1EVP_ENCRYPTINIT(3) OpenSSL EVP_ENCRYPTINIT(3)
2
6 EVP_CIPHER_CTX_new, EVP_CIPHER_CTX_reset, EVP_CIPHER_CTX_free,
7 EVP_EncryptInit_ex, EVP_EncryptUpdate, EVP_EncryptFinal_ex,
8 EVP_DecryptInit_ex, EVP_DecryptUpdate, EVP_DecryptFinal_ex,
9 EVP_CipherInit_ex, EVP_CipherUpdate, EVP_CipherFinal_ex,
10 EVP_CIPHER_CTX_set_key_length, EVP_CIPHER_CTX_ctrl, EVP_EncryptInit,
11 EVP_EncryptFinal, EVP_DecryptInit, EVP_DecryptFinal, EVP_CipherInit,
12 EVP_CipherFinal, EVP_get_cipherbyname, EVP_get_cipherbynid,
13 EVP_get_cipherbyobj, EVP_CIPHER_nid, EVP_CIPHER_block_size,
14 EVP_CIPHER_key_length, EVP_CIPHER_iv_length, EVP_CIPHER_flags,
15 EVP_CIPHER_mode, EVP_CIPHER_type, EVP_CIPHER_CTX_cipher,
16 EVP_CIPHER_CTX_nid, EVP_CIPHER_CTX_block_size,
17 EVP_CIPHER_CTX_key_length, EVP_CIPHER_CTX_iv_length,
18 EVP_CIPHER_CTX_get_app_data, EVP_CIPHER_CTX_set_app_data,
19 EVP_CIPHER_CTX_type, EVP_CIPHER_CTX_flags, EVP_CIPHER_CTX_mode,
20 EVP_CIPHER_param_to_asn1, EVP_CIPHER_asn1_to_param,
21 EVP_CIPHER_CTX_set_padding, EVP_enc_null - EVP cipher routines
22
24 #include <openssl/evp.h>
25 EVP_CIPHER_CTX *EVP_CIPHER_CTX_new(void);
27 int EVP_CIPHER_CTX_reset(EVP_CIPHER_CTX *ctx);
28 void EVP_CIPHER_CTX_free(EVP_CIPHER_CTX *ctx);
29 int EVP_EncryptInit_ex(EVP_CIPHER_CTX *ctx, const EVP_CIPHER *type,
31 ENGINE *impl, const unsigned char *key, const unsigned char *iv);
32 int EVP_EncryptUpdate(EVP_CIPHER_CTX *ctx, unsigned char *out,
33 int *outl, const unsigned char *in, int inl);
34 int EVP_EncryptFinal_ex(EVP_CIPHER_CTX *ctx, unsigned char *out, int *outl);
35 int EVP_DecryptInit_ex(EVP_CIPHER_CTX *ctx, const EVP_CIPHER *type,
37 ENGINE *impl, const unsigned char *key, const unsigned char *iv);
38 int EVP_DecryptUpdate(EVP_CIPHER_CTX *ctx, unsigned char *out,
39 int *outl, const unsigned char *in, int inl);
40 int EVP_DecryptFinal_ex(EVP_CIPHER_CTX *ctx, unsigned char *outm, int *outl);
41 int EVP_CipherInit_ex(EVP_CIPHER_CTX *ctx, const EVP_CIPHER *type,
43 ENGINE *impl, const unsigned char *key, const unsigned char *iv, int enc);
44 int EVP_CipherUpdate(EVP_CIPHER_CTX *ctx, unsigned char *out,
45 int *outl, const unsigned char *in, int inl);
46 int EVP_CipherFinal_ex(EVP_CIPHER_CTX *ctx, unsigned char *outm, int *outl);
47 int EVP_EncryptInit(EVP_CIPHER_CTX *ctx, const EVP_CIPHER *type,
49 const unsigned char *key, const unsigned char *iv);
50 int EVP_EncryptFinal(EVP_CIPHER_CTX *ctx, unsigned char *out, int *outl);
51 int EVP_DecryptInit(EVP_CIPHER_CTX *ctx, const EVP_CIPHER *type,
53 const unsigned char *key, const unsigned char *iv);
54 int EVP_DecryptFinal(EVP_CIPHER_CTX *ctx, unsigned char *outm, int *outl);
55 int EVP_CipherInit(EVP_CIPHER_CTX *ctx, const EVP_CIPHER *type,
57 const unsigned char *key, const unsigned char *iv, int enc);
58 int EVP_CipherFinal(EVP_CIPHER_CTX *ctx, unsigned char *outm, int *outl);
59 int EVP_CIPHER_CTX_set_padding(EVP_CIPHER_CTX *x, int padding);
61 int EVP_CIPHER_CTX_set_key_length(EVP_CIPHER_CTX *x, int keylen);
62 int EVP_CIPHER_CTX_ctrl(EVP_CIPHER_CTX *ctx, int type, int arg, void *ptr);
63 int EVP_CIPHER_CTX_rand_key(EVP_CIPHER_CTX *ctx, unsigned char *key);
64 const EVP_CIPHER *EVP_get_cipherbyname(const char *name);
66 const EVP_CIPHER *EVP_get_cipherbynid(int nid);
67 const EVP_CIPHER *EVP_get_cipherbyobj(const ASN1_OBJECT *a);
68 int EVP_CIPHER_nid(const EVP_CIPHER *e);
70 int EVP_CIPHER_block_size(const EVP_CIPHER *e);
71 int EVP_CIPHER_key_length(const EVP_CIPHER *e);
72 int EVP_CIPHER_iv_length(const EVP_CIPHER *e);
73 unsigned long EVP_CIPHER_flags(const EVP_CIPHER *e);
74 unsigned long EVP_CIPHER_mode(const EVP_CIPHER *e);
75 int EVP_CIPHER_type(const EVP_CIPHER *ctx);
76 const EVP_CIPHER *EVP_CIPHER_CTX_cipher(const EVP_CIPHER_CTX *ctx);
78 int EVP_CIPHER_CTX_nid(const EVP_CIPHER_CTX *ctx);
79 int EVP_CIPHER_CTX_block_size(const EVP_CIPHER_CTX *ctx);
80 int EVP_CIPHER_CTX_key_length(const EVP_CIPHER_CTX *ctx);
81 int EVP_CIPHER_CTX_iv_length(const EVP_CIPHER_CTX *ctx);
82 void *EVP_CIPHER_CTX_get_app_data(const EVP_CIPHER_CTX *ctx);
83 void EVP_CIPHER_CTX_set_app_data(const EVP_CIPHER_CTX *ctx, void *data);
84 int EVP_CIPHER_CTX_type(const EVP_CIPHER_CTX *ctx);
85 int EVP_CIPHER_CTX_mode(const EVP_CIPHER_CTX *ctx);
86 int EVP_CIPHER_param_to_asn1(EVP_CIPHER_CTX *c, ASN1_TYPE *type);
88 int EVP_CIPHER_asn1_to_param(EVP_CIPHER_CTX *c, ASN1_TYPE *type);
89
91 The EVP cipher routines are a high-level interface to certain symmetric
92 ciphers.
93 EVP_CIPHER_CTX_new() creates a cipher context.
95 EVP_CIPHER_CTX_free() clears all information from a cipher context and
97 free up any allocated memory associate with it, including ctx itself.
98 This function should be called after all operations using a cipher are
99 complete so sensitive information does not remain in memory.
100 EVP_EncryptInit_ex() sets up cipher context ctx for encryption with
102 cipher type from ENGINE impl. ctx must be created before calling this
103 function. type is normally supplied by a function such as
104 EVP_aes_256_cbc(). If impl is NULL then the default implementation is
105 used. key is the symmetric key to use and iv is the IV to use (if
106 necessary), the actual number of bytes used for the key and IV depends
107 on the cipher. It is possible to set all parameters to NULL except type
108 in an initial call and supply the remaining parameters in subsequent
109 calls, all of which have type set to NULL. This is done when the
110 default cipher parameters are not appropriate.
111 EVP_EncryptUpdate() encrypts inl bytes from the buffer in and writes
113 the encrypted version to out. This function can be called multiple
114 times to encrypt successive blocks of data. The amount of data written
115 depends on the block alignment of the encrypted data. For most ciphers
116 and modes, the amount of data written can be anything from zero bytes
117 to (inl + cipher_block_size - 1) bytes. For wrap cipher modes, the
118 amount of data written can be anything from zero bytes to (inl +
119 cipher_block_size) bytes. For stream ciphers, the amount of data
120 written can be anything from zero bytes to inl bytes. Thus, out should
121 contain sufficient room for the operation being performed. The actual
122 number of bytes written is placed in outl. It also checks if in and out
123 are partially overlapping, and if they are 0 is returned to indicate
124 failure.
125 If padding is enabled (the default) then EVP_EncryptFinal_ex() encrypts
127 the "final" data, that is any data that remains in a partial block. It
128 uses standard block padding (aka PKCS padding) as described in the
129 NOTES section, below. The encrypted final data is written to out which
130 should have sufficient space for one cipher block. The number of bytes
131 written is placed in outl. After this function is called the encryption
132 operation is finished and no further calls to EVP_EncryptUpdate()
133 should be made.
134 If padding is disabled then EVP_EncryptFinal_ex() will not encrypt any
136 more data and it will return an error if any data remains in a partial
137 block: that is if the total data length is not a multiple of the block
138 size.
139 EVP_DecryptInit_ex(), EVP_DecryptUpdate() and EVP_DecryptFinal_ex() are
141 the corresponding decryption operations. EVP_DecryptFinal() will return
142 an error code if padding is enabled and the final block is not
143 correctly formatted. The parameters and restrictions are identical to
144 the encryption operations except that if padding is enabled the
145 decrypted data buffer out passed to EVP_DecryptUpdate() should have
146 sufficient room for (inl + cipher_block_size) bytes unless the cipher
147 block size is 1 in which case inl bytes is sufficient.
148 EVP_CipherInit_ex(), EVP_CipherUpdate() and EVP_CipherFinal_ex() are
150 functions that can be used for decryption or encryption. The operation
151 performed depends on the value of the enc parameter. It should be set
152 to 1 for encryption, 0 for decryption and -1 to leave the value
153 unchanged (the actual value of 'enc' being supplied in a previous
154 call).
155 EVP_CIPHER_CTX_reset() clears all information from a cipher context and
157 free up any allocated memory associate with it, except the ctx itself.
158 This function should be called anytime ctx is to be reused for another
159 EVP_CipherInit() / EVP_CipherUpdate() / EVP_CipherFinal() series of
160 calls.
161 EVP_EncryptInit(), EVP_DecryptInit() and EVP_CipherInit() behave in a
163 similar way to EVP_EncryptInit_ex(), EVP_DecryptInit_ex() and
164 EVP_CipherInit_ex() except they always use the default cipher
165 implementation.
166 EVP_EncryptFinal(), EVP_DecryptFinal() and EVP_CipherFinal() are
168 identical to EVP_EncryptFinal_ex(), EVP_DecryptFinal_ex() and
169 EVP_CipherFinal_ex(). In previous releases they also cleaned up the
170 ctx, but this is no longer done and EVP_CIPHER_CTX_clean() must be
171 called to free any context resources.
172 EVP_get_cipherbyname(), EVP_get_cipherbynid() and EVP_get_cipherbyobj()
174 return an EVP_CIPHER structure when passed a cipher name, a NID or an
175 ASN1_OBJECT structure.
176 EVP_CIPHER_nid() and EVP_CIPHER_CTX_nid() return the NID of a cipher
178 when passed an EVP_CIPHER or EVP_CIPHER_CTX structure. The actual NID
179 value is an internal value which may not have a corresponding OBJECT
180 IDENTIFIER.
181 EVP_CIPHER_CTX_set_padding() enables or disables padding. This function
183 should be called after the context is set up for encryption or
184 decryption with EVP_EncryptInit_ex(), EVP_DecryptInit_ex() or
185 EVP_CipherInit_ex(). By default encryption operations are padded using
186 standard block padding and the padding is checked and removed when
187 decrypting. If the pad parameter is zero then no padding is performed,
188 the total amount of data encrypted or decrypted must then be a multiple
189 of the block size or an error will occur.
190 EVP_CIPHER_key_length() and EVP_CIPHER_CTX_key_length() return the key
192 length of a cipher when passed an EVP_CIPHER or EVP_CIPHER_CTX
193 structure. The constant EVP_MAX_KEY_LENGTH is the maximum key length
194 for all ciphers. Note: although EVP_CIPHER_key_length() is fixed for a
195 given cipher, the value of EVP_CIPHER_CTX_key_length() may be different
196 for variable key length ciphers.
197 EVP_CIPHER_CTX_set_key_length() sets the key length of the cipher ctx.
199 If the cipher is a fixed length cipher then attempting to set the key
200 length to any value other than the fixed value is an error.
201 EVP_CIPHER_iv_length() and EVP_CIPHER_CTX_iv_length() return the IV
203 length of a cipher when passed an EVP_CIPHER or EVP_CIPHER_CTX. It
204 will return zero if the cipher does not use an IV. The constant
205 EVP_MAX_IV_LENGTH is the maximum IV length for all ciphers.
206 EVP_CIPHER_block_size() and EVP_CIPHER_CTX_block_size() return the
208 block size of a cipher when passed an EVP_CIPHER or EVP_CIPHER_CTX
209 structure. The constant EVP_MAX_BLOCK_LENGTH is also the maximum block
210 length for all ciphers.
211 EVP_CIPHER_type() and EVP_CIPHER_CTX_type() return the type of the
213 passed cipher or context. This "type" is the actual NID of the cipher
214 OBJECT IDENTIFIER as such it ignores the cipher parameters and 40 bit
215 RC2 and 128 bit RC2 have the same NID. If the cipher does not have an
216 object identifier or does not have ASN1 support this function will
217 return NID_undef.
218 EVP_CIPHER_CTX_cipher() returns the EVP_CIPHER structure when passed an
220 EVP_CIPHER_CTX structure.
221 EVP_CIPHER_mode() and EVP_CIPHER_CTX_mode() return the block cipher
223 mode: EVP_CIPH_ECB_MODE, EVP_CIPH_CBC_MODE, EVP_CIPH_CFB_MODE,
224 EVP_CIPH_OFB_MODE, EVP_CIPH_CTR_MODE, EVP_CIPH_GCM_MODE,
225 EVP_CIPH_CCM_MODE, EVP_CIPH_XTS_MODE, EVP_CIPH_WRAP_MODE or
226 EVP_CIPH_OCB_MODE. If the cipher is a stream cipher then
227 EVP_CIPH_STREAM_CIPHER is returned.
228 EVP_CIPHER_param_to_asn1() sets the AlgorithmIdentifier "parameter"
230 based on the passed cipher. This will typically include any parameters
231 and an IV. The cipher IV (if any) must be set when this call is made.
232 This call should be made before the cipher is actually "used" (before
233 any EVP_EncryptUpdate(), EVP_DecryptUpdate() calls for example). This
234 function may fail if the cipher does not have any ASN1 support.
235 EVP_CIPHER_asn1_to_param() sets the cipher parameters based on an ASN1
237 AlgorithmIdentifier "parameter". The precise effect depends on the
238 cipher In the case of RC2, for example, it will set the IV and
239 effective key length. This function should be called after the base
240 cipher type is set but before the key is set. For example
241 EVP_CipherInit() will be called with the IV and key set to NULL,
242 EVP_CIPHER_asn1_to_param() will be called and finally EVP_CipherInit()
243 again with all parameters except the key set to NULL. It is possible
244 for this function to fail if the cipher does not have any ASN1 support
245 or the parameters cannot be set (for example the RC2 effective key
246 length is not supported.
247 EVP_CIPHER_CTX_ctrl() allows various cipher specific parameters to be
249 determined and set.
250 EVP_CIPHER_CTX_rand_key() generates a random key of the appropriate
252 length based on the cipher context. The EVP_CIPHER can provide its own
253 random key generation routine to support keys of a specific form. Key
254 must point to a buffer at least as big as the value returned by
255 EVP_CIPHER_CTX_key_length().
256
258 EVP_CIPHER_CTX_new() returns a pointer to a newly created
259 EVP_CIPHER_CTX for success and NULL for failure.
260 EVP_EncryptInit_ex(), EVP_EncryptUpdate() and EVP_EncryptFinal_ex()
262 return 1 for success and 0 for failure.
263 EVP_DecryptInit_ex() and EVP_DecryptUpdate() return 1 for success and 0
265 for failure. EVP_DecryptFinal_ex() returns 0 if the decrypt failed or
266 1 for success.
267 EVP_CipherInit_ex() and EVP_CipherUpdate() return 1 for success and 0
269 for failure. EVP_CipherFinal_ex() returns 0 for a decryption failure
270 or 1 for success.
271 EVP_CIPHER_CTX_reset() returns 1 for success and 0 for failure.
273 EVP_get_cipherbyname(), EVP_get_cipherbynid() and EVP_get_cipherbyobj()
275 return an EVP_CIPHER structure or NULL on error.
276 EVP_CIPHER_nid() and EVP_CIPHER_CTX_nid() return a NID.
278 EVP_CIPHER_block_size() and EVP_CIPHER_CTX_block_size() return the
280 block size.
281 EVP_CIPHER_key_length() and EVP_CIPHER_CTX_key_length() return the key
283 length.
284 EVP_CIPHER_CTX_set_padding() always returns 1.
286 EVP_CIPHER_iv_length() and EVP_CIPHER_CTX_iv_length() return the IV
288 length or zero if the cipher does not use an IV.
289 EVP_CIPHER_type() and EVP_CIPHER_CTX_type() return the NID of the
291 cipher's OBJECT IDENTIFIER or NID_undef if it has no defined OBJECT
292 IDENTIFIER.
293 EVP_CIPHER_CTX_cipher() returns an EVP_CIPHER structure.
295 EVP_CIPHER_param_to_asn1() and EVP_CIPHER_asn1_to_param() return
297 greater than zero for success and zero or a negative number on failure.
298 EVP_CIPHER_CTX_rand_key() returns 1 for success.
300
302 All algorithms have a fixed key length unless otherwise stated.
303 Refer to "SEE ALSO" for the full list of ciphers available through the
305 EVP interface.
306 EVP_enc_null()
308 Null cipher: does nothing.
309
311 The EVP interface for Authenticated Encryption with Associated Data
312 (AEAD) modes are subtly altered and several additional ctrl operations
313 are supported depending on the mode specified.
314 To specify additional authenticated data (AAD), a call to
316 EVP_CipherUpdate(), EVP_EncryptUpdate() or EVP_DecryptUpdate() should
317 be made with the output parameter out set to NULL.
318 When decrypting, the return value of EVP_DecryptFinal() or
320 EVP_CipherFinal() indicates whether the operation was successful. If it
321 does not indicate success, the authentication operation has failed and
322 any output data MUST NOT be used as it is corrupted.
323 GCM and OCB Modes
325 The following ctrls are supported in GCM and OCB modes.
326 EVP_CIPHER_CTX_ctrl(ctx, EVP_CTRL_AEAD_SET_IVLEN, ivlen, NULL)
328 Sets the IV length. This call can only be made before specifying an
329 IV. If not called a default IV length is used.
330 For GCM AES and OCB AES the default is 12 (i.e. 96 bits). For OCB
332 mode the maximum is 15.
333 EVP_CIPHER_CTX_ctrl(ctx, EVP_CTRL_AEAD_GET_TAG, taglen, tag)
335 Writes "taglen" bytes of the tag value to the buffer indicated by
336 "tag". This call can only be made when encrypting data and after
337 all data has been processed (e.g. after an EVP_EncryptFinal()
338 call).
339 For OCB, "taglen" must either be 16 or the value previously set via
341 EVP_CTRL_AEAD_SET_TAG.
342 EVP_CIPHER_CTX_ctrl(ctx, EVP_CTRL_AEAD_SET_TAG, taglen, tag)
344 When decrypting, this call sets the expected tag to "taglen" bytes
345 from "tag". "taglen" must be between 1 and 16 inclusive. The tag
346 must be set prior to any call to EVP_DecryptFinal() or
347 EVP_DecryptFinal_ex().
348 For GCM, this call is only valid when decrypting data.
350 For OCB, this call is valid when decrypting data to set the
352 expected tag, and when encrypting to set the desired tag length.
353 In OCB mode, calling this when encrypting with "tag" set to "NULL"
355 sets the tag length. The tag length can only be set before
356 specifying an IV. If this is not called prior to setting the IV
357 during encryption, then a default tag length is used.
358 For OCB AES, the default tag length is 16 (i.e. 128 bits). It is
360 also the maximum tag length for OCB.
361 CCM Mode
363 The EVP interface for CCM mode is similar to that of the GCM mode but
364 with a few additional requirements and different ctrl values.
365 For CCM mode, the total plaintext or ciphertext length MUST be passed
367 to EVP_CipherUpdate(), EVP_EncryptUpdate() or EVP_DecryptUpdate() with
368 the output and input parameters (in and out) set to NULL and the length
369 passed in the inl parameter.
370 The following ctrls are supported in CCM mode.
372 EVP_CIPHER_CTX_ctrl(ctx, EVP_CTRL_AEAD_SET_TAG, taglen, tag)
374 This call is made to set the expected CCM tag value when decrypting
375 or the length of the tag (with the "tag" parameter set to NULL)
376 when encrypting. The tag length is often referred to as M. If not
377 set a default value is used (12 for AES). When decrypting, the tag
378 needs to be set before passing in data to be decrypted, but as in
379 GCM and OCB mode, it can be set after passing additional
380 authenticated data (see "AEAD Interface").
381 EVP_CIPHER_CTX_ctrl(ctx, EVP_CTRL_CCM_SET_L, ivlen, NULL)
383 Sets the CCM L value. If not set a default is used (8 for AES).
384 EVP_CIPHER_CTX_ctrl(ctx, EVP_CTRL_AEAD_SET_IVLEN, ivlen, NULL)
386 Sets the CCM nonce (IV) length. This call can only be made before
387 specifying a nonce value. The nonce length is given by 15 - L so it
388 is 7 by default for AES.
389 ChaCha20-Poly1305
391 The following ctrls are supported for the ChaCha20-Poly1305 AEAD
392 algorithm.
393 EVP_CIPHER_CTX_ctrl(ctx, EVP_CTRL_AEAD_SET_IVLEN, ivlen, NULL)
395 Sets the nonce length. This call can only be made before specifying
396 the nonce. If not called a default nonce length of 12 (i.e. 96
397 bits) is used. The maximum nonce length is 12 bytes (i.e. 96-bits).
398 If a nonce of less than 12 bytes is set then the nonce is
399 automatically padded with leading 0 bytes to make it 12 bytes in
400 length.
401 EVP_CIPHER_CTX_ctrl(ctx, EVP_CTRL_AEAD_GET_TAG, taglen, tag)
403 Writes "taglen" bytes of the tag value to the buffer indicated by
404 "tag". This call can only be made when encrypting data and after
405 all data has been processed (e.g. after an EVP_EncryptFinal()
406 call).
407 "taglen" specified here must be 16 (POLY1305_BLOCK_SIZE, i.e.
409 128-bits) or less.
410 EVP_CIPHER_CTX_ctrl(ctx, EVP_CTRL_AEAD_SET_TAG, taglen, tag)
412 Sets the expected tag to "taglen" bytes from "tag". The tag length
413 can only be set before specifying an IV. "taglen" must be between
414 1 and 16 (POLY1305_BLOCK_SIZE) inclusive. This call is only valid
415 when decrypting data.
416
418 Where possible the EVP interface to symmetric ciphers should be used in
419 preference to the low-level interfaces. This is because the code then
420 becomes transparent to the cipher used and much more flexible.
421 Additionally, the EVP interface will ensure the use of platform
422 specific cryptographic acceleration such as AES-NI (the low-level
423 interfaces do not provide the guarantee).
424 PKCS padding works by adding n padding bytes of value n to make the
426 total length of the encrypted data a multiple of the block size.
427 Padding is always added so if the data is already a multiple of the
428 block size n will equal the block size. For example if the block size
429 is 8 and 11 bytes are to be encrypted then 5 padding bytes of value 5
430 will be added.
431 When decrypting the final block is checked to see if it has the correct
433 form.
434 Although the decryption operation can produce an error if padding is
436 enabled, it is not a strong test that the input data or key is correct.
437 A random block has better than 1 in 256 chance of being of the correct
438 format and problems with the input data earlier on will not produce a
439 final decrypt error.
440 If padding is disabled then the decryption operation will always
442 succeed if the total amount of data decrypted is a multiple of the
443 block size.
444 The functions EVP_EncryptInit(), EVP_EncryptFinal(), EVP_DecryptInit(),
446 EVP_CipherInit() and EVP_CipherFinal() are obsolete but are retained
447 for compatibility with existing code. New code should use
448 EVP_EncryptInit_ex(), EVP_EncryptFinal_ex(), EVP_DecryptInit_ex(),
449 EVP_DecryptFinal_ex(), EVP_CipherInit_ex() and EVP_CipherFinal_ex()
450 because they can reuse an existing context without allocating and
451 freeing it up on each call.
452 There are some differences between functions EVP_CipherInit() and
454 EVP_CipherInit_ex(), significant in some circumstances.
455 EVP_CipherInit() fills the passed context object with zeros. As a
456 consequence, EVP_CipherInit() does not allow step-by-step
457 initialization of the ctx when the key and iv are passed in separate
458 calls. It also means that the flags set for the CTX are removed, and it
459 is especially important for the EVP_CIPHER_CTX_FLAG_WRAP_ALLOW flag
460 treated specially in EVP_CipherInit_ex().
461 EVP_get_cipherbynid(), and EVP_get_cipherbyobj() are implemented as
463 macros.
464
466 EVP_MAX_KEY_LENGTH and EVP_MAX_IV_LENGTH only refer to the internal
467 ciphers with default key lengths. If custom ciphers exceed these values
468 the results are unpredictable. This is because it has become standard
469 practice to define a generic key as a fixed unsigned char array
470 containing EVP_MAX_KEY_LENGTH bytes.
471 The ASN1 code is incomplete (and sometimes inaccurate) it has only been
473 tested for certain common S/MIME ciphers (RC2, DES, triple DES) in CBC
474 mode.
475
477 Encrypt a string using IDEA:
478 int do_crypt(char *outfile)
480 {
481 unsigned char outbuf[1024];
482 int outlen, tmplen;
483 /*
484 * Bogus key and IV: we'd normally set these from
485 * another source.
486 */
487 unsigned char key[] = {0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15};
488 unsigned char iv[] = {1,2,3,4,5,6,7,8};
489 char intext[] = "Some Crypto Text";
490 EVP_CIPHER_CTX *ctx;
491 FILE *out;
492 ctx = EVP_CIPHER_CTX_new();
494 EVP_EncryptInit_ex(ctx, EVP_idea_cbc(), NULL, key, iv);
495 if (!EVP_EncryptUpdate(ctx, outbuf, &outlen, intext, strlen(intext))) {
497 /* Error */
498 EVP_CIPHER_CTX_free(ctx);
499 return 0;
500 }
501 /*
502 * Buffer passed to EVP_EncryptFinal() must be after data just
503 * encrypted to avoid overwriting it.
504 */
505 if (!EVP_EncryptFinal_ex(ctx, outbuf + outlen, &tmplen)) {
506 /* Error */
507 EVP_CIPHER_CTX_free(ctx);
508 return 0;
509 }
510 outlen += tmplen;
511 EVP_CIPHER_CTX_free(ctx);
512 /*
513 * Need binary mode for fopen because encrypted data is
514 * binary data. Also cannot use strlen() on it because
515 * it won't be NUL terminated and may contain embedded
516 * NULs.
517 */
518 out = fopen(outfile, "wb");
519 if (out == NULL) {
520 /* Error */
521 return 0;
522 }
523 fwrite(outbuf, 1, outlen, out);
524 fclose(out);
525 return 1;
526 }
527 The ciphertext from the above example can be decrypted using the
529 openssl utility with the command line (shown on two lines for clarity):
530 openssl idea -d \
532 -K 000102030405060708090A0B0C0D0E0F -iv 0102030405060708 <filename
533 General encryption and decryption function example using FILE I/O and
535 AES128 with a 128-bit key:
536 int do_crypt(FILE *in, FILE *out, int do_encrypt)
538 {
539 /* Allow enough space in output buffer for additional block */
540 unsigned char inbuf[1024], outbuf[1024 + EVP_MAX_BLOCK_LENGTH];
541 int inlen, outlen;
542 EVP_CIPHER_CTX *ctx;
543 /*
544 * Bogus key and IV: we'd normally set these from
545 * another source.
546 */
547 unsigned char key[] = "0123456789abcdeF";
548 unsigned char iv[] = "1234567887654321";
549 /* Don't set key or IV right away; we want to check lengths */
551 ctx = EVP_CIPHER_CTX_new();
552 EVP_CipherInit_ex(ctx, EVP_aes_128_cbc(), NULL, NULL, NULL,
553 do_encrypt);
554 OPENSSL_assert(EVP_CIPHER_CTX_key_length(ctx) == 16);
555 OPENSSL_assert(EVP_CIPHER_CTX_iv_length(ctx) == 16);
556 /* Now we can set key and IV */
558 EVP_CipherInit_ex(ctx, NULL, NULL, key, iv, do_encrypt);
559 for (;;) {
561 inlen = fread(inbuf, 1, 1024, in);
562 if (inlen <= 0)
563 break;
564 if (!EVP_CipherUpdate(ctx, outbuf, &outlen, inbuf, inlen)) {
565 /* Error */
566 EVP_CIPHER_CTX_free(ctx);
567 return 0;
568 }
569 fwrite(outbuf, 1, outlen, out);
570 }
571 if (!EVP_CipherFinal_ex(ctx, outbuf, &outlen)) {
572 /* Error */
573 EVP_CIPHER_CTX_free(ctx);
574 return 0;
575 }
576 fwrite(outbuf, 1, outlen, out);
577 EVP_CIPHER_CTX_free(ctx);
579 return 1;
580 }
581
583 evp(7)
584 Supported ciphers are listed in:
586 EVP_aes(3), EVP_aria(3), EVP_bf(3), EVP_camellia(3), EVP_cast5(3),
588 EVP_chacha20(3), EVP_des(3), EVP_desx(3), EVP_idea(3), EVP_rc2(3),
589 EVP_rc4(3), EVP_rc5(3), EVP_seed(3), EVP_sm4(3)
590
592 Support for OCB mode was added in OpenSSL 1.1.0.
593 EVP_CIPHER_CTX was made opaque in OpenSSL 1.1.0. As a result,
595 EVP_CIPHER_CTX_reset() appeared and EVP_CIPHER_CTX_cleanup()
596 disappeared. EVP_CIPHER_CTX_init() remains as an alias for
597 EVP_CIPHER_CTX_reset().
598
600 Copyright 2000-2021 The OpenSSL Project Authors. All Rights Reserved.
601 Licensed under the OpenSSL license (the "License"). You may not use
603 this file except in compliance with the License. You can obtain a copy
604 in the file LICENSE in the source distribution or at
605 <https://www.openssl.org/source/license.html>.
6061.1.1q 2022-07-07 EVP_ENCRYPTINIT(3)