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| author | cvs2svn <admin@example.com> | 2001-04-23 15:30:26 +0000 |
|---|---|---|
| committer | cvs2svn <admin@example.com> | 2001-04-23 15:30:26 +0000 |
| commit | 5c517720d5b21a720e400586177c050d4bc95721 (patch) | |
| tree | 34ec35b1061b27f8770c5ac5ee02aad558cbfc90 /src/lib/libcrypto/doc/EVP_EncryptInit.pod | |
| parent | d2092adc32c6de492232ba39518f9091db6bc67f (diff) | |
| download | openbsd-OPENBSD_2_9_BASE.tar.gz openbsd-OPENBSD_2_9_BASE.tar.bz2 openbsd-OPENBSD_2_9_BASE.zip | |
This commit was manufactured by cvs2git to create tag 'OPENBSD_2_9_BASE'.OPENBSD_2_9_BASE
Diffstat (limited to 'src/lib/libcrypto/doc/EVP_EncryptInit.pod')
| -rw-r--r-- | src/lib/libcrypto/doc/EVP_EncryptInit.pod | 359 |
1 files changed, 0 insertions, 359 deletions
diff --git a/src/lib/libcrypto/doc/EVP_EncryptInit.pod b/src/lib/libcrypto/doc/EVP_EncryptInit.pod deleted file mode 100644 index 9afe2396e2..0000000000 --- a/src/lib/libcrypto/doc/EVP_EncryptInit.pod +++ /dev/null | |||
| @@ -1,359 +0,0 @@ | |||
| 1 | =pod | ||
| 2 | |||
| 3 | =head1 NAME | ||
| 4 | |||
| 5 | EVP_EncryptInit, EVP_EncryptUpdate, EVP_EncryptFinal, EVP_DecryptInit, | ||
| 6 | EVP_DecryptUpdate, EVP_DecryptFinal, EVP_CipherInit, EVP_CipherUpdate, | ||
| 7 | EVP_CipherFinal, EVP_CIPHER_CTX_set_key_length, EVP_CIPHER_CTX_ctrl, | ||
| 8 | EVP_CIPHER_CTX_cleanup, EVP_get_cipherbyname, EVP_get_cipherbynid, | ||
| 9 | EVP_get_cipherbyobj, EVP_CIPHER_nid, EVP_CIPHER_block_size, | ||
| 10 | EVP_CIPHER_key_length, EVP_CIPHER_iv_length, EVP_CIPHER_flags, | ||
| 11 | EVP_CIPHER_mode, EVP_CIPHER_type, EVP_CIPHER_CTX_cipher, EVP_CIPHER_CTX_nid, | ||
| 12 | EVP_CIPHER_CTX_block_size, EVP_CIPHER_CTX_key_length, EVP_CIPHER_CTX_iv_length, | ||
| 13 | EVP_CIPHER_CTX_get_app_data, EVP_CIPHER_CTX_set_app_data, EVP_CIPHER_CTX_type, | ||
| 14 | EVP_CIPHER_CTX_flags, EVP_CIPHER_CTX_mode, EVP_CIPHER_param_to_asn1, | ||
| 15 | EVP_CIPHER_asn1_to_param - EVP cipher routines | ||
| 16 | |||
| 17 | =head1 SYNOPSIS | ||
| 18 | |||
| 19 | #include <openssl/evp.h> | ||
| 20 | |||
| 21 | int EVP_EncryptInit(EVP_CIPHER_CTX *ctx, const EVP_CIPHER *type, | ||
| 22 | unsigned char *key, unsigned char *iv); | ||
| 23 | int EVP_EncryptUpdate(EVP_CIPHER_CTX *ctx, unsigned char *out, | ||
| 24 | int *outl, unsigned char *in, int inl); | ||
| 25 | int EVP_EncryptFinal(EVP_CIPHER_CTX *ctx, unsigned char *out, | ||
| 26 | int *outl); | ||
| 27 | |||
| 28 | int EVP_DecryptInit(EVP_CIPHER_CTX *ctx, const EVP_CIPHER *type, | ||
| 29 | unsigned char *key, unsigned char *iv); | ||
| 30 | int EVP_DecryptUpdate(EVP_CIPHER_CTX *ctx, unsigned char *out, | ||
| 31 | int *outl, unsigned char *in, int inl); | ||
| 32 | int EVP_DecryptFinal(EVP_CIPHER_CTX *ctx, unsigned char *outm, | ||
| 33 | int *outl); | ||
| 34 | |||
| 35 | int EVP_CipherInit(EVP_CIPHER_CTX *ctx, const EVP_CIPHER *type, | ||
| 36 | unsigned char *key, unsigned char *iv, int enc); | ||
| 37 | int EVP_CipherUpdate(EVP_CIPHER_CTX *ctx, unsigned char *out, | ||
| 38 | int *outl, unsigned char *in, int inl); | ||
| 39 | int EVP_CipherFinal(EVP_CIPHER_CTX *ctx, unsigned char *outm, | ||
| 40 | int *outl); | ||
| 41 | |||
| 42 | int EVP_CIPHER_CTX_set_key_length(EVP_CIPHER_CTX *x, int keylen); | ||
| 43 | int EVP_CIPHER_CTX_ctrl(EVP_CIPHER_CTX *ctx, int type, int arg, void *ptr); | ||
| 44 | int EVP_CIPHER_CTX_cleanup(EVP_CIPHER_CTX *a); | ||
| 45 | |||
| 46 | const EVP_CIPHER *EVP_get_cipherbyname(const char *name); | ||
| 47 | #define EVP_get_cipherbynid(a) EVP_get_cipherbyname(OBJ_nid2sn(a)) | ||
| 48 | #define EVP_get_cipherbyobj(a) EVP_get_cipherbynid(OBJ_obj2nid(a)) | ||
| 49 | |||
| 50 | #define EVP_CIPHER_nid(e) ((e)->nid) | ||
| 51 | #define EVP_CIPHER_block_size(e) ((e)->block_size) | ||
| 52 | #define EVP_CIPHER_key_length(e) ((e)->key_len) | ||
| 53 | #define EVP_CIPHER_iv_length(e) ((e)->iv_len) | ||
| 54 | #define EVP_CIPHER_flags(e) ((e)->flags) | ||
| 55 | #define EVP_CIPHER_mode(e) ((e)->flags) & EVP_CIPH_MODE) | ||
| 56 | int EVP_CIPHER_type(const EVP_CIPHER *ctx); | ||
| 57 | |||
| 58 | #define EVP_CIPHER_CTX_cipher(e) ((e)->cipher) | ||
| 59 | #define EVP_CIPHER_CTX_nid(e) ((e)->cipher->nid) | ||
| 60 | #define EVP_CIPHER_CTX_block_size(e) ((e)->cipher->block_size) | ||
| 61 | #define EVP_CIPHER_CTX_key_length(e) ((e)->key_len) | ||
| 62 | #define EVP_CIPHER_CTX_iv_length(e) ((e)->cipher->iv_len) | ||
| 63 | #define EVP_CIPHER_CTX_get_app_data(e) ((e)->app_data) | ||
| 64 | #define EVP_CIPHER_CTX_set_app_data(e,d) ((e)->app_data=(char *)(d)) | ||
| 65 | #define EVP_CIPHER_CTX_type(c) EVP_CIPHER_type(EVP_CIPHER_CTX_cipher(c)) | ||
| 66 | #define EVP_CIPHER_CTX_flags(e) ((e)->cipher->flags) | ||
| 67 | #define EVP_CIPHER_CTX_mode(e) ((e)->cipher->flags & EVP_CIPH_MODE) | ||
| 68 | |||
| 69 | int EVP_CIPHER_param_to_asn1(EVP_CIPHER_CTX *c, ASN1_TYPE *type); | ||
| 70 | int EVP_CIPHER_asn1_to_param(EVP_CIPHER_CTX *c, ASN1_TYPE *type); | ||
| 71 | |||
| 72 | =head1 DESCRIPTION | ||
| 73 | |||
| 74 | The EVP cipher routines are a high level interface to certain | ||
| 75 | symmetric ciphers. | ||
| 76 | |||
| 77 | EVP_EncryptInit() initializes a cipher context B<ctx> for encryption | ||
| 78 | with cipher B<type>. B<type> is normally supplied by a function such | ||
| 79 | as EVP_des_cbc() . B<key> is the symmetric key to use and B<iv> is the | ||
| 80 | IV to use (if necessary), the actual number of bytes used for the | ||
| 81 | key and IV depends on the cipher. It is possible to set all parameters | ||
| 82 | to NULL except B<type> in an initial call and supply the remaining | ||
| 83 | parameters in subsequent calls, all of which have B<type> set to NULL. | ||
| 84 | This is done when the default cipher parameters are not appropriate. | ||
| 85 | |||
| 86 | EVP_EncryptUpdate() encrypts B<inl> bytes from the buffer B<in> and | ||
| 87 | writes the encrypted version to B<out>. This function can be called | ||
| 88 | multiple times to encrypt successive blocks of data. The amount | ||
| 89 | of data written depends on the block alignment of the encrypted data: | ||
| 90 | as a result the amount of data written may be anything from zero bytes | ||
| 91 | to (inl + cipher_block_size - 1) so B<outl> should contain sufficient | ||
| 92 | room. The actual number of bytes written is placed in B<outl>. | ||
| 93 | |||
| 94 | EVP_EncryptFinal() encrypts the "final" data, that is any data that | ||
| 95 | remains in a partial block. It uses L<standard block padding|/NOTES> (aka PKCS | ||
| 96 | padding). The encrypted final data is written to B<out> which should | ||
| 97 | have sufficient space for one cipher block. The number of bytes written | ||
| 98 | is placed in B<outl>. After this function is called the encryption operation | ||
| 99 | is finished and no further calls to EVP_EncryptUpdate() should be made. | ||
| 100 | |||
| 101 | EVP_DecryptInit(), EVP_DecryptUpdate() and EVP_DecryptFinal() are the | ||
| 102 | corresponding decryption operations. EVP_DecryptFinal() will return an | ||
| 103 | error code if the final block is not correctly formatted. The parameters | ||
| 104 | and restrictions are identical to the encryption operations except that | ||
| 105 | the decrypted data buffer B<out> passed to EVP_DecryptUpdate() should | ||
| 106 | have sufficient room for (B<inl> + cipher_block_size) bytes unless the | ||
| 107 | cipher block size is 1 in which case B<inl> bytes is sufficient. | ||
| 108 | |||
| 109 | EVP_CipherInit(), EVP_CipherUpdate() and EVP_CipherFinal() are functions | ||
| 110 | that can be used for decryption or encryption. The operation performed | ||
| 111 | depends on the value of the B<enc> parameter. It should be set to 1 for | ||
| 112 | encryption, 0 for decryption and -1 to leave the value unchanged (the | ||
| 113 | actual value of 'enc' being supplied in a previous call). | ||
| 114 | |||
| 115 | EVP_CIPHER_CTX_cleanup() clears all information from a cipher context. | ||
| 116 | It should be called after all operations using a cipher are complete | ||
| 117 | so sensitive information does not remain in memory. | ||
| 118 | |||
| 119 | EVP_get_cipherbyname(), EVP_get_cipherbynid() and EVP_get_cipherbyobj() | ||
| 120 | return an EVP_CIPHER structure when passed a cipher name, a NID or an | ||
| 121 | ASN1_OBJECT structure. | ||
| 122 | |||
| 123 | EVP_CIPHER_nid() and EVP_CIPHER_CTX_nid() return the NID of a cipher when | ||
| 124 | passed an B<EVP_CIPHER> or B<EVP_CIPHER_CTX> structure. The actual NID | ||
| 125 | value is an internal value which may not have a corresponding OBJECT | ||
| 126 | IDENTIFIER. | ||
| 127 | |||
| 128 | EVP_CIPHER_key_length() and EVP_CIPHER_CTX_key_length() return the key | ||
| 129 | length of a cipher when passed an B<EVP_CIPHER> or B<EVP_CIPHER_CTX> | ||
| 130 | structure. The constant B<EVP_MAX_KEY_LENGTH> is the maximum key length | ||
| 131 | for all ciphers. Note: although EVP_CIPHER_key_length() is fixed for a | ||
| 132 | given cipher, the value of EVP_CIPHER_CTX_key_length() may be different | ||
| 133 | for variable key length ciphers. | ||
| 134 | |||
| 135 | EVP_CIPHER_CTX_set_key_length() sets the key length of the cipher ctx. | ||
| 136 | If the cipher is a fixed length cipher then attempting to set the key | ||
| 137 | length to any value other than the fixed value is an error. | ||
| 138 | |||
| 139 | EVP_CIPHER_iv_length() and EVP_CIPHER_CTX_iv_length() return the IV | ||
| 140 | length of a cipher when passed an B<EVP_CIPHER> or B<EVP_CIPHER_CTX>. | ||
| 141 | It will return zero if the cipher does not use an IV. The constant | ||
| 142 | B<EVP_MAX_IV_LENGTH> is the maximum IV length for all ciphers. | ||
| 143 | |||
| 144 | EVP_CIPHER_block_size() and EVP_CIPHER_CTX_block_size() return the block | ||
| 145 | size of a cipher when passed an B<EVP_CIPHER> or B<EVP_CIPHER_CTX> | ||
| 146 | structure. The constant B<EVP_MAX_IV_LENGTH> is also the maximum block | ||
| 147 | length for all ciphers. | ||
| 148 | |||
| 149 | EVP_CIPHER_type() and EVP_CIPHER_CTX_type() return the type of the passed | ||
| 150 | cipher or context. This "type" is the actual NID of the cipher OBJECT | ||
| 151 | IDENTIFIER as such it ignores the cipher parameters and 40 bit RC2 and | ||
| 152 | 128 bit RC2 have the same NID. If the cipher does not have an object | ||
| 153 | identifier or does not have ASN1 support this function will return | ||
| 154 | B<NID_undef>. | ||
| 155 | |||
| 156 | EVP_CIPHER_CTX_cipher() returns the B<EVP_CIPHER> structure when passed | ||
| 157 | an B<EVP_CIPHER_CTX> structure. | ||
| 158 | |||
| 159 | EVP_CIPHER_mode() and EVP_CIPHER_CTX_mode() return the block cipher mode: | ||
| 160 | EVP_CIPH_ECB_MODE, EVP_CIPH_CBC_MODE, EVP_CIPH_CFB_MODE or | ||
| 161 | EVP_CIPH_OFB_MODE. If the cipher is a stream cipher then | ||
| 162 | EVP_CIPH_STREAM_CIPHER is returned. | ||
| 163 | |||
| 164 | EVP_CIPHER_param_to_asn1() sets the AlgorithmIdentifier "parameter" based | ||
| 165 | on the passed cipher. This will typically include any parameters and an | ||
| 166 | IV. The cipher IV (if any) must be set when this call is made. This call | ||
| 167 | should be made before the cipher is actually "used" (before any | ||
| 168 | EVP_EncryptUpdate(), EVP_DecryptUpdate() calls for example). This function | ||
| 169 | may fail if the cipher does not have any ASN1 support. | ||
| 170 | |||
| 171 | EVP_CIPHER_asn1_to_param() sets the cipher parameters based on an ASN1 | ||
| 172 | AlgorithmIdentifier "parameter". The precise effect depends on the cipher | ||
| 173 | In the case of RC2, for example, it will set the IV and effective key length. | ||
| 174 | This function should be called after the base cipher type is set but before | ||
| 175 | the key is set. For example EVP_CipherInit() will be called with the IV and | ||
| 176 | key set to NULL, EVP_CIPHER_asn1_to_param() will be called and finally | ||
| 177 | EVP_CipherInit() again with all parameters except the key set to NULL. It is | ||
| 178 | possible for this function to fail if the cipher does not have any ASN1 support | ||
| 179 | or the parameters cannot be set (for example the RC2 effective key length | ||
| 180 | is not supported. | ||
| 181 | |||
| 182 | EVP_CIPHER_CTX_ctrl() allows various cipher specific parameters to be determined | ||
| 183 | and set. Currently only the RC2 effective key length and the number of rounds of | ||
| 184 | RC5 can be set. | ||
| 185 | |||
| 186 | =head1 RETURN VALUES | ||
| 187 | |||
| 188 | EVP_EncryptInit(), EVP_EncryptUpdate() and EVP_EncryptFinal() return 1 for success | ||
| 189 | and 0 for failure. | ||
| 190 | |||
| 191 | EVP_DecryptInit() and EVP_DecryptUpdate() return 1 for success and 0 for failure. | ||
| 192 | EVP_DecryptFinal() returns 0 if the decrypt failed or 1 for success. | ||
| 193 | |||
| 194 | EVP_CipherInit() and EVP_CipherUpdate() return 1 for success and 0 for failure. | ||
| 195 | EVP_CipherFinal() returns 1 for a decryption failure or 1 for success. | ||
| 196 | |||
| 197 | EVP_CIPHER_CTX_cleanup() returns 1 for success and 0 for failure. | ||
| 198 | |||
| 199 | EVP_get_cipherbyname(), EVP_get_cipherbynid() and EVP_get_cipherbyobj() | ||
| 200 | return an B<EVP_CIPHER> structure or NULL on error. | ||
| 201 | |||
| 202 | EVP_CIPHER_nid() and EVP_CIPHER_CTX_nid() return a NID. | ||
| 203 | |||
| 204 | EVP_CIPHER_block_size() and EVP_CIPHER_CTX_block_size() return the block | ||
| 205 | size. | ||
| 206 | |||
| 207 | EVP_CIPHER_key_length() and EVP_CIPHER_CTX_key_length() return the key | ||
| 208 | length. | ||
| 209 | |||
| 210 | EVP_CIPHER_iv_length() and EVP_CIPHER_CTX_iv_length() return the IV | ||
| 211 | length or zero if the cipher does not use an IV. | ||
| 212 | |||
| 213 | EVP_CIPHER_type() and EVP_CIPHER_CTX_type() return the NID of the cipher's | ||
| 214 | OBJECT IDENTIFIER or NID_undef if it has no defined OBJECT IDENTIFIER. | ||
| 215 | |||
| 216 | EVP_CIPHER_CTX_cipher() returns an B<EVP_CIPHER> structure. | ||
| 217 | |||
| 218 | EVP_CIPHER_param_to_asn1() and EVP_CIPHER_asn1_to_param() return 1 for | ||
| 219 | success or zero for failure. | ||
| 220 | |||
| 221 | =head1 CIPHER LISTING | ||
| 222 | |||
| 223 | All algorithms have a fixed key length unless otherwise stated. | ||
| 224 | |||
| 225 | =over 4 | ||
| 226 | |||
| 227 | =item EVP_enc_null() | ||
| 228 | |||
| 229 | Null cipher: does nothing. | ||
| 230 | |||
| 231 | =item EVP_des_cbc(void), EVP_des_ecb(void), EVP_des_cfb(void), EVP_des_ofb(void) | ||
| 232 | |||
| 233 | DES in CBC, ECB, CFB and OFB modes respectively. | ||
| 234 | |||
| 235 | =item EVP_des_ede_cbc(void), EVP_des_ede(), EVP_des_ede_ofb(void), EVP_des_ede_cfb(void) | ||
| 236 | |||
| 237 | Two key triple DES in CBC, ECB, CFB and OFB modes respectively. | ||
| 238 | |||
| 239 | =item EVP_des_ede3_cbc(void), EVP_des_ede3(), EVP_des_ede3_ofb(void), EVP_des_ede3_cfb(void) | ||
| 240 | |||
| 241 | Three key triple DES in CBC, ECB, CFB and OFB modes respectively. | ||
| 242 | |||
| 243 | =item EVP_desx_cbc(void) | ||
| 244 | |||
| 245 | DESX algorithm in CBC mode. | ||
| 246 | |||
| 247 | =item EVP_rc4(void) | ||
| 248 | |||
| 249 | RC4 stream cipher. This is a variable key length cipher with default key length 128 bits. | ||
| 250 | |||
| 251 | =item EVP_rc4_40(void) | ||
| 252 | |||
| 253 | RC4 stream cipher with 40 bit key length. This is obsolete and new code should use EVP_rc4() | ||
| 254 | and the EVP_CIPHER_CTX_set_key_length() function. | ||
| 255 | |||
| 256 | =item EVP_idea_cbc() EVP_idea_ecb(void), EVP_idea_cfb(void), EVP_idea_ofb(void), EVP_idea_cbc(void) | ||
| 257 | |||
| 258 | IDEA encryption algorithm in CBC, ECB, CFB and OFB modes respectively. | ||
| 259 | |||
| 260 | =item EVP_rc2_cbc(void), EVP_rc2_ecb(void), EVP_rc2_cfb(void), EVP_rc2_ofb(void) | ||
| 261 | |||
| 262 | RC2 encryption algorithm in CBC, ECB, CFB and OFB modes respectively. This is a variable key | ||
| 263 | length cipher with an additional parameter called "effective key bits" or "effective key length". | ||
| 264 | By default both are set to 128 bits. | ||
| 265 | |||
| 266 | =item EVP_rc2_40_cbc(void), EVP_rc2_64_cbc(void) | ||
| 267 | |||
| 268 | RC2 algorithm in CBC mode with a default key length and effective key length of 40 and 64 bits. | ||
| 269 | These are obsolete and new code should use EVP_rc2_cbc(), EVP_CIPHER_CTX_set_key_length() and | ||
| 270 | EVP_CIPHER_CTX_ctrl() to set the key length and effective key length. | ||
| 271 | |||
| 272 | =item EVP_bf_cbc(void), EVP_bf_ecb(void), EVP_bf_cfb(void), EVP_bf_ofb(void); | ||
| 273 | |||
| 274 | Blowfish encryption algorithm in CBC, ECB, CFB and OFB modes respectively. This is a variable key | ||
| 275 | length cipher. | ||
| 276 | |||
| 277 | =item EVP_cast5_cbc(void), EVP_cast5_ecb(void), EVP_cast5_cfb(void), EVP_cast5_ofb(void) | ||
| 278 | |||
| 279 | CAST encryption algorithm in CBC, ECB, CFB and OFB modes respectively. This is a variable key | ||
| 280 | length cipher. | ||
| 281 | |||
| 282 | =item EVP_rc5_32_12_16_cbc(void), EVP_rc5_32_12_16_ecb(void), EVP_rc5_32_12_16_cfb(void), EVP_rc5_32_12_16_ofb(void) | ||
| 283 | |||
| 284 | RC5 encryption algorithm in CBC, ECB, CFB and OFB modes respectively. This is a variable key length | ||
| 285 | cipher with an additional "number of rounds" parameter. By default the key length is set to 128 | ||
| 286 | bits and 12 rounds. | ||
| 287 | |||
| 288 | =back | ||
| 289 | |||
| 290 | =head1 NOTES | ||
| 291 | |||
| 292 | Where possible the B<EVP> interface to symmetric ciphers should be used in | ||
| 293 | preference to the low level interfaces. This is because the code then becomes | ||
| 294 | transparent to the cipher used and much more flexible. | ||
| 295 | |||
| 296 | PKCS padding works by adding B<n> padding bytes of value B<n> to make the total | ||
| 297 | length of the encrypted data a multiple of the block size. Padding is always | ||
| 298 | added so if the data is already a multiple of the block size B<n> will equal | ||
| 299 | the block size. For example if the block size is 8 and 11 bytes are to be | ||
| 300 | encrypted then 5 padding bytes of value 5 will be added. | ||
| 301 | |||
| 302 | When decrypting the final block is checked to see if it has the correct form. | ||
| 303 | |||
| 304 | Although the decryption operation can produce an error, it is not a strong | ||
| 305 | test that the input data or key is correct. A random block has better than | ||
| 306 | 1 in 256 chance of being of the correct format and problems with the | ||
| 307 | input data earlier on will not produce a final decrypt error. | ||
| 308 | |||
| 309 | The functions EVP_EncryptInit(), EVP_EncryptUpdate(), EVP_EncryptFinal(), | ||
| 310 | EVP_DecryptInit(), EVP_DecryptUpdate(), EVP_CipherInit() and EVP_CipherUpdate() | ||
| 311 | and EVP_CIPHER_CTX_cleanup() did not return errors in OpenSSL version 0.9.5a or | ||
| 312 | earlier. Software only versions of encryption algorithms will never return | ||
| 313 | error codes for these functions, unless there is a programming error (for example | ||
| 314 | and attempt to set the key before the cipher is set in EVP_EncryptInit() ). | ||
| 315 | |||
| 316 | =head1 BUGS | ||
| 317 | |||
| 318 | For RC5 the number of rounds can currently only be set to 8, 12 or 16. This is | ||
| 319 | a limitation of the current RC5 code rather than the EVP interface. | ||
| 320 | |||
| 321 | It should be possible to disable PKCS padding: currently it isn't. | ||
| 322 | |||
| 323 | EVP_MAX_KEY_LENGTH and EVP_MAX_IV_LENGTH only refer to the internal ciphers with | ||
| 324 | default key lengths. If custom ciphers exceed these values the results are | ||
| 325 | unpredictable. This is because it has become standard practice to define a | ||
| 326 | generic key as a fixed unsigned char array containing EVP_MAX_KEY_LENGTH bytes. | ||
| 327 | |||
| 328 | The ASN1 code is incomplete (and sometimes inaccurate) it has only been tested | ||
| 329 | for certain common S/MIME ciphers (RC2, DES, triple DES) in CBC mode. | ||
| 330 | |||
| 331 | =head1 EXAMPLES | ||
| 332 | |||
| 333 | Get the number of rounds used in RC5: | ||
| 334 | |||
| 335 | int nrounds; | ||
| 336 | EVP_CIPHER_CTX_ctrl(ctx, EVP_CTRL_GET_RC5_ROUNDS, 0, &i); | ||
| 337 | |||
| 338 | Get the RC2 effective key length: | ||
| 339 | |||
| 340 | int key_bits; | ||
| 341 | EVP_CIPHER_CTX_ctrl(ctx, EVP_CTRL_GET_RC2_KEY_BITS, 0, &i); | ||
| 342 | |||
| 343 | Set the number of rounds used in RC5: | ||
| 344 | |||
| 345 | int nrounds; | ||
| 346 | EVP_CIPHER_CTX_ctrl(ctx, EVP_CTRL_SET_RC5_ROUNDS, i, NULL); | ||
| 347 | |||
| 348 | Set the number of rounds used in RC2: | ||
| 349 | |||
| 350 | int nrounds; | ||
| 351 | EVP_CIPHER_CTX_ctrl(ctx, EVP_CTRL_SET_RC2_KEY_BITS, i, NULL); | ||
| 352 | |||
| 353 | =head1 SEE ALSO | ||
| 354 | |||
| 355 | L<evp(3)|evp(3)> | ||
| 356 | |||
| 357 | =head1 HISTORY | ||
| 358 | |||
| 359 | =cut | ||
