1 /* LibTomCrypt, modular cryptographic library -- Tom St Denis
2 *
3 * LibTomCrypt is a library that provides various cryptographic
4 * algorithms in a highly modular and flexible manner.
5 *
6 * The library is free for all purposes without any express
7 * guarantee it works.
8 */
9 #include "tomcrypt.h"
10
11 /**
12 @file dsa_encrypt_key.c
13 DSA Crypto, Tom St Denis
14 */
15
16 #ifdef LTC_MDSA
17
18 /**
19 Encrypt a symmetric key with DSA
20 @param in The symmetric key you want to encrypt
21 @param inlen The length of the key to encrypt (octets)
22 @param out [out] The destination for the ciphertext
23 @param outlen [in/out] The max size and resulting size of the ciphertext
24 @param prng An active PRNG state
25 @param wprng The index of the PRNG you wish to use
26 @param hash The index of the hash you want to use
27 @param key The DSA key you want to encrypt to
28 @return CRYPT_OK if successful
29 */
dsa_encrypt_key(const unsigned char * in,unsigned long inlen,unsigned char * out,unsigned long * outlen,prng_state * prng,int wprng,int hash,dsa_key * key)30 int dsa_encrypt_key(const unsigned char *in, unsigned long inlen,
31 unsigned char *out, unsigned long *outlen,
32 prng_state *prng, int wprng, int hash,
33 dsa_key *key)
34 {
35 unsigned char *expt, *skey;
36 void *g_pub, *g_priv;
37 unsigned long x, y;
38 int err;
39
40 LTC_ARGCHK(in != NULL);
41 LTC_ARGCHK(out != NULL);
42 LTC_ARGCHK(outlen != NULL);
43 LTC_ARGCHK(key != NULL);
44
45 /* check that wprng/cipher/hash are not invalid */
46 if ((err = prng_is_valid(wprng)) != CRYPT_OK) {
47 return err;
48 }
49
50 if ((err = hash_is_valid(hash)) != CRYPT_OK) {
51 return err;
52 }
53
54 if (inlen > hash_descriptor[hash].hashsize) {
55 return CRYPT_INVALID_HASH;
56 }
57
58 /* make a random key and export the public copy */
59 if ((err = mp_init_multi(&g_pub, &g_priv, NULL)) != CRYPT_OK) {
60 return err;
61 }
62
63 expt = XMALLOC(mp_unsigned_bin_size(key->p) + 1);
64 skey = XMALLOC(MAXBLOCKSIZE);
65 if (expt == NULL || skey == NULL) {
66 if (expt != NULL) {
67 XFREE(expt);
68 }
69 if (skey != NULL) {
70 XFREE(skey);
71 }
72 mp_clear_multi(g_pub, g_priv, NULL);
73 return CRYPT_MEM;
74 }
75
76 /* make a random g_priv, g_pub = g^x pair
77 private key x should be in range: 1 <= x <= q-1 (see FIPS 186-4 B.1.2)
78 */
79 if ((err = rand_bn_upto(g_priv, key->q, prng, wprng)) != CRYPT_OK) {
80 goto LBL_ERR;
81 }
82
83 /* compute y */
84 if ((err = mp_exptmod(key->g, g_priv, key->p, g_pub)) != CRYPT_OK) {
85 goto LBL_ERR;
86 }
87
88 /* make random key */
89 x = mp_unsigned_bin_size(key->p) + 1;
90 if ((err = dsa_shared_secret(g_priv, key->y, key, expt, &x)) != CRYPT_OK) {
91 goto LBL_ERR;
92 }
93
94 y = MAXBLOCKSIZE;
95 if ((err = hash_memory(hash, expt, x, skey, &y)) != CRYPT_OK) {
96 goto LBL_ERR;
97 }
98
99 /* Encrypt key */
100 for (x = 0; x < inlen; x++) {
101 skey[x] ^= in[x];
102 }
103
104 err = der_encode_sequence_multi(out, outlen,
105 LTC_ASN1_OBJECT_IDENTIFIER, hash_descriptor[hash].OIDlen, hash_descriptor[hash].OID,
106 LTC_ASN1_INTEGER, 1UL, g_pub,
107 LTC_ASN1_OCTET_STRING, inlen, skey,
108 LTC_ASN1_EOL, 0UL, NULL);
109
110 LBL_ERR:
111 #ifdef LTC_CLEAN_STACK
112 /* clean up */
113 zeromem(expt, mp_unsigned_bin_size(key->p) + 1);
114 zeromem(skey, MAXBLOCKSIZE);
115 #endif
116
117 XFREE(skey);
118 XFREE(expt);
119
120 mp_clear_multi(g_pub, g_priv, NULL);
121 return err;
122 }
123
124 #endif
125 /* ref: HEAD -> master, tag: v1.18.2 */
126 /* git commit: 7e7eb695d581782f04b24dc444cbfde86af59853 */
127 /* commit time: 2018-07-01 22:49:01 +0200 */
128
129