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135 .\" ========================================================================
136 .\"
137 .IX Title "EVP_EncryptInit 3"
138 .TH EVP_EncryptInit 3 "2015-01-13" "1.0.1n" "OpenSSL"
139 .\" For nroff, turn off justification. Always turn off hyphenation; it makes
140 .\" way too many mistakes in technical documents.
141 .if n .ad l
142 .nh
143 .SH "NAME"
144 EVP_CIPHER_CTX_init, EVP_EncryptInit_ex, EVP_EncryptUpdate,
145 EVP_EncryptFinal_ex, EVP_DecryptInit_ex, EVP_DecryptUpdate,
146 EVP_DecryptFinal_ex, EVP_CipherInit_ex, EVP_CipherUpdate,
147 EVP_CipherFinal_ex, EVP_CIPHER_CTX_set_key_length,
148 EVP_CIPHER_CTX_ctrl, EVP_CIPHER_CTX_cleanup, EVP_EncryptInit,
149 EVP_EncryptFinal, EVP_DecryptInit, EVP_DecryptFinal,
150 EVP_CipherInit, EVP_CipherFinal, EVP_get_cipherbyname,
151 EVP_get_cipherbynid, EVP_get_cipherbyobj, EVP_CIPHER_nid,
152 EVP_CIPHER_block_size, EVP_CIPHER_key_length, EVP_CIPHER_iv_length,
153 EVP_CIPHER_flags, EVP_CIPHER_mode, EVP_CIPHER_type, EVP_CIPHER_CTX_cipher,
154 EVP_CIPHER_CTX_nid, EVP_CIPHER_CTX_block_size, EVP_CIPHER_CTX_key_length,
155 EVP_CIPHER_CTX_iv_length, EVP_CIPHER_CTX_get_app_data,
156 EVP_CIPHER_CTX_set_app_data, EVP_CIPHER_CTX_type, EVP_CIPHER_CTX_flags,
157 EVP_CIPHER_CTX_mode, EVP_CIPHER_param_to_asn1, EVP_CIPHER_asn1_to_param,
158 EVP_CIPHER_CTX_set_padding \- EVP cipher routines
159 .SH "LIBRARY"
160 libcrypto, -lcrypto
161 .SH "SYNOPSIS"
162 .IX Header "SYNOPSIS"
163 .Vb 1
164 \& #include <openssl/evp.h>
165 \&
166 \& void EVP_CIPHER_CTX_init(EVP_CIPHER_CTX *a);
167 \&
168 \& int EVP_EncryptInit_ex(EVP_CIPHER_CTX *ctx, const EVP_CIPHER *type,
169 \& ENGINE *impl, unsigned char *key, unsigned char *iv);
170 \& int EVP_EncryptUpdate(EVP_CIPHER_CTX *ctx, unsigned char *out,
171 \& int *outl, unsigned char *in, int inl);
172 \& int EVP_EncryptFinal_ex(EVP_CIPHER_CTX *ctx, unsigned char *out,
173 \& int *outl);
174 \&
175 \& int EVP_DecryptInit_ex(EVP_CIPHER_CTX *ctx, const EVP_CIPHER *type,
176 \& ENGINE *impl, unsigned char *key, unsigned char *iv);
177 \& int EVP_DecryptUpdate(EVP_CIPHER_CTX *ctx, unsigned char *out,
178 \& int *outl, unsigned char *in, int inl);
179 \& int EVP_DecryptFinal_ex(EVP_CIPHER_CTX *ctx, unsigned char *outm,
180 \& int *outl);
181 \&
182 \& int EVP_CipherInit_ex(EVP_CIPHER_CTX *ctx, const EVP_CIPHER *type,
183 \& ENGINE *impl, unsigned char *key, unsigned char *iv, int enc);
184 \& int EVP_CipherUpdate(EVP_CIPHER_CTX *ctx, unsigned char *out,
185 \& int *outl, unsigned char *in, int inl);
186 \& int EVP_CipherFinal_ex(EVP_CIPHER_CTX *ctx, unsigned char *outm,
187 \& int *outl);
188 \&
189 \& int EVP_EncryptInit(EVP_CIPHER_CTX *ctx, const EVP_CIPHER *type,
190 \& unsigned char *key, unsigned char *iv);
191 \& int EVP_EncryptFinal(EVP_CIPHER_CTX *ctx, unsigned char *out,
192 \& int *outl);
193 \&
194 \& int EVP_DecryptInit(EVP_CIPHER_CTX *ctx, const EVP_CIPHER *type,
195 \& unsigned char *key, unsigned char *iv);
196 \& int EVP_DecryptFinal(EVP_CIPHER_CTX *ctx, unsigned char *outm,
197 \& int *outl);
198 \&
199 \& int EVP_CipherInit(EVP_CIPHER_CTX *ctx, const EVP_CIPHER *type,
200 \& unsigned char *key, unsigned char *iv, int enc);
201 \& int EVP_CipherFinal(EVP_CIPHER_CTX *ctx, unsigned char *outm,
202 \& int *outl);
203 \&
204 \& int EVP_CIPHER_CTX_set_padding(EVP_CIPHER_CTX *x, int padding);
205 \& int EVP_CIPHER_CTX_set_key_length(EVP_CIPHER_CTX *x, int keylen);
206 \& int EVP_CIPHER_CTX_ctrl(EVP_CIPHER_CTX *ctx, int type, int arg, void *ptr);
207 \& int EVP_CIPHER_CTX_cleanup(EVP_CIPHER_CTX *a);
208 \&
209 \& const EVP_CIPHER *EVP_get_cipherbyname(const char *name);
210 \& #define EVP_get_cipherbynid(a) EVP_get_cipherbyname(OBJ_nid2sn(a))
211 \& #define EVP_get_cipherbyobj(a) EVP_get_cipherbynid(OBJ_obj2nid(a))
212 \&
213 \& #define EVP_CIPHER_nid(e) ((e)\->nid)
214 \& #define EVP_CIPHER_block_size(e) ((e)\->block_size)
215 \& #define EVP_CIPHER_key_length(e) ((e)\->key_len)
216 \& #define EVP_CIPHER_iv_length(e) ((e)\->iv_len)
217 \& #define EVP_CIPHER_flags(e) ((e)\->flags)
218 \& #define EVP_CIPHER_mode(e) ((e)\->flags) & EVP_CIPH_MODE)
219 \& int EVP_CIPHER_type(const EVP_CIPHER *ctx);
220 \&
221 \& #define EVP_CIPHER_CTX_cipher(e) ((e)\->cipher)
222 \& #define EVP_CIPHER_CTX_nid(e) ((e)\->cipher\->nid)
223 \& #define EVP_CIPHER_CTX_block_size(e) ((e)\->cipher\->block_size)
224 \& #define EVP_CIPHER_CTX_key_length(e) ((e)\->key_len)
225 \& #define EVP_CIPHER_CTX_iv_length(e) ((e)\->cipher\->iv_len)
226 \& #define EVP_CIPHER_CTX_get_app_data(e) ((e)\->app_data)
227 \& #define EVP_CIPHER_CTX_set_app_data(e,d) ((e)\->app_data=(char *)(d))
228 \& #define EVP_CIPHER_CTX_type(c) EVP_CIPHER_type(EVP_CIPHER_CTX_cipher(c))
229 \& #define EVP_CIPHER_CTX_flags(e) ((e)\->cipher\->flags)
230 \& #define EVP_CIPHER_CTX_mode(e) ((e)\->cipher\->flags & EVP_CIPH_MODE)
231 \&
232 \& int EVP_CIPHER_param_to_asn1(EVP_CIPHER_CTX *c, ASN1_TYPE *type);
233 \& int EVP_CIPHER_asn1_to_param(EVP_CIPHER_CTX *c, ASN1_TYPE *type);
234 .Ve
235 .SH "DESCRIPTION"
236 .IX Header "DESCRIPTION"
237 The \s-1EVP\s0 cipher routines are a high level interface to certain
238 symmetric ciphers.
239 .PP
240 \&\fIEVP_CIPHER_CTX_init()\fR initializes cipher contex \fBctx\fR.
241 .PP
242 \&\fIEVP_EncryptInit_ex()\fR sets up cipher context \fBctx\fR for encryption
243 with cipher \fBtype\fR from \s-1ENGINE \s0\fBimpl\fR. \fBctx\fR must be initialized
244 before calling this function. \fBtype\fR is normally supplied
245 by a function such as \fIEVP_des_cbc()\fR. If \fBimpl\fR is \s-1NULL\s0 then the
246 default implementation is used. \fBkey\fR is the symmetric key to use
247 and \fBiv\fR is the \s-1IV\s0 to use (if necessary), the actual number of bytes
248 used for the key and \s-1IV\s0 depends on the cipher. It is possible to set
249 all parameters to \s-1NULL\s0 except \fBtype\fR in an initial call and supply
250 the remaining parameters in subsequent calls, all of which have \fBtype\fR
251 set to \s-1NULL.\s0 This is done when the default cipher parameters are not
252 appropriate.
253 .PP
254 \&\fIEVP_EncryptUpdate()\fR encrypts \fBinl\fR bytes from the buffer \fBin\fR and
255 writes the encrypted version to \fBout\fR. This function can be called
256 multiple times to encrypt successive blocks of data. The amount
257 of data written depends on the block alignment of the encrypted data:
258 as a result the amount of data written may be anything from zero bytes
259 to (inl + cipher_block_size \- 1) so \fBout\fR should contain sufficient
260 room. The actual number of bytes written is placed in \fBoutl\fR.
261 .PP
262 If padding is enabled (the default) then \fIEVP_EncryptFinal_ex()\fR encrypts
263 the \*(L"final\*(R" data, that is any data that remains in a partial block.
264 It uses standard block padding (aka \s-1PKCS\s0 padding). The encrypted
265 final data is written to \fBout\fR which should have sufficient space for
266 one cipher block. The number of bytes written is placed in \fBoutl\fR. After
267 this function is called the encryption operation is finished and no further
268 calls to \fIEVP_EncryptUpdate()\fR should be made.
269 .PP
270 If padding is disabled then \fIEVP_EncryptFinal_ex()\fR will not encrypt any more
271 data and it will return an error if any data remains in a partial block:
272 that is if the total data length is not a multiple of the block size.
273 .PP
274 \&\fIEVP_DecryptInit_ex()\fR, \fIEVP_DecryptUpdate()\fR and \fIEVP_DecryptFinal_ex()\fR are the
275 corresponding decryption operations. \fIEVP_DecryptFinal()\fR will return an
276 error code if padding is enabled and the final block is not correctly
277 formatted. The parameters and restrictions are identical to the encryption
278 operations except that if padding is enabled the decrypted data buffer \fBout\fR
279 passed to \fIEVP_DecryptUpdate()\fR should have sufficient room for
280 (\fBinl\fR + cipher_block_size) bytes unless the cipher block size is 1 in
281 which case \fBinl\fR bytes is sufficient.
282 .PP
283 \&\fIEVP_CipherInit_ex()\fR, \fIEVP_CipherUpdate()\fR and \fIEVP_CipherFinal_ex()\fR are
284 functions that can be used for decryption or encryption. The operation
285 performed depends on the value of the \fBenc\fR parameter. It should be set
286 to 1 for encryption, 0 for decryption and \-1 to leave the value unchanged
287 (the actual value of 'enc' being supplied in a previous call).
288 .PP
289 \&\fIEVP_CIPHER_CTX_cleanup()\fR clears all information from a cipher context
290 and free up any allocated memory associate with it. It should be called
291 after all operations using a cipher are complete so sensitive information
292 does not remain in memory.
293 .PP
294 \&\fIEVP_EncryptInit()\fR, \fIEVP_DecryptInit()\fR and \fIEVP_CipherInit()\fR behave in a
295 similar way to \fIEVP_EncryptInit_ex()\fR, EVP_DecryptInit_ex and
296 \&\fIEVP_CipherInit_ex()\fR except the \fBctx\fR parameter does not need to be
297 initialized and they always use the default cipher implementation.
298 .PP
299 \&\fIEVP_EncryptFinal()\fR, \fIEVP_DecryptFinal()\fR and \fIEVP_CipherFinal()\fR behave in a
300 similar way to \fIEVP_EncryptFinal_ex()\fR, \fIEVP_DecryptFinal_ex()\fR and
301 \&\fIEVP_CipherFinal_ex()\fR except \fBctx\fR is automatically cleaned up
302 after the call.
303 .PP
304 \&\fIEVP_get_cipherbyname()\fR, \fIEVP_get_cipherbynid()\fR and \fIEVP_get_cipherbyobj()\fR
305 return an \s-1EVP_CIPHER\s0 structure when passed a cipher name, a \s-1NID\s0 or an
306 \&\s-1ASN1_OBJECT\s0 structure.
307 .PP
308 \&\fIEVP_CIPHER_nid()\fR and \fIEVP_CIPHER_CTX_nid()\fR return the \s-1NID\s0 of a cipher when
309 passed an \fB\s-1EVP_CIPHER\s0\fR or \fB\s-1EVP_CIPHER_CTX\s0\fR structure. The actual \s-1NID\s0
310 value is an internal value which may not have a corresponding \s-1OBJECT
311 IDENTIFIER.\s0
312 .PP
313 \&\fIEVP_CIPHER_CTX_set_padding()\fR enables or disables padding. By default
314 encryption operations are padded using standard block padding and the
315 padding is checked and removed when decrypting. If the \fBpad\fR parameter
316 is zero then no padding is performed, the total amount of data encrypted
317 or decrypted must then be a multiple of the block size or an error will
318 occur.
319 .PP
320 \&\fIEVP_CIPHER_key_length()\fR and \fIEVP_CIPHER_CTX_key_length()\fR return the key
321 length of a cipher when passed an \fB\s-1EVP_CIPHER\s0\fR or \fB\s-1EVP_CIPHER_CTX\s0\fR
322 structure. The constant \fB\s-1EVP_MAX_KEY_LENGTH\s0\fR is the maximum key length
323 for all ciphers. Note: although \fIEVP_CIPHER_key_length()\fR is fixed for a
324 given cipher, the value of \fIEVP_CIPHER_CTX_key_length()\fR may be different
325 for variable key length ciphers.
326 .PP
327 \&\fIEVP_CIPHER_CTX_set_key_length()\fR sets the key length of the cipher ctx.
328 If the cipher is a fixed length cipher then attempting to set the key
329 length to any value other than the fixed value is an error.
330 .PP
331 \&\fIEVP_CIPHER_iv_length()\fR and \fIEVP_CIPHER_CTX_iv_length()\fR return the \s-1IV\s0
332 length of a cipher when passed an \fB\s-1EVP_CIPHER\s0\fR or \fB\s-1EVP_CIPHER_CTX\s0\fR.
333 It will return zero if the cipher does not use an \s-1IV. \s0 The constant
334 \&\fB\s-1EVP_MAX_IV_LENGTH\s0\fR is the maximum \s-1IV\s0 length for all ciphers.
335 .PP
336 \&\fIEVP_CIPHER_block_size()\fR and \fIEVP_CIPHER_CTX_block_size()\fR return the block
337 size of a cipher when passed an \fB\s-1EVP_CIPHER\s0\fR or \fB\s-1EVP_CIPHER_CTX\s0\fR
338 structure. The constant \fB\s-1EVP_MAX_IV_LENGTH\s0\fR is also the maximum block
339 length for all ciphers.
340 .PP
341 \&\fIEVP_CIPHER_type()\fR and \fIEVP_CIPHER_CTX_type()\fR return the type of the passed
342 cipher or context. This \*(L"type\*(R" is the actual \s-1NID\s0 of the cipher \s-1OBJECT
343 IDENTIFIER\s0 as such it ignores the cipher parameters and 40 bit \s-1RC2\s0 and
344 128 bit \s-1RC2\s0 have the same \s-1NID.\s0 If the cipher does not have an object
345 identifier or does not have \s-1ASN1\s0 support this function will return
346 \&\fBNID_undef\fR.
347 .PP
348 \&\fIEVP_CIPHER_CTX_cipher()\fR returns the \fB\s-1EVP_CIPHER\s0\fR structure when passed
349 an \fB\s-1EVP_CIPHER_CTX\s0\fR structure.
350 .PP
351 \&\fIEVP_CIPHER_mode()\fR and \fIEVP_CIPHER_CTX_mode()\fR return the block cipher mode:
352 \&\s-1EVP_CIPH_ECB_MODE, EVP_CIPH_CBC_MODE, EVP_CIPH_CFB_MODE\s0 or
353 \&\s-1EVP_CIPH_OFB_MODE.\s0 If the cipher is a stream cipher then
354 \&\s-1EVP_CIPH_STREAM_CIPHER\s0 is returned.
355 .PP
356 \&\fIEVP_CIPHER_param_to_asn1()\fR sets the AlgorithmIdentifier \*(L"parameter\*(R" based
357 on the passed cipher. This will typically include any parameters and an
358 \&\s-1IV.\s0 The cipher \s-1IV \s0(if any) must be set when this call is made. This call
359 should be made before the cipher is actually \*(L"used\*(R" (before any
360 \&\fIEVP_EncryptUpdate()\fR, \fIEVP_DecryptUpdate()\fR calls for example). This function
361 may fail if the cipher does not have any \s-1ASN1\s0 support.
362 .PP
363 \&\fIEVP_CIPHER_asn1_to_param()\fR sets the cipher parameters based on an \s-1ASN1\s0
364 AlgorithmIdentifier \*(L"parameter\*(R". The precise effect depends on the cipher
365 In the case of \s-1RC2,\s0 for example, it will set the \s-1IV\s0 and effective key length.
366 This function should be called after the base cipher type is set but before
367 the key is set. For example \fIEVP_CipherInit()\fR will be called with the \s-1IV\s0 and
368 key set to \s-1NULL,\s0 \fIEVP_CIPHER_asn1_to_param()\fR will be called and finally
369 \&\fIEVP_CipherInit()\fR again with all parameters except the key set to \s-1NULL.\s0 It is
370 possible for this function to fail if the cipher does not have any \s-1ASN1\s0 support
371 or the parameters cannot be set (for example the \s-1RC2\s0 effective key length
372 is not supported.
373 .PP
374 \&\fIEVP_CIPHER_CTX_ctrl()\fR allows various cipher specific parameters to be determined
375 and set. Currently only the \s-1RC2\s0 effective key length and the number of rounds of
376 \&\s-1RC5\s0 can be set.
377 .SH "RETURN VALUES"
378 .IX Header "RETURN VALUES"
379 \&\fIEVP_EncryptInit_ex()\fR, \fIEVP_EncryptUpdate()\fR and \fIEVP_EncryptFinal_ex()\fR
380 return 1 for success and 0 for failure.
381 .PP
382 \&\fIEVP_DecryptInit_ex()\fR and \fIEVP_DecryptUpdate()\fR return 1 for success and 0 for failure.
383 \&\fIEVP_DecryptFinal_ex()\fR returns 0 if the decrypt failed or 1 for success.
384 .PP
385 \&\fIEVP_CipherInit_ex()\fR and \fIEVP_CipherUpdate()\fR return 1 for success and 0 for failure.
386 \&\fIEVP_CipherFinal_ex()\fR returns 0 for a decryption failure or 1 for success.
387 .PP
388 \&\fIEVP_CIPHER_CTX_cleanup()\fR returns 1 for success and 0 for failure.
389 .PP
390 \&\fIEVP_get_cipherbyname()\fR, \fIEVP_get_cipherbynid()\fR and \fIEVP_get_cipherbyobj()\fR
391 return an \fB\s-1EVP_CIPHER\s0\fR structure or \s-1NULL\s0 on error.
392 .PP
393 \&\fIEVP_CIPHER_nid()\fR and \fIEVP_CIPHER_CTX_nid()\fR return a \s-1NID.\s0
394 .PP
395 \&\fIEVP_CIPHER_block_size()\fR and \fIEVP_CIPHER_CTX_block_size()\fR return the block
396 size.
397 .PP
398 \&\fIEVP_CIPHER_key_length()\fR and \fIEVP_CIPHER_CTX_key_length()\fR return the key
399 length.
400 .PP
401 \&\fIEVP_CIPHER_CTX_set_padding()\fR always returns 1.
402 .PP
403 \&\fIEVP_CIPHER_iv_length()\fR and \fIEVP_CIPHER_CTX_iv_length()\fR return the \s-1IV\s0
404 length or zero if the cipher does not use an \s-1IV.\s0
405 .PP
406 \&\fIEVP_CIPHER_type()\fR and \fIEVP_CIPHER_CTX_type()\fR return the \s-1NID\s0 of the cipher's
407 \&\s-1OBJECT IDENTIFIER\s0 or NID_undef if it has no defined \s-1OBJECT IDENTIFIER.\s0
408 .PP
409 \&\fIEVP_CIPHER_CTX_cipher()\fR returns an \fB\s-1EVP_CIPHER\s0\fR structure.
410 .PP
411 \&\fIEVP_CIPHER_param_to_asn1()\fR and \fIEVP_CIPHER_asn1_to_param()\fR return 1 for
412 success or zero for failure.
413 .SH "CIPHER LISTING"
414 .IX Header "CIPHER LISTING"
415 All algorithms have a fixed key length unless otherwise stated.
416 .IP "\fIEVP_enc_null()\fR" 4
417 .IX Item "EVP_enc_null()"
418 Null cipher: does nothing.
419 .IP "EVP_des_cbc(void), EVP_des_ecb(void), EVP_des_cfb(void), EVP_des_ofb(void)" 4
420 .IX Item "EVP_des_cbc(void), EVP_des_ecb(void), EVP_des_cfb(void), EVP_des_ofb(void)"
421 \&\s-1DES\s0 in \s-1CBC, ECB, CFB\s0 and \s-1OFB\s0 modes respectively.
422 .IP "EVP_des_ede_cbc(void), \fIEVP_des_ede()\fR, EVP_des_ede_ofb(void), EVP_des_ede_cfb(void)" 4
423 .IX Item "EVP_des_ede_cbc(void), EVP_des_ede(), EVP_des_ede_ofb(void), EVP_des_ede_cfb(void)"
424 Two key triple \s-1DES\s0 in \s-1CBC, ECB, CFB\s0 and \s-1OFB\s0 modes respectively.
425 .IP "EVP_des_ede3_cbc(void), \fIEVP_des_ede3()\fR, EVP_des_ede3_ofb(void), EVP_des_ede3_cfb(void)" 4
426 .IX Item "EVP_des_ede3_cbc(void), EVP_des_ede3(), EVP_des_ede3_ofb(void), EVP_des_ede3_cfb(void)"
427 Three key triple \s-1DES\s0 in \s-1CBC, ECB, CFB\s0 and \s-1OFB\s0 modes respectively.
428 .IP "EVP_desx_cbc(void)" 4
429 .IX Item "EVP_desx_cbc(void)"
430 \&\s-1DESX\s0 algorithm in \s-1CBC\s0 mode.
431 .IP "EVP_rc4(void)" 4
432 .IX Item "EVP_rc4(void)"
433 \&\s-1RC4\s0 stream cipher. This is a variable key length cipher with default key length 128 bits.
434 .IP "EVP_rc4_40(void)" 4
435 .IX Item "EVP_rc4_40(void)"
436 \&\s-1RC4\s0 stream cipher with 40 bit key length. This is obsolete and new code should use \fIEVP_rc4()\fR
437 and the \fIEVP_CIPHER_CTX_set_key_length()\fR function.
438 .IP "\fIEVP_idea_cbc()\fR EVP_idea_ecb(void), EVP_idea_cfb(void), EVP_idea_ofb(void), EVP_idea_cbc(void)" 4
439 .IX Item "EVP_idea_cbc() EVP_idea_ecb(void), EVP_idea_cfb(void), EVP_idea_ofb(void), EVP_idea_cbc(void)"
440 \&\s-1IDEA\s0 encryption algorithm in \s-1CBC, ECB, CFB\s0 and \s-1OFB\s0 modes respectively.
441 .IP "EVP_rc2_cbc(void), EVP_rc2_ecb(void), EVP_rc2_cfb(void), EVP_rc2_ofb(void)" 4
442 .IX Item "EVP_rc2_cbc(void), EVP_rc2_ecb(void), EVP_rc2_cfb(void), EVP_rc2_ofb(void)"
443 \&\s-1RC2\s0 encryption algorithm in \s-1CBC, ECB, CFB\s0 and \s-1OFB\s0 modes respectively. This is a variable key
444 length cipher with an additional parameter called \*(L"effective key bits\*(R" or \*(L"effective key length\*(R".
445 By default both are set to 128 bits.
446 .IP "EVP_rc2_40_cbc(void), EVP_rc2_64_cbc(void)" 4
447 .IX Item "EVP_rc2_40_cbc(void), EVP_rc2_64_cbc(void)"
448 \&\s-1RC2\s0 algorithm in \s-1CBC\s0 mode with a default key length and effective key length of 40 and 64 bits.
449 These are obsolete and new code should use \fIEVP_rc2_cbc()\fR, \fIEVP_CIPHER_CTX_set_key_length()\fR and
450 \&\fIEVP_CIPHER_CTX_ctrl()\fR to set the key length and effective key length.
451 .IP "EVP_bf_cbc(void), EVP_bf_ecb(void), EVP_bf_cfb(void), EVP_bf_ofb(void);" 4
452 .IX Item "EVP_bf_cbc(void), EVP_bf_ecb(void), EVP_bf_cfb(void), EVP_bf_ofb(void);"
453 Blowfish encryption algorithm in \s-1CBC, ECB, CFB\s0 and \s-1OFB\s0 modes respectively. This is a variable key
454 length cipher.
455 .IP "EVP_cast5_cbc(void), EVP_cast5_ecb(void), EVP_cast5_cfb(void), EVP_cast5_ofb(void)" 4
456 .IX Item "EVP_cast5_cbc(void), EVP_cast5_ecb(void), EVP_cast5_cfb(void), EVP_cast5_ofb(void)"
457 \&\s-1CAST\s0 encryption algorithm in \s-1CBC, ECB, CFB\s0 and \s-1OFB\s0 modes respectively. This is a variable key
458 length cipher.
459 .IP "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)" 4
460 .IX 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)"
461 \&\s-1RC5\s0 encryption algorithm in \s-1CBC, ECB, CFB\s0 and \s-1OFB\s0 modes respectively. This is a variable key length
462 cipher with an additional \*(L"number of rounds\*(R" parameter. By default the key length is set to 128
463 bits and 12 rounds.
464 .SH "NOTES"
465 .IX Header "NOTES"
466 Where possible the \fB\s-1EVP\s0\fR interface to symmetric ciphers should be used in
467 preference to the low level interfaces. This is because the code then becomes
468 transparent to the cipher used and much more flexible. Additionally, the
469 \&\fB\s-1EVP\s0\fR interface will ensure the use of platform specific cryptographic
470 acceleration such as AES-NI (the low level interfaces do not provide the
471 guarantee).
472 .PP
473 \&\s-1PKCS\s0 padding works by adding \fBn\fR padding bytes of value \fBn\fR to make the total
474 length of the encrypted data a multiple of the block size. Padding is always
475 added so if the data is already a multiple of the block size \fBn\fR will equal
476 the block size. For example if the block size is 8 and 11 bytes are to be
477 encrypted then 5 padding bytes of value 5 will be added.
478 .PP
479 When decrypting the final block is checked to see if it has the correct form.
480 .PP
481 Although the decryption operation can produce an error if padding is enabled,
482 it is not a strong test that the input data or key is correct. A random block
483 has better than 1 in 256 chance of being of the correct format and problems with
484 the input data earlier on will not produce a final decrypt error.
485 .PP
486 If padding is disabled then the decryption operation will always succeed if
487 the total amount of data decrypted is a multiple of the block size.
488 .PP
489 The functions \fIEVP_EncryptInit()\fR, \fIEVP_EncryptFinal()\fR, \fIEVP_DecryptInit()\fR,
490 \&\fIEVP_CipherInit()\fR and \fIEVP_CipherFinal()\fR are obsolete but are retained for
491 compatibility with existing code. New code should use \fIEVP_EncryptInit_ex()\fR,
492 \&\fIEVP_EncryptFinal_ex()\fR, \fIEVP_DecryptInit_ex()\fR, \fIEVP_DecryptFinal_ex()\fR,
493 \&\fIEVP_CipherInit_ex()\fR and \fIEVP_CipherFinal_ex()\fR because they can reuse an
494 existing context without allocating and freeing it up on each call.
495 .SH "BUGS"
496 .IX Header "BUGS"
497 For \s-1RC5\s0 the number of rounds can currently only be set to 8, 12 or 16. This is
498 a limitation of the current \s-1RC5\s0 code rather than the \s-1EVP\s0 interface.
499 .PP
500 \&\s-1EVP_MAX_KEY_LENGTH\s0 and \s-1EVP_MAX_IV_LENGTH\s0 only refer to the internal ciphers with
501 default key lengths. If custom ciphers exceed these values the results are
502 unpredictable. This is because it has become standard practice to define a
503 generic key as a fixed unsigned char array containing \s-1EVP_MAX_KEY_LENGTH\s0 bytes.
504 .PP
505 The \s-1ASN1\s0 code is incomplete (and sometimes inaccurate) it has only been tested
506 for certain common S/MIME ciphers (\s-1RC2, DES,\s0 triple \s-1DES\s0) in \s-1CBC\s0 mode.
507 .SH "EXAMPLES"
508 .IX Header "EXAMPLES"
509 Encrypt a string using \s-1IDEA:\s0
510 .PP
511 .Vb 12
512 \& int do_crypt(char *outfile)
513 \& {
514 \& unsigned char outbuf[1024];
515 \& int outlen, tmplen;
516 \& /* Bogus key and IV: we\*(Aqd normally set these from
517 \& * another source.
518 \& */
519 \& unsigned char key[] = {0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15};
520 \& unsigned char iv[] = {1,2,3,4,5,6,7,8};
521 \& char intext[] = "Some Crypto Text";
522 \& EVP_CIPHER_CTX ctx;
523 \& FILE *out;
524 \&
525 \& EVP_CIPHER_CTX_init(&ctx);
526 \& EVP_EncryptInit_ex(&ctx, EVP_idea_cbc(), NULL, key, iv);
527 \&
528 \& if(!EVP_EncryptUpdate(&ctx, outbuf, &outlen, intext, strlen(intext)))
529 \& {
530 \& /* Error */
531 \& return 0;
532 \& }
533 \& /* Buffer passed to EVP_EncryptFinal() must be after data just
534 \& * encrypted to avoid overwriting it.
535 \& */
536 \& if(!EVP_EncryptFinal_ex(&ctx, outbuf + outlen, &tmplen))
537 \& {
538 \& /* Error */
539 \& return 0;
540 \& }
541 \& outlen += tmplen;
542 \& EVP_CIPHER_CTX_cleanup(&ctx);
543 \& /* Need binary mode for fopen because encrypted data is
544 \& * binary data. Also cannot use strlen() on it because
545 \& * it wont be null terminated and may contain embedded
546 \& * nulls.
547 \& */
548 \& out = fopen(outfile, "wb");
549 \& fwrite(outbuf, 1, outlen, out);
550 \& fclose(out);
551 \& return 1;
552 \& }
553 .Ve
554 .PP
555 The ciphertext from the above example can be decrypted using the \fBopenssl\fR
556 utility with the command line (shown on two lines for clarity):
557 .PP
558 .Vb 2
559 \& openssl idea \-d <filename
560 \& \-K 000102030405060708090A0B0C0D0E0F \-iv 0102030405060708
561 .Ve
562 .PP
563 General encryption and decryption function example using \s-1FILE I/O\s0 and \s-1AES128\s0
564 with a 128\-bit key:
565 .PP
566 .Vb 11
567 \& int do_crypt(FILE *in, FILE *out, int do_encrypt)
568 \& {
569 \& /* Allow enough space in output buffer for additional block */
570 \& unsigned char inbuf[1024], outbuf[1024 + EVP_MAX_BLOCK_LENGTH];
571 \& int inlen, outlen;
572 \& EVP_CIPHER_CTX ctx;
573 \& /* Bogus key and IV: we\*(Aqd normally set these from
574 \& * another source.
575 \& */
576 \& unsigned char key[] = "0123456789abcdeF";
577 \& unsigned char iv[] = "1234567887654321";
578 \&
579 \& /* Don\*(Aqt set key or IV right away; we want to check lengths */
580 \& EVP_CIPHER_CTX_init(&ctx);
581 \& EVP_CipherInit_ex(&ctx, EVP_aes_128_cbc(), NULL, NULL, NULL,
582 \& do_encrypt);
583 \& OPENSSL_assert(EVP_CIPHER_CTX_key_length(&ctx) == 16);
584 \& OPENSSL_assert(EVP_CIPHER_CTX_iv_length(&ctx) == 16);
585 \&
586 \& /* Now we can set key and IV */
587 \& EVP_CipherInit_ex(&ctx, NULL, NULL, key, iv, do_encrypt);
588 \&
589 \& for(;;)
590 \& {
591 \& inlen = fread(inbuf, 1, 1024, in);
592 \& if(inlen <= 0) break;
593 \& if(!EVP_CipherUpdate(&ctx, outbuf, &outlen, inbuf, inlen))
594 \& {
595 \& /* Error */
596 \& EVP_CIPHER_CTX_cleanup(&ctx);
597 \& return 0;
598 \& }
599 \& fwrite(outbuf, 1, outlen, out);
600 \& }
601 \& if(!EVP_CipherFinal_ex(&ctx, outbuf, &outlen))
602 \& {
603 \& /* Error */
604 \& EVP_CIPHER_CTX_cleanup(&ctx);
605 \& return 0;
606 \& }
607 \& fwrite(outbuf, 1, outlen, out);
608 \&
609 \& EVP_CIPHER_CTX_cleanup(&ctx);
610 \& return 1;
611 \& }
612 .Ve
613 .SH "SEE ALSO"
614 .IX Header "SEE ALSO"
615 \&\fIopenssl_evp\fR\|(3)
616 .SH "HISTORY"
617 .IX Header "HISTORY"
618 \&\fIEVP_CIPHER_CTX_init()\fR, \fIEVP_EncryptInit_ex()\fR, \fIEVP_EncryptFinal_ex()\fR,
619 \&\fIEVP_DecryptInit_ex()\fR, \fIEVP_DecryptFinal_ex()\fR, \fIEVP_CipherInit_ex()\fR,
620 \&\fIEVP_CipherFinal_ex()\fR and \fIEVP_CIPHER_CTX_set_padding()\fR appeared in
621 OpenSSL 0.9.7.
622 .PP
623 \&\s-1IDEA\s0 appeared in OpenSSL 0.9.7 but was often disabled due to
624 patent concerns; the last patents expired in 2012.