5 EVP_CIPHER_CTX_init, EVP_EncryptInit_ex, EVP_EncryptUpdate,
6 EVP_EncryptFinal_ex, EVP_DecryptInit_ex, EVP_DecryptUpdate,
7 EVP_DecryptFinal_ex, EVP_CipherInit_ex, EVP_CipherUpdate,
8 EVP_CipherFinal_ex, EVP_CIPHER_CTX_set_key_length,
9 EVP_CIPHER_CTX_ctrl, EVP_CIPHER_CTX_cleanup, 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 void EVP_CIPHER_CTX_init(EVP_CIPHER_CTX *a);
40 int EVP_EncryptInit_ex(EVP_CIPHER_CTX *ctx, const EVP_CIPHER *type,
41 ENGINE *impl, unsigned char *key, unsigned char *iv);
42 int EVP_EncryptUpdate(EVP_CIPHER_CTX *ctx, unsigned char *out,
43 int *outl, unsigned char *in, int inl);
44 int EVP_EncryptFinal_ex(EVP_CIPHER_CTX *ctx, unsigned char *out,
47 int EVP_DecryptInit_ex(EVP_CIPHER_CTX *ctx, const EVP_CIPHER *type,
48 ENGINE *impl, unsigned char *key, unsigned char *iv);
49 int EVP_DecryptUpdate(EVP_CIPHER_CTX *ctx, unsigned char *out,
50 int *outl, unsigned char *in, int inl);
51 int EVP_DecryptFinal_ex(EVP_CIPHER_CTX *ctx, unsigned char *outm,
54 int EVP_CipherInit_ex(EVP_CIPHER_CTX *ctx, const EVP_CIPHER *type,
55 ENGINE *impl, unsigned char *key, unsigned char *iv, int enc);
56 int EVP_CipherUpdate(EVP_CIPHER_CTX *ctx, unsigned char *out,
57 int *outl, unsigned char *in, int inl);
58 int EVP_CipherFinal_ex(EVP_CIPHER_CTX *ctx, unsigned char *outm,
61 int EVP_EncryptInit(EVP_CIPHER_CTX *ctx, const EVP_CIPHER *type,
62 unsigned char *key, unsigned char *iv);
63 int EVP_EncryptFinal(EVP_CIPHER_CTX *ctx, unsigned char *out,
66 int EVP_DecryptInit(EVP_CIPHER_CTX *ctx, const EVP_CIPHER *type,
67 unsigned char *key, unsigned char *iv);
68 int EVP_DecryptFinal(EVP_CIPHER_CTX *ctx, unsigned char *outm,
71 int EVP_CipherInit(EVP_CIPHER_CTX *ctx, const EVP_CIPHER *type,
72 unsigned char *key, unsigned char *iv, int enc);
73 int EVP_CipherFinal(EVP_CIPHER_CTX *ctx, unsigned char *outm,
76 int EVP_CIPHER_CTX_set_padding(EVP_CIPHER_CTX *x, int padding);
77 int EVP_CIPHER_CTX_set_key_length(EVP_CIPHER_CTX *x, int keylen);
78 int EVP_CIPHER_CTX_ctrl(EVP_CIPHER_CTX *ctx, int type, int arg, void *ptr);
79 int EVP_CIPHER_CTX_cleanup(EVP_CIPHER_CTX *a);
81 const EVP_CIPHER *EVP_get_cipherbyname(const char *name);
82 #define EVP_get_cipherbynid(a) EVP_get_cipherbyname(OBJ_nid2sn(a))
83 #define EVP_get_cipherbyobj(a) EVP_get_cipherbynid(OBJ_obj2nid(a))
85 #define EVP_CIPHER_nid(e) ((e)->nid)
86 #define EVP_CIPHER_block_size(e) ((e)->block_size)
87 #define EVP_CIPHER_key_length(e) ((e)->key_len)
88 #define EVP_CIPHER_iv_length(e) ((e)->iv_len)
89 #define EVP_CIPHER_flags(e) ((e)->flags)
90 #define EVP_CIPHER_mode(e) ((e)->flags) & EVP_CIPH_MODE)
91 int EVP_CIPHER_type(const EVP_CIPHER *ctx);
93 #define EVP_CIPHER_CTX_cipher(e) ((e)->cipher)
94 #define EVP_CIPHER_CTX_nid(e) ((e)->cipher->nid)
95 #define EVP_CIPHER_CTX_block_size(e) ((e)->cipher->block_size)
96 #define EVP_CIPHER_CTX_key_length(e) ((e)->key_len)
97 #define EVP_CIPHER_CTX_iv_length(e) ((e)->cipher->iv_len)
98 #define EVP_CIPHER_CTX_get_app_data(e) ((e)->app_data)
99 #define EVP_CIPHER_CTX_set_app_data(e,d) ((e)->app_data=(char *)(d))
100 #define EVP_CIPHER_CTX_type(c) EVP_CIPHER_type(EVP_CIPHER_CTX_cipher(c))
101 #define EVP_CIPHER_CTX_flags(e) ((e)->cipher->flags)
102 #define EVP_CIPHER_CTX_mode(e) ((e)->cipher->flags & EVP_CIPH_MODE)
104 int EVP_CIPHER_param_to_asn1(EVP_CIPHER_CTX *c, ASN1_TYPE *type);
105 int EVP_CIPHER_asn1_to_param(EVP_CIPHER_CTX *c, ASN1_TYPE *type);
109 The EVP cipher routines are a high level interface to certain
112 EVP_CIPHER_CTX_init() initializes cipher contex B<ctx>.
114 EVP_EncryptInit_ex() sets up cipher context B<ctx> for encryption
115 with cipher B<type> from ENGINE B<impl>. B<ctx> must be initialized
116 before calling this function. B<type> is normally supplied
117 by a function such as EVP_des_cbc(). If B<impl> is NULL then the
118 default implementation is used. B<key> is the symmetric key to use
119 and B<iv> is the IV to use (if necessary), the actual number of bytes
120 used for the key and IV depends on the cipher. It is possible to set
121 all parameters to NULL except B<type> in an initial call and supply
122 the remaining parameters in subsequent calls, all of which have B<type>
123 set to NULL. This is done when the default cipher parameters are not
126 EVP_EncryptUpdate() encrypts B<inl> bytes from the buffer B<in> and
127 writes the encrypted version to B<out>. This function can be called
128 multiple times to encrypt successive blocks of data. The amount
129 of data written depends on the block alignment of the encrypted data:
130 as a result the amount of data written may be anything from zero bytes
131 to (inl + cipher_block_size - 1) so B<out> should contain sufficient
132 room. The actual number of bytes written is placed in B<outl>.
134 If padding is enabled (the default) then EVP_EncryptFinal_ex() encrypts
135 the "final" data, that is any data that remains in a partial block.
136 It uses standard block padding (aka PKCS padding) as described in
137 the NOTES section, below. The encrypted
138 final data is written to B<out> which should have sufficient space for
139 one cipher block. The number of bytes written is placed in B<outl>. After
140 this function is called the encryption operation is finished and no further
141 calls to EVP_EncryptUpdate() should be made.
143 If padding is disabled then EVP_EncryptFinal_ex() will not encrypt any more
144 data and it will return an error if any data remains in a partial block:
145 that is if the total data length is not a multiple of the block size.
147 EVP_DecryptInit_ex(), EVP_DecryptUpdate() and EVP_DecryptFinal_ex() are the
148 corresponding decryption operations. EVP_DecryptFinal() will return an
149 error code if padding is enabled and the final block is not correctly
150 formatted. The parameters and restrictions are identical to the encryption
151 operations except that if padding is enabled the decrypted data buffer B<out>
152 passed to EVP_DecryptUpdate() should have sufficient room for
153 (B<inl> + cipher_block_size) bytes unless the cipher block size is 1 in
154 which case B<inl> bytes is sufficient.
156 EVP_CipherInit_ex(), EVP_CipherUpdate() and EVP_CipherFinal_ex() are
157 functions that can be used for decryption or encryption. The operation
158 performed depends on the value of the B<enc> parameter. It should be set
159 to 1 for encryption, 0 for decryption and -1 to leave the value unchanged
160 (the actual value of 'enc' being supplied in a previous call).
162 EVP_CIPHER_CTX_cleanup() clears all information from a cipher context
163 and free up any allocated memory associate with it. It should be called
164 after all operations using a cipher are complete so sensitive information
165 does not remain in memory.
167 EVP_EncryptInit(), EVP_DecryptInit() and EVP_CipherInit() behave in a
168 similar way to EVP_EncryptInit_ex(), EVP_DecryptInit_ex() and
169 EVP_CipherInit_ex() except the B<ctx> parameter does not need to be
170 initialized and they always use the default cipher implementation.
172 EVP_EncryptFinal(), EVP_DecryptFinal() and EVP_CipherFinal() are
173 identical to EVP_EncryptFinal_ex(), EVP_DecryptFinal_ex() and
174 EVP_CipherFinal_ex(). In previous releases they also cleaned up
175 the B<ctx>, but this is no longer done and EVP_CIPHER_CTX_clean()
176 must be called to free any context resources.
178 EVP_get_cipherbyname(), EVP_get_cipherbynid() and EVP_get_cipherbyobj()
179 return an EVP_CIPHER structure when passed a cipher name, a NID or an
180 ASN1_OBJECT structure.
182 EVP_CIPHER_nid() and EVP_CIPHER_CTX_nid() return the NID of a cipher when
183 passed an B<EVP_CIPHER> or B<EVP_CIPHER_CTX> structure. The actual NID
184 value is an internal value which may not have a corresponding OBJECT
187 EVP_CIPHER_CTX_set_padding() enables or disables padding. By default
188 encryption operations are padded using standard block padding and the
189 padding is checked and removed when decrypting. If the B<pad> parameter
190 is zero then no padding is performed, the total amount of data encrypted
191 or decrypted must then be a multiple of the block size or an error will
194 EVP_CIPHER_key_length() and EVP_CIPHER_CTX_key_length() return the key
195 length of a cipher when passed an B<EVP_CIPHER> or B<EVP_CIPHER_CTX>
196 structure. The constant B<EVP_MAX_KEY_LENGTH> is the maximum key length
197 for all ciphers. Note: although EVP_CIPHER_key_length() is fixed for a
198 given cipher, the value of EVP_CIPHER_CTX_key_length() may be different
199 for variable key length ciphers.
201 EVP_CIPHER_CTX_set_key_length() sets the key length of the cipher ctx.
202 If the cipher is a fixed length cipher then attempting to set the key
203 length to any value other than the fixed value is an error.
205 EVP_CIPHER_iv_length() and EVP_CIPHER_CTX_iv_length() return the IV
206 length of a cipher when passed an B<EVP_CIPHER> or B<EVP_CIPHER_CTX>.
207 It will return zero if the cipher does not use an IV. The constant
208 B<EVP_MAX_IV_LENGTH> is the maximum IV length for all ciphers.
210 EVP_CIPHER_block_size() and EVP_CIPHER_CTX_block_size() return the block
211 size of a cipher when passed an B<EVP_CIPHER> or B<EVP_CIPHER_CTX>
212 structure. The constant B<EVP_MAX_IV_LENGTH> is also the maximum block
213 length for all ciphers.
215 EVP_CIPHER_type() and EVP_CIPHER_CTX_type() return the type of the passed
216 cipher or context. This "type" is the actual NID of the cipher OBJECT
217 IDENTIFIER as such it ignores the cipher parameters and 40 bit RC2 and
218 128 bit RC2 have the same NID. If the cipher does not have an object
219 identifier or does not have ASN1 support this function will return
222 EVP_CIPHER_CTX_cipher() returns the B<EVP_CIPHER> structure when passed
223 an B<EVP_CIPHER_CTX> structure.
225 EVP_CIPHER_mode() and EVP_CIPHER_CTX_mode() return the block cipher mode:
226 EVP_CIPH_ECB_MODE, EVP_CIPH_CBC_MODE, EVP_CIPH_CFB_MODE or
227 EVP_CIPH_OFB_MODE. If the cipher is a stream cipher then
228 EVP_CIPH_STREAM_CIPHER is returned.
230 EVP_CIPHER_param_to_asn1() sets the AlgorithmIdentifier "parameter" based
231 on the passed cipher. This will typically include any parameters and an
232 IV. The cipher IV (if any) must be set when this call is made. This call
233 should be made before the cipher is actually "used" (before any
234 EVP_EncryptUpdate(), EVP_DecryptUpdate() calls for example). This function
235 may fail if the cipher does not have any ASN1 support.
237 EVP_CIPHER_asn1_to_param() sets the cipher parameters based on an ASN1
238 AlgorithmIdentifier "parameter". The precise effect depends on the cipher
239 In the case of RC2, for example, it will set the IV and effective key length.
240 This function should be called after the base cipher type is set but before
241 the key is set. For example EVP_CipherInit() will be called with the IV and
242 key set to NULL, EVP_CIPHER_asn1_to_param() will be called and finally
243 EVP_CipherInit() again with all parameters except the key set to NULL. It is
244 possible 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 length
248 EVP_CIPHER_CTX_ctrl() allows various cipher specific parameters to be determined
253 EVP_EncryptInit_ex(), EVP_EncryptUpdate() and EVP_EncryptFinal_ex()
254 return 1 for success and 0 for failure.
256 EVP_DecryptInit_ex() and EVP_DecryptUpdate() return 1 for success and 0 for failure.
257 EVP_DecryptFinal_ex() returns 0 if the decrypt failed or 1 for success.
259 EVP_CipherInit_ex() and EVP_CipherUpdate() return 1 for success and 0 for failure.
260 EVP_CipherFinal_ex() returns 0 for a decryption failure or 1 for success.
262 EVP_CIPHER_CTX_cleanup() returns 1 for success and 0 for failure.
264 EVP_get_cipherbyname(), EVP_get_cipherbynid() and EVP_get_cipherbyobj()
265 return an B<EVP_CIPHER> structure or NULL on error.
267 EVP_CIPHER_nid() and EVP_CIPHER_CTX_nid() return a NID.
269 EVP_CIPHER_block_size() and EVP_CIPHER_CTX_block_size() return the block
272 EVP_CIPHER_key_length() and EVP_CIPHER_CTX_key_length() return the key
275 EVP_CIPHER_CTX_set_padding() always returns 1.
277 EVP_CIPHER_iv_length() and EVP_CIPHER_CTX_iv_length() return the IV
278 length or zero if the cipher does not use an IV.
280 EVP_CIPHER_type() and EVP_CIPHER_CTX_type() return the NID of the cipher's
281 OBJECT IDENTIFIER or NID_undef if it has no defined OBJECT IDENTIFIER.
283 EVP_CIPHER_CTX_cipher() returns an B<EVP_CIPHER> structure.
285 EVP_CIPHER_param_to_asn1() and EVP_CIPHER_asn1_to_param() return 1 for
286 success or zero for failure.
288 =head1 CIPHER LISTING
290 All algorithms have a fixed key length unless otherwise stated.
296 Null cipher: does nothing.
298 =item EVP_aes_128_cbc(), EVP_aes_128_ecb(), EVP_aes_128_cfb(), EVP_aes_128_ofb()
300 AES with a 128-bit key in CBC, ECB, CFB and OFB modes respectively.
302 =item EVP_aes_192_cbc(), EVP_aes_192_ecb(), EVP_aes_192_cfb(), EVP_aes_192_ofb()
304 AES with a 192-bit key in CBC, ECB, CFB and OFB modes respectively.
306 =item EVP_aes_256_cbc(), EVP_aes_256_ecb(), EVP_aes_256_cfb(), EVP_aes_256_ofb()
308 AES with a 256-bit key in CBC, ECB, CFB and OFB modes respectively.
310 =item EVP_des_cbc(), EVP_des_ecb(), EVP_des_cfb(), EVP_des_ofb()
312 DES in CBC, ECB, CFB and OFB modes respectively.
314 =item EVP_des_ede_cbc(), EVP_des_ede(), EVP_des_ede_ofb(), EVP_des_ede_cfb()
316 Two key triple DES in CBC, ECB, CFB and OFB modes respectively.
318 =item EVP_des_ede3_cbc(), EVP_des_ede3(), EVP_des_ede3_ofb(), EVP_des_ede3_cfb()
320 Three key triple DES in CBC, ECB, CFB and OFB modes respectively.
324 DESX algorithm in CBC mode.
328 RC4 stream cipher. This is a variable key length cipher with default key length 128 bits.
332 RC4 stream cipher with 40 bit key length.
333 This is obsolete and new code should use EVP_rc4()
334 and the EVP_CIPHER_CTX_set_key_length() function.
336 =item EVP_idea_cbc() EVP_idea_ecb(), EVP_idea_cfb(), EVP_idea_ofb()
338 IDEA encryption algorithm in CBC, ECB, CFB and OFB modes respectively.
340 =item EVP_rc2_cbc(), EVP_rc2_ecb(), EVP_rc2_cfb(), EVP_rc2_ofb()
342 RC2 encryption algorithm in CBC, ECB, CFB and OFB modes respectively. This is a variable key
343 length cipher with an additional parameter called "effective key bits" or "effective key length".
344 By default both are set to 128 bits.
346 =item EVP_rc2_40_cbc(), EVP_rc2_64_cbc()
348 RC2 algorithm in CBC mode with a default key length and effective key length of 40 and 64 bits.
349 These are obsolete and new code should use EVP_rc2_cbc(), EVP_CIPHER_CTX_set_key_length() and
350 EVP_CIPHER_CTX_ctrl() to set the key length and effective key length.
352 =item EVP_bf_cbc(), EVP_bf_ecb(), EVP_bf_cfb(), EVP_bf_ofb()
354 Blowfish encryption algorithm in CBC, ECB, CFB and OFB modes respectively. This is a variable key
357 =item EVP_cast5_cbc(), EVP_cast5_ecb(), EVP_cast5_cfb(), EVP_cast5_ofb()
359 CAST encryption algorithm in CBC, ECB, CFB and OFB modes respectively. This is a variable key
362 =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()
364 RC5 encryption algorithm in CBC, ECB, CFB and OFB modes respectively. This is a variable key length
365 cipher with an additional "number of rounds" parameter. By default the key length is set to 128
368 =item EVP_aes_128_gcm(), EVP_aes_192_gcm(), EVP_aes_256_gcm()
370 AES Galois Counter Mode (GCM) for 128, 192 and 256 bit keys respectively.
371 These ciphers require additional control operations to function correctly: see
372 the L<GCM and OCB modes> section below for details.
374 =item EVP_aes_128_ocb(void), EVP_aes_192_ocb(void), EVP_aes_256_ocb(void)
376 Offest Codebook Mode (OCB) for 128, 192 and 256 bit keys respectively.
377 These ciphers require additional control operations to function correctly: see
378 the L<GCM and OCB modes> section below for details.
380 =item EVP_aes_128_ccm(), EVP_aes_192_ccm(), EVP_aes_256_ccm()
382 AES Counter with CBC-MAC Mode (CCM) for 128, 192 and 256 bit keys respectively.
383 These ciphers require additional control operations to function correctly: see
384 CCM mode section below for details.
388 =head1 GCM and OCB Modes
390 For GCM and OCB mode ciphers the behaviour of the EVP interface is subtly
391 altered and several additional ctrl operations are supported.
393 To specify any additional authenticated data (AAD) a call to EVP_CipherUpdate(),
394 EVP_EncryptUpdate() or EVP_DecryptUpdate() should be made with the output
395 parameter B<out> set to B<NULL>.
397 When decrypting the return value of EVP_DecryptFinal() or EVP_CipherFinal()
398 indicates if the operation was successful. If it does not indicate success
399 the authentication operation has failed and any output data B<MUST NOT>
400 be used as it is corrupted.
402 The following ctrls are supported in both GCM and OCB modes:
404 EVP_CIPHER_CTX_ctrl(ctx, EVP_CTRL_AEAD_SET_IVLEN, ivlen, NULL);
406 Sets the IV length: this call can only be made before specifying an IV. If
407 not called a default IV length is used. For GCM AES and OCB AES the default is
408 12 (i.e. 96 bits). For OCB mode the maximum is 15.
410 EVP_CIPHER_CTX_ctrl(ctx, EVP_CTRL_AEAD_GET_TAG, taglen, tag);
412 Writes B<taglen> bytes of the tag value to the buffer indicated by B<tag>.
413 This call can only be made when encrypting data and B<after> all data has been
414 processed (e.g. after an EVP_EncryptFinal() call). For OCB mode the taglen must
415 either be 16 or the value previously set via EVP_CTRL_OCB_SET_TAGLEN.
417 EVP_CIPHER_CTX_ctrl(ctx, EVP_CTRL_AEAD_SET_TAG, taglen, tag);
419 Sets the expected tag to B<taglen> bytes from B<tag>. This call is only legal
420 when decrypting data and must be made B<before> any data is processed (e.g.
421 before any EVP_DecryptUpdate() call). For OCB mode the taglen must
422 either be 16 or the value previously set via EVP_CTRL_AEAD_SET_TAG.
424 In OCB mode calling this with B<tag> set to NULL sets the tag length. The tag
425 length can only be set before specifying an IV. If not called a default tag
426 length is used. For OCB AES the default is 16 (i.e. 128 bits). This is also the
427 maximum tag length for OCB.
429 See L<EXAMPLES> below for an example of the use of GCM mode.
433 The behaviour of CCM mode ciphers is similar to GCM mode but with a few
434 additional requirements and different ctrl values.
436 Like GCM and OCB modes any additional authenticated data (AAD) is passed by calling
437 EVP_CipherUpdate(), EVP_EncryptUpdate() or EVP_DecryptUpdate() with the output
438 parameter B<out> set to B<NULL>. Additionally the total plaintext or ciphertext
439 length B<MUST> be passed to EVP_CipherUpdate(), EVP_EncryptUpdate() or
440 EVP_DecryptUpdate() with the output and input parameters (B<in> and B<out>)
441 set to B<NULL> and the length passed in the B<inl> parameter.
443 The following ctrls are supported in CCM mode:
445 EVP_CIPHER_CTX_ctrl(ctx, EVP_CTRL_AEAD_SET_TAG, taglen, tag);
447 This call is made to set the expected B<CCM> tag value when decrypting or
448 the length of the tag (with the B<tag> parameter set to NULL) when encrypting.
449 The tag length is often referred to as B<M>. If not set a default value is
452 EVP_CIPHER_CTX_ctrl(ctx, EVP_CTRL_CCM_SET_L, ivlen, NULL);
454 Sets the CCM B<L> value. If not set a default is used (8 for AES).
456 EVP_CIPHER_CTX_ctrl(ctx, EVP_CTRL_AEAD_SET_IVLEN, ivlen, NULL);
458 Sets the CCM nonce (IV) length: this call can only be made before specifying
459 an nonce value. The nonce length is given by B<15 - L> so it is 7 by default
466 Where possible the B<EVP> 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 B<EVP> interface will ensure the use of platform specific cryptographic
470 acceleration such as AES-NI (the low level interfaces do not provide the
473 PKCS padding works by adding B<n> padding bytes of value B<n> 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 B<n> 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.
479 When decrypting the final block is checked to see if it has the correct form.
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.
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.
489 The functions EVP_EncryptInit(), EVP_EncryptFinal(), EVP_DecryptInit(),
490 EVP_CipherInit() and EVP_CipherFinal() are obsolete but are retained for
491 compatibility with existing code. New code should use EVP_EncryptInit_ex(),
492 EVP_EncryptFinal_ex(), EVP_DecryptInit_ex(), EVP_DecryptFinal_ex(),
493 EVP_CipherInit_ex() and EVP_CipherFinal_ex() because they can reuse an
494 existing context without allocating and freeing it up on each call.
498 For RC5 the number of rounds can currently only be set to 8, 12 or 16. This is
499 a limitation of the current RC5 code rather than the EVP interface.
501 EVP_MAX_KEY_LENGTH and EVP_MAX_IV_LENGTH only refer to the internal ciphers with
502 default key lengths. If custom ciphers exceed these values the results are
503 unpredictable. This is because it has become standard practice to define a
504 generic key as a fixed unsigned char array containing EVP_MAX_KEY_LENGTH bytes.
506 The ASN1 code is incomplete (and sometimes inaccurate) it has only been tested
507 for certain common S/MIME ciphers (RC2, DES, triple DES) in CBC mode.
511 Encrypt a string using IDEA:
513 int do_crypt(char *outfile)
515 unsigned char outbuf[1024];
517 /* Bogus key and IV: we'd normally set these from
520 unsigned char key[] = {0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15};
521 unsigned char iv[] = {1,2,3,4,5,6,7,8};
522 char intext[] = "Some Crypto Text";
526 EVP_CIPHER_CTX_init(&ctx);
527 EVP_EncryptInit_ex(&ctx, EVP_idea_cbc(), NULL, key, iv);
529 if(!EVP_EncryptUpdate(&ctx, outbuf, &outlen, intext, strlen(intext)))
534 /* Buffer passed to EVP_EncryptFinal() must be after data just
535 * encrypted to avoid overwriting it.
537 if(!EVP_EncryptFinal_ex(&ctx, outbuf + outlen, &tmplen))
543 EVP_CIPHER_CTX_cleanup(&ctx);
544 /* Need binary mode for fopen because encrypted data is
545 * binary data. Also cannot use strlen() on it because
546 * it wont be null terminated and may contain embedded
549 out = fopen(outfile, "wb");
550 fwrite(outbuf, 1, outlen, out);
555 The ciphertext from the above example can be decrypted using the B<openssl>
556 utility with the command line (shown on two lines for clarity):
558 openssl idea -d <filename
559 -K 000102030405060708090A0B0C0D0E0F -iv 0102030405060708
561 General encryption and decryption function example using FILE I/O and AES128
564 int do_crypt(FILE *in, FILE *out, int do_encrypt)
566 /* Allow enough space in output buffer for additional block */
567 unsigned char inbuf[1024], outbuf[1024 + EVP_MAX_BLOCK_LENGTH];
570 /* Bogus key and IV: we'd normally set these from
573 unsigned char key[] = "0123456789abcdeF";
574 unsigned char iv[] = "1234567887654321";
576 /* Don't set key or IV right away; we want to check lengths */
577 EVP_CIPHER_CTX_init(&ctx);
578 EVP_CipherInit_ex(&ctx, EVP_aes_128_cbc(), NULL, NULL, NULL,
580 OPENSSL_assert(EVP_CIPHER_CTX_key_length(&ctx) == 16);
581 OPENSSL_assert(EVP_CIPHER_CTX_iv_length(&ctx) == 16);
583 /* Now we can set key and IV */
584 EVP_CipherInit_ex(&ctx, NULL, NULL, key, iv, do_encrypt);
588 inlen = fread(inbuf, 1, 1024, in);
589 if(inlen <= 0) break;
590 if(!EVP_CipherUpdate(&ctx, outbuf, &outlen, inbuf, inlen))
593 EVP_CIPHER_CTX_cleanup(&ctx);
596 fwrite(outbuf, 1, outlen, out);
598 if(!EVP_CipherFinal_ex(&ctx, outbuf, &outlen))
601 EVP_CIPHER_CTX_cleanup(&ctx);
604 fwrite(outbuf, 1, outlen, out);
606 EVP_CIPHER_CTX_cleanup(&ctx);
617 EVP_CIPHER_CTX_init(), EVP_EncryptInit_ex(), EVP_EncryptFinal_ex(),
618 EVP_DecryptInit_ex(), EVP_DecryptFinal_ex(), EVP_CipherInit_ex(),
619 EVP_CipherFinal_ex() and EVP_CIPHER_CTX_set_padding() appeared in
622 IDEA appeared in OpenSSL 0.9.7 but was often disabled due to
623 patent concerns; the last patents expired in 2012.
625 Support for OCB mode was added in OpenSSL 1.1.0