des.pod 16 KB

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  1. =pod
  2. =head1 NAME
  3. DES_random_key, DES_set_key, DES_key_sched, DES_set_key_checked,
  4. DES_set_key_unchecked, DES_set_odd_parity, DES_is_weak_key,
  5. DES_ecb_encrypt, DES_ecb2_encrypt, DES_ecb3_encrypt, DES_ncbc_encrypt,
  6. DES_cfb_encrypt, DES_ofb_encrypt, DES_pcbc_encrypt, DES_cfb64_encrypt,
  7. DES_ofb64_encrypt, DES_xcbc_encrypt, DES_ede2_cbc_encrypt,
  8. DES_ede2_cfb64_encrypt, DES_ede2_ofb64_encrypt, DES_ede3_cbc_encrypt,
  9. DES_ede3_cbcm_encrypt, DES_ede3_cfb64_encrypt, DES_ede3_ofb64_encrypt,
  10. DES_cbc_cksum, DES_quad_cksum, DES_string_to_key, DES_string_to_2keys,
  11. DES_fcrypt, DES_crypt, DES_enc_read, DES_enc_write - DES encryption
  12. =head1 SYNOPSIS
  13. #include <openssl/des.h>
  14. void DES_random_key(DES_cblock *ret);
  15. int DES_set_key(const_DES_cblock *key, DES_key_schedule *schedule);
  16. int DES_key_sched(const_DES_cblock *key, DES_key_schedule *schedule);
  17. int DES_set_key_checked(const_DES_cblock *key,
  18. DES_key_schedule *schedule);
  19. void DES_set_key_unchecked(const_DES_cblock *key,
  20. DES_key_schedule *schedule);
  21. void DES_set_odd_parity(DES_cblock *key);
  22. int DES_is_weak_key(const_DES_cblock *key);
  23. void DES_ecb_encrypt(const_DES_cblock *input, DES_cblock *output,
  24. DES_key_schedule *ks, int enc);
  25. void DES_ecb2_encrypt(const_DES_cblock *input, DES_cblock *output,
  26. DES_key_schedule *ks1, DES_key_schedule *ks2, int enc);
  27. void DES_ecb3_encrypt(const_DES_cblock *input, DES_cblock *output,
  28. DES_key_schedule *ks1, DES_key_schedule *ks2,
  29. DES_key_schedule *ks3, int enc);
  30. void DES_ncbc_encrypt(const unsigned char *input, unsigned char *output,
  31. long length, DES_key_schedule *schedule, DES_cblock *ivec,
  32. int enc);
  33. void DES_cfb_encrypt(const unsigned char *in, unsigned char *out,
  34. int numbits, long length, DES_key_schedule *schedule,
  35. DES_cblock *ivec, int enc);
  36. void DES_ofb_encrypt(const unsigned char *in, unsigned char *out,
  37. int numbits, long length, DES_key_schedule *schedule,
  38. DES_cblock *ivec);
  39. void DES_pcbc_encrypt(const unsigned char *input, unsigned char *output,
  40. long length, DES_key_schedule *schedule, DES_cblock *ivec,
  41. int enc);
  42. void DES_cfb64_encrypt(const unsigned char *in, unsigned char *out,
  43. long length, DES_key_schedule *schedule, DES_cblock *ivec,
  44. int *num, int enc);
  45. void DES_ofb64_encrypt(const unsigned char *in, unsigned char *out,
  46. long length, DES_key_schedule *schedule, DES_cblock *ivec,
  47. int *num);
  48. void DES_xcbc_encrypt(const unsigned char *input, unsigned char *output,
  49. long length, DES_key_schedule *schedule, DES_cblock *ivec,
  50. const_DES_cblock *inw, const_DES_cblock *outw, int enc);
  51. void DES_ede2_cbc_encrypt(const unsigned char *input,
  52. unsigned char *output, long length, DES_key_schedule *ks1,
  53. DES_key_schedule *ks2, DES_cblock *ivec, int enc);
  54. void DES_ede2_cfb64_encrypt(const unsigned char *in,
  55. unsigned char *out, long length, DES_key_schedule *ks1,
  56. DES_key_schedule *ks2, DES_cblock *ivec, int *num, int enc);
  57. void DES_ede2_ofb64_encrypt(const unsigned char *in,
  58. unsigned char *out, long length, DES_key_schedule *ks1,
  59. DES_key_schedule *ks2, DES_cblock *ivec, int *num);
  60. void DES_ede3_cbc_encrypt(const unsigned char *input,
  61. unsigned char *output, long length, DES_key_schedule *ks1,
  62. DES_key_schedule *ks2, DES_key_schedule *ks3, DES_cblock *ivec,
  63. int enc);
  64. void DES_ede3_cbcm_encrypt(const unsigned char *in, unsigned char *out,
  65. long length, DES_key_schedule *ks1, DES_key_schedule *ks2,
  66. DES_key_schedule *ks3, DES_cblock *ivec1, DES_cblock *ivec2,
  67. int enc);
  68. void DES_ede3_cfb64_encrypt(const unsigned char *in, unsigned char *out,
  69. long length, DES_key_schedule *ks1, DES_key_schedule *ks2,
  70. DES_key_schedule *ks3, DES_cblock *ivec, int *num, int enc);
  71. void DES_ede3_ofb64_encrypt(const unsigned char *in, unsigned char *out,
  72. long length, DES_key_schedule *ks1,
  73. DES_key_schedule *ks2, DES_key_schedule *ks3,
  74. DES_cblock *ivec, int *num);
  75. DES_LONG DES_cbc_cksum(const unsigned char *input, DES_cblock *output,
  76. long length, DES_key_schedule *schedule,
  77. const_DES_cblock *ivec);
  78. DES_LONG DES_quad_cksum(const unsigned char *input, DES_cblock output[],
  79. long length, int out_count, DES_cblock *seed);
  80. void DES_string_to_key(const char *str, DES_cblock *key);
  81. void DES_string_to_2keys(const char *str, DES_cblock *key1,
  82. DES_cblock *key2);
  83. char *DES_fcrypt(const char *buf, const char *salt, char *ret);
  84. char *DES_crypt(const char *buf, const char *salt);
  85. int DES_enc_read(int fd, void *buf, int len, DES_key_schedule *sched,
  86. DES_cblock *iv);
  87. int DES_enc_write(int fd, const void *buf, int len,
  88. DES_key_schedule *sched, DES_cblock *iv);
  89. =head1 DESCRIPTION
  90. This library contains a fast implementation of the DES encryption
  91. algorithm.
  92. There are two phases to the use of DES encryption. The first is the
  93. generation of a I<DES_key_schedule> from a key, the second is the
  94. actual encryption. A DES key is of type I<DES_cblock>. This type is
  95. consists of 8 bytes with odd parity. The least significant bit in
  96. each byte is the parity bit. The key schedule is an expanded form of
  97. the key; it is used to speed the encryption process.
  98. DES_random_key() generates a random key. The PRNG must be seeded
  99. prior to using this function (see L<rand(3)|rand(3)>). If the PRNG
  100. could not generate a secure key, 0 is returned.
  101. Before a DES key can be used, it must be converted into the
  102. architecture dependent I<DES_key_schedule> via the
  103. DES_set_key_checked() or DES_set_key_unchecked() function.
  104. DES_set_key_checked() will check that the key passed is of odd parity
  105. and is not a week or semi-weak key. If the parity is wrong, then -1
  106. is returned. If the key is a weak key, then -2 is returned. If an
  107. error is returned, the key schedule is not generated.
  108. DES_set_key() works like
  109. DES_set_key_checked() if the I<DES_check_key> flag is non-zero,
  110. otherwise like DES_set_key_unchecked(). These functions are available
  111. for compatibility; it is recommended to use a function that does not
  112. depend on a global variable.
  113. DES_set_odd_parity() sets the parity of the passed I<key> to odd.
  114. DES_is_weak_key() returns 1 is the passed key is a weak key, 0 if it
  115. is ok. The probability that a randomly generated key is weak is
  116. 1/2^52, so it is not really worth checking for them.
  117. The following routines mostly operate on an input and output stream of
  118. I<DES_cblock>s.
  119. DES_ecb_encrypt() is the basic DES encryption routine that encrypts or
  120. decrypts a single 8-byte I<DES_cblock> in I<electronic code book>
  121. (ECB) mode. It always transforms the input data, pointed to by
  122. I<input>, into the output data, pointed to by the I<output> argument.
  123. If the I<encrypt> argument is non-zero (DES_ENCRYPT), the I<input>
  124. (cleartext) is encrypted in to the I<output> (ciphertext) using the
  125. key_schedule specified by the I<schedule> argument, previously set via
  126. I<DES_set_key>. If I<encrypt> is zero (DES_DECRYPT), the I<input> (now
  127. ciphertext) is decrypted into the I<output> (now cleartext). Input
  128. and output may overlap. DES_ecb_encrypt() does not return a value.
  129. DES_ecb3_encrypt() encrypts/decrypts the I<input> block by using
  130. three-key Triple-DES encryption in ECB mode. This involves encrypting
  131. the input with I<ks1>, decrypting with the key schedule I<ks2>, and
  132. then encrypting with I<ks3>. This routine greatly reduces the chances
  133. of brute force breaking of DES and has the advantage of if I<ks1>,
  134. I<ks2> and I<ks3> are the same, it is equivalent to just encryption
  135. using ECB mode and I<ks1> as the key.
  136. The macro DES_ecb2_encrypt() is provided to perform two-key Triple-DES
  137. encryption by using I<ks1> for the final encryption.
  138. DES_ncbc_encrypt() encrypts/decrypts using the I<cipher-block-chaining>
  139. (CBC) mode of DES. If the I<encrypt> argument is non-zero, the
  140. routine cipher-block-chain encrypts the cleartext data pointed to by
  141. the I<input> argument into the ciphertext pointed to by the I<output>
  142. argument, using the key schedule provided by the I<schedule> argument,
  143. and initialization vector provided by the I<ivec> argument. If the
  144. I<length> argument is not an integral multiple of eight bytes, the
  145. last block is copied to a temporary area and zero filled. The output
  146. is always an integral multiple of eight bytes.
  147. DES_xcbc_encrypt() is RSA's DESX mode of DES. It uses I<inw> and
  148. I<outw> to 'whiten' the encryption. I<inw> and I<outw> are secret
  149. (unlike the iv) and are as such, part of the key. So the key is sort
  150. of 24 bytes. This is much better than CBC DES.
  151. DES_ede3_cbc_encrypt() implements outer triple CBC DES encryption with
  152. three keys. This means that each DES operation inside the CBC mode is
  153. really an C<C=E(ks3,D(ks2,E(ks1,M)))>. This mode is used by SSL.
  154. The DES_ede2_cbc_encrypt() macro implements two-key Triple-DES by
  155. reusing I<ks1> for the final encryption. C<C=E(ks1,D(ks2,E(ks1,M)))>.
  156. This form of Triple-DES is used by the RSAREF library.
  157. DES_pcbc_encrypt() encrypt/decrypts using the propagating cipher block
  158. chaining mode used by Kerberos v4. Its parameters are the same as
  159. DES_ncbc_encrypt().
  160. DES_cfb_encrypt() encrypt/decrypts using cipher feedback mode. This
  161. method takes an array of characters as input and outputs and array of
  162. characters. It does not require any padding to 8 character groups.
  163. Note: the I<ivec> variable is changed and the new changed value needs to
  164. be passed to the next call to this function. Since this function runs
  165. a complete DES ECB encryption per I<numbits>, this function is only
  166. suggested for use when sending small numbers of characters.
  167. DES_cfb64_encrypt()
  168. implements CFB mode of DES with 64bit feedback. Why is this
  169. useful you ask? Because this routine will allow you to encrypt an
  170. arbitrary number of bytes, no 8 byte padding. Each call to this
  171. routine will encrypt the input bytes to output and then update ivec
  172. and num. num contains 'how far' we are though ivec. If this does
  173. not make much sense, read more about cfb mode of DES :-).
  174. DES_ede3_cfb64_encrypt() and DES_ede2_cfb64_encrypt() is the same as
  175. DES_cfb64_encrypt() except that Triple-DES is used.
  176. DES_ofb_encrypt() encrypts using output feedback mode. This method
  177. takes an array of characters as input and outputs and array of
  178. characters. It does not require any padding to 8 character groups.
  179. Note: the I<ivec> variable is changed and the new changed value needs to
  180. be passed to the next call to this function. Since this function runs
  181. a complete DES ECB encryption per numbits, this function is only
  182. suggested for use when sending small numbers of characters.
  183. DES_ofb64_encrypt() is the same as DES_cfb64_encrypt() using Output
  184. Feed Back mode.
  185. DES_ede3_ofb64_encrypt() and DES_ede2_ofb64_encrypt() is the same as
  186. DES_ofb64_encrypt(), using Triple-DES.
  187. The following functions are included in the DES library for
  188. compatibility with the MIT Kerberos library.
  189. DES_cbc_cksum() produces an 8 byte checksum based on the input stream
  190. (via CBC encryption). The last 4 bytes of the checksum are returned
  191. and the complete 8 bytes are placed in I<output>. This function is
  192. used by Kerberos v4. Other applications should use
  193. L<EVP_DigestInit(3)|EVP_DigestInit(3)> etc. instead.
  194. DES_quad_cksum() is a Kerberos v4 function. It returns a 4 byte
  195. checksum from the input bytes. The algorithm can be iterated over the
  196. input, depending on I<out_count>, 1, 2, 3 or 4 times. If I<output> is
  197. non-NULL, the 8 bytes generated by each pass are written into
  198. I<output>.
  199. The following are DES-based transformations:
  200. DES_fcrypt() is a fast version of the Unix crypt(3) function. This
  201. version takes only a small amount of space relative to other fast
  202. crypt() implementations. This is different to the normal crypt in
  203. that the third parameter is the buffer that the return value is
  204. written into. It needs to be at least 14 bytes long. This function
  205. is thread safe, unlike the normal crypt.
  206. DES_crypt() is a faster replacement for the normal system crypt().
  207. This function calls DES_fcrypt() with a static array passed as the
  208. third parameter. This emulates the normal non-thread safe semantics
  209. of crypt(3).
  210. DES_enc_write() writes I<len> bytes to file descriptor I<fd> from
  211. buffer I<buf>. The data is encrypted via I<pcbc_encrypt> (default)
  212. using I<sched> for the key and I<iv> as a starting vector. The actual
  213. data send down I<fd> consists of 4 bytes (in network byte order)
  214. containing the length of the following encrypted data. The encrypted
  215. data then follows, padded with random data out to a multiple of 8
  216. bytes.
  217. DES_enc_read() is used to read I<len> bytes from file descriptor
  218. I<fd> into buffer I<buf>. The data being read from I<fd> is assumed to
  219. have come from DES_enc_write() and is decrypted using I<sched> for
  220. the key schedule and I<iv> for the initial vector.
  221. B<Warning:> The data format used by DES_enc_write() and DES_enc_read()
  222. has a cryptographic weakness: When asked to write more than MAXWRITE
  223. bytes, DES_enc_write() will split the data into several chunks that
  224. are all encrypted using the same IV. So don't use these functions
  225. unless you are sure you know what you do (in which case you might not
  226. want to use them anyway). They cannot handle non-blocking sockets.
  227. DES_enc_read() uses an internal state and thus cannot be used on
  228. multiple files.
  229. I<DES_rw_mode> is used to specify the encryption mode to use with
  230. DES_enc_read() and DES_end_write(). If set to I<DES_PCBC_MODE> (the
  231. default), DES_pcbc_encrypt is used. If set to I<DES_CBC_MODE>
  232. DES_cbc_encrypt is used.
  233. =head1 NOTES
  234. Single-key DES is insecure due to its short key size. ECB mode is
  235. not suitable for most applications; see L<des_modes(7)|des_modes(7)>.
  236. The L<evp(3)|evp(3)> library provides higher-level encryption functions.
  237. =head1 BUGS
  238. DES_3cbc_encrypt() is flawed and must not be used in applications.
  239. DES_cbc_encrypt() does not modify B<ivec>; use DES_ncbc_encrypt()
  240. instead.
  241. DES_cfb_encrypt() and DES_ofb_encrypt() operates on input of 8 bits.
  242. What this means is that if you set numbits to 12, and length to 2, the
  243. first 12 bits will come from the 1st input byte and the low half of
  244. the second input byte. The second 12 bits will have the low 8 bits
  245. taken from the 3rd input byte and the top 4 bits taken from the 4th
  246. input byte. The same holds for output. This function has been
  247. implemented this way because most people will be using a multiple of 8
  248. and because once you get into pulling bytes input bytes apart things
  249. get ugly!
  250. DES_string_to_key() is available for backward compatibility with the
  251. MIT library. New applications should use a cryptographic hash function.
  252. The same applies for DES_string_to_2key().
  253. =head1 CONFORMING TO
  254. ANSI X3.106
  255. The B<des> library was written to be source code compatible with
  256. the MIT Kerberos library.
  257. =head1 SEE ALSO
  258. crypt(3), L<des_modes(7)|des_modes(7)>, L<evp(3)|evp(3)>, L<rand(3)|rand(3)>
  259. =head1 HISTORY
  260. In OpenSSL 0.9.7, all des_ functions were renamed to DES_ to avoid
  261. clashes with older versions of libdes. Compatibility des_ functions
  262. are provided for a short while, as well as crypt().
  263. Declarations for these are in <openssl/des_old.h>. There is no DES_
  264. variant for des_random_seed().
  265. This will happen to other functions
  266. as well if they are deemed redundant (des_random_seed() just calls
  267. RAND_seed() and is present for backward compatibility only), buggy or
  268. already scheduled for removal.
  269. des_cbc_cksum(), des_cbc_encrypt(), des_ecb_encrypt(),
  270. des_is_weak_key(), des_key_sched(), des_pcbc_encrypt(),
  271. des_quad_cksum(), des_random_key() and des_string_to_key()
  272. are available in the MIT Kerberos library;
  273. des_check_key_parity(), des_fixup_key_parity() and des_is_weak_key()
  274. are available in newer versions of that library.
  275. des_set_key_checked() and des_set_key_unchecked() were added in
  276. OpenSSL 0.9.5.
  277. des_generate_random_block(), des_init_random_number_generator(),
  278. des_new_random_key(), des_set_random_generator_seed() and
  279. des_set_sequence_number() and des_rand_data() are used in newer
  280. versions of Kerberos but are not implemented here.
  281. des_random_key() generated cryptographically weak random data in
  282. SSLeay and in OpenSSL prior version 0.9.5, as well as in the original
  283. MIT library.
  284. =head1 AUTHOR
  285. Eric Young (eay@cryptsoft.com). Modified for the OpenSSL project
  286. (http://www.openssl.org).
  287. =cut