1=pod
2
3=head1 NAME
4
5des_random_key, des_set_key, des_key_sched, des_set_key_checked,
6des_set_key_unchecked, des_set_odd_parity, des_is_weak_key,
7des_ecb_encrypt, des_ecb2_encrypt, des_ecb3_encrypt, des_ncbc_encrypt,
8des_cfb_encrypt, des_ofb_encrypt, des_pcbc_encrypt, des_cfb64_encrypt,
9des_ofb64_encrypt, des_xcbc_encrypt, des_ede2_cbc_encrypt,
10des_ede2_cfb64_encrypt, des_ede2_ofb64_encrypt, des_ede3_cbc_encrypt,
11des_ede3_cbcm_encrypt, des_ede3_cfb64_encrypt, des_ede3_ofb64_encrypt,
12des_read_password, des_read_2passwords, des_read_pw_string,
13des_cbc_cksum, des_quad_cksum, des_string_to_key, des_string_to_2keys,
14des_fcrypt, des_crypt, des_enc_read, des_enc_write - DES encryption
15
16=head1 SYNOPSIS
17
18 #include <openssl/des.h>
19
20 void des_random_key(des_cblock *ret);
21
22 int des_set_key(const_des_cblock *key, des_key_schedule schedule);
23 int des_key_sched(const_des_cblock *key, des_key_schedule schedule);
24 int des_set_key_checked(const_des_cblock *key,
25        des_key_schedule schedule);
26 void des_set_key_unchecked(const_des_cblock *key,
27        des_key_schedule schedule);
28
29 void des_set_odd_parity(des_cblock *key);
30 int des_is_weak_key(const_des_cblock *key);
31
32 void des_ecb_encrypt(const_des_cblock *input, des_cblock *output,
33        des_key_schedule ks, int enc);
34 void des_ecb2_encrypt(const_des_cblock *input, des_cblock *output,
35        des_key_schedule ks1, des_key_schedule ks2, int enc);
36 void des_ecb3_encrypt(const_des_cblock *input, des_cblock *output,
37        des_key_schedule ks1, des_key_schedule ks2,
38        des_key_schedule ks3, int enc);
39
40 void des_ncbc_encrypt(const unsigned char *input, unsigned char *output,
41        long length, des_key_schedule schedule, des_cblock *ivec,
42        int enc);
43 void des_cfb_encrypt(const unsigned char *in, unsigned char *out,
44        int numbits, long length, des_key_schedule schedule,
45        des_cblock *ivec, int enc);
46 void des_ofb_encrypt(const unsigned char *in, unsigned char *out,
47        int numbits, long length, des_key_schedule schedule,
48        des_cblock *ivec);
49 void des_pcbc_encrypt(const unsigned char *input, unsigned char *output,
50        long length, des_key_schedule schedule, des_cblock *ivec,
51        int enc);
52 void des_cfb64_encrypt(const unsigned char *in, unsigned char *out,
53        long length, des_key_schedule schedule, des_cblock *ivec,
54        int *num, int enc);
55 void des_ofb64_encrypt(const unsigned char *in, unsigned char *out,
56        long length, des_key_schedule schedule, des_cblock *ivec,
57        int *num);
58
59 void des_xcbc_encrypt(const unsigned char *input, unsigned char *output,
60        long length, des_key_schedule schedule, des_cblock *ivec,
61        const_des_cblock *inw, const_des_cblock *outw, int enc);
62
63 void des_ede2_cbc_encrypt(const unsigned char *input,
64        unsigned char *output, long length, des_key_schedule ks1,
65        des_key_schedule ks2, des_cblock *ivec, int enc);
66 void des_ede2_cfb64_encrypt(const unsigned char *in,
67        unsigned char *out, long length, des_key_schedule ks1,
68        des_key_schedule ks2, des_cblock *ivec, int *num, int enc);
69 void des_ede2_ofb64_encrypt(const unsigned char *in,
70        unsigned char *out, long length, des_key_schedule ks1,
71        des_key_schedule ks2, des_cblock *ivec, int *num);
72
73 void des_ede3_cbc_encrypt(const unsigned char *input,
74        unsigned char *output, long length, des_key_schedule ks1,
75        des_key_schedule ks2, des_key_schedule ks3, des_cblock *ivec,
76        int enc);
77 void des_ede3_cbcm_encrypt(const unsigned char *in, unsigned char *out,
78        long length, des_key_schedule ks1, des_key_schedule ks2,
79        des_key_schedule ks3, des_cblock *ivec1, des_cblock *ivec2,
80        int enc);
81 void des_ede3_cfb64_encrypt(const unsigned char *in, unsigned char *out,
82        long length, des_key_schedule ks1, des_key_schedule ks2,
83        des_key_schedule ks3, des_cblock *ivec, int *num, int enc);
84 void des_ede3_ofb64_encrypt(const unsigned char *in, unsigned char *out,
85        long length, des_key_schedule ks1,
86        des_key_schedule ks2, des_key_schedule ks3,
87        des_cblock *ivec, int *num);
88
89 int des_read_password(des_cblock *key, const char *prompt, int verify);
90 int des_read_2passwords(des_cblock *key1, des_cblock *key2,
91        const char *prompt, int verify);
92 int des_read_pw_string(char *buf, int length, const char *prompt,
93        int verify);
94
95 DES_LONG des_cbc_cksum(const unsigned char *input, des_cblock *output,
96        long length, des_key_schedule schedule,
97        const_des_cblock *ivec);
98 DES_LONG des_quad_cksum(const unsigned char *input, des_cblock output[],
99        long length, int out_count, des_cblock *seed);
100 void des_string_to_key(const char *str, des_cblock *key);
101 void des_string_to_2keys(const char *str, des_cblock *key1,
102        des_cblock *key2);
103
104 char *des_fcrypt(const char *buf, const char *salt, char *ret);
105 char *des_crypt(const char *buf, const char *salt);
106 char *crypt(const char *buf, const char *salt);
107
108 int des_enc_read(int fd, void *buf, int len, des_key_schedule sched,
109        des_cblock *iv);
110 int des_enc_write(int fd, const void *buf, int len,
111        des_key_schedule sched, des_cblock *iv);
112
113=head1 DESCRIPTION
114
115This library contains a fast implementation of the DES encryption
116algorithm.
117
118There are two phases to the use of DES encryption.  The first is the
119generation of a I<des_key_schedule> from a key, the second is the
120actual encryption.  A DES key is of type I<des_cblock>. This type is
121consists of 8 bytes with odd parity.  The least significant bit in
122each byte is the parity bit.  The key schedule is an expanded form of
123the key; it is used to speed the encryption process.
124
125des_random_key() generates a random key.  The PRNG must be seeded
126prior to using this function (see L<rand(3)|rand(3)>; for backward
127compatibility the function des_random_seed() is available as well).
128If the PRNG could not generate a secure key, 0 is returned.  In
129earlier versions of the library, des_random_key() did not generate
130secure keys.
131
132Before a DES key can be used, it must be converted into the
133architecture dependent I<des_key_schedule> via the
134des_set_key_checked() or des_set_key_unchecked() function.
135
136des_set_key_checked() will check that the key passed is of odd parity
137and is not a week or semi-weak key.  If the parity is wrong, then -1
138is returned.  If the key is a weak key, then -2 is returned.  If an
139error is returned, the key schedule is not generated.
140
141des_set_key() (called des_key_sched() in the MIT library) works like
142des_set_key_checked() if the I<des_check_key> flag is non-zero,
143otherwise like des_set_key_unchecked().  These functions are available
144for compatibility; it is recommended to use a function that does not
145depend on a global variable.
146
147des_set_odd_parity() (called des_fixup_key_parity() in the MIT
148library) sets the parity of the passed I<key> to odd.
149
150des_is_weak_key() returns 1 is the passed key is a weak key, 0 if it
151is ok.  The probability that a randomly generated key is weak is
1521/2^52, so it is not really worth checking for them.
153
154The following routines mostly operate on an input and output stream of
155I<des_cblock>s.
156
157des_ecb_encrypt() is the basic DES encryption routine that encrypts or
158decrypts a single 8-byte I<des_cblock> in I<electronic code book>
159(ECB) mode.  It always transforms the input data, pointed to by
160I<input>, into the output data, pointed to by the I<output> argument.
161If the I<encrypt> argument is non-zero (DES_ENCRYPT), the I<input>
162(cleartext) is encrypted in to the I<output> (ciphertext) using the
163key_schedule specified by the I<schedule> argument, previously set via
164I<des_set_key>. If I<encrypt> is zero (DES_DECRYPT), the I<input> (now
165ciphertext) is decrypted into the I<output> (now cleartext).  Input
166and output may overlap.  des_ecb_encrypt() does not return a value.
167
168des_ecb3_encrypt() encrypts/decrypts the I<input> block by using
169three-key Triple-DES encryption in ECB mode.  This involves encrypting
170the input with I<ks1>, decrypting with the key schedule I<ks2>, and
171then encrypting with I<ks3>.  This routine greatly reduces the chances
172of brute force breaking of DES and has the advantage of if I<ks1>,
173I<ks2> and I<ks3> are the same, it is equivalent to just encryption
174using ECB mode and I<ks1> as the key.
175
176The macro des_ecb2_encrypt() is provided to perform two-key Triple-DES
177encryption by using I<ks1> for the final encryption.
178
179des_ncbc_encrypt() encrypts/decrypts using the I<cipher-block-chaining>
180(CBC) mode of DES.  If the I<encrypt> argument is non-zero, the
181routine cipher-block-chain encrypts the cleartext data pointed to by
182the I<input> argument into the ciphertext pointed to by the I<output>
183argument, using the key schedule provided by the I<schedule> argument,
184and initialization vector provided by the I<ivec> argument.  If the
185I<length> argument is not an integral multiple of eight bytes, the
186last block is copied to a temporary area and zero filled.  The output
187is always an integral multiple of eight bytes.
188
189des_xcbc_encrypt() is RSA's DESX mode of DES.  It uses I<inw> and
190I<outw> to 'whiten' the encryption.  I<inw> and I<outw> are secret
191(unlike the iv) and are as such, part of the key.  So the key is sort
192of 24 bytes.  This is much better than CBC DES.
193
194des_ede3_cbc_encrypt() implements outer triple CBC DES encryption with
195three keys. This means that each DES operation inside the CBC mode is
196really an C<C=E(ks3,D(ks2,E(ks1,M)))>.  This mode is used by SSL.
197
198The des_ede2_cbc_encrypt() macro implements two-key Triple-DES by
199reusing I<ks1> for the final encryption.  C<C=E(ks1,D(ks2,E(ks1,M)))>.
200This form of Triple-DES is used by the RSAREF library.
201
202des_pcbc_encrypt() encrypt/decrypts using the propagating cipher block
203chaining mode used by Kerberos v4. Its parameters are the same as
204des_ncbc_encrypt().
205
206des_cfb_encrypt() encrypt/decrypts using cipher feedback mode.  This
207method takes an array of characters as input and outputs and array of
208characters.  It does not require any padding to 8 character groups.
209Note: the I<ivec> variable is changed and the new changed value needs to
210be passed to the next call to this function.  Since this function runs
211a complete DES ECB encryption per I<numbits>, this function is only
212suggested for use when sending small numbers of characters.
213
214des_cfb64_encrypt()
215implements CFB mode of DES with 64bit feedback.  Why is this
216useful you ask?  Because this routine will allow you to encrypt an
217arbitrary number of bytes, no 8 byte padding.  Each call to this
218routine will encrypt the input bytes to output and then update ivec
219and num.  num contains 'how far' we are though ivec.  If this does
220not make much sense, read more about cfb mode of DES :-).
221
222des_ede3_cfb64_encrypt() and des_ede2_cfb64_encrypt() is the same as
223des_cfb64_encrypt() except that Triple-DES is used.
224
225des_ofb_encrypt() encrypts using output feedback mode.  This method
226takes an array of characters as input and outputs and array of
227characters.  It does not require any padding to 8 character groups.
228Note: the I<ivec> variable is changed and the new changed value needs to
229be passed to the next call to this function.  Since this function runs
230a complete DES ECB encryption per numbits, this function is only
231suggested for use when sending small numbers of characters.
232
233des_ofb64_encrypt() is the same as des_cfb64_encrypt() using Output
234Feed Back mode.
235
236des_ede3_ofb64_encrypt() and des_ede2_ofb64_encrypt() is the same as
237des_ofb64_encrypt(), using Triple-DES.
238
239The following functions are included in the DES library for
240compatibility with the MIT Kerberos library. des_read_pw_string()
241is also available under the name EVP_read_pw_string().
242
243des_read_pw_string() writes the string specified by I<prompt> to
244standard output, turns echo off and reads in input string from the
245terminal.  The string is returned in I<buf>, which must have space for
246at least I<length> bytes.  If I<verify> is set, the user is asked for
247the password twice and unless the two copies match, an error is
248returned.  A return code of -1 indicates a system error, 1 failure due
249to use interaction, and 0 is success.
250
251des_read_password() does the same and converts the password to a DES
252key by calling des_string_to_key(); des_read_2password() operates in
253the same way as des_read_password() except that it generates two keys
254by using the des_string_to_2key() function.  des_string_to_key() is
255available for backward compatibility with the MIT library.  New
256applications should use a cryptographic hash function.  The same
257applies for des_string_to_2key().
258
259des_cbc_cksum() produces an 8 byte checksum based on the input stream
260(via CBC encryption).  The last 4 bytes of the checksum are returned
261and the complete 8 bytes are placed in I<output>. This function is
262used by Kerberos v4.  Other applications should use
263L<EVP_DigestInit(3)|EVP_DigestInit(3)> etc. instead.
264
265des_quad_cksum() is a Kerberos v4 function.  It returns a 4 byte
266checksum from the input bytes.  The algorithm can be iterated over the
267input, depending on I<out_count>, 1, 2, 3 or 4 times.  If I<output> is
268non-NULL, the 8 bytes generated by each pass are written into
269I<output>.
270
271The following are DES-based transformations:
272
273des_fcrypt() is a fast version of the Unix crypt(3) function.  This
274version takes only a small amount of space relative to other fast
275crypt() implementations.  This is different to the normal crypt in
276that the third parameter is the buffer that the return value is
277written into.  It needs to be at least 14 bytes long.  This function
278is thread safe, unlike the normal crypt.
279
280des_crypt() is a faster replacement for the normal system crypt().
281This function calls des_fcrypt() with a static array passed as the
282third parameter.  This emulates the normal non-thread safe semantics
283of crypt(3).
284
285des_enc_write() writes I<len> bytes to file descriptor I<fd> from
286buffer I<buf>. The data is encrypted via I<pcbc_encrypt> (default)
287using I<sched> for the key and I<iv> as a starting vector.  The actual
288data send down I<fd> consists of 4 bytes (in network byte order)
289containing the length of the following encrypted data.  The encrypted
290data then follows, padded with random data out to a multiple of 8
291bytes.
292
293des_enc_read() is used to read I<len> bytes from file descriptor
294I<fd> into buffer I<buf>. The data being read from I<fd> is assumed to
295have come from des_enc_write() and is decrypted using I<sched> for
296the key schedule and I<iv> for the initial vector.
297
298B<Warning:> The data format used by des_enc_write() and des_enc_read()
299has a cryptographic weakness: When asked to write more than MAXWRITE
300bytes, des_enc_write() will split the data into several chunks that
301are all encrypted using the same IV.  So don't use these functions
302unless you are sure you know what you do (in which case you might not
303want to use them anyway).  They cannot handle non-blocking sockets.
304des_enc_read() uses an internal state and thus cannot be used on
305multiple files.
306
307I<des_rw_mode> is used to specify the encryption mode to use with
308des_enc_read() and des_end_write().  If set to I<DES_PCBC_MODE> (the
309default), des_pcbc_encrypt is used.  If set to I<DES_CBC_MODE>
310des_cbc_encrypt is used.
311
312=head1 NOTES
313
314Single-key DES is insecure due to its short key size.  ECB mode is
315not suitable for most applications; see L<des_modes(7)|des_modes(7)>.
316
317The L<evp(3)|evp(3)> library provides higher-level encryption functions.
318
319=head1 BUGS
320
321des_3cbc_encrypt() is flawed and must not be used in applications.
322
323des_cbc_encrypt() does not modify B<ivec>; use des_ncbc_encrypt()
324instead.
325
326des_cfb_encrypt() and des_ofb_encrypt() operates on input of 8 bits.
327What this means is that if you set numbits to 12, and length to 2, the
328first 12 bits will come from the 1st input byte and the low half of
329the second input byte.  The second 12 bits will have the low 8 bits
330taken from the 3rd input byte and the top 4 bits taken from the 4th
331input byte.  The same holds for output.  This function has been
332implemented this way because most people will be using a multiple of 8
333and because once you get into pulling bytes input bytes apart things
334get ugly!
335
336des_read_pw_string() is the most machine/OS dependent function and
337normally generates the most problems when porting this code.
338
339=head1 CONFORMING TO
340
341ANSI X3.106
342
343The B<des> library was written to be source code compatible with
344the MIT Kerberos library.
345
346=head1 SEE ALSO
347
348crypt(3), L<des_modes(7)|des_modes(7)>, L<evp(3)|evp(3)>, L<rand(3)|rand(3)>
349
350=head1 HISTORY
351
352des_cbc_cksum(), des_cbc_encrypt(), des_ecb_encrypt(),
353des_is_weak_key(), des_key_sched(), des_pcbc_encrypt(),
354des_quad_cksum(), des_random_key(), des_read_password() and
355des_string_to_key() are available in the MIT Kerberos library;
356des_check_key_parity(), des_fixup_key_parity() and des_is_weak_key()
357are available in newer versions of that library.
358
359des_set_key_checked() and des_set_key_unchecked() were added in
360OpenSSL 0.9.5.
361
362des_generate_random_block(), des_init_random_number_generator(),
363des_new_random_key(), des_set_random_generator_seed() and
364des_set_sequence_number() and des_rand_data() are used in newer
365versions of Kerberos but are not implemented here.
366
367des_random_key() generated cryptographically weak random data in
368SSLeay and in OpenSSL prior version 0.9.5, as well as in the original
369MIT library.
370
371=head1 AUTHOR
372
373Eric Young (eay@cryptsoft.com). Modified for the OpenSSL project
374(http://www.openssl.org).
375
376=cut
377