our peer. If our HVI was lower than our
 * peer's HVI then we switched to Responder and handle our peer's commit packet
 * here. This method takes care to delete and refresh data left over from a
 * possible Initiator preparation. This belongs to prepared DH data, message
 * hash SHA context
 */
ZrtpPacketDHPart* ZRtp::prepareDHPart1(ZrtpPacketCommit *commit, uint32_t* errMsg) {

    sendInfo(Info, InfoRespCommitReceived);

    if (!commit->isLengthOk(ZrtpPacketCommit::DhExchange)) {
        *errMsg = CriticalSWError;
        return NULL;
    }

    // Check if ZID in Commit is the same as we got in Hello
    uint8_t tmpZid[ZID_SIZE];
    memcpy(tmpZid, commit->getZid(), ZID_SIZE);
    if (memcmp(peerZid, tmpZid, ZID_SIZE) != 0) {       // ZIDs do not match????
        sendInfo(Severe, SevereProtocolError);
        *errMsg = CriticalSWError;
        return NULL;
    }

    // The following code checks the hash chain according chapter 10 to detect false ZRTP packets.
    // Must use the implicit hash function.
    uint8_t tmpH3[IMPL_MAX_DIGEST_LENGTH];
    memcpy(peerH2, commit->getH2(), HASH_IMAGE_SIZE);
    hashFunctionImpl(peerH2, HASH_IMAGE_SIZE, tmpH3);

    if (memcmp(tmpH3, peerH3, HASH_IMAGE_SIZE) != 0) {
        *errMsg = IgnorePacket;
        return NULL;
    }

    // Check HMAC of previous Hello packet stored in temporary buffer. The
    // HMAC key of peer's Hello packet is peer's H2 that is contained in the
    // Commit packet. Refer to chapter 9.1.
    if (!checkMsgHmac(peerH2)) {
        sendInfo(Severe, SevereHelloHMACFailed);
        *errMsg = CriticalSWError;
        return NULL;
    }

    // check if we support the commited Cipher type
    AlgorithmEnum* cp = &zrtpSymCiphers.getByName((const char*)commit->getCipherType());
    if (!cp->isValid()) { // no match - something went wrong
        *errMsg = UnsuppCiphertype;
        return NULL;
    }
    cipher = cp;

    // check if we support the commited Authentication length
    cp = &zrtpAuthLengths.getByName((const char*)commit->getAuthLen());
    if (!cp->isValid()) { // no match - something went wrong
        *errMsg = UnsuppSRTPAuthTag;
        return NULL;
    }
    authLength = cp;

    // check if we support the commited hash type
    cp = &zrtpHashes.getByName((const char*)commit->getHashType());
    if (!cp->isValid()) { // no match - something went wrong
        *errMsg = UnsuppHashType;
        return NULL;
    }
    // check if the peer's commited hash is the same that we used when
    // preparing our commit packet. If not do the necessary resets and
    // recompute some data.
    if (*(int32_t*)(hash->getName()) != *(int32_t*)(cp->getName())) {
        hash = cp;
        setNegotiatedHash(hash);
        // Compute the Initator's and Responder's retained secret ids
        // with the committed hash.
        computeSharedSecretSet(zidRec);
    }
    // check if we support the commited pub key type
    cp = &zrtpPubKeys.getByName((const char*)commit->getPubKeysType());
    if (!cp->isValid()) { // no match - something went wrong
        *errMsg = UnsuppPKExchange;
        return NULL;
    }
    if (*(int32_t*)(cp->getName()) == *(int32_t*)ec38 || *(int32_t*)(cp->getName()) == *(int32_t*)e414) {
        if (!(*(int32_t*)(hash->getName()) == *(int32_t*)s384 || *(int32_t*)(hash->getName()) == *(int32_t*)skn3)) {
            *errMsg = UnsuppHashType;
            return NULL;
        }
    }
    pubKey = cp;

    // check if we support the commited SAS type
    cp = &zrtpSasTypes.getByName((const char*)commit->getSasType());
    if (!cp->isValid()) { // no match - something went wrong
        *errMsg = UnsuppSASScheme;
        return NULL;
    }
    sasType = cp;

    // dhContext cannot be NULL - always setup during prepareCommit()
    // check if we can use the dhContext prepared by prepareCommit(),
    // if not delete old DH context and generate new one
    // The algorithm names are 4 chars only, thus we can cast to int32_t
    if (*(int32_t*)(dhContext->getDHtype()) != *(int32_t*)(pubKey->getName())) {
        delete dhContext;
        dhContext = new ZrtpDH(pubKey->getName());
        dhContext->generatePublicKey();
    }
    sendInfo(Info, InfoDH1DHGenerated);

    dhContext->getPubKeyBytes(pubKeyBytes);

    // Re-compute auxSecretIDr because we changed roles *IDr with my H3, *IDi with peer's H3
    // Setup a DHPart1 packet.
    myRole = Responder;
    computeAuxSecretIds();                 // recompute AUX secret ids because we are now Responder, use different H3

    zrtpDH1.setPubKeyType(pubKey->getName());
    zrtpDH1.setMessageType((uint8_t*)DHPart1Msg);
    zrtpDH1.setRs1Id(rs1IDr);
    zrtpDH1.setRs2Id(rs2IDr);
    zrtpDH1.setAuxSecretId(auxSecretIDr);
    zrtpDH1.setPbxSecretId(pbxSecretIDr);
    zrtpDH1.setPv(pubKeyBytes);
    zrtpDH1.setH1(H1);

    int32_t len = zrtpDH1.getLength() * ZRTP_WORD_SIZE;

    // Compute HMAC over DHPart1, excluding the HMAC field (HMAC_SIZE)
    // and store in DHPart1.
    // Use implicit Hash function
    uint8_t hmac[IMPL_MAX_DIGEST_LENGTH];
    uint32_t macLen;
    hmacFunctionImpl(H0, HASH_IMAGE_SIZE, (uint8_t*)zrtpDH1.getHeaderBase(), len-(HMAC_SIZE), hmac, &macLen);
    zrtpDH1.setHMAC(hmac);

    // We are definitly responder. Save the peer's hvi for later compare.
    memcpy(peerHvi, commit->getHvi(), HVI_SIZE);

    // We are responder. Release the pre-computed SHA context because it was prepared for Initiator.
    // Setup and compute for Responder.
    if (msgShaContext != NULL) {
        closeHashCtx(msgShaContext, NULL);
    }
    msgShaContext = createHashCtx(msgShaContext);

    // Hash messages to produce overall message hash:
    // First the Responder's (my) Hello message, second the Commit (always Initator's),
    // then the DH1 message (which is always a Responder's message).
    // Must use negotiated hash.
    hashCtxFunction(msgShaContext, (unsigned char*)currentHelloPacket->getHeaderBase(), currentHelloPacket->getLength() * ZRTP_WORD_SIZE);
    hashCtxFunction(msgShaContext, (unsigned char*)commit->getHeaderBase(), commit->getLength() * ZRTP_WORD_SIZE);
    hashCtxFunction(msgShaContext, (unsigned char*)zrtpDH1.getHeaderBase(), zrtpDH1.getLength() * ZRTP_WORD_SIZE);

    // store Commit data temporarily until we can check HMAC after we got DHPart2
    storeMsgTemp(commit);

    return &zrtpDH1;
}

/*
 * At this point we will take the role of the Initiator.
 */
ZrtpPacketDHPart* ZRtp::prepareDHPart2(ZrtpPacketDHPart *dhPart1, uint32_t* errMsg) {

    uint8_t* pvr;

    sendInfo(Info, InfoInitDH1Received);

    if (!dhPart1->isLengthOk()) {
        *errMsg = CriticalSWError;
        return NULL;
    }
    // Because we are initiator the protocol engine didn't receive Commit
    // thus could not store a peer's H2. A two step SHA256 is required to
    // re-compute H3. Then compare with peer's H3 from peer's Hello packet.
    // Must use implicit hash function.
    uint8_t tmpHash[IMPL_MAX_DIGEST_LENGTH];
    hashFunctionImpl(dhPart1->getH1(), HASH_IMAGE_SIZE, tmpHash); // Compute peer's H2
    memcpy(peerH2, tmpHash, HASH_IMAGE_SIZE);
    hashFunctionImpl(peerH2, HASH_IMAGE_SIZE, tmpHash);          // Compute peer's H3 (tmpHash)

    if (memcmp(tmpHash, peerH3, HASH_IMAGE_SIZE) != 0) {
        *errMsg = IgnorePacket;
        return NULL;
    }

    // Check HMAC of previous Hello packet stored in temporary buffer. The
    // HMAC key of the Hello packet is peer's H2 that was computed above.
    // Refer to chapter 9.1 and chapter 10.
    if (!checkMsgHmac(peerH2)) {
        sendInfo(Severe, SevereHelloHMACFailed);
        *errMsg = CriticalSWError;
        return NULL;
    }

    // get memory to store DH result TODO: make it fixed memory
    DHss = new uint8_t[dhContext->getDhSize()];
    if (DHss == NULL) {
        *errMsg = CriticalSWError;
        return NULL;
    }

    // get and check Responder's public value, see chap. 5.4.3 in the spec
    pvr = dhPart1->getPv();
    if (pvr == NULL) {
        *errMsg = IgnorePacket;
        return NULL;
    }
    if (!dhContext->checkPubKey(pvr)) {
        *errMsg = DHErrorWrongPV;
        return NULL;
    }
    dhContext->computeSecretKey(pvr, DHss);

    // We are Initiator: the Responder's Hello and the Initiator's (our) Commit
    // are already hashed in the context. Now hash the Responder's DH1 and then
    // the Initiator's (our) DH2 in that order.
    // Use the negotiated hash function.
    hashCtxFunction(msgShaContext, (unsigned char*)dhPart1->getHeaderBase(), dhPart1->getLength() * ZRTP_WORD_SIZE);
    hashCtxFunction(msgShaContext, (unsigned char*)zrtpDH2.getHeaderBase(), zrtpDH2.getLength() * ZRTP_WORD_SIZE);

    // Compute the message Hash
    closeHashCtx(msgShaContext, messageHash);
    msgShaContext = NULL;
    // Now compute the S0, all dependend keys and the new RS1. The function
    // also performs sign SAS callback if it's active.
    generateKeysInitiator(dhPart1, zidRec);

    delete dhContext;
    dhContext = NULL;

    // TODO: at initiator we can call signSAS at this point, don't dealy until confirm1 reveived
    // store DHPart1 data temporarily until we can check HMAC after receiving Confirm1
    storeMsgTemp(dhPart1);
    return &zrtpDH2;
}

/*
 * At this point we are Responder.
 */
ZrtpPacketConfirm* ZRtp::prepareConfirm1(ZrtpPacketDHPart* dhPart2, uint32_t* errMsg) {

    uint8_t* pvi;

    sendInfo(Info, InfoRespDH2Received);

    if (!dhPart2->isLengthOk()) {
        *errMsg = CriticalSWError;
        return NULL;
    }
    // Because we are responder we received a Commit and stored its H2.
    // Now re-compute H2 from received H1 and compare with stored peer's H2.
    // Use implicit hash function
    uint8_t tmpHash[IMPL_MAX_DIGEST_LENGTH];
    hashFunctionImpl(dhPart2->getH1(), HASH_IMAGE_SIZE, tmpHash);
    if (memcmp(tmpHash, peerH2, HASH_IMAGE_SIZE) != 0) {
        *errMsg = IgnorePacket;
        return NULL;
    }

    // Check HMAC of Commit packet stored in temporary buffer. The
    // HMAC key of the Commit packet is peer's H1 that is contained in
    // DHPart2. Refer to chapter 9.1 and chapter 10.
    if (!checkMsgHmac(dhPart2->getH1())) {
        sendInfo(Severe, SevereCommitHMACFailed);
        *errMsg = CriticalSWError;
        return NULL;
    }
    // Now we have the peer's pvi. Because we are responder re-compute my hvi
    // using my Hello packet and the Initiator's DHPart2 and compare with
    // hvi sent in commit packet. If it doesn't macht then a MitM attack
    // may have occured.
    computeHvi(dhPart2, currentHelloPacket);
    if (memcmp(hvi, peerHvi, HVI_SIZE) != 0) {
        *errMsg = DHErrorWrongHVI;
        return NULL;
    }
    DHss = new uint8_t[dhContext->getDhSize()];
    if (DHss == NULL) {
        *errMsg = CriticalSWError;
        return NULL;
    }
    // Get and check the Initiator's public value, see chap. 5.4.2 of the spec
    pvi = dhPart2->getPv();
    if (!dhContext->checkPubKey(pvi)) {
        *errMsg = DHErrorWrongPV;
        return NULL;
    }
    dhContext->computeSecretKey(pvi, DHss);

    // Hash the Initiator's DH2 into the message Hash (other messages already prepared, see method prepareDHPart1().
    // Use neotiated hash function
    hashCtxFunction(msgShaContext, (unsigned char*)dhPart2->getHeaderBase(), dhPart2->getLength() * ZRTP_WORD_SIZE);

    closeHashCtx(msgShaContext, messageHash);
    msgShaContext = NULL;
    /*
     * The expected shared secret Ids were already computed when we built the
     * DHPart1 packet. Generate s0, all depended keys, and the new RS1 value
     * for the ZID record. The functions also performs sign SAS callback if it's
     * active. May reset the verify flag in ZID record.
     */
    generateKeysResponder(dhPart2, zidRec);

    delete dhContext;
    dhContext = NULL;

    // Fill in Confirm1 packet.
    zrtpConfirm1.setMessageType((uint8_t*)Confirm1Msg);

    // Check if user verfied the SAS in a previous call and thus verfied
    // the retained secret. Don't set the verified flag if paranoidMode is true.
    if (zidRec->isSasVerified() && !paranoidMode) {
        zrtpConfirm1.setSASFlag();
    }
    if (configureAlgos.isDisclosureFlag()) {
        zrtpConfirm1.setDisclosureFlag();
    }
    zrtpConfirm1.setExpTime(0xFFFFFFFF);
    zrtpConfirm1.setIv(randomIV);
    zrtpConfirm1.setHashH0(H0);

#ifdef ZRTP_SAS_RELAY_SUPPORT
    // if this runs at PBX user agent enrollment service then set flag in confirm
    // packet and store the MitM key
    if (enrollmentMode) {
        // As clarification to RFC6189: store new PBX secret only if we don't have
        // a matching PBX secret for the peer's ZID.
        if (!peerIsEnrolled) {
            computePBXSecret();
            zidRec->setMiTMData(pbxSecretTmp);
        }
        // Set flag to enable user's client to ask for confirmation or re-confirmation.
        zrtpConfirm1.setPBXEnrollment();
    }
#endif
    uint8_t confMac[MAX_DIGEST_LENGTH];
    uint32_t macLen;

    // Encrypt and HMAC with Responder's key - we are Respondere here
    int hmlen = (zrtpConfirm1.getLength() - 9) * ZRTP_WORD_SIZE;
    cipher->getEncrypt()(zrtpKeyR, cipher->getKeylen(), randomIV, zrtpConfirm1.getHashH0(), hmlen);
    hmacFunction(hmacKeyR, hashLength, (unsigned char*)zrtpConfirm1.getHashH0(), hmlen, confMac, &macLen);

    zrtpConfirm1.setHmac(confMac);

    // store DHPart2 data temporarily until we can check HMAC after receiving Confirm2
    storeMsgTemp(dhPart2);
    return &zrtpConfirm1;
}

/*
 * At this point we are Responder.
 */
ZrtpPacketConfirm* ZRtp::prepareConfirm1MultiStream(ZrtpPacketCommit* commit, uint32_t* errMsg) {

    sendInfo(Info, InfoRespCommitReceived);

    if (!commit->isLengthOk(ZrtpPacketCommit::MultiStream)) {
        *errMsg = CriticalSWError;
        return NULL;
    }
    // The following code checks the hash chain according chapter 10 to detect
    // false ZRTP packets.
    // Use implicit hash function
    uint8_t tmpH3[IMPL_MAX_DIGEST_LENGTH];
    memcpy(peerH2, commit->getH2(), HASH_IMAGE_SIZE);
    hashFunctionImpl(peerH2, HASH_IMAGE_SIZE, tmpH3);

    if (memcmp(tmpH3, peerH3, HASH_IMAGE_SIZE) != 0) {
        *errMsg = IgnorePacket;
        return NULL;
    }

    // Check HMAC of previous Hello packet stored in temporary buffer. The
    // HMAC key of peer's Hello packet is peer's H2 that is contained in the
    // Commit packet. Refer to chapter 9.1.
    if (!checkMsgHmac(peerH2)) {
        sendInfo(Severe, SevereHelloHMACFailed);
        *errMsg = CriticalSWError;
        return NULL;
    }

    if (!checkAndSetNonce(commit->getNonce())) {
        *errMsg = NonceReused;
        return NULL;
    }
    // check if Commit contains "Mult" as pub key type
    AlgorithmEnum* cp = &zrtpPubKeys.getByName((const char*)commit->getPubKeysType());
    if (!cp->isValid() || *(int32_t*)(cp->getName()) != *(int32_t*)mult) {
        *errMsg = UnsuppPKExchange;
        return NULL;
    }

    // check if we support the commited cipher
    cp = &zrtpSymCiphers.getByName((const char*)commit->getCipherType());
    if (!cp->isValid()) { // no match - something went wrong
        *errMsg = UnsuppCiphertype;
        return NULL;
    }
    cipher = cp;

    // check if we support the commited Authentication length
    cp = &zrtpAuthLengths.getByName((const char*)commit->getAuthLen());
    if (!cp->isValid()) { // no match - something went wrong
        *errMsg = UnsuppSRTPAuthTag;
        return NULL;
    }
    authLength = cp;

    // check if we support the commited hash type
    cp = &zrtpHashes.getByName((const char*)commit->getHashType());
    if (!cp->isValid()) { // no match - something went wrong
        *errMsg = UnsuppHashType;
        return NULL;
    }
    // check if the peer's commited hash is the same that we used when
    // preparing our commit packet. If not do the necessary resets and
    // recompute some data.
    if (*(int32_t*)(hash->getName()) != *(int32_t*)(cp->getName())) {
        hash = cp;
        setNegotiatedHash(hash);
    }
    myRole = Responder;

    // We are responder. Release a possibly pre-computed SHA256 context
    // because this was prepared for Initiator. Then create a new one.
    if (msgShaContext != NULL) {
        closeHashCtx(msgShaContext, NULL);
    }
    msgShaContext = createHashCtx(msgShaContext);

    // Hash messages to produce overall message hash:
    // First the Responder's (my) Hello message, second the Commit
    // (always Initator's)
    // use negotiated hash
    hashCtxFunction(msgShaContext, (unsigned char*)currentHelloPacket->getHeaderBase(), currentHelloPacket->getLength() * ZRTP_WORD_SIZE);
    hashCtxFunction(msgShaContext, (unsigned char*)commit->getHeaderBase(), commit->getLength() * ZRTP_WORD_SIZE);

    closeHashCtx(msgShaContext, messageHash);
    msgShaContext = NULL;

    generateKeysMultiStream();

    // Fill in Confirm1 packet.
    zrtpConfirm1.setMessageType((uint8_t*)Confirm1Msg);
    if (configureAlgos.isDisclosureFlag()) {
        zrtpConfirm1.setDisclosureFlag();
    }
    zrtpConfirm1.setExpTime(0xFFFFFFFF);
    zrtpConfirm1.setIv(randomIV);
    zrtpConfirm1.setHashH0(H0);

    uint8_t confMac[MAX_DIGEST_LENGTH];
    uint32_t macLen;

    // Encrypt and HMAC with Responder's key - we are Respondere here
    int32_t hmlen = (zrtpConfirm1.getLength() - 9) * ZRTP_WORD_SIZE;
    cipher->getEncrypt()(zrtpKeyR, cipher->getKeylen(), randomIV, zrtpConfirm1.getHashH0(), hmlen);

    // Use negotiated HMAC (hash)
    hmacFunction(hmacKeyR, hashLength, (unsigned char*)zrtpConfirm1.getHashH0(), hmlen, confMac, &macLen);

    zrtpConfirm1.setHmac(confMac);

    // Store Commit data temporarily until we can check HMAC after receiving Confirm2
    storeMsgTemp(commit);
    return &zrtpConfirm1;
}

/*
 * At this point we are Initiator.
 */
ZrtpPacketConfirm* ZRtp::prepareConfirm2(ZrtpPacketConfirm* confirm1, uint32_t* errMsg) {

    sendInfo(Info, InfoInitConf1Received);

    if (!confirm1->isLengthOk()) {
        *errMsg = CriticalSWError;
        return NULL;
    }
    uint8_t confMac[MAX_DIGEST_LENGTH];
    uint32_t macLen;

    // Use the Responder's keys here because we are Initiator here and
    // receive packets from Responder
    int16_t hmlen = (confirm1->getLength() - 9) * ZRTP_WORD_SIZE;

    // Use negotiated HMAC (hash)
    hmacFunction(hmacKeyR, hashLength, (unsigned char*)confirm1->getHashH0(), hmlen, confMac, &macLen);

    if (memcmp(confMac, confirm1->getHmac(), HMAC_SIZE) != 0) {
        *errMsg = ConfirmHMACWrong;
        return NULL;
    }
    cipher->getDecrypt()(zrtpKeyR, cipher->getKeylen(), (uint8_t*)confirm1->getIv(), confirm1->getHashH0(), hmlen);

    // Check HMAC of DHPart1 packet stored in temporary buffer. The
    // HMAC key of the DHPart1 packet is peer's H0 that is contained in
    // Confirm1. Refer to chapter 9.
    if (!checkMsgHmac(confirm1->getHashH0())) {
        sendInfo(Severe, SevereDH1HMACFailed);
        *errMsg = CriticalSWError;
        return NULL;
    }
    /*
     * The Confirm1 is ok, handle the Retained secret stuff and inform
     * GUI about state.
     */
    bool sasFlag = confirm1->isSASFlag();

    // Our peer did not confirm the SAS in last session, thus reset
    // our SAS flag too. Reset the flag also if paranoidMode is true.
    if (!sasFlag || paranoidMode) {
        zidRec->resetSasVerified();
    }

    // Store the status of the Disclosure flag
    peerDisclosureFlagSeen = confirm1->isDisclosureFlag();

    // get verified flag from current RS1 before set a new RS1. This
    // may not be set even if peer's flag is set in confirm1 message.
    sasFlag = zidRec->isSasVerified();

    signatureLength = confirm1->getSignatureLength();
    if (signSasSeen && signatureLength > 0 && confirm1->isSignatureLengthOk()) {
        signatureData = confirm1->getSignatureData();
        callback->checkSASSignature(sasHash);
        // TODO: error handling if checkSASSignature returns false.
    }
    // now we are ready to save the new RS1 which inherits the verified
    // flag from old RS1
    zidRec->setNewRs1((const uint8_t*)newRs1);

    // now generate my Confirm2 message
    zrtpConfirm2.setMessageType((uint8_t*)Confirm2Msg);
    zrtpConfirm2.setHashH0(H0);

    if (sasFlag) {
        zrtpConfirm2.setSASFlag();
    }
    if (configureAlgos.isDisclosureFlag()) {
        zrtpConfirm2.setDisclosureFlag();
    }
    zrtpConfirm2.setExpTime(0xFFFFFFFF);
    zrtpConfirm2.setIv(randomIV);

#ifdef ZRTP_SAS_RELAY_SUPPORT
    // Compute PBX secret if we are in enrollemnt mode (PBX user agent)
    // or enrollment was enabled at normal user agent and flag in confirm packet
    if (enrollmentMode || (enableMitmEnrollment && confirm1->isPBXEnrollment())) {
        computePBXSecret();

        // if this runs at PBX user agent enrollment service then set flag in confirm
        // packet and store the MitM key. The PBX user agent service always stores
        // its MitM key.
        if (enrollmentMode) {
            // As clarification to RFC6189: store new PBX secret only if we don't have
            // a matching PBX secret for the peer's ZID.
            if (!peerIsEnrolled) {
                computePBXSecret();
                zidRec->setMiTMData(pbxSecretTmp);
            }
            // Set flag to enable user's client to ask for confirmation or re-confirmation.
            zrtpConfirm2.setPBXEnrollment();
        }
    }
#endif
    if (saveZidRecord)
        getZidCacheInstance()->saveRecord(zidRec);

    // Encrypt and HMAC with Initiator's key - we are Initiator here
    hmlen = (zrtpConfirm2.getLength() - 9) * ZRTP_WORD_SIZE;
    cipher->getEncrypt()(zrtpKeyI, cipher->getKeylen(), randomIV, zrtpConfirm2.getHashH0(), hmlen);

    // Use negotiated HMAC (hash)
    hmacFunction(hmacKeyI, hashLength, (unsigned char*)zrtpConfirm2.getHashH0(), hmlen, confMac, &macLen);

    zrtpConfirm2.setHmac(confMac);

#ifdef ZRTP_SAS_RELAY_SUPPORT
    // Ask for enrollment only if enabled via configuration and the
    // confirm1 packet contains the enrollment flag. The enrolling user
    // agent stores the MitM key only if the user accepts the enrollment
    // request.
    if (enableMitmEnrollment && confirm1->isPBXEnrollment()) {
        // As clarification to RFC6189: if already enrolled (having a matching PBX secret)
        // ask for reconfirmation.
        if (!peerIsEnrolled) {
            callback->zrtpAskEnrollment(EnrollmentRequest);
        }
        else {
            callback->zrtpAskEnrollment(EnrollmentReconfirm);
        }
    }
#endif
    return &zrtpConfirm2;
}

/*
 * At this point we are Initiator.
 */
ZrtpPacketConfirm* ZRtp::prepareConfirm2MultiStream(ZrtpPacketConfirm* confirm1, uint32_t* errMsg) {

    // check Confirm1 packet using the keys
    // prepare Confirm2 packet
    // don't update SAS, RS
    sendInfo(Info, InfoInitConf1Received);

    if (!confirm1->isLengthOk()) {
        *errMsg = CriticalSWError;
        return NULL;
    }
    uint8_t confMac[MAX_DIGEST_LENGTH];
    uint32_t macLen;

    closeHashCtx(msgShaContext, messageHash);
    msgShaContext = NULL;
    myRole = Initiator;

    generateKeysMultiStream();

    // Use the Responder's keys here because we are Initiator here and
    // receive packets from Responder
    int32_t hmlen = (confirm1->getLength() - 9) * ZRTP_WORD_SIZE;

    // Use negotiated HMAC (hash)
    hmacFunction(hmacKeyR, hashLength, (unsigned char*)confirm1->getHashH0(), hmlen, confMac, &macLen);

    if (memcmp(confMac, confirm1->getHmac(), HMAC_SIZE) != 0) {
        *errMsg = ConfirmHMACWrong;
        return NULL;
    }
    // Cast away the const for the IV - the standalone AES CFB modifies IV on return
    cipher->getDecrypt()(zrtpKeyR, cipher->getKeylen(), (uint8_t*)confirm1->getIv(), confirm1->getHashH0(), hmlen);

    // Because we are initiator the protocol engine didn't receive Commit and
    // because we are using multi-stream mode here we also did not receive a DHPart1 and
    // thus could not store a responder's H2 or H1. A two step hash is required to
    // re-compute H1, H2.
    // USe implicit hash function.
    uint8_t tmpHash[IMPL_MAX_DIGEST_LENGTH];
    hashFunctionImpl(confirm1->getHashH0(), HASH_IMAGE_SIZE, tmpHash); // Compute peer's H1 in tmpHash
    hashFunctionImpl(tmpHash, HASH_IMAGE_SIZE, tmpHash);               // Compute peer's H2 in tmpHash
    memcpy(peerH2, tmpHash, HASH_IMAGE_SIZE);                          // copy and truncate to peerH2

    // Check HMAC of previous Hello packet stored in temporary buffer. The
    // HMAC key of the Hello packet is peer's H2 that was computed above.
    // Refer to chapter 9.1 and chapter 10.
    if (!checkMsgHmac(peerH2)) {
        sendInfo(Severe, SevereHelloHMACFailed);
        *errMsg = CriticalSWError;
        return NULL;
    }
    // Store the status of the Disclosure flag
    peerDisclosureFlagSeen = confirm1->isDisclosureFlag();

    // now generate my Confirm2 message
    zrtpConfirm2.setMessageType((uint8_t*)Confirm2Msg);
    if (configureAlgos.isDisclosureFlag()) {
        zrtpConfirm2.setDisclosureFlag();
    }
    zrtpConfirm2.setHashH0(H0);
    zrtpConfirm2.setExpTime(0xFFFFFFFF);
    zrtpConfirm2.setIv(randomIV);

    // Encrypt and HMAC with Initiator's key - we are Initiator here
    hmlen = (zrtpConfirm2.getLength() - 9) * ZRTP_WORD_SIZE;
    cipher->getEncrypt()(zrtpKeyI, cipher->getKeylen(), randomIV, zrtpConfirm2.getHashH0(), hmlen);

    // Use negotiated HMAC (hash)
    hmacFunction(hmacKeyI, hashLength, (unsigned char*)zrtpConfirm2.getHashH0(), hmlen, confMac, &macLen);

    zrtpConfirm2.setHmac(confMac);
    return &zrtpConfirm2;
}

/*
 * At this point we are Responder.
 */
ZrtpPacketConf2Ack* ZRtp::prepareConf2Ack(ZrtpPacketConfirm *confirm2, uint32_t* errMsg) {

    sendInfo(Info, InfoRespConf2Received);

    if (!confirm2->isLengthOk()) {
        *errMsg = CriticalSWError;
        return NULL;
    }
    uint8_t confMac[MAX_DIGEST_LENGTH];
    uint32_t macLen;

    // Use the Initiator's keys here because we are Responder here and
    // reveice packets from Initiator
    int16_t hmlen = (confirm2->getLength() - 9) * ZRTP_WORD_SIZE;

    // Use negotiated HMAC (hash)
    hmacFunction(hmacKeyI, hashLength,
                 (unsigned char*)confirm2->getHashH0(),
                 hmlen, confMac, &macLen);

    if (memcmp(confMac, confirm2->getHmac(), HMAC_SIZE) != 0) {
        *errMsg = ConfirmHMACWrong;
        return NULL;
    }
    // Cast away the const for the IV - the standalone AES CFB modifies IV on return
    cipher->getDecrypt()(zrtpKeyI, cipher->getKeylen(), (uint8_t*)confirm2->getIv(), confirm2->getHashH0(), hmlen);

    if (!multiStream) {
        // Check HMAC of DHPart2 packet stored in temporary buffer. The
        // HMAC key of the DHPart2 packet is peer's H0 that is contained in
        // Confirm2. Refer to chapter 9.1 and chapter 10.
        if (!checkMsgHmac(confirm2->getHashH0())) {
            sendInfo(Severe, SevereDH2HMACFailed);
            *errMsg = CriticalSWError;
            return NULL;
        }
        /*
         * The Confirm2 is ok, handle the Retained secret stuff and inform
         * GUI about state.
         */
        bool sasFlag = confirm2->isSASFlag();
        // Our peer did not confirm the SAS in last session, thus reset
        // our SAS flag too. Reset the flag also if paranoidMode is true.
        if (!sasFlag || paranoidMode) {
            zidRec->resetSasVerified();
        }
        signatureLength = confirm2->getSignatureLength();
        if (signSasSeen && signatureLength > 0 && confirm2->isSignatureLengthOk() ) {
            signatureData = confirm2->getSignatureData();
            callback->checkSASSignature(sasHash);
            // TODO: error handling if checkSASSignature returns false.
        }
        // save new RS1, this inherits the verified flag from old RS1
        zidRec->setNewRs1((const uint8_t*)newRs1);
        if (saveZidRecord)
            getZidCacheInstance()->saveRecord(zidRec);

#ifdef ZRTP_SAS_RELAY_SUPPORT
        // Ask for enrollment only if enabled via configuration and the
        // confirm packet contains the enrollment flag. The enrolling user
        // agent stores the MitM key only if the user accepts the enrollment
        // request.
        if (enableMitmEnrollment && confirm2->isPBXEnrollment()) {
            computePBXSecret();
            // As clarification to RFC6189: if already enrolled (having a matching PBX secret)
            // ask for reconfirmation.
            if (!peerIsEnrolled) {
                callback->zrtpAskEnrollment(EnrollmentRequest);
            }
            else {
                callback->zrtpAskEnrollment(EnrollmentReconfirm);
            }
        }
#endif
    }
    else {
        // Check HMAC of Commit packet stored in temporary buffer. The
        // HMAC key of the Commit packet is initiator's H1
        // use implicit hash function.
        uint8_t tmpHash[IMPL_MAX_DIGEST_LENGTH];
        hashFunctionImpl(confirm2->getHashH0(), HASH_IMAGE_SIZE, tmpHash); // Compute initiator's H1 in tmpHash

        if (!checkMsgHmac(tmpHash)) {
            sendInfo(Severe, SevereCommitHMACFailed);
            *errMsg = CriticalSWError;
            return NULL;
        }
    }
    // Store the status of the Disclosure flag
    peerDisclosureFlagSeen = confirm2->isDisclosureFlag();

    return &zrtpConf2Ack;
}

ZrtpPacketErrorAck* ZRtp::prepareErrorAck(ZrtpPacketError* epkt) {
    if (epkt->getLength() < 4)
        sendInfo(ZrtpError, CriticalSWError * -1);
    else
        sendInfo(ZrtpError, epkt->getErrorCode() * -1);
    return &zrtpErrorAck;
}

ZrtpPacketError* ZRtp::prepareError(uint32_t errMsg) {
    zrtpError.setErrorCode(errMsg);
    return &zrtpError;
}

ZrtpPacketPingAck* ZRtp::preparePingAck(ZrtpPacketPing* ppkt) {
    if (ppkt->getLength() != 6)                    // A PING packet must have a length of 6 words
        return NULL;
    // Because we do not support ZRTP proxy mode use the truncated ZID.
    // If this code shall be used in ZRTP proxy implementation the computation
    // of the endpoint hash must be enhanced (see chaps 5.15ff and 5.16)
    zrtpPingAck.setLocalEpHash(ownZid);
    zrtpPingAck.setRemoteEpHash(ppkt->getEpHash());
    zrtpPingAck.setSSRC(peerSSRC);
    return &zrtpPingAck;
}

ZrtpPacketRelayAck* ZRtp::prepareRelayAck(ZrtpPacketSASrelay* srly, uint32_t* errMsg) {

#ifdef ZRTP_SAS_RELAY_SUPPORT
    // handle and render SAS relay data only if the peer announced that it is a trusted
    // PBX. Don't handle SAS relay in paranoidMode.
    if (!mitmSeen || paranoidMode)
        return &zrtpRelayAck;

    if (!srly->isLengthOk()) {
        *errMsg = CriticalSWError;
        return NULL;
    }
    uint8_t* hkey, *ekey;
    // If we are responder then the PBX used it's Initiator keys
    if (myRole == Responder) {
        hkey = hmacKeyI;
        ekey = zrtpKeyI;
    }
    else {
        hkey = hmacKeyR;
        ekey = zrtpKeyR;
    }

    uint8_t confMac[MAX_DIGEST_LENGTH];
    uint32_t macLen;

    int16_t hmlen = (srly->getLength() - 9) * ZRTP_WORD_SIZE;

    // Use negotiated HMAC (hash)
    hmacFunction(hkey, hashLength, (unsigned char*)srly->getFiller(), hmlen, confMac, &macLen);

    if (memcmp(confMac, srly->getHmac(), HMAC_SIZE) != 0) {
        *errMsg = ConfirmHMACWrong;
        return NULL;                // TODO - check error handling
    }
    // Cast away the const for the IV - the standalone AES CFB modifies IV on return
    cipher->getDecrypt()(ekey, cipher->getKeylen(), (uint8_t*)srly->getIv(), (uint8_t*)srly->getFiller(), hmlen);

    const uint8_t* newSasHash = srly->getTrustedSas();
    bool sasHashNull = true;
    for (int i = 0; i < HASH_IMAGE_SIZE; i++) {
        if (newSasHash[i] != 0) {
            sasHashNull = false;
            break;
        }
    }
    std::string cs(cipher->getReadable());
    cs.append("/").append(pubKey->getName());

    // Check if new SAS is null or a trusted MitM relationship doesn't exist.
    // If this is the case then don't render and don't show the new SAS - use
    // our computed SAS hash but we may use a different SAS rendering algorithm to
    // render the computed SAS.
    if (sasHashNull || !peerIsEnrolled) {
        cs.append("/MitM");
        newSasHash = sasHash;
    }
    else {
        cs.append("/SASviaMitM");
    }
    // If other SAS schemes required - check here and use others
    const uint8_t* render = srly->getSasAlgo();
    AlgorithmEnum* renderAlgo = &zrtpSasTypes.getByName((const char*)render);
    uint8_t sasBytes[4];
    if (renderAlgo->isValid()) {
        sasBytes[0] = newSasHash[0];
        sasBytes[1] = newSasHash[1];
        sasBytes[2] = newSasHash[2] & 0xf0;
        sasBytes[3] = 0;
        if (*(int32_t*)b32 == *(int32_t*)(renderAlgo->getName())) {
            SAS = Base32(sasBytes, 20).getEncoded();
        }
        else if (*(int32_t*)b32e == *(int32_t*)(renderAlgo->getName())) {
            SAS = *EmojiBase32::u32StringToUtf8(EmojiBase32(sasBytes, 20).getEncoded());
        }
        else {
            SAS.assign(sas256WordsEven[sasBytes[0]]).append(":").append(sas256WordsOdd[sasBytes[1]]);
        }
    }
    bool verify = zidRec->isSasVerified() && srly->isSASFlag();
    callback->srtpSecretsOn(cs, SAS, verify);

#endif
    return &zrtpRelayAck;
}

// TODO Implement GoClear handling
ZrtpPacketClearAck* ZRtp::prepareClearAck(ZrtpPacketGoClear* gpkt) {
    sendInfo(Warning, WarningGoClearReceived);
    return &zrtpClearAck;
}

ZrtpPacketGoClear* ZRtp::prepareGoClear(uint32_t errMsg) {
    ZrtpPacketGoClear* gclr = &zrtpGoClear;
    gclr->clrClearHmac();
    return gclr;
}

/*
 * The next functions look up and return a prefered algorithm. These
 * functions work as follows:
 * - If the Hello packet does not contain an algorithm (number of algorithms
*    is zero) then return the mandatory algorithm.
 * - Build a list of algorithm names and ids from configuration data. If
 *   the configuration data does not contain a mandatory algorithm append
 *   the mandatory algorithm to the list and ids.
 * - Build a list of algorithm names from the Hello message. If
 *   the Hello message does not contain a mandatory algorithm append
 *   the mandatory algorithm to the list.
 * - Lookup a matching algorithm. The list built from Hello takes
 *   precedence in the lookup (indexed by the outermost loop).
 *
 * This guarantees that we always return a supported alogrithm respecting
 * the order of algorithms in the Hello message
 *
 * The mandatory algorithms are: (internal enums are our prefered algoritms)
 * Hash:                S256 (SHA 256)             (internal enum Sha256)
 * Symmetric Cipher:    AES1 (AES 128)             (internal enum Aes128)
 * SRTP Authentication: HS32 and HS80 (32/80 bits) (internal enum AuthLen32)
 * Key Agreement:       DH3k (3072 Diffie-Helman)  (internal enum Dh3072)
 *
 */
AlgorithmEnum* ZRtp::findBestHash(ZrtpPacketHello *hello) {

    int i;
    int ii;
    int numAlgosOffered;
    AlgorithmEnum* algosOffered[ZrtpConfigure::maxNoOfAlgos+1];

    int numAlgosConf;
    AlgorithmEnum* algosConf[ZrtpConfigure::maxNoOfAlgos+1];

    // If Hello does not contain any hash names return Sha256, its mandatory
    int num = hello->getNumHashes();
    if (num == 0) {
        return &zrtpHashes.getByName(mandatoryHash);
    }
    // Build list of configured hash algorithm names.
    numAlgosConf = configureAlgos.getNumConfiguredAlgos(HashAlgorithm);
    for (i = 0; i < numAlgosConf; i++) {
        algosConf[i] = &configureAlgos.getAlgoAt(HashAlgorithm, i);
    }

    // Build list of offered known algos in Hello, append mandatory algos if necessary
    for (numAlgosOffered = 0, i = 0; i < num; i++) {
        algosOffered[numAlgosOffered] = &zrtpHashes.getByName((const char*)hello->getHashType(i));
        if (!algosOffered[numAlgosOffered]->isValid())
            continue;
        numAlgosOffered++;
    }

    // Lookup offered algos in configured algos.
    for (i = 0; i < numAlgosOffered; i++) {
        for (ii = 0; ii < numAlgosConf; ii++) {
            if (*(int32_t*)(algosOffered[i]->getName()) == *(int32_t*)(algosConf[ii]->getName())) {
                return algosConf[ii];
            }
        }
    }
    return &zrtpHashes.getByName(mandatoryHash);
}


AlgorithmEnum* ZRtp::findBestCipher(ZrtpPacketHello *hello, AlgorithmEnum* pk) {

    int i;
    int ii;
    int numAlgosOffered;
    AlgorithmEnum* algosOffered[ZrtpConfigure::maxNoOfAlgos+1];

    int numAlgosConf;
    AlgorithmEnum* algosConf[ZrtpConfigure::maxNoOfAlgos+1];

    int num = hello->getNumCiphers();
    if (num == 0 || (*(int32_t*)(pk->getName()) == *(int32_t*)dh2k)) {
        return &zrtpSymCiphers.getByName(aes1);
    }

    // Build list of configured cipher algorithm names.
    numAlgosConf = configureAlgos.getNumConfiguredAlgos(CipherAlgorithm);
    for (i = 0; i < numAlgosConf; i++) {
        algosConf[i] = &configureAlgos.getAlgoAt(CipherAlgorithm, i);
    }
    // Build list of offered known algos names in Hello.
    for (numAlgosOffered = 0, i = 0; i < num; i++) {
        algosOffered[numAlgosOffered] = &zrtpSymCiphers.getByName((const char*)hello->getCipherType(i));
        if (!algosOffered[numAlgosOffered]->isValid())
            continue;
        numAlgosOffered++;
    }
    // Lookup offered algos in configured algos.  Prefer algorithms that appear first in Hello packet (offered).
    for (i = 0; i < numAlgosOffered; i++) {
        for (ii = 0; ii < numAlgosConf; ii++) {
            if (*(int32_t*)(algosOffered[i]->getName()) == *(int32_t*)(algosConf[ii]->getName())) {
                return algosConf[ii];
            }
        }
    }
    // If we don't have a match - use the mandatory algorithm
    return &zrtpSymCiphers.getByName(mandatoryCipher);
}

// We can have the non-NIST in the list of orderedAlgos even if they are not available
// in the code (refer to ZrtpConfigure.cpp). If they are not build in they cannot appear
// in'configureAlgos' and thus not in the intersection lists. Thus a ZRTP build that
// does not include the non-NIST curves also works without problems.
//
AlgorithmEnum* ZRtp::findBestPubkey(ZrtpPacketHello *hello) {

    AlgorithmEnum* peerIntersect[ZrtpConfigure::maxNoOfAlgos+1];
    AlgorithmEnum* ownIntersect[ZrtpConfigure::maxNoOfAlgos+1];

    // Build list of own pubkey algorithm names, must follow the order
    // defined in RFC 6189, chapter 4.1.2.
    const char *orderedAlgos[] = {dh2k, e255, ec25, dh3k, e414, ec38};
    int numOrderedAlgos = sizeof(orderedAlgos) / sizeof(const char*);

    int numAlgosPeer = hello->getNumPubKeys();
    if (numAlgosPeer == 0) {
        hash = findBestHash(hello);                    // find a hash algorithm
        return &zrtpPubKeys.getByName(mandatoryPubKey);
    }
    // Build own list of intersecting algos, keep own order or algorithms
    // The list must include real public key algorithms only, so skip mult-stream mode,
    // preshared and alike.
    int numAlgosOwn = configureAlgos.getNumConfiguredAlgos(PubKeyAlgorithm);
    int numOwnIntersect = 0;
    for (int i = 0; i < numAlgosOwn; i++) {
        ownIntersect[numOwnIntersect] = &configureAlgos.getAlgoAt(PubKeyAlgorithm, i);
        if (*(int32_t*)(ownIntersect[numOwnIntersect]->getName()) == *(int32_t*)mult) {
            continue;                               // skip multi-stream mode
        }
        for (int ii = 0; ii < numAlgosPeer; ii++) {
            if (*(int32_t*)(ownIntersect[numOwnIntersect]->getName()) == *(int32_t*)(zrtpPubKeys.getByName((const char*)hello->getPubKeyType(ii)).getName())) {
                numOwnIntersect++;
                break;
            }
        }
    }
    // Build list of peer's intersecting algos: take own list as input and build a
    // list of algorithms that we have in common. The order of the list is according
    // to peer's Hello packet (peer's preferences).
    int numPeerIntersect = 0;
    for (int i = 0; i < numAlgosPeer; i++) {
        peerIntersect[numPeerIntersect] = &zrtpPubKeys.getByName((const char*)hello->getPubKeyType(i));
        for (int ii = 0; ii < numOwnIntersect; ii++) {
            if (*(int32_t*)(ownIntersect[ii]->getName()) == *(int32_t*)(peerIntersect[numPeerIntersect]->getName())) {
                numPeerIntersect++;
                break;
            }
        }
    }
    if (numPeerIntersect == 0) {       // If we don't have a common algorithm - use mandatory algorithms
        hash = findBestHash(hello);
        return &zrtpPubKeys.getByName(mandatoryPubKey);
    }

    // If we have only one algorithm in common or if the first entry matches - take it.
    // Otherwise determine which algorithm from the intersection lists is first in the
    // list of ordered algorithms and select it (RFC6189, section 4.1.2).
    AlgorithmEnum* useAlgo;
    if (numPeerIntersect > 1 && *(int32_t*)(ownIntersect[0]->getName()) != *(int32_t*)(peerIntersect[0]->getName())) {
        int own, peer;

        const int32_t *name = (int32_t*)ownIntersect[0]->getName();
        for (own = 0; own < numOrderedAlgos; own++) {
            if (*name == *(int32_t*)orderedAlgos[own])
                break;
        }
        name = (int32_t*)peerIntersect[0]->getName();
        for (peer = 0; peer < numOrderedAlgos; peer++) {
            if (*name == *(int32_t*)orderedAlgos[peer])
                break;
        }
        if (own < peer) {
            useAlgo = ownIntersect[0];
        }
        else {
            useAlgo = peerIntersect[0];
        }
        // find fastest of conf vs intersecting
    }
    else {
        useAlgo = peerIntersect[0];
    }
    int32_t algoName = *(int32_t*)(useAlgo->getName());

    // select a corresponding strong hash if necessary.
    if (algoName == *(int32_t*)ec38 || algoName == *(int32_t*)e414) {
        hash = getStrongHashOffered(hello, algoName);
        cipher = getStrongCipherOffered(hello, algoName);
    }
    else {
        hash = getHashOffered(hello, algoName);;
        cipher = getCipherOffered(hello, algoName);
    }
    authLength = getAuthLenOffered(hello, algoName);
    return useAlgo;
}

AlgorithmEnum* ZRtp::findBestSASType(ZrtpPacketHello *hello) {

    int  i;
    int ii;
    int numAlgosOffered;
    AlgorithmEnum* algosOffered[ZrtpConfigure::maxNoOfAlgos+1];

    int numAlgosConf;
    AlgorithmEnum* algosConf[ZrtpConfigure::maxNoOfAlgos+1];

    int num = hello->getNumSas();
    if (num == 0) {
        return &zrtpSasTypes.getByName(mandatorySasType);
    }
    // Build list of configured SAS algorithm names
    numAlgosConf = configureAlgos.getNumConfiguredAlgos(SasType);
    for (i = 0; i < numAlgosConf; i++) {
        algosConf[i] = &configureAlgos.getAlgoAt(SasType, i);
    }
    // Build list of offered known algos in Hello,
    for (numAlgosOffered = 0, i = 0; i < num; i++) {
        algosOffered[numAlgosOffered] = &zrtpSasTypes.getByName((const char*)hello->getSasType(i));
        if (!algosOffered[numAlgosOffered]->isValid())
            continue;
        numAlgosOffered++;
    }
    // Lookup offered algos in configured algos. Prefer algorithms that appear first in Hello packet (offered).
    for (i = 0; i < numAlgosOffered; i++) {
        for (ii = 0; ii < numAlgosConf; ii++) {
            if (*(int32_t*)(algosOffered[i]->getName()) == *(int32_t*)(algosConf[ii]->getName())) {
                return algosConf[ii];
            }
        }
    }
    // If we don't have a match - use the mandatory algorithm
    return &zrtpSasTypes.getByName(mandatorySasType);
}

AlgorithmEnum* ZRtp::findBestAuthLen(ZrtpPacketHello *hello) {

    int  i;
    int ii;
    int numAlgosOffered;
    AlgorithmEnum* algosOffered[ZrtpConfigure::maxNoOfAlgos+2];

    int numAlgosConf;
    AlgorithmEnum* algosConf[ZrtpConfigure::maxNoOfAlgos+2];

    int num = hello->getNumAuth();
    if (num == 0) {
        return &zrtpAuthLengths.getByName(mandatoryAuthLen_1);
    }

    // Build list of configured Authentication tag length algorithm names.
    numAlgosConf = configureAlgos.getNumConfiguredAlgos(AuthLength);
    for (i = 0; i < numAlgosConf; i++) {
        algosConf[i] = &configureAlgos.getAlgoAt(AuthLength, i);
    }

    // Build list of offered known algos in Hello.
    for (numAlgosOffered = 0, i = 0; i < num; i++) {
        algosOffered[numAlgosOffered] = &zrtpAuthLengths.getByName((const char*)hello->getAuthLen(i));
        if (!algosOffered[numAlgosOffered]->isValid())
            continue;
        numAlgosOffered++;
    }

    // Lookup offered algos in configured algos. Prefer algorithms that appear first in Hello packet (offered).
    for (i = 0; i < numAlgosOffered; i++) {
        for (ii = 0; ii < numAlgosConf; ii++) {
            if (*(int32_t*)(algosOffered[i]->getName()) == *(int32_t*)(algosConf[ii]->getName())) {
                return algosConf[ii];
            }
        }
    }
    // If we don't have a match - use the mandatory algorithm
    return &zrtpAuthLengths.getByName(mandatoryAuthLen_1);
}

// The following set of functions implement a 'non-NIST first policy' if nonNist computes
// to true. They prefer nonNist algorithms if these are available. Otherwise they use the NIST
// counterpart or simply call the according findBest*(...) function.
//
// Only the findBestPubkey(...) function calls them after it selected the public key algorithm.
// If the public key algorithm is non-NIST and if the policy is set to PreferNonNist then
// nonNist becomes true.
//
// The functions work according to the RFC6189 spec: the initiator can select every algorithm
// that both parties support. Thus the Initiator can even select an algorithm the wasn't offered
// in its own Hello packet but that the Initiator found in the peer's Hello and that is available
// for it.
//
AlgorithmEnum* ZRtp::getStrongHashOffered(ZrtpPacketHello *hello, int32_t algoName) {

    int numHash = hello->getNumHashes();
    bool nonNist = (algoName == *(int32_t*)e414 || algoName == *(int32_t*)e255) && configureAlgos.getSelectionPolicy() == ZrtpConfigure::PreferNonNist;

    if (nonNist) {
        for (int i = 0; i < numHash; i++) {
            int32_t nm = *(int32_t*)(hello->getHashType(i));
            if (nm == *(int32_t*)skn3) {
                return &zrtpHashes.getByName((const char*)hello->getHashType(i));
            }
        }
    }
    for (int i = 0; i < numHash; i++) {
        int32_t nm = *(int32_t*)(hello->getHashType(i));
        if (nm == *(int32_t*)s384 || nm == *(int32_t*)skn3) {
            return &zrtpHashes.getByName((const char*)hello->getHashType(i));
        }
    }
    return NULL;         // returning NULL -> prepareCommit(...) terminates ZRTP, missing strong hash is an error
}

AlgorithmEnum* ZRtp::getStrongCipherOffered(ZrtpPacketHello *hello, int32_t algoName) {

    int num = hello->getNumCiphers();
    bool nonNist = (algoName == *(int32_t*)e414 || algoName == *(int32_t*)e255) && configureAlgos.getSelectionPolicy() == ZrtpConfigure::PreferNonNist;

    if (nonNist) {
        for (int i = 0; i < num; i++) {
            int32_t nm = *(int32_t*)(hello->getCipherType(i));
            if (nm == *(int32_t*)two3) {
                return &zrtpSymCiphers.getByName((const char*)hello->getCipherType(i));
            }
        }
    }
    for (int i = 0; i < num; i++) {
        int32_t nm = *(int32_t*)(hello->getCipherType(i));
        if (nm == *(int32_t*)aes3 || nm == *(int32_t*)two3) {
            return &zrtpSymCiphers.getByName((const char*)hello->getCipherType(i));
        }
    }
    return NULL;       // returning NULL -> prepareCommit(...) finds the best cipher
}

AlgorithmEnum* ZRtp::getHashOffered(ZrtpPacketHello *hello, int32_t algoName) {

    int num = hello->getNumHashes();
    bool nonNist = (algoName == *(int32_t*)e414 || algoName == *(int32_t*)e255) && configureAlgos.getSelectionPolicy() == ZrtpConfigure::PreferNonNist;

    if (nonNist) {
        for (int i = 0; i < num; i++) {
            int32_t nm = *(int32_t*)(hello->getHashType(i));
            if (nm == *(int32_t*)skn2 || nm == *(int32_t*)skn3) {
                return &zrtpHashes.getByName((const char*)hello->getHashType(i));
            }
        }
    }
    return findBestHash(hello);
}

AlgorithmEnum* ZRtp::getCipherOffered(ZrtpPacketHello *hello, int32_t algoName) {

    int num = hello->getNumCiphers();
    bool nonNist = (algoName == *(int32_t*)e414 || algoName == *(int32_t*)e255) && configureAlgos.getSelectionPolicy() == ZrtpConfigure::PreferNonNist;

    if (nonNist) {
        for (int i = 0; i < num; i++) {
            int32_t nm = *(int32_t*)(hello->getCipherType(i));
            if (nm == *(int32_t*)two2 || nm == *(int32_t*)two3) {
                return &zrtpSymCiphers.getByName((const char*)hello->getCipherType(i));
            }
        }
    }
    return NULL;       // returning NULL -> prepareCommit(...) finds the best cipher
}

AlgorithmEnum* ZRtp::getAuthLenOffered(ZrtpPacketHello *hello, int32_t algoName) {

    int num = hello->getNumAuth();
    bool nonNist = (algoName == *(int32_t*)e414 || algoName == *(int32_t*)e255) && configureAlgos.getSelectionPolicy() == ZrtpConfigure::PreferNonNist;

    if (nonNist) {
        for (int i = 0; i < num; i++) {
            int32_t nm = *(int32_t*)(hello->getAuthLen(i));
            if (nm == *(int32_t*)sk32 || nm == *(int32_t*)sk64) {
                return &zrtpAuthLengths.getByName((const char*)hello->getAuthLen(i));
            }
        }
    }
    return findBestAuthLen(hello);
}

bool ZRtp::checkMultiStream(ZrtpPacketHello *hello) {

    int  i;
    int num = hello->getNumPubKeys();

    // Multi Stream mode is mandatory, thus if nothing is offered then it is supported :-)
    if (num == 0) {
        return true;
    }
    for (i = 0; i < num; i++) {
        if (*(int32_t*)(hello->getPubKeyType(i)) == *(int32_t*)mult) {
            return true;
        }
    }
    return false;
}

bool ZRtp::verifyH2(ZrtpPacketCommit *commit) {
    uint8_t tmpH3[IMPL_MAX_DIGEST_LENGTH];

    // packet does not have the correct size, treat H2 verfication as failed.
    if (!commit->isLengthOk(multiStream ? ZrtpPacketCommit::MultiStream : ZrtpPacketCommit::DhExchange))
        return false;

    sha256(commit->getH2(), HASH_IMAGE_SIZE, tmpH3);
    if (memcmp(tmpH3, peerH3, HASH_IMAGE_SIZE) != 0) {
        return false;
    }
    return true;
}

void ZRtp::computeHvi(ZrtpPacketDHPart* dh, ZrtpPacketHello *hello) {

    unsigned char* data[3];
    unsigned int length[3];
    /*
     * populate the vector to compute the HVI hash according to the
     * ZRTP specification.
     */
    data[0] = (uint8_t*)dh->getHeaderBase();
    length[0] = dh->getLength() * ZRTP_WORD_SIZE;

    data[1] = (uint8_t*)hello->getHeaderBase();
    length[1] = hello->getLength() * ZRTP_WORD_SIZE;

    data[2] = NULL;            // terminate data chunks
    hashListFunction(data, length, hvi);
    return;
}

void ZRtp:: computeSharedSecretSet(ZIDRecord *zidRec) {

    /*
     * Compute the Initiator's and Reponder's retained shared secret Ids.
     * Use negotiated HMAC.
     */
    uint8_t randBuf[RS_LENGTH];
    uint32_t macLen;

    detailInfo.secretsCached = 0;
    if (!zidRec->isRs1Valid()) {
        randomZRTP(randBuf, RS_LENGTH);
        hmacFunction(randBuf, RS_LENGTH, (unsigned char*)initiator, strlen(initiator), rs1IDi, &macLen);
        hmacFunction(randBuf, RS_LENGTH, (unsigned char*)responder, strlen(responder), rs1IDr, &macLen);
    }
    else {
        rs1Valid = true;
        hmacFunction((unsigned char*)zidRec->getRs1(), RS_LENGTH, (unsigned char*)initiator, strlen(initiator), rs1IDi, &macLen);
        hmacFunction((unsigned char*)zidRec->getRs1(), RS_LENGTH, (unsigned char*)responder, strlen(responder), rs1IDr, &macLen);
        detailInfo.secretsCached = Rs1;
    }

    if (!zidRec->isRs2Valid()) {
        randomZRTP(randBuf, RS_LENGTH);
        hmacFunction(randBuf, RS_LENGTH, (unsigned char*)initiator, strlen(initiator), rs2IDi, &macLen);
        hmacFunction(randBuf, RS_LENGTH, (unsigned char*)responder, strlen(responder), rs2IDr, &macLen);
    }
    else {
        rs2Valid = true;
        hmacFunction((unsigned char*)zidRec->getRs2(), RS_LENGTH, (unsigned char*)initiator, strlen(initiator), rs2IDi, &macLen);
        hmacFunction((unsigned char*)zidRec->getRs2(), RS_LENGTH, (unsigned char*)responder, strlen(responder), rs2IDr, &macLen);
        detailInfo.secretsCached |= Rs2;
    }

    if (!zidRec->isMITMKeyAvailable()) {
        randomZRTP(randBuf, RS_LENGTH);
        hmacFunction(randBuf, RS_LENGTH, (unsigned char*)initiator, strlen(initiator), pbxSecretIDi, &macLen);
        hmacFunction(randBuf, RS_LENGTH, (unsigned char*)responder, strlen(responder), pbxSecretIDr, &macLen);

    }
    else {
        hmacFunction((unsigned char*)zidRec->getMiTMData(), RS_LENGTH, (unsigned char*)initiator, strlen(initiator), pbxSecretIDi, &macLen);
        hmacFunction((unsigned char*)zidRec->getMiTMData(), RS_LENGTH, (unsigned char*)responder, strlen(responder), pbxSecretIDr, &macLen);
        detailInfo.secretsCached |= Pbx;
    }
    computeAuxSecretIds();
}

void ZRtp::computeAuxSecretIds() {
    uint8_t randBuf[RS_LENGTH];
    uint32_t macLen;

    if (auxSecret == NULL) {
        randomZRTP(randBuf, RS_LENGTH);
        hmacFunction(randBuf, RS_LENGTH, H3, HASH_IMAGE_SIZE, auxSecretIDi, &macLen);
        hmacFunction(randBuf, RS_LENGTH, H3, HASH_IMAGE_SIZE, auxSecretIDr, &macLen);
    }
    else {
        if (myRole == Initiator) {  // I'm initiator thus use my H3 for initiator's IDi, peerH3 for respnder's IDr
            hmacFunction(auxSecret, auxSecretLength, H3, HASH_IMAGE_SIZE, auxSecretIDi, &macLen);
            hmacFunction(auxSecret, auxSecretLength, peerH3, HASH_IMAGE_SIZE, auxSecretIDr, &macLen);
        }
        else {
            hmacFunction(auxSecret, auxSecretLength, peerH3, HASH_IMAGE_SIZE, auxSecretIDi, &macLen);
            hmacFunction(auxSecret, auxSecretLength, H3, HASH_IMAGE_SIZE, auxSecretIDr, &macLen);
        }
    }
}

/*
 * memset_volatile is a volatile pointer to the memset function.
 * You can call (*memset_volatile)(buf, val, len) or even
 * memset_volatile(buf, val, len) just as you would call
 * memset(buf, val, len), but the use of a volatile pointer
 * guarantees that the compiler will not optimise the call away.
 */
static void * (*volatile memset_volatile)(void *, int, size_t) = memset;

/*
 * The DH packet for this function is DHPart1 and contains the Responder's
 * retained secret ids. Compare them with the expected secret ids (refer
 * to chapter 5.3 in the specification).
 * When using this method then we are in Initiator role.
 */
void ZRtp::generateKeysInitiator(ZrtpPacketDHPart *dhPart, ZIDRecord *zidRec) {
    const uint8_t* setD[3];
    int32_t rsFound = 0;

    setD[0] = setD[1] = setD[2] = NULL;

    detailInfo.secretsMatchedDH = 0;
    if (memcmp(rs1IDr, dhPart->getRs1Id(), HMAC_SIZE) == 0 || memcmp(rs1IDr, dhPart->getRs2Id(), HMAC_SIZE) == 0)
        detailInfo.secretsMatchedDH |= Rs1;
    if (memcmp(rs2IDr, dhPart->getRs1Id(), HMAC_SIZE) == 0 || memcmp(rs2IDr, dhPart->getRs2Id(), HMAC_SIZE) == 0)
        detailInfo.secretsMatchedDH |= Rs2;
    /*
     * Select the real secrets into setD. The dhPart is DHpart1 message
     * received from responder. rs1IDr and rs2IDr are the expected ids using
     * the initator's cached retained secrets.
     */
    // Check which RS we shall use for first place (s1)
    detailInfo.secretsMatched = 0;
    if (memcmp(rs1IDr, dhPart->getRs1Id(), HMAC_SIZE) == 0) {
        setD[0] = zidRec->getRs1();
        rsFound = 0x1;
        detailInfo.secretsMatched = Rs1;
    }
    else if (memcmp(rs1IDr, dhPart->getRs2Id(), HMAC_SIZE) == 0) {
        setD[0] = zidRec->getRs1();
        rsFound = 0x2;
        detailInfo.secretsMatched = Rs1;
    }
    else if (memcmp(rs2IDr, dhPart->getRs1Id(), HMAC_SIZE) == 0) {
        setD[0] = zidRec->getRs2();
        rsFound = 0x4;
        detailInfo.secretsMatched = Rs2;
    }
    else if (memcmp(rs2IDr, dhPart->getRs2Id(), HMAC_SIZE) == 0) {
        setD[0] = zidRec->getRs2();
        rsFound = 0x8;
        detailInfo.secretsMatched = Rs2;
    }

    if (memcmp(auxSecretIDr, dhPart->getAuxSecretId(), 8) == 0) {
        DEBUGOUT((fprintf(stdout, "Initiator: Match for aux secret found\n")));
        setD[1] = auxSecret;
        detailInfo.secretsMatched |= Aux;
        detailInfo.secretsMatchedDH |= Aux;
    }
    if (auxSecret != NULL && (detailInfo.secretsMatched & Aux) == 0) {
        sendInfo(Warning, WarningNoExpectedAuxMatch);
    }

#ifdef ZRTP_SAS_RELAY_SUPPORT
    // check if we have a matching PBX secret and place it third (s3)
    if (memcmp(pbxSecretIDr, dhPart->getPbxSecretId(), HMAC_SIZE) == 0) {
        DEBUGOUT((fprintf(stdout, "%c: Match for Other_secret found\n", zid[0])));
        setD[2] = zidRec->getMiTMData();
        detailInfo.secretsMatched |= Pbx;
        detailInfo.secretsMatchedDH |= Pbx;
        // Flag to record that fact that we have a MitM key of the other peer.
        peerIsEnrolled = true;
    }
#endif
    // Check if some retained secrets found
    if (rsFound == 0) {                        // no RS matches found
        if (rs1Valid || rs2Valid) {            // but valid RS records in cache
            sendInfo(Warning, WarningNoExpectedRSMatch);
            zidRec->resetSasVerified();
            saveZidRecord = false;             // Don't save RS until user verfied/confirmed SAS
        }
        else {                                 // No valid RS record in cache
            sendInfo(Warning, WarningNoRSMatch);
        }
    }
    else {                                     // at least one RS matches
        sendInfo(Info, InfoRSMatchFound);
    }
    /*
     * Ready to generate s0 here.
     * The formular to compute S0 (Refer to ZRTP specification 5.4.4):
     *
      s0 = hash( counter | DHResult | "ZRTP-HMAC-KDF" | ZIDi | ZIDr | \
      total_hash | len(s1) | s1 | len(s2) | s2 | len(s3) | s3)
     *
     * Note: in this function we are Initiator, thus ZIDi is our zid
     * (zid), ZIDr is the peer's zid (peerZid).
     */

    /*
     * These arrays hold the pointers and lengths of the data that must be
     * hashed to create S0.  According to the formula the max number of
     * elements to hash is 12, add one for the terminating "NULL"
     */
    unsigned char* data[13];
    unsigned int   length[13];
    uint32_t pos = 0;                  // index into the array

    // we need a number of length data items, so define them here
    uint32_t counter, sLen[3];

    //Very first element is a fixed counter, big endian
    counter = 1;
    counter = zrtpHtonl(counter);
    data[pos] = (unsigned char*)&counter;
    length[pos++] = sizeof(uint32_t);

    // Next is the DH result itself
    data[pos] = DHss;
    length[pos++] = dhContext->getDhSize();

    // Next the fixed string "ZRTP-HMAC-KDF"
    data[pos] = (unsigned char*)KDFString;
    length[pos++] = strlen(KDFString);

    // Next is Initiator's id (ZIDi), in this case as Initiator
    // it is zid
    data[pos] = ownZid;
    length[pos++] = ZID_SIZE;

    // Next is Responder's id (ZIDr), in this case our peer's id
    data[pos] = peerZid;
    length[pos++] = ZID_SIZE;

    // Next ist total hash (messageHash) itself
    data[pos] = messageHash;
    length[pos++] = hashLength;

    /*
     * For each matching shared secret hash the length of
     * the shared secret as 32 bit big-endian number followd by the
     * shared secret itself. The length of a shared seceret is
     * currently fixed to RS_LENGTH. If a shared
     * secret is not used _only_ its length is hased as zero
     * length. NOTE: if implementing auxSecret and/or pbxSecret -> check
     * this length stuff again.
     */
    int secretHashLen = RS_LENGTH;
    secretHashLen = zrtpHtonl(secretHashLen);        // prepare 32 bit big-endian number

    for (int32_t i = 0; i < 3; i++) {
        if (setD[i] != NULL) {           // a matching secret, set length, then secret
            sLen[i] = secretHashLen;
            data[pos] = (unsigned char*)&sLen[i];
            length[pos++] = sizeof(uint32_t);
            data[pos] = (unsigned char*)setD[i];
            length[pos++] = (i != 1) ? RS_LENGTH : auxSecretLength;
        }
        else {                           // no machting secret, set length 0, skip secret
            sLen[i] = 0;
            data[pos] = (unsigned char*)&sLen[i];
            length[pos++] = sizeof(uint32_t);
        }
    }

    data[pos] = NULL;
    hashListFunction(data, length, s0);
//  hexdump("S0 I", s0, hashLength);

    memset_volatile(DHss, 0, dhContext->getDhSize());
    delete[] DHss;
    DHss = NULL;

    computeSRTPKeys();
    memset(s0, 0, MAX_DIGEST_LENGTH);
}
/*
 * The DH packet for this function is DHPart2 and contains the Initiator's
 * retained secret ids. Compare them with the expected secret ids (refer
 * to chapter 5.3.1 in the specification).
 */
void ZRtp::generateKeysResponder(ZrtpPacketDHPart *dhPart, ZIDRecord *zidRec) {
    const uint8_t* setD[3];
    int32_t rsFound = 0;

    setD[0] = setD[1] = setD[2] = NULL;

    detailInfo.secretsMatchedDH = 0;
    if (memcmp(rs1IDi, dhPart->getRs1Id(), HMAC_SIZE) == 0 || memcmp(rs1IDi, dhPart->getRs2Id(), HMAC_SIZE) == 0)
        detailInfo.secretsMatchedDH |= Rs1;
    if (memcmp(rs2IDi, dhPart->getRs1Id(), HMAC_SIZE) == 0 || memcmp(rs2IDi, dhPart->getRs2Id(), HMAC_SIZE) == 0)
        detailInfo.secretsMatchedDH |= Rs2;

    /*
     * Select the real secrets into setD
     */
    // Check which RS we shall use for first place (s1)
    detailInfo.secretsMatched = 0;
    if (memcmp(rs1IDi, dhPart->getRs1Id(), HMAC_SIZE) == 0) {
        setD[0] = zidRec->getRs1();
        rsFound = 0x1;
        detailInfo.secretsMatched = Rs1;
    }
    else if (memcmp(rs1IDi, dhPart->getRs2Id(), HMAC_SIZE) == 0) {
        setD[0] = zidRec->getRs1();
        rsFound = 0x2;
        detailInfo.secretsMatched = Rs1;
    }
    else if (memcmp(rs2IDi, dhPart->getRs1Id(), HMAC_SIZE) == 0) {
        setD[0] = zidRec->getRs2();
        rsFound |= 0x4;
        detailInfo.secretsMatched = Rs2;
    }
    else if (memcmp(rs2IDi, dhPart->getRs2Id(), HMAC_SIZE) == 0) {
        setD[0] = zidRec->getRs2();
        rsFound |= 0x8;
        detailInfo.secretsMatched = Rs2;
    }

    if (memcmp(auxSecretIDi, dhPart->getAuxSecretId(), 8) == 0) {
        DEBUGOUT((fprintf(stdout, "Responder: Match for aux secret found\n")));
        setD[1] = auxSecret;
        detailInfo.secretsMatched |= Aux;
        detailInfo.secretsMatchedDH |= Aux;
    }
    // If we have an auxSecret but no match from peer - report this.
    if (auxSecret != NULL && (detailInfo.secretsMatched & Aux) == 0) {
        sendInfo(Warning, WarningNoExpectedAuxMatch);
    }

#ifdef ZRTP_SAS_RELAY_SUPPORT
    if (memcmp(pbxSecretIDi, dhPart->getPbxSecretId(), 8) == 0) {
        DEBUGOUT((fprintf(stdout, "%c: Match for PBX secret found\n", ownZid[0])));
        setD[2] = zidRec->getMiTMData();
        detailInfo.secretsMatched |= Pbx;
        detailInfo.secretsMatchedDH |= Pbx;
        peerIsEnrolled = true;
    }
#endif
    // Check if some retained secrets found
    if (rsFound == 0) {                        // no RS matches found
        if (rs1Valid || rs2Valid) {            // but valid RS records in cache
            sendInfo(Warning, WarningNoExpectedRSMatch);
            zidRec->resetSasVerified();
            saveZidRecord = false;             // Don't save RS until user verfied/confirmed SAS
        }
        else {                                 // No valid RS record in cache
            sendInfo(Warning, WarningNoRSMatch);
        }
    }
    else {                                     // at least one RS matches
        sendInfo(Info, InfoRSMatchFound);
    }

    /*
     * ready to generate s0 here.
     * The formular to compute S0 (Refer to ZRTP specification 5.4.4):
     *
      s0 = hash( counter | DHResult | "ZRTP-HMAC-KDF" | ZIDi | ZIDr | \
      total_hash | len(s1) | s1 | len(s2) | s2 | len(s3) | s3)
     *
     * Note: in this function we are Responder, thus ZIDi is the peer's zid
     * (peerZid), ZIDr is our zid.
     */

    /*
     * These arrays hold the pointers and lengths of the data that must be
     * hashed to create S0.  According to the formula the max number of
     * elements to hash is 12, add one for the terminating "NULL"
     */
    unsigned char* data[13];
    unsigned int   length[13];
    uint32_t pos = 0;                  // index into the array


    // we need a number of length data items, so define them here
    uint32_t counter, sLen[3];

    //Very first element is a fixed counter, big endian
    counter = 1;
    counter = zrtpHtonl(counter);
    data[pos] = (unsigned char*)&counter;
    length[pos++] = sizeof(uint32_t);

    // Next is the DH result itself
    data[pos] = DHss;
    length[pos++] = dhContext->getDhSize();

    // Next the fixed string "ZRTP-HMAC-KDF"
    data[pos] = (unsigned char*)KDFString;
    length[pos++] = strlen(KDFString);

    // Next is Initiator's id (ZIDi), in this case as Responder
    // it is peerZid
    data[pos] = peerZid;
    length[pos++] = ZID_SIZE;

    // Next is Responder's id (ZIDr), in this case our own zid
    data[pos] = ownZid;
    length[pos++] = ZID_SIZE;

    // Next ist total hash (messageHash) itself
    data[pos] = messageHash;
    length[pos++] = hashLength;

    /*
     * For each matching shared secret hash the length of
     * the shared secret as 32 bit big-endian number followd by the
     * shared secret itself. The length of a shared seceret is
     * currently fixed to SHA256_DIGEST_LENGTH. If a shared
     * secret is not used _only_ its length is hased as zero
     * length. NOTE: if implementing auxSecret and/or pbxSecret -> check
     * this length stuff again.
     */
    int secretHashLen = RS_LENGTH;
    secretHashLen = zrtpHtonl(secretHashLen);        // prepare 32 bit big-endian number

    for (int32_t i = 0; i < 3; i++) {
        if (setD[i] != NULL) {           // a matching secret, set length, then secret
            sLen[i] = secretHashLen;
            data[pos] = (unsigned char*)&sLen[i];
            length[pos++] = sizeof(uint32_t);
            data[pos] = (unsigned char*)setD[i];
            length[pos++] = (i != 1) ? RS_LENGTH : auxSecretLength;
        }
        else {                           // no machting secret, set length 0, skip secret
            sLen[i] = 0;
            data[pos] = (unsigned char*)&sLen[i];
            length[pos++] = sizeof(uint32_t);
        }
    }

    data[pos] = NULL;
    hashListFunction(data, length, s0);
//  hexdump("S0 R", s0, hashLength);

    memset_volatile(DHss, 0, dhContext->getDhSize());
    delete[] DHss;
    DHss = NULL;

    computeSRTPKeys();
    memset(s0, 0, MAX_DIGEST_LENGTH);
}


void ZRtp::KDF(uint8_t* key, uint32_t keyLength, uint8_t* label, int32_t labelLength,
               uint8_t* context, int32_t contextLength, int32_t L, uint8_t* output) {

    unsigned char* data[6];
    uint32_t length[6];
    uint32_t pos = 0;                  // index into the array
    uint32_t maclen = 0;

    // Very first element is a fixed counter, big endian
    uint32_t counter = 1;
    counter = zrtpHtonl(counter);
    data[pos] = (unsigned char*)&counter;
    length[pos++] = sizeof(uint32_t);

    // Next element is the label, null terminated, labelLength includes null byte.
    data[pos] = label;
    length[pos++] = labelLength;

    // Next is the KDF context
    data[pos] = context;
    length[pos++] = contextLength;

    // last element is HMAC length in bits, big endian
    uint32_t len = zrtpHtonl(L);
    data[pos] = (unsigned char*)&len;
    length[pos++] = sizeof(uint32_t);

    data[pos] = NULL;

    // Use negotiated hash.
    hmacListFunction(key, keyLength, data, length, output, &maclen);
}

// Compute the Multi Stream mode s0
void ZRtp::generateKeysMultiStream() {

    // allocate the maximum size, compute real size to use
    uint8_t KDFcontext[sizeof(peerZid)+sizeof(ownZid)+sizeof(messageHash)];
    int32_t kdfSize = sizeof(peerZid)+sizeof(ownZid)+hashLength;

    if (myRole == Responder) {
        memcpy(KDFcontext, peerZid, sizeof(peerZid));
        memcpy(KDFcontext+sizeof(peerZid), ownZid, sizeof(ownZid));
    }
    else {
        memcpy(KDFcontext, ownZid, sizeof(ownZid));
        memcpy(KDFcontext+sizeof(ownZid), peerZid, sizeof(peerZid));
    }
    memcpy(KDFcontext+sizeof(ownZid)+sizeof(peerZid), messageHash, hashLength);

    KDF(zrtpSession, hashLength, (unsigned char*)zrtpMsk, strlen(zrtpMsk)+1, KDFcontext, kdfSize, hashLength*8, s0);

    memset(KDFcontext, 0, sizeof(KDFcontext));

    computeSRTPKeys();
}

void ZRtp::computePBXSecret() {
#ifdef ZRTP_SAS_RELAY_SUPPORT
    // Construct the KDF context as per ZRTP specification chap 7.3.1:
    // ZIDi || ZIDr
    uint8_t KDFcontext[sizeof(peerZid)+sizeof(ownZid)];
    int32_t kdfSize = sizeof(peerZid)+sizeof(ownZid);

    if (myRole == Responder) {
        memcpy(KDFcontext, peerZid, sizeof(peerZid));
        memcpy(KDFcontext+sizeof(peerZid), ownZid, sizeof(ownZid));
    }
    else {
        memcpy(KDFcontext, ownZid, sizeof(ownZid));
        memcpy(KDFcontext+sizeof(ownZid), peerZid, sizeof(peerZid));
    }

    KDF(zrtpSession, hashLength, (unsigned char*)zrtpTrustedMitm, strlen(zrtpTrustedMitm)+1, KDFcontext,
        kdfSize, SHA256_DIGEST_LENGTH * 8, pbxSecretTmpBuffer);

    pbxSecretTmp = pbxSecretTmpBuffer;  // set pointer to buffer, signal PBX secret was computed
#endif
}

void ZRtp::computeSRTPKeys() {

    // allocate the maximum size, compute real size to use
    uint8_t KDFcontext[sizeof(peerZid)+sizeof(ownZid)+sizeof(messageHash)];
    int32_t kdfSize = sizeof(peerZid)+sizeof(ownZid)+hashLength;

    int32_t keyLen = cipher->getKeylen() * 8;

    if (myRole == Responder) {
        memcpy(KDFcontext, peerZid, sizeof(peerZid));
        memcpy(KDFcontext+sizeof(peerZid), ownZid, sizeof(ownZid));
    }
    else {
        memcpy(KDFcontext, ownZid, sizeof(ownZid));
        memcpy(KDFcontext+sizeof(ownZid), peerZid, sizeof(peerZid));
    }
    memcpy(KDFcontext+sizeof(ownZid)+sizeof(peerZid), messageHash, hashLength);

    // Inititiator key and salt
    KDF(s0, hashLength, (unsigned char*)iniMasterKey, strlen(iniMasterKey)+1, KDFcontext, kdfSize, keyLen, srtpKeyI);
    KDF(s0, hashLength, (unsigned char*)iniMasterSalt, strlen(iniMasterSalt)+1, KDFcontext, kdfSize, 112, srtpSaltI);

    // Responder key and salt
    KDF(s0, hashLength, (unsigned char*)respMasterKey, strlen(respMasterKey)+1, KDFcontext, kdfSize, keyLen, srtpKeyR);
    KDF(s0, hashLength, (unsigned char*)respMasterSalt, strlen(respMasterSalt)+1, KDFcontext, kdfSize, 112, srtpSaltR);

    // The HMAC keys for GoClear
    KDF(s0, hashLength, (unsigned char*)iniHmacKey, strlen(iniHmacKey)+1, KDFcontext, kdfSize, hashLength*8, hmacKeyI);
    KDF(s0, hashLength, (unsigned char*)respHmacKey, strlen(respHmacKey)+1, KDFcontext, kdfSize, hashLength*8, hmacKeyR);

    // The keys for Confirm messages
    KDF(s0, hashLength, (unsigned char*)iniZrtpKey, strlen(iniZrtpKey)+1, KDFcontext, kdfSize, keyLen, zrtpKeyI);
    KDF(s0, hashLength, (unsigned char*)respZrtpKey, strlen(respZrtpKey)+1, KDFcontext, kdfSize, keyLen, zrtpKeyR);

    detailInfo.pubKey = detailInfo.sasType = NULL;
    if (!multiStream) {
        // Compute the new Retained Secret
        KDF(s0, hashLength, (unsigned char*)retainedSec, strlen(retainedSec)+1, KDFcontext, kdfSize, SHA256_DIGEST_LENGTH*8, newRs1);

        // Compute the ZRTP Session Key
        KDF(s0, hashLength, (unsigned char*)zrtpSessionKey, strlen(zrtpSessionKey)+1, KDFcontext, kdfSize, hashLength*8, zrtpSession);

        // Compute the exported Key
        KDF(s0, hashLength, (unsigned char*)zrtpExportedKey, strlen(zrtpExportedKey)+1, KDFcontext, kdfSize, hashLength*8, zrtpExport);
        // perform  generation according to chapter 5.5 and 8.
        // we don't need a speciai sasValue filed. sasValue are the first
        // (leftmost) 32 bits (4 bytes) of sasHash
        uint8_t sasBytes[4];
        KDF(s0, hashLength, (unsigned char*)sasString, strlen(sasString)+1, KDFcontext, kdfSize, SHA256_DIGEST_LENGTH*8, sasHash);

        // according to chapter 8 only the leftmost 20 bits of sasValue (aka
        //  sasHash) are used to create the character SAS string of type SAS
        // base 32 (5 bits per character)
        sasBytes[0] = sasHash[0];
        sasBytes[1] = sasHash[1];
        sasBytes[2] = sasHash[2] & 0xf0;
        sasBytes[3] = 0;
        if (*(int32_t*)b32 == *(int32_t*)(sasType->getName())) {
            SAS = Base32(sasBytes, 20).getEncoded();
        }
        else if (*(int32_t*)b32e == *(int32_t*)(sasType->getName())) {
            SAS = *EmojiBase32::u32StringToUtf8(EmojiBase32(sasBytes, 20).getEncoded());
        }
        else {
            SAS.assign(sas256WordsEven[sasBytes[0]]).append(":").append(sas256WordsOdd[sasBytes[1]]);
        }

        if (signSasSeen)
             callback->signSAS(sasHash);

        detailInfo.pubKey = pubKey->getReadable();
        detailInfo.sasType = sasType->getReadable();
    }
    // set algorithm names into detailInfo structure
    detailInfo.authLength = authLength->getReadable();
    detailInfo.cipher = cipher->getReadable();
    detailInfo.hash = hash->getReadable();

    memset(KDFcontext, 0, sizeof(KDFcontext));
}

bool ZRtp::srtpSecretsReady(EnableSecurity part) {

    SrtpSecret_t sec;

    sec.symEncAlgorithm = cipher->getAlgoId();

    sec.keyInitiator = srtpKeyI;
    sec.initKeyLen = cipher->getKeylen() * 8;
    sec.saltInitiator = srtpSaltI;
    sec.initSaltLen = 112;

    sec.keyResponder = srtpKeyR;
    sec.respKeyLen = cipher->getKeylen() * 8;
    sec.saltResponder = srtpSaltR;
    sec.respSaltLen = 112;

    sec.authAlgorithm = authLength->getAlgoId();
    sec.srtpAuthTagLen = authLength->getKeylen();

    sec.sas = SAS;
    sec.role = myRole;

    bool rc = callback->srtpSecretsReady(&sec, part);

    // The call state engine calls ForSender always after ForReceiver.
    if (part == ForSender) {
        std::string cs(cipher->getReadable());
        if (!multiStream) {
            cs.append("/").append(pubKey->getName());
            if (mitmSeen)
                cs.append("/EndAtMitM");
            callback->srtpSecretsOn(cs, SAS, zidRec->isSasVerified());
        }
        else {
            std::string cs1("");
            if (mitmSeen)
                cs.append("/EndAtMitM");
            callback->srtpSecretsOn(cs, cs1, true);
        }
    }
    return rc;
}


void ZRtp::setNegotiatedHash(AlgorithmEnum* hash) {
    switch (zrtpHashes.getOrdinal(*hash)) {
    case 0:
        hashLength = SHA256_DIGEST_LENGTH;
        hashFunction = sha256;
        hashListFunction = sha256;

        hmacFunction = hmac_sha256;
        hmacListFunction = hmac_sha256;

        createHashCtx = initializeSha256Context;
        msgShaContext = &hashCtx.sha256Ctx;
        closeHashCtx = finalizeSha256Context;
        hashCtxFunction = sha256Ctx;
        hashCtxListFunction = sha256Ctx;
        break;

    case 1:
        hashLength = SHA384_DIGEST_LENGTH;
        hashFunction = sha384;
        hashListFunction = sha384;

        hmacFunction = hmac_sha384;
        hmacListFunction = hmac_sha384;

        createHashCtx = initializeSha384Context;
        msgShaContext = &hashCtx.sha384Ctx;
        closeHashCtx = finalizeSha384Context;
        hashCtxFunction = sha384Ctx;
        hashCtxListFunction = sha384Ctx;
        break;

    case 2:
        hashLength = SKEIN256_DIGEST_LENGTH;
        hashFunction = skein256;
        hashListFunction = skein256;

        hmacFunction = macSkein256;
        hmacListFunction = macSkein256;

        createHashCtx = initializeSkein256Context;
        msgShaContext = &hashCtx.skeinCtx;
        closeHashCtx = finalizeSkein256Context;
        hashCtxFunction = skein256Ctx;
        hashCtxListFunction = skein256Ctx;
        break;

    case 3:
        hashLength = SKEIN384_DIGEST_LENGTH;
        hashFunction = skein384;
        hashListFunction = skein384;

        hmacFunction = macSkein384;
        hmacListFunction = macSkein384;

        createHashCtx = initializeSkein384Context;
        msgShaContext = &hashCtx.skeinCtx;
        closeHashCtx = finalizeSkein384Context;
        hashCtxFunction = skein384Ctx;
        hashCtxListFunction = skein384Ctx;
        break;
    }
}


void ZRtp::srtpSecretsOff(EnableSecurity part) {
    callback->srtpSecretsOff(part);
}

void ZRtp::SASVerified() {
    if (paranoidMode)
        return;

    zidRec->setSasVerified();
    saveZidRecord = true;
    getZidCacheInstance()->saveRecord(zidRec);
}

void ZRtp::resetSASVerified() {

    zidRec->resetSasVerified();
    getZidCacheInstance()->saveRecord(zidRec);
}

bool ZRtp::isSASVerified() {
    return zidRec->isSasVerified();
}

void ZRtp::setRs2Valid() {

    if (zidRec != NULL) {
        zidRec->setRs2Valid();
        if (saveZidRecord)
            getZidCacheInstance()->saveRecord(zidRec);
    }
}

int64_t ZRtp::getSecureSince() {
    if (zidRec != NULL)
        return zidRec->getSecureSince();
    return 0;
}


void ZRtp::sendInfo(GnuZrtpCodes::MessageSeverity severity, int32_t subCode) {

    // We've reached secure state: overwrite the SRTP master key and master salt.
    if (severity == Info && subCode == InfoSecureStateOn) {
        memset(srtpKeyI, 0, cipher->getKeylen());
        memset(srtpSaltI, 0, 112/8);
        memset(srtpKeyR, 0, cipher->getKeylen());
        memset(srtpSaltR, 0, 112/8);
    }
    callback->sendInfo(severity, subCode);
}


void ZRtp::zrtpNegotiationFailed(GnuZrtpCodes::MessageSeverity severity, int32_t subCode) {
    callback->zrtpNegotiationFailed(severity, subCode);
}

void ZRtp::zrtpNotSuppOther() {
    callback->zrtpNotSuppOther();
}

void ZRtp::synchEnter() {
    callback->synchEnter();
}

void ZRtp::synchLeave() {
    callback->synchLeave();
}

int32_t ZRtp::sendPacketZRTP(ZrtpPacketBase *packet) {
    return ((packet == NULL) ? 0 :
            callback->sendDataZRTP(packet->getHeaderBase(), (packet->getLength() * 4) + 4));
}

int32_t ZRtp::activateTimer(int32_t tm) {
    return (callback->activateTimer(tm));
}

int32_t ZRtp::cancelTimer() {
    return (callback->cancelTimer());
}

void ZRtp::setAuxSecret(uint8_t* data, int32_t length) {
    if (length > 0) {
        auxSecret = new uint8_t[length];
        auxSecretLength = length;
        memcpy(auxSecret, data, length);
    }
}

void ZRtp::setClientId(std::string id, HelloPacketVersion* hpv) {

    unsigned char tmp[CLIENT_ID_SIZE +1] = {' '};
    memcpy(tmp, id.c_str(), id.size() > CLIENT_ID_SIZE ? CLIENT_ID_SIZE : id.size());
    tmp[CLIENT_ID_SIZE] = 0;

    hpv->packet->setClientId(tmp);

    int32_t len = hpv->packet->getLength() * ZRTP_WORD_SIZE;

    // Hello packets are ready now, compute its HMAC
    // (excluding the HMAC field (2*ZTP_WORD_SIZE)) and store in Hello
    // use the implicit hash function
    uint8_t hmac[IMPL_MAX_DIGEST_LENGTH];
    uint32_t macLen;
    hmacFunctionImpl(H2, HASH_IMAGE_SIZE, (uint8_t*)hpv->packet->getHeaderBase(), len-(2*ZRTP_WORD_SIZE), hmac, &macLen);
    hpv->packet->setHMAC(hmac);

    // calculate hash over the final Hello packet, refer to chap 9.1 how to
    // use this hash in SIP/SDP.
    hashFunctionImpl((uint8_t*)hpv->packet->getHeaderBase(), len, hpv->helloHash);
}

void ZRtp::storeMsgTemp(ZrtpPacketBase* pkt) {
    uint32_t length = pkt->getLength() * ZRTP_WORD_SIZE;
    length = (length > sizeof(tempMsgBuffer)) ? sizeof(tempMsgBuffer) : length;
    memset(tempMsgBuffer, 0, sizeof(tempMsgBuffer));
    memcpy(tempMsgBuffer, (uint8_t*)pkt->getHeaderBase(), length);
    lengthOfMsgData = length;
}

bool ZRtp::checkMsgHmac(uint8_t* key) {
    uint8_t hmac[IMPL_MAX_DIGEST_LENGTH];
    uint32_t macLen;
    int32_t len = lengthOfMsgData-(HMAC_SIZE);  // compute HMAC, but exlude the stored HMAC :-)

    // Use the implicit hash function
    hmacFunctionImpl(key, HASH_IMAGE_SIZE, tempMsgBuffer, len, hmac, &macLen);
    return (memcmp(hmac, tempMsgBuffer+len, (HMAC_SIZE)) == 0 ? true : false);
}

std::string ZRtp::getHelloHash(int32_t index) {
    std::ostringstream stm;

    if (index < 0 || index >= MAX_ZRTP_VERSIONS)
        return std::string();

    uint8_t* hp = helloPackets[index].helloHash;

    char version[5] = {'\0'};
    strncpy(version, (const char*)helloPackets[index].packet->getVersion(), ZRTP_WORD_SIZE);

    stm << version;
    stm << " ";
    stm.fill('0');
    stm << hex;
    for (int i = 0; i < hashLengthImpl; i++) {
        stm.width(2);
        stm << static_cast<uint32_t>(*hp++);
    }
    return stm.str();
}

std::string ZRtp::getPeerHelloHash() {
    std::ostringstream stm;

    if (peerHelloVersion[0] == 0)
        return std::string();

    uint8_t* hp = peerHelloHash;

    stm << peerHelloVersion;
    stm << " ";
    stm.fill('0');
    stm << hex;
    for (int i = 0; i < hashLengthImpl; i++) {
        stm.width(2);
        stm << static_cast<uint32_t>(*hp++);
    }
    return stm.str();
}

std::string ZRtp::getMultiStrParams(ZRtp **zrtpMaster) {

    // the string will hold binary data - it's opaque to the application
    std::string str("");
    char tmp[MAX_DIGEST_LENGTH + 1 + 1 + 1]; // hash length + cipher + authLength + hash

    if (inState(SecureState) && !multiStream) {
        // construct array that holds zrtpSession, cipher type, auth-length, and hash type
        tmp[0] = zrtpHashes.getOrdinal(*hash);
        tmp[1] = zrtpAuthLengths.getOrdinal(*authLength);
        tmp[2] = zrtpSymCiphers.getOrdinal(*cipher);
        memcpy(tmp+3, zrtpSession, hashLength);
        str.assign(tmp, hashLength + 1 + 1 + 1); // set chars (bytes) to the string
        if (zrtpMaster != NULL)
            *zrtpMaster = this;
    }
    return str;
}

void ZRtp::setMultiStrParams(std::string parameters, ZRtp *zrtpMaster) {

    char tmp[MAX_DIGEST_LENGTH + 1 + 1 + 1]; // max. hash length + cipher + authLength + hash

    // First get negotiated hash from parameters, set algorithms and length
    int i = parameters.at(0) & 0xff;
    hash = &zrtpHashes.getByOrdinal(i);
    setNegotiatedHash(hash);           // sets hashlength

    // use string.copy(buffer, num, start=0) to retrieve chars (bytes) from the string
    parameters.copy(tmp, hashLength + 1 + 1 + 1, 0);

    i = tmp[1] & 0xff;
    authLength = &zrtpAuthLengths.getByOrdinal(i);
    i = tmp[2] & 0xff;
    cipher = &zrtpSymCiphers.getByOrdinal(i);
    memcpy(zrtpSession, tmp+3, hashLength);

    // after setting zrtpSession, cipher, and auth-length set multi-stream to true
    multiStream = true;
    stateEngine->setMultiStream(true);
    if (zrtpMaster != NULL)
        masterStream = zrtpMaster;
}

bool ZRtp::isMultiStream() {
    return multiStream;
}

bool ZRtp::isMultiStreamAvailable() {
    return multiStreamAvailable;
}

void ZRtp::acceptEnrollment(bool accepted) {
#ifdef ZRTP_SAS_RELAY_SUPPORT
    if (!accepted) {
        zidRec->resetMITMKeyAvailable();
        callback->zrtpInformEnrollment(EnrollmentCanceled);
        getZidCacheInstance()->saveRecord(zidRec);
        return;
    }
    if (pbxSecretTmp != NULL) {
        zidRec->setMiTMData(pbxSecretTmp);
        getZidCacheInstance()->saveRecord(zidRec);
        callback->zrtpInformEnrollment(EnrollmentOk);
    }
    else {
        callback->zrtpInformEnrollment(EnrollmentFailed);
    }
#endif
}

bool ZRtp::setSignatureData(uint8_t* data, int32_t length) {
    if ((length % 4) != 0)
        return false;

    ZrtpPacketConfirm* cfrm = (myRole == Responder) ? &zrtpConfirm1 : &zrtpConfirm2;
    cfrm->setSignatureLength(length / 4);
    return cfrm->setSignatureData(data, length);
}

const uint8_t* ZRtp::getSignatureData() {
    return signatureData;
}

int32_t ZRtp::getSignatureLength() {
    return signatureLength * ZRTP_WORD_SIZE;
}

void ZRtp::conf2AckSecure() {
    Event_t ev;

    ev.type = ZrtpPacket;
    ev.packet = (uint8_t*)zrtpConf2Ack.getHeaderBase();
    ev.length = sizeof (Conf2AckPacket_t) + 12;  // 12 is fixed ZRTP (RTP) header size

    if (stateEngine != NULL) {
        stateEngine->processEvent(&ev);
    }
}

int32_t ZRtp::compareCommit(ZrtpPacketCommit *commit) {
    // TODO: enhance to compare according to rules defined in chapter 4.2,
    // but we don't support Preshared.
    int32_t len = 0;
    len = !multiStream ? HVI_SIZE : (4 * ZRTP_WORD_SIZE);
    return (memcmp(hvi, commit->getHvi(), len));
}

bool ZRtp::isEnrollmentMode() {
    return enrollmentMode;
}

void ZRtp::setEnrollmentMode(bool enrollmentMode) {
#ifdef ZRTP_SAS_RELAY_SUPPORT
    this->enrollmentMode = enrollmentMode;
#else
    this->enrollmentMode = false;
#endif
}

bool ZRtp::isPeerEnrolled() {
    return peerIsEnrolled;
}

bool ZRtp::sendSASRelayPacket(uint8_t* sh, std::string render) {

    uint8_t confMac[MAX_DIGEST_LENGTH];
    uint32_t macLen;
    uint8_t* hkey, *ekey;

    // If we are responder then the PBX used it's Initiator keys
    if (myRole == Responder) {
        hkey = hmacKeyR;
        ekey = zrtpKeyR;
        // TODO: check signature length in zrtpConfirm1 and if not zero copy Signature data
    }
    else {
        hkey = hmacKeyI;
        ekey = zrtpKeyI;
        // TODO: check signature length in zrtpConfirm2 and if not zero copy Signature data
    }
    // Prepare IV data that we will use during confirm packet encryption.
    randomZRTP(randomIV, sizeof(randomIV));
    zrtpSasRelay.setIv(randomIV);
    zrtpSasRelay.setTrustedSas(sh);
    zrtpSasRelay.setSasAlgo((uint8_t*)render.c_str());

    int16_t hmlen = (zrtpSasRelay.getLength() - 9) * ZRTP_WORD_SIZE;
    cipher->getEncrypt()(ekey, cipher->getKeylen(), randomIV, (uint8_t*)zrtpSasRelay.getFiller(), hmlen);

    // Use negotiated HMAC (hash)
    hmacFunction(hkey, hashLength, (unsigned char*)zrtpSasRelay.getFiller(), hmlen, confMac, &macLen);

    zrtpSasRelay.setHmac(confMac);

    stateEngine->sendSASRelay(&zrtpSasRelay);
    return true;
}

std::string ZRtp::getSasType() {
    std::string sasT(sasType->getName());
    return sasT;
}

uint8_t* ZRtp::getSasHash() {
    return sasHash;
}

int32_t ZRtp::getPeerZid(uint8_t* data) {
    memcpy(data, peerZid, IDENTIFIER_LEN);
    return IDENTIFIER_LEN;
}

const ZRtp::zrtpInfo* ZRtp::getDetailInfo() {
    return &detailInfo;
}

std::string ZRtp::getPeerClientId() {
    if (peerClientId.empty())
        return std::string();
    return peerClientId;
}

std::string ZRtp::getPeerProtcolVersion() {
    if (peerHelloVersion[0] == 0)
        return std::string();
    return std::string((char*)peerHelloVersion);
}

void ZRtp::setT1Resend(int32_t counter) {
    if (counter < 0 || counter > 10)
        stateEngine->setT1Resend(counter);
}

void ZRtp::setT1ResendExtend(int32_t counter) {
    stateEngine->setT1ResendExtend(counter);
}

void ZRtp::setT1Capping(int32_t capping) {
    if (capping >= 50)
        stateEngine->setT1Capping(capping);
}

void ZRtp::setT2Resend(int32_t counter) {
    if (counter < 0 || counter > 10)
        stateEngine->setT2Resend(counter);
}

void ZRtp::setT2Capping(int32_t capping) {
    if (capping >= 150)
        stateEngine->setT2Capping(capping);
}

int ZRtp::getNumberOfCountersZrtp() {
    // If we add some other counters add them here before returning
    return stateEngine->getNumberOfRetryCounters();
}

int ZRtp::getCountersZrtp(int32_t* counters) {
    return stateEngine->getRetryCounters(counters);
}

uint8_t* ZRtp::getExportedKey(int32_t *length) {
    if (length != NULL)
        *length = hashLength;
    return zrtpExport;
}

bool ZRtp::checkAndSetNonce(uint8_t* nonce) {
    // This is for backward compatibility if an applications uses the old
    // get- and setMultiStrParams functions
    if (masterStream == NULL)
        return true;

    for (std::vector<std::string>::iterator it = masterStream->peerNonces.begin() ; it != masterStream->peerNonces.end(); ++it) {
        if (memcmp((*it).data(), nonce, ZRTP_WORD_SIZE * 4) == 0) {
            return false;
        }
    }
    // the string holds the binary nonce
    std::string str("");
    str.assign((char *)nonce, ZRTP_WORD_SIZE * 4);
    masterStream->peerNonces.push_back(str);
    return true;
}

/** EMACS **
 * Local variables:
 * mode: c++
 * c-default-style: ellemtel
 * c-basic-offset: 4
 * End:
 */