5 EVP_CIPHER_CTX_new, EVP_CIPHER_CTX_reset, EVP_CIPHER_CTX_free,
6 EVP_EncryptInit_ex, EVP_EncryptUpdate, EVP_EncryptFinal_ex,
7 EVP_DecryptInit_ex, EVP_DecryptUpdate, EVP_DecryptFinal_ex,
8 EVP_CipherInit_ex, EVP_CipherUpdate, EVP_CipherFinal_ex,
9 EVP_CIPHER_CTX_set_key_length, EVP_CIPHER_CTX_ctrl, EVP_EncryptInit,
10 EVP_EncryptFinal, EVP_DecryptInit, EVP_DecryptFinal,
11 EVP_CipherInit, EVP_CipherFinal, EVP_get_cipherbyname,
12 EVP_get_cipherbynid, EVP_get_cipherbyobj, EVP_CIPHER_nid,
13 EVP_CIPHER_block_size, EVP_CIPHER_key_length, EVP_CIPHER_iv_length,
14 EVP_CIPHER_flags, EVP_CIPHER_mode, EVP_CIPHER_type, EVP_CIPHER_CTX_cipher,
15 EVP_CIPHER_CTX_nid, EVP_CIPHER_CTX_block_size, EVP_CIPHER_CTX_key_length,
16 EVP_CIPHER_CTX_iv_length, EVP_CIPHER_CTX_get_app_data,
17 EVP_CIPHER_CTX_set_app_data, EVP_CIPHER_CTX_type, EVP_CIPHER_CTX_flags,
18 EVP_CIPHER_CTX_mode, EVP_CIPHER_param_to_asn1, EVP_CIPHER_asn1_to_param,
19 EVP_CIPHER_CTX_set_padding, EVP_enc_null, EVP_des_cbc, EVP_des_ecb,
20 EVP_des_cfb, EVP_des_ofb, EVP_des_ede_cbc, EVP_des_ede, EVP_des_ede_ofb,
21 EVP_des_ede_cfb, EVP_des_ede3_cbc, EVP_des_ede3, EVP_des_ede3_ofb,
22 EVP_des_ede3_cfb, EVP_desx_cbc, EVP_rc4, EVP_rc4_40, EVP_idea_cbc,
23 EVP_idea_ecb, EVP_idea_cfb, EVP_idea_ofb, EVP_rc2_cbc,
24 EVP_rc2_ecb, EVP_rc2_cfb, EVP_rc2_ofb, EVP_rc2_40_cbc, EVP_rc2_64_cbc,
25 EVP_bf_cbc, EVP_bf_ecb, EVP_bf_cfb, EVP_bf_ofb, EVP_cast5_cbc,
26 EVP_cast5_ecb, EVP_cast5_cfb, EVP_cast5_ofb, EVP_rc5_32_12_16_cbc,
27 EVP_rc5_32_12_16_ecb, EVP_rc5_32_12_16_cfb, EVP_rc5_32_12_16_ofb,
28 EVP_aes_128_cbc, EVP_aes_128_ecb, EVP_aes_128_cfb, EVP_aes_128_ofb,
29 EVP_aes_192_cbc, EVP_aes_192_ecb, EVP_aes_192_cfb, EVP_aes_192_ofb,
30 EVP_aes_256_cbc, EVP_aes_256_ecb, EVP_aes_256_cfb, EVP_aes_256_ofb,
31 EVP_aes_128_gcm, EVP_aes_192_gcm, EVP_aes_256_gcm,
32 EVP_aes_128_ccm, EVP_aes_192_ccm, EVP_aes_256_ccm - EVP cipher routines
36 #include <openssl/evp.h>
38 EVP_CIPHER_CTX *EVP_CIPHER_CTX_new(void);
39 int EVP_CIPHER_CTX_reset(EVP_CIPHER_CTX *ctx);
40 void EVP_CIPHER_CTX_free(EVP_CIPHER_CTX *ctx);
42 int EVP_EncryptInit_ex(EVP_CIPHER_CTX *ctx, const EVP_CIPHER *type,
43 ENGINE *impl, unsigned char *key, unsigned char *iv);
44 int EVP_EncryptUpdate(EVP_CIPHER_CTX *ctx, unsigned char *out,
45 int *outl, unsigned char *in, int inl);
46 int EVP_EncryptFinal_ex(EVP_CIPHER_CTX *ctx, unsigned char *out,
49 int EVP_DecryptInit_ex(EVP_CIPHER_CTX *ctx, const EVP_CIPHER *type,
50 ENGINE *impl, unsigned char *key, unsigned char *iv);
51 int EVP_DecryptUpdate(EVP_CIPHER_CTX *ctx, unsigned char *out,
52 int *outl, unsigned char *in, int inl);
53 int EVP_DecryptFinal_ex(EVP_CIPHER_CTX *ctx, unsigned char *outm,
56 int EVP_CipherInit_ex(EVP_CIPHER_CTX *ctx, const EVP_CIPHER *type,
57 ENGINE *impl, unsigned char *key, unsigned char *iv, int enc);
58 int EVP_CipherUpdate(EVP_CIPHER_CTX *ctx, unsigned char *out,
59 int *outl, unsigned char *in, int inl);
60 int EVP_CipherFinal_ex(EVP_CIPHER_CTX *ctx, unsigned char *outm,
63 int EVP_EncryptInit(EVP_CIPHER_CTX *ctx, const EVP_CIPHER *type,
64 unsigned char *key, unsigned char *iv);
65 int EVP_EncryptFinal(EVP_CIPHER_CTX *ctx, unsigned char *out,
68 int EVP_DecryptInit(EVP_CIPHER_CTX *ctx, const EVP_CIPHER *type,
69 unsigned char *key, unsigned char *iv);
70 int EVP_DecryptFinal(EVP_CIPHER_CTX *ctx, unsigned char *outm,
73 int EVP_CipherInit(EVP_CIPHER_CTX *ctx, const EVP_CIPHER *type,
74 unsigned char *key, unsigned char *iv, int enc);
75 int EVP_CipherFinal(EVP_CIPHER_CTX *ctx, unsigned char *outm,
78 int EVP_CIPHER_CTX_set_padding(EVP_CIPHER_CTX *x, int padding);
79 int EVP_CIPHER_CTX_set_key_length(EVP_CIPHER_CTX *x, int keylen);
80 int EVP_CIPHER_CTX_ctrl(EVP_CIPHER_CTX *ctx, int type, int arg, void *ptr);
82 const EVP_CIPHER *EVP_get_cipherbyname(const char *name);
83 #define EVP_get_cipherbynid(a) EVP_get_cipherbyname(OBJ_nid2sn(a))
84 #define EVP_get_cipherbyobj(a) EVP_get_cipherbynid(OBJ_obj2nid(a))
86 #define EVP_CIPHER_nid(e) ((e)->nid)
87 #define EVP_CIPHER_block_size(e) ((e)->block_size)
88 #define EVP_CIPHER_key_length(e) ((e)->key_len)
89 #define EVP_CIPHER_iv_length(e) ((e)->iv_len)
90 #define EVP_CIPHER_flags(e) ((e)->flags)
91 #define EVP_CIPHER_mode(e) ((e)->flags) & EVP_CIPH_MODE)
92 int EVP_CIPHER_type(const EVP_CIPHER *ctx);
94 const EVP_CIPHER *EVP_CIPHER_CTX_cipher(const EVP_CIPHER_CTX *ctx);
95 int EVP_CIPHER_CTX_nid(const EVP_CIPHER_CTX *ctx);
96 int EVP_CIPHER_CTX_block_size(const EVP_CIPHER_CTX *ctx);
97 int EVP_CIPHER_CTX_key_length(const EVP_CIPHER_CTX *ctx);
98 int EVP_CIPHER_CTX_iv_length(const EVP_CIPHER_CTX *ctx);
99 void *EVP_CIPHER_CTX_get_app_data(const EVP_CIPHER_CTX *ctx);
100 void EVP_CIPHER_CTX_set_app_data(const EVP_CIPHER_CTX *ctx, void *data);
101 int EVP_CIPHER_CTX_type(const EVP_CIPHER_CTX *ctx);
102 void EVP_CIPHER_CTX_set_flags(const EVP_CIPHER_CTX *ctx, int flags);
103 void EVP_CIPHER_CTX_clear_flags(const EVP_CIPHER_CTX *ctx, int flags);
104 int EVP_CIPHER_CTX_test_flags(const EVP_CIPHER_CTX *ctx, int flags);
105 int EVP_CIPHER_CTX_mode(const EVP_CIPHER_CTX *ctx);
107 int EVP_CIPHER_param_to_asn1(EVP_CIPHER_CTX *c, ASN1_TYPE *type);
108 int EVP_CIPHER_asn1_to_param(EVP_CIPHER_CTX *c, ASN1_TYPE *type);
112 The EVP cipher routines are a high level interface to certain
115 EVP_CIPHER_CTX_new() creates a cipher context.
117 EVP_CIPHER_CTX_free() clears all information from a cipher context
118 and free up any allocated memory associate with it, including B<ctx>
119 itself. This function should be called after all operations using a
120 cipher are complete so sensitive information does not remain in
123 EVP_EncryptInit_ex() sets up cipher context B<ctx> for encryption
124 with cipher B<type> from ENGINE B<impl>. B<ctx> must be created
125 before calling this function. B<type> is normally supplied
126 by a function such as EVP_aes_256_cbc(). If B<impl> is NULL then the
127 default implementation is used. B<key> is the symmetric key to use
128 and B<iv> is the IV to use (if necessary), the actual number of bytes
129 used for the key and IV depends on the cipher. It is possible to set
130 all parameters to NULL except B<type> in an initial call and supply
131 the remaining parameters in subsequent calls, all of which have B<type>
132 set to NULL. This is done when the default cipher parameters are not
135 EVP_EncryptUpdate() encrypts B<inl> bytes from the buffer B<in> and
136 writes the encrypted version to B<out>. This function can be called
137 multiple times to encrypt successive blocks of data. The amount
138 of data written depends on the block alignment of the encrypted data:
139 as a result the amount of data written may be anything from zero bytes
140 to (inl + cipher_block_size - 1) so B<out> should contain sufficient
141 room. The actual number of bytes written is placed in B<outl>.
143 If padding is enabled (the default) then EVP_EncryptFinal_ex() encrypts
144 the "final" data, that is any data that remains in a partial block.
145 It uses standard block padding (aka PKCS padding) as described in
146 the NOTES section, below. The encrypted
147 final data is written to B<out> which should have sufficient space for
148 one cipher block. The number of bytes written is placed in B<outl>. After
149 this function is called the encryption operation is finished and no further
150 calls to EVP_EncryptUpdate() should be made.
152 If padding is disabled then EVP_EncryptFinal_ex() will not encrypt any more
153 data and it will return an error if any data remains in a partial block:
154 that is if the total data length is not a multiple of the block size.
156 EVP_DecryptInit_ex(), EVP_DecryptUpdate() and EVP_DecryptFinal_ex() are the
157 corresponding decryption operations. EVP_DecryptFinal() will return an
158 error code if padding is enabled and the final block is not correctly
159 formatted. The parameters and restrictions are identical to the encryption
160 operations except that if padding is enabled the decrypted data buffer B<out>
161 passed to EVP_DecryptUpdate() should have sufficient room for
162 (B<inl> + cipher_block_size) bytes unless the cipher block size is 1 in
163 which case B<inl> bytes is sufficient.
165 EVP_CipherInit_ex(), EVP_CipherUpdate() and EVP_CipherFinal_ex() are
166 functions that can be used for decryption or encryption. The operation
167 performed depends on the value of the B<enc> parameter. It should be set
168 to 1 for encryption, 0 for decryption and -1 to leave the value unchanged
169 (the actual value of 'enc' being supplied in a previous call).
171 EVP_CIPHER_CTX_reset() clears all information from a cipher context
172 and free up any allocated memory associate with it, except the B<ctx>
173 itself. This function should be called anytime B<ctx> is to be reused
174 for another EVP_CipherInit() / EVP_CipherUpdate() / EVP_CipherFinal()
177 EVP_EncryptInit(), EVP_DecryptInit() and EVP_CipherInit() behave in a
178 similar way to EVP_EncryptInit_ex(), EVP_DecryptInit_ex() and
179 EVP_CipherInit_ex() except the B<ctx> parameter does not need to be
180 initialized and they always use the default cipher implementation.
182 EVP_EncryptFinal(), EVP_DecryptFinal() and EVP_CipherFinal() are
183 identical to EVP_EncryptFinal_ex(), EVP_DecryptFinal_ex() and
184 EVP_CipherFinal_ex(). In previous releases they also cleaned up
185 the B<ctx>, but this is no longer done and EVP_CIPHER_CTX_clean()
186 must be called to free any context resources.
188 EVP_get_cipherbyname(), EVP_get_cipherbynid() and EVP_get_cipherbyobj()
189 return an EVP_CIPHER structure when passed a cipher name, a NID or an
190 ASN1_OBJECT structure.
192 EVP_CIPHER_nid() and EVP_CIPHER_CTX_nid() return the NID of a cipher when
193 passed an B<EVP_CIPHER> or B<EVP_CIPHER_CTX> structure. The actual NID
194 value is an internal value which may not have a corresponding OBJECT
197 EVP_CIPHER_CTX_set_padding() enables or disables padding. This
198 function should be called after the context is set up for encryption
199 or decryption with EVP_EncryptInit_ex(), EVP_DecryptInit_ex() or
200 EVP_CipherInit_ex(). By default encryption operations are padded using
201 standard block padding and the padding is checked and removed when
202 decrypting. If the B<pad> parameter is zero then no padding is
203 performed, the total amount of data encrypted or decrypted must then
204 be a multiple of the block size or an error will occur.
206 EVP_CIPHER_key_length() and EVP_CIPHER_CTX_key_length() return the key
207 length of a cipher when passed an B<EVP_CIPHER> or B<EVP_CIPHER_CTX>
208 structure. The constant B<EVP_MAX_KEY_LENGTH> is the maximum key length
209 for all ciphers. Note: although EVP_CIPHER_key_length() is fixed for a
210 given cipher, the value of EVP_CIPHER_CTX_key_length() may be different
211 for variable key length ciphers.
213 EVP_CIPHER_CTX_set_key_length() sets the key length of the cipher ctx.
214 If the cipher is a fixed length cipher then attempting to set the key
215 length to any value other than the fixed value is an error.
217 EVP_CIPHER_iv_length() and EVP_CIPHER_CTX_iv_length() return the IV
218 length of a cipher when passed an B<EVP_CIPHER> or B<EVP_CIPHER_CTX>.
219 It will return zero if the cipher does not use an IV. The constant
220 B<EVP_MAX_IV_LENGTH> is the maximum IV length for all ciphers.
222 EVP_CIPHER_block_size() and EVP_CIPHER_CTX_block_size() return the block
223 size of a cipher when passed an B<EVP_CIPHER> or B<EVP_CIPHER_CTX>
224 structure. The constant B<EVP_MAX_IV_LENGTH> is also the maximum block
225 length for all ciphers.
227 EVP_CIPHER_type() and EVP_CIPHER_CTX_type() return the type of the passed
228 cipher or context. This "type" is the actual NID of the cipher OBJECT
229 IDENTIFIER as such it ignores the cipher parameters and 40 bit RC2 and
230 128 bit RC2 have the same NID. If the cipher does not have an object
231 identifier or does not have ASN1 support this function will return
234 EVP_CIPHER_CTX_cipher() returns the B<EVP_CIPHER> structure when passed
235 an B<EVP_CIPHER_CTX> structure.
237 EVP_CIPHER_mode() and EVP_CIPHER_CTX_mode() return the block cipher mode:
238 EVP_CIPH_ECB_MODE, EVP_CIPH_CBC_MODE, EVP_CIPH_CFB_MODE or
239 EVP_CIPH_OFB_MODE. If the cipher is a stream cipher then
240 EVP_CIPH_STREAM_CIPHER is returned.
242 EVP_CIPHER_param_to_asn1() sets the AlgorithmIdentifier "parameter" based
243 on the passed cipher. This will typically include any parameters and an
244 IV. The cipher IV (if any) must be set when this call is made. This call
245 should be made before the cipher is actually "used" (before any
246 EVP_EncryptUpdate(), EVP_DecryptUpdate() calls for example). This function
247 may fail if the cipher does not have any ASN1 support.
249 EVP_CIPHER_asn1_to_param() sets the cipher parameters based on an ASN1
250 AlgorithmIdentifier "parameter". The precise effect depends on the cipher
251 In the case of RC2, for example, it will set the IV and effective key length.
252 This function should be called after the base cipher type is set but before
253 the key is set. For example EVP_CipherInit() will be called with the IV and
254 key set to NULL, EVP_CIPHER_asn1_to_param() will be called and finally
255 EVP_CipherInit() again with all parameters except the key set to NULL. It is
256 possible for this function to fail if the cipher does not have any ASN1 support
257 or the parameters cannot be set (for example the RC2 effective key length
260 EVP_CIPHER_CTX_ctrl() allows various cipher specific parameters to be determined
265 EVP_CIPHER_CTX_new() returns a pointer to a newly created
266 B<EVP_CIPHER_CTX> for success and B<NULL> for failure.
268 EVP_EncryptInit_ex(), EVP_EncryptUpdate() and EVP_EncryptFinal_ex()
269 return 1 for success and 0 for failure.
271 EVP_DecryptInit_ex() and EVP_DecryptUpdate() return 1 for success and 0 for failure.
272 EVP_DecryptFinal_ex() returns 0 if the decrypt failed or 1 for success.
274 EVP_CipherInit_ex() and EVP_CipherUpdate() return 1 for success and 0 for failure.
275 EVP_CipherFinal_ex() returns 0 for a decryption failure or 1 for success.
277 EVP_CIPHER_CTX_reset() returns 1 for success and 0 for failure.
279 EVP_get_cipherbyname(), EVP_get_cipherbynid() and EVP_get_cipherbyobj()
280 return an B<EVP_CIPHER> structure or NULL on error.
282 EVP_CIPHER_nid() and EVP_CIPHER_CTX_nid() return a NID.
284 EVP_CIPHER_block_size() and EVP_CIPHER_CTX_block_size() return the block
287 EVP_CIPHER_key_length() and EVP_CIPHER_CTX_key_length() return the key
290 EVP_CIPHER_CTX_set_padding() always returns 1.
292 EVP_CIPHER_iv_length() and EVP_CIPHER_CTX_iv_length() return the IV
293 length or zero if the cipher does not use an IV.
295 EVP_CIPHER_type() and EVP_CIPHER_CTX_type() return the NID of the cipher's
296 OBJECT IDENTIFIER or NID_undef if it has no defined OBJECT IDENTIFIER.
298 EVP_CIPHER_CTX_cipher() returns an B<EVP_CIPHER> structure.
300 EVP_CIPHER_param_to_asn1() and EVP_CIPHER_asn1_to_param() return greater
301 than zero for success and zero or a negative number.
303 =head1 CIPHER LISTING
305 All algorithms have a fixed key length unless otherwise stated.
311 Null cipher: does nothing.
313 =item EVP_aes_128_cbc(), EVP_aes_128_ecb(), EVP_aes_128_cfb(), EVP_aes_128_ofb()
315 AES with a 128-bit key in CBC, ECB, CFB and OFB modes respectively.
317 =item EVP_aes_192_cbc(), EVP_aes_192_ecb(), EVP_aes_192_cfb(), EVP_aes_192_ofb()
319 AES with a 192-bit key in CBC, ECB, CFB and OFB modes respectively.
321 =item EVP_aes_256_cbc(), EVP_aes_256_ecb(), EVP_aes_256_cfb(), EVP_aes_256_ofb()
323 AES with a 256-bit key in CBC, ECB, CFB and OFB modes respectively.
325 =item EVP_des_cbc(), EVP_des_ecb(), EVP_des_cfb(), EVP_des_ofb()
327 DES in CBC, ECB, CFB and OFB modes respectively.
329 =item EVP_des_ede_cbc(), EVP_des_ede(), EVP_des_ede_ofb(), EVP_des_ede_cfb()
331 Two key triple DES in CBC, ECB, CFB and OFB modes respectively.
333 =item EVP_des_ede3_cbc(), EVP_des_ede3(), EVP_des_ede3_ofb(), EVP_des_ede3_cfb()
335 Three key triple DES in CBC, ECB, CFB and OFB modes respectively.
339 DESX algorithm in CBC mode.
343 RC4 stream cipher. This is a variable key length cipher with default key length 128 bits.
347 RC4 stream cipher with 40 bit key length.
348 This is obsolete and new code should use EVP_rc4()
349 and the EVP_CIPHER_CTX_set_key_length() function.
351 =item EVP_idea_cbc() EVP_idea_ecb(), EVP_idea_cfb(), EVP_idea_ofb()
353 IDEA encryption algorithm in CBC, ECB, CFB and OFB modes respectively.
355 =item EVP_rc2_cbc(), EVP_rc2_ecb(), EVP_rc2_cfb(), EVP_rc2_ofb()
357 RC2 encryption algorithm in CBC, ECB, CFB and OFB modes respectively. This is a variable key
358 length cipher with an additional parameter called "effective key bits" or "effective key length".
359 By default both are set to 128 bits.
361 =item EVP_rc2_40_cbc(), EVP_rc2_64_cbc()
363 RC2 algorithm in CBC mode with a default key length and effective key length of 40 and 64 bits.
364 These are obsolete and new code should use EVP_rc2_cbc(), EVP_CIPHER_CTX_set_key_length() and
365 EVP_CIPHER_CTX_ctrl() to set the key length and effective key length.
367 =item EVP_bf_cbc(), EVP_bf_ecb(), EVP_bf_cfb(), EVP_bf_ofb()
369 Blowfish encryption algorithm in CBC, ECB, CFB and OFB modes respectively. This is a variable key
372 =item EVP_cast5_cbc(), EVP_cast5_ecb(), EVP_cast5_cfb(), EVP_cast5_ofb()
374 CAST encryption algorithm in CBC, ECB, CFB and OFB modes respectively. This is a variable key
377 =item EVP_rc5_32_12_16_cbc(), EVP_rc5_32_12_16_ecb(), EVP_rc5_32_12_16_cfb(), EVP_rc5_32_12_16_ofb()
379 RC5 encryption algorithm in CBC, ECB, CFB and OFB modes respectively. This is a variable key length
380 cipher with an additional "number of rounds" parameter. By default the key length is set to 128
383 =item EVP_aes_128_gcm(), EVP_aes_192_gcm(), EVP_aes_256_gcm()
385 AES Galois Counter Mode (GCM) for 128, 192 and 256 bit keys respectively.
386 These ciphers require additional control operations to function correctly: see
387 the L</GCM and OCB modes> section below for details.
389 =item EVP_aes_128_ocb(void), EVP_aes_192_ocb(void), EVP_aes_256_ocb(void)
391 Offset Codebook Mode (OCB) for 128, 192 and 256 bit keys respectively.
392 These ciphers require additional control operations to function correctly: see
393 the L</GCM and OCB modes> section below for details.
395 =item EVP_aes_128_ccm(), EVP_aes_192_ccm(), EVP_aes_256_ccm()
397 AES Counter with CBC-MAC Mode (CCM) for 128, 192 and 256 bit keys respectively.
398 These ciphers require additional control operations to function correctly: see
399 CCM mode section below for details.
403 =head1 GCM and OCB Modes
405 For GCM and OCB mode ciphers the behaviour of the EVP interface is subtly
406 altered and several additional ctrl operations are supported.
408 To specify any additional authenticated data (AAD) a call to EVP_CipherUpdate(),
409 EVP_EncryptUpdate() or EVP_DecryptUpdate() should be made with the output
410 parameter B<out> set to B<NULL>.
412 When decrypting the return value of EVP_DecryptFinal() or EVP_CipherFinal()
413 indicates if the operation was successful. If it does not indicate success
414 the authentication operation has failed and any output data B<MUST NOT>
415 be used as it is corrupted.
417 The following ctrls are supported in both GCM and OCB modes:
419 EVP_CIPHER_CTX_ctrl(ctx, EVP_CTRL_AEAD_SET_IVLEN, ivlen, NULL);
421 Sets the IV length: this call can only be made before specifying an IV. If
422 not called a default IV length is used. For GCM AES and OCB AES the default is
423 12 (i.e. 96 bits). For OCB mode the maximum is 15.
425 EVP_CIPHER_CTX_ctrl(ctx, EVP_CTRL_AEAD_GET_TAG, taglen, tag);
427 Writes B<taglen> bytes of the tag value to the buffer indicated by B<tag>.
428 This call can only be made when encrypting data and B<after> all data has been
429 processed (e.g. after an EVP_EncryptFinal() call). For OCB mode the taglen must
430 either be 16 or the value previously set via EVP_CTRL_OCB_SET_TAGLEN.
432 EVP_CIPHER_CTX_ctrl(ctx, EVP_CTRL_AEAD_SET_TAG, taglen, tag);
434 Sets the expected tag to B<taglen> bytes from B<tag>. This call is only legal
435 when decrypting data and must be made B<before> any data is processed (e.g.
436 before any EVP_DecryptUpdate() call). For OCB mode the taglen must
437 either be 16 or the value previously set via EVP_CTRL_AEAD_SET_TAG.
439 In OCB mode calling this with B<tag> set to NULL sets the tag length. The tag
440 length can only be set before specifying an IV. If not called a default tag
441 length is used. For OCB AES the default is 16 (i.e. 128 bits). This is also the
442 maximum tag length for OCB.
444 See L</EXAMPLES> below for an example of the use of GCM mode.
448 The behaviour of CCM mode ciphers is similar to GCM mode but with a few
449 additional requirements and different ctrl values.
451 Like GCM and OCB modes any additional authenticated data (AAD) is passed by calling
452 EVP_CipherUpdate(), EVP_EncryptUpdate() or EVP_DecryptUpdate() with the output
453 parameter B<out> set to B<NULL>. Additionally the total plaintext or ciphertext
454 length B<MUST> be passed to EVP_CipherUpdate(), EVP_EncryptUpdate() or
455 EVP_DecryptUpdate() with the output and input parameters (B<in> and B<out>)
456 set to B<NULL> and the length passed in the B<inl> parameter.
458 The following ctrls are supported in CCM mode:
460 EVP_CIPHER_CTX_ctrl(ctx, EVP_CTRL_AEAD_SET_TAG, taglen, tag);
462 This call is made to set the expected B<CCM> tag value when decrypting or
463 the length of the tag (with the B<tag> parameter set to NULL) when encrypting.
464 The tag length is often referred to as B<M>. If not set a default value is
467 EVP_CIPHER_CTX_ctrl(ctx, EVP_CTRL_CCM_SET_L, ivlen, NULL);
469 Sets the CCM B<L> value. If not set a default is used (8 for AES).
471 EVP_CIPHER_CTX_ctrl(ctx, EVP_CTRL_AEAD_SET_IVLEN, ivlen, NULL);
473 Sets the CCM nonce (IV) length: this call can only be made before specifying
474 an nonce value. The nonce length is given by B<15 - L> so it is 7 by default
481 Where possible the B<EVP> interface to symmetric ciphers should be used in
482 preference to the low level interfaces. This is because the code then becomes
483 transparent to the cipher used and much more flexible. Additionally, the
484 B<EVP> interface will ensure the use of platform specific cryptographic
485 acceleration such as AES-NI (the low level interfaces do not provide the
488 PKCS padding works by adding B<n> padding bytes of value B<n> to make the total
489 length of the encrypted data a multiple of the block size. Padding is always
490 added so if the data is already a multiple of the block size B<n> will equal
491 the block size. For example if the block size is 8 and 11 bytes are to be
492 encrypted then 5 padding bytes of value 5 will be added.
494 When decrypting the final block is checked to see if it has the correct form.
496 Although the decryption operation can produce an error if padding is enabled,
497 it is not a strong test that the input data or key is correct. A random block
498 has better than 1 in 256 chance of being of the correct format and problems with
499 the input data earlier on will not produce a final decrypt error.
501 If padding is disabled then the decryption operation will always succeed if
502 the total amount of data decrypted is a multiple of the block size.
504 The functions EVP_EncryptInit(), EVP_EncryptFinal(), EVP_DecryptInit(),
505 EVP_CipherInit() and EVP_CipherFinal() are obsolete but are retained for
506 compatibility with existing code. New code should use EVP_EncryptInit_ex(),
507 EVP_EncryptFinal_ex(), EVP_DecryptInit_ex(), EVP_DecryptFinal_ex(),
508 EVP_CipherInit_ex() and EVP_CipherFinal_ex() because they can reuse an
509 existing context without allocating and freeing it up on each call.
513 For RC5 the number of rounds can currently only be set to 8, 12 or 16. This is
514 a limitation of the current RC5 code rather than the EVP interface.
516 EVP_MAX_KEY_LENGTH and EVP_MAX_IV_LENGTH only refer to the internal ciphers with
517 default key lengths. If custom ciphers exceed these values the results are
518 unpredictable. This is because it has become standard practice to define a
519 generic key as a fixed unsigned char array containing EVP_MAX_KEY_LENGTH bytes.
521 The ASN1 code is incomplete (and sometimes inaccurate) it has only been tested
522 for certain common S/MIME ciphers (RC2, DES, triple DES) in CBC mode.
526 Encrypt a string using IDEA:
528 int do_crypt(char *outfile)
530 unsigned char outbuf[1024];
532 /* Bogus key and IV: we'd normally set these from
535 unsigned char key[] = {0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15};
536 unsigned char iv[] = {1,2,3,4,5,6,7,8};
537 char intext[] = "Some Crypto Text";
541 ctx = EVP_CIPHER_CTX_new();
542 EVP_EncryptInit_ex(ctx, EVP_idea_cbc(), NULL, key, iv);
544 if(!EVP_EncryptUpdate(ctx, outbuf, &outlen, intext, strlen(intext)))
549 /* Buffer passed to EVP_EncryptFinal() must be after data just
550 * encrypted to avoid overwriting it.
552 if(!EVP_EncryptFinal_ex(ctx, outbuf + outlen, &tmplen))
558 EVP_CIPHER_CTX_free(ctx);
559 /* Need binary mode for fopen because encrypted data is
560 * binary data. Also cannot use strlen() on it because
561 * it wont be null terminated and may contain embedded
564 out = fopen(outfile, "wb");
565 fwrite(outbuf, 1, outlen, out);
570 The ciphertext from the above example can be decrypted using the B<openssl>
571 utility with the command line (shown on two lines for clarity):
573 openssl idea -d <filename
574 -K 000102030405060708090A0B0C0D0E0F -iv 0102030405060708
576 General encryption and decryption function example using FILE I/O and AES128
579 int do_crypt(FILE *in, FILE *out, int do_encrypt)
581 /* Allow enough space in output buffer for additional block */
582 unsigned char inbuf[1024], outbuf[1024 + EVP_MAX_BLOCK_LENGTH];
585 /* Bogus key and IV: we'd normally set these from
588 unsigned char key[] = "0123456789abcdeF";
589 unsigned char iv[] = "1234567887654321";
591 /* Don't set key or IV right away; we want to check lengths */
592 ctx = EVP_CIPHER_CTX_new();
593 EVP_CipherInit_ex(&ctx, EVP_aes_128_cbc(), NULL, NULL, NULL,
595 OPENSSL_assert(EVP_CIPHER_CTX_key_length(ctx) == 16);
596 OPENSSL_assert(EVP_CIPHER_CTX_iv_length(ctx) == 16);
598 /* Now we can set key and IV */
599 EVP_CipherInit_ex(ctx, NULL, NULL, key, iv, do_encrypt);
603 inlen = fread(inbuf, 1, 1024, in);
604 if(inlen <= 0) break;
605 if(!EVP_CipherUpdate(ctx, outbuf, &outlen, inbuf, inlen))
608 EVP_CIPHER_CTX_free(ctx);
611 fwrite(outbuf, 1, outlen, out);
613 if(!EVP_CipherFinal_ex(ctx, outbuf, &outlen))
616 EVP_CIPHER_CTX_free(ctx);
619 fwrite(outbuf, 1, outlen, out);
621 EVP_CIPHER_CTX_free(ctx);
632 Support for OCB mode was added in OpenSSL 1.1.0
634 B<EVP_CIPHER_CTX> was made opaque in OpenSSL 1.1.0. As a result,
635 EVP_CIPHER_CTX_reset() appeared and EVP_CIPHER_CTX_cleanup()
636 disappeared. EVP_CIPHER_CTX_init() remains as an alias for
637 EVP_CIPHER_CTX_reset().