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_rc4_hmac_md5,
23 EVP_idea_cbc, 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,
33 EVP_aes_128_cbc_hmac_sha1, EVP_aes_256_cbc_hmac_sha1,
34 EVP_aes_128_cbc_hmac_sha256, EVP_aes_256_cbc_hmac_sha256,
35 EVP_chacha20, EVP_chacha20_poly1305 - EVP cipher routines
41 #include <openssl/evp.h>
43 EVP_CIPHER_CTX *EVP_CIPHER_CTX_new(void);
44 int EVP_CIPHER_CTX_reset(EVP_CIPHER_CTX *ctx);
45 void EVP_CIPHER_CTX_free(EVP_CIPHER_CTX *ctx);
47 int EVP_EncryptInit_ex(EVP_CIPHER_CTX *ctx, const EVP_CIPHER *type,
48 ENGINE *impl, unsigned char *key, unsigned char *iv);
49 int EVP_EncryptUpdate(EVP_CIPHER_CTX *ctx, unsigned char *out,
50 int *outl, unsigned char *in, int inl);
51 int EVP_EncryptFinal_ex(EVP_CIPHER_CTX *ctx, unsigned char *out, int *outl);
53 int EVP_DecryptInit_ex(EVP_CIPHER_CTX *ctx, const EVP_CIPHER *type,
54 ENGINE *impl, unsigned char *key, unsigned char *iv);
55 int EVP_DecryptUpdate(EVP_CIPHER_CTX *ctx, unsigned char *out,
56 int *outl, unsigned char *in, int inl);
57 int EVP_DecryptFinal_ex(EVP_CIPHER_CTX *ctx, unsigned char *outm, int *outl);
59 int EVP_CipherInit_ex(EVP_CIPHER_CTX *ctx, const EVP_CIPHER *type,
60 ENGINE *impl, unsigned char *key, unsigned char *iv, int enc);
61 int EVP_CipherUpdate(EVP_CIPHER_CTX *ctx, unsigned char *out,
62 int *outl, unsigned char *in, int inl);
63 int EVP_CipherFinal_ex(EVP_CIPHER_CTX *ctx, unsigned char *outm, int *outl);
65 int EVP_EncryptInit(EVP_CIPHER_CTX *ctx, const EVP_CIPHER *type,
66 unsigned char *key, unsigned char *iv);
67 int EVP_EncryptFinal(EVP_CIPHER_CTX *ctx, unsigned char *out, int *outl);
69 int EVP_DecryptInit(EVP_CIPHER_CTX *ctx, const EVP_CIPHER *type,
70 unsigned char *key, unsigned char *iv);
71 int EVP_DecryptFinal(EVP_CIPHER_CTX *ctx, unsigned char *outm, int *outl);
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, int *outl);
77 int EVP_CIPHER_CTX_set_padding(EVP_CIPHER_CTX *x, int padding);
78 int EVP_CIPHER_CTX_set_key_length(EVP_CIPHER_CTX *x, int keylen);
79 int EVP_CIPHER_CTX_ctrl(EVP_CIPHER_CTX *ctx, int type, int arg, void *ptr);
81 const EVP_CIPHER *EVP_get_cipherbyname(const char *name);
82 const EVP_CIPHER *EVP_get_cipherbynid(int nid);
83 const EVP_CIPHER *EVP_get_cipherbyobj(const ASN1_OBJECT *a);
85 int EVP_CIPHER_nid(const EVP_CIPHER *e);
86 int EVP_CIPHER_block_size(const EVP_CIPHER *e);
87 int EVP_CIPHER_key_length(const EVP_CIPHER *e)
88 int EVP_CIPHER_key_length(const EVP_CIPHER *e);
89 int EVP_CIPHER_iv_length(const EVP_CIPHER *e);
90 unsigned long EVP_CIPHER_flags(const EVP_CIPHER *e);
91 unsigned long EVP_CIPHER_mode(const EVP_CIPHER *e);
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 int EVP_CIPHER_CTX_mode(const EVP_CIPHER_CTX *ctx);
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_new() creates a cipher context.
114 EVP_CIPHER_CTX_free() clears all information from a cipher context
115 and free up any allocated memory associate with it, including B<ctx>
116 itself. This function should be called after all operations using a
117 cipher are complete so sensitive information does not remain in
120 EVP_EncryptInit_ex() sets up cipher context B<ctx> for encryption
121 with cipher B<type> from ENGINE B<impl>. B<ctx> must be created
122 before calling this function. B<type> is normally supplied
123 by a function such as EVP_aes_256_cbc(). If B<impl> is NULL then the
124 default implementation is used. B<key> is the symmetric key to use
125 and B<iv> is the IV to use (if necessary), the actual number of bytes
126 used for the key and IV depends on the cipher. It is possible to set
127 all parameters to NULL except B<type> in an initial call and supply
128 the remaining parameters in subsequent calls, all of which have B<type>
129 set to NULL. This is done when the default cipher parameters are not
132 EVP_EncryptUpdate() encrypts B<inl> bytes from the buffer B<in> and
133 writes the encrypted version to B<out>. This function can be called
134 multiple times to encrypt successive blocks of data. The amount
135 of data written depends on the block alignment of the encrypted data:
136 as a result the amount of data written may be anything from zero bytes
137 to (inl + cipher_block_size - 1) so B<out> should contain sufficient
138 room. The actual number of bytes written is placed in B<outl>. It also
139 checks if B<in> and B<out> are partially overlapping, and if they are
140 0 is returned to indicate failure.
142 If padding is enabled (the default) then EVP_EncryptFinal_ex() encrypts
143 the "final" data, that is any data that remains in a partial block.
144 It uses standard block padding (aka PKCS padding) as described in
145 the NOTES section, below. The encrypted
146 final data is written to B<out> which should have sufficient space for
147 one cipher block. The number of bytes written is placed in B<outl>. After
148 this function is called the encryption operation is finished and no further
149 calls to EVP_EncryptUpdate() should be made.
151 If padding is disabled then EVP_EncryptFinal_ex() will not encrypt any more
152 data and it will return an error if any data remains in a partial block:
153 that is if the total data length is not a multiple of the block size.
155 EVP_DecryptInit_ex(), EVP_DecryptUpdate() and EVP_DecryptFinal_ex() are the
156 corresponding decryption operations. EVP_DecryptFinal() will return an
157 error code if padding is enabled and the final block is not correctly
158 formatted. The parameters and restrictions are identical to the encryption
159 operations except that if padding is enabled the decrypted data buffer B<out>
160 passed to EVP_DecryptUpdate() should have sufficient room for
161 (B<inl> + cipher_block_size) bytes unless the cipher block size is 1 in
162 which case B<inl> bytes is sufficient.
164 EVP_CipherInit_ex(), EVP_CipherUpdate() and EVP_CipherFinal_ex() are
165 functions that can be used for decryption or encryption. The operation
166 performed depends on the value of the B<enc> parameter. It should be set
167 to 1 for encryption, 0 for decryption and -1 to leave the value unchanged
168 (the actual value of 'enc' being supplied in a previous call).
170 EVP_CIPHER_CTX_reset() clears all information from a cipher context
171 and free up any allocated memory associate with it, except the B<ctx>
172 itself. This function should be called anytime B<ctx> is to be reused
173 for another EVP_CipherInit() / EVP_CipherUpdate() / EVP_CipherFinal()
176 EVP_EncryptInit(), EVP_DecryptInit() and EVP_CipherInit() behave in a
177 similar way to EVP_EncryptInit_ex(), EVP_DecryptInit_ex() and
178 EVP_CipherInit_ex() except the B<ctx> parameter does not need to be
179 initialized and they always use the default cipher implementation.
181 EVP_EncryptFinal(), EVP_DecryptFinal() and EVP_CipherFinal() are
182 identical to EVP_EncryptFinal_ex(), EVP_DecryptFinal_ex() and
183 EVP_CipherFinal_ex(). In previous releases they also cleaned up
184 the B<ctx>, but this is no longer done and EVP_CIPHER_CTX_clean()
185 must be called to free any context resources.
187 EVP_get_cipherbyname(), EVP_get_cipherbynid() and EVP_get_cipherbyobj()
188 return an EVP_CIPHER structure when passed a cipher name, a NID or an
189 ASN1_OBJECT structure.
191 EVP_CIPHER_nid() and EVP_CIPHER_CTX_nid() return the NID of a cipher when
192 passed an B<EVP_CIPHER> or B<EVP_CIPHER_CTX> structure. The actual NID
193 value is an internal value which may not have a corresponding OBJECT
196 EVP_CIPHER_CTX_set_padding() enables or disables padding. This
197 function should be called after the context is set up for encryption
198 or decryption with EVP_EncryptInit_ex(), EVP_DecryptInit_ex() or
199 EVP_CipherInit_ex(). By default encryption operations are padded using
200 standard block padding and the padding is checked and removed when
201 decrypting. If the B<pad> parameter is zero then no padding is
202 performed, the total amount of data encrypted or decrypted must then
203 be a multiple of the block size or an error will occur.
205 EVP_CIPHER_key_length() and EVP_CIPHER_CTX_key_length() return the key
206 length of a cipher when passed an B<EVP_CIPHER> or B<EVP_CIPHER_CTX>
207 structure. The constant B<EVP_MAX_KEY_LENGTH> is the maximum key length
208 for all ciphers. Note: although EVP_CIPHER_key_length() is fixed for a
209 given cipher, the value of EVP_CIPHER_CTX_key_length() may be different
210 for variable key length ciphers.
212 EVP_CIPHER_CTX_set_key_length() sets the key length of the cipher ctx.
213 If the cipher is a fixed length cipher then attempting to set the key
214 length to any value other than the fixed value is an error.
216 EVP_CIPHER_iv_length() and EVP_CIPHER_CTX_iv_length() return the IV
217 length of a cipher when passed an B<EVP_CIPHER> or B<EVP_CIPHER_CTX>.
218 It will return zero if the cipher does not use an IV. The constant
219 B<EVP_MAX_IV_LENGTH> is the maximum IV length for all ciphers.
221 EVP_CIPHER_block_size() and EVP_CIPHER_CTX_block_size() return the block
222 size of a cipher when passed an B<EVP_CIPHER> or B<EVP_CIPHER_CTX>
223 structure. The constant B<EVP_MAX_BLOCK_LENGTH> is also the maximum block
224 length for all ciphers.
226 EVP_CIPHER_type() and EVP_CIPHER_CTX_type() return the type of the passed
227 cipher or context. This "type" is the actual NID of the cipher OBJECT
228 IDENTIFIER as such it ignores the cipher parameters and 40 bit RC2 and
229 128 bit RC2 have the same NID. If the cipher does not have an object
230 identifier or does not have ASN1 support this function will return
233 EVP_CIPHER_CTX_cipher() returns the B<EVP_CIPHER> structure when passed
234 an B<EVP_CIPHER_CTX> structure.
236 EVP_CIPHER_mode() and EVP_CIPHER_CTX_mode() return the block cipher mode:
237 EVP_CIPH_ECB_MODE, EVP_CIPH_CBC_MODE, EVP_CIPH_CFB_MODE or
238 EVP_CIPH_OFB_MODE. If the cipher is a stream cipher then
239 EVP_CIPH_STREAM_CIPHER is returned.
241 EVP_CIPHER_param_to_asn1() sets the AlgorithmIdentifier "parameter" based
242 on the passed cipher. This will typically include any parameters and an
243 IV. The cipher IV (if any) must be set when this call is made. This call
244 should be made before the cipher is actually "used" (before any
245 EVP_EncryptUpdate(), EVP_DecryptUpdate() calls for example). This function
246 may fail if the cipher does not have any ASN1 support.
248 EVP_CIPHER_asn1_to_param() sets the cipher parameters based on an ASN1
249 AlgorithmIdentifier "parameter". The precise effect depends on the cipher
250 In the case of RC2, for example, it will set the IV and effective key length.
251 This function should be called after the base cipher type is set but before
252 the key is set. For example EVP_CipherInit() will be called with the IV and
253 key set to NULL, EVP_CIPHER_asn1_to_param() will be called and finally
254 EVP_CipherInit() again with all parameters except the key set to NULL. It is
255 possible for this function to fail if the cipher does not have any ASN1 support
256 or the parameters cannot be set (for example the RC2 effective key length
259 EVP_CIPHER_CTX_ctrl() allows various cipher specific parameters to be determined
264 EVP_CIPHER_CTX_new() returns a pointer to a newly created
265 B<EVP_CIPHER_CTX> for success and B<NULL> for failure.
267 EVP_EncryptInit_ex(), EVP_EncryptUpdate() and EVP_EncryptFinal_ex()
268 return 1 for success and 0 for failure.
270 EVP_DecryptInit_ex() and EVP_DecryptUpdate() return 1 for success and 0 for failure.
271 EVP_DecryptFinal_ex() returns 0 if the decrypt failed or 1 for success.
273 EVP_CipherInit_ex() and EVP_CipherUpdate() return 1 for success and 0 for failure.
274 EVP_CipherFinal_ex() returns 0 for a decryption failure or 1 for success.
276 EVP_CIPHER_CTX_reset() returns 1 for success and 0 for failure.
278 EVP_get_cipherbyname(), EVP_get_cipherbynid() and EVP_get_cipherbyobj()
279 return an B<EVP_CIPHER> structure or NULL on error.
281 EVP_CIPHER_nid() and EVP_CIPHER_CTX_nid() return a NID.
283 EVP_CIPHER_block_size() and EVP_CIPHER_CTX_block_size() return the block
286 EVP_CIPHER_key_length() and EVP_CIPHER_CTX_key_length() return the key
289 EVP_CIPHER_CTX_set_padding() always returns 1.
291 EVP_CIPHER_iv_length() and EVP_CIPHER_CTX_iv_length() return the IV
292 length or zero if the cipher does not use an IV.
294 EVP_CIPHER_type() and EVP_CIPHER_CTX_type() return the NID of the cipher's
295 OBJECT IDENTIFIER or NID_undef if it has no defined OBJECT IDENTIFIER.
297 EVP_CIPHER_CTX_cipher() returns an B<EVP_CIPHER> structure.
299 EVP_CIPHER_param_to_asn1() and EVP_CIPHER_asn1_to_param() return greater
300 than zero for success and zero or a negative number.
302 =head1 CIPHER LISTING
304 All algorithms have a fixed key length unless otherwise stated.
310 Null cipher: does nothing.
312 =item EVP_aes_128_cbc(), EVP_aes_128_ecb(), EVP_aes_128_cfb(), EVP_aes_128_ofb()
314 AES with a 128-bit key in CBC, ECB, CFB and OFB modes respectively.
316 =item EVP_aes_192_cbc(), EVP_aes_192_ecb(), EVP_aes_192_cfb(), EVP_aes_192_ofb()
318 AES with a 192-bit key in CBC, ECB, CFB and OFB modes respectively.
320 =item EVP_aes_256_cbc(), EVP_aes_256_ecb(), EVP_aes_256_cfb(), EVP_aes_256_ofb()
322 AES with a 256-bit key in CBC, ECB, CFB and OFB modes respectively.
324 =item EVP_des_cbc(), EVP_des_ecb(), EVP_des_cfb(), EVP_des_ofb()
326 DES in CBC, ECB, CFB and OFB modes respectively.
328 =item EVP_des_ede_cbc(), EVP_des_ede(), EVP_des_ede_ofb(), EVP_des_ede_cfb()
330 Two key triple DES in CBC, ECB, CFB and OFB modes respectively.
332 =item EVP_des_ede3_cbc(), EVP_des_ede3(), EVP_des_ede3_ofb(), EVP_des_ede3_cfb()
334 Three key triple DES in CBC, ECB, CFB and OFB modes respectively.
338 DESX algorithm in CBC mode.
342 RC4 stream cipher. This is a variable key length cipher with default key length 128 bits.
346 RC4 stream cipher with 40 bit key length.
347 This is obsolete and new code should use EVP_rc4()
348 and the EVP_CIPHER_CTX_set_key_length() function.
350 =item EVP_idea_cbc() EVP_idea_ecb(), EVP_idea_cfb(), EVP_idea_ofb()
352 IDEA encryption algorithm in CBC, ECB, CFB and OFB modes respectively.
354 =item EVP_rc2_cbc(), EVP_rc2_ecb(), EVP_rc2_cfb(), EVP_rc2_ofb()
356 RC2 encryption algorithm in CBC, ECB, CFB and OFB modes respectively. This is a variable key
357 length cipher with an additional parameter called "effective key bits" or "effective key length".
358 By default both are set to 128 bits.
360 =item EVP_rc2_40_cbc(), EVP_rc2_64_cbc()
362 RC2 algorithm in CBC mode with a default key length and effective key length of 40 and 64 bits.
363 These are obsolete and new code should use EVP_rc2_cbc(), EVP_CIPHER_CTX_set_key_length() and
364 EVP_CIPHER_CTX_ctrl() to set the key length and effective key length.
366 =item EVP_bf_cbc(), EVP_bf_ecb(), EVP_bf_cfb(), EVP_bf_ofb()
368 Blowfish encryption algorithm in CBC, ECB, CFB and OFB modes respectively. This is a variable key
371 =item EVP_cast5_cbc(), EVP_cast5_ecb(), EVP_cast5_cfb(), EVP_cast5_ofb()
373 CAST encryption algorithm in CBC, ECB, CFB and OFB modes respectively. This is a variable key
376 =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()
378 RC5 encryption algorithm in CBC, ECB, CFB and OFB modes respectively. This is a variable key length
379 cipher with an additional "number of rounds" parameter. By default the key length is set to 128
382 =item EVP_aes_128_gcm(), EVP_aes_192_gcm(), EVP_aes_256_gcm()
384 AES Galois Counter Mode (GCM) for 128, 192 and 256 bit keys respectively.
385 These ciphers require additional control operations to function correctly: see
386 the L</GCM and OCB Modes> section below for details.
388 =item EVP_aes_128_ocb(void), EVP_aes_192_ocb(void), EVP_aes_256_ocb(void)
390 Offset Codebook Mode (OCB) for 128, 192 and 256 bit keys respectively.
391 These ciphers require additional control operations to function correctly: see
392 the L</GCM and OCB Modes> section below for details.
394 =item EVP_aes_128_ccm(), EVP_aes_192_ccm(), EVP_aes_256_ccm()
396 AES Counter with CBC-MAC Mode (CCM) for 128, 192 and 256 bit keys respectively.
397 These ciphers require additional control operations to function correctly: see
398 CCM mode section below for details.
402 The ChaCha20 stream cipher. The key length is 256 bits, the IV is 96 bits long.
404 =item EVP_chacha20_poly1305()
406 Authenticated encryption with ChaCha20-Poly1305. Like EVP_chacha20() the key is
407 256 bits and the IV is 96 bits. This supports additional authenticated
408 data (AAD) and produces a 128 bit authentication tag. See the
409 L</GCM and OCB Modes> section for more information.
413 =head1 GCM and OCB Modes
415 For GCM and OCB mode ciphers the behaviour of the EVP interface is subtly
416 altered and several additional ctrl operations are supported.
418 To specify any additional authenticated data (AAD) a call to EVP_CipherUpdate(),
419 EVP_EncryptUpdate() or EVP_DecryptUpdate() should be made with the output
420 parameter B<out> set to B<NULL>.
422 When decrypting the return value of EVP_DecryptFinal() or EVP_CipherFinal()
423 indicates if the operation was successful. If it does not indicate success
424 the authentication operation has failed and any output data B<MUST NOT>
425 be used as it is corrupted.
427 The following ctrls are supported in both GCM and OCB modes:
429 EVP_CIPHER_CTX_ctrl(ctx, EVP_CTRL_AEAD_SET_IVLEN, ivlen, NULL);
431 Sets the IV length: this call can only be made before specifying an IV. If
432 not called a default IV length is used. For GCM AES and OCB AES the default is
433 12 (i.e. 96 bits). For OCB mode the maximum is 15.
435 EVP_CIPHER_CTX_ctrl(ctx, EVP_CTRL_AEAD_GET_TAG, taglen, tag);
437 Writes B<taglen> bytes of the tag value to the buffer indicated by B<tag>.
438 This call can only be made when encrypting data and B<after> all data has been
439 processed (e.g. after an EVP_EncryptFinal() call). For OCB mode the taglen must
440 either be 16 or the value previously set via EVP_CTRL_OCB_SET_TAGLEN.
442 EVP_CIPHER_CTX_ctrl(ctx, EVP_CTRL_AEAD_SET_TAG, taglen, tag);
444 Sets the expected tag to B<taglen> bytes from B<tag>. This call is only legal
445 when decrypting data and must be made B<before> any data is processed (e.g.
446 before any EVP_DecryptUpdate() call). For OCB mode the taglen must
447 either be 16 or the value previously set via EVP_CTRL_AEAD_SET_TAG.
449 In OCB mode calling this with B<tag> set to NULL sets the tag length. The tag
450 length can only be set before specifying an IV. If not called a default tag
451 length is used. For OCB AES the default is 16 (i.e. 128 bits). This is also the
452 maximum tag length for OCB.
456 The behaviour of CCM mode ciphers is similar to GCM mode but with a few
457 additional requirements and different ctrl values.
459 Like GCM and OCB modes any additional authenticated data (AAD) is passed by calling
460 EVP_CipherUpdate(), EVP_EncryptUpdate() or EVP_DecryptUpdate() with the output
461 parameter B<out> set to B<NULL>. Additionally the total plaintext or ciphertext
462 length B<MUST> be passed to EVP_CipherUpdate(), EVP_EncryptUpdate() or
463 EVP_DecryptUpdate() with the output and input parameters (B<in> and B<out>)
464 set to B<NULL> and the length passed in the B<inl> parameter.
466 The following ctrls are supported in CCM mode:
468 EVP_CIPHER_CTX_ctrl(ctx, EVP_CTRL_AEAD_SET_TAG, taglen, tag);
470 This call is made to set the expected B<CCM> tag value when decrypting or
471 the length of the tag (with the B<tag> parameter set to NULL) when encrypting.
472 The tag length is often referred to as B<M>. If not set a default value is
475 EVP_CIPHER_CTX_ctrl(ctx, EVP_CTRL_CCM_SET_L, ivlen, NULL);
477 Sets the CCM B<L> value. If not set a default is used (8 for AES).
479 EVP_CIPHER_CTX_ctrl(ctx, EVP_CTRL_AEAD_SET_IVLEN, ivlen, NULL);
481 Sets the CCM nonce (IV) length: this call can only be made before specifying
482 an nonce value. The nonce length is given by B<15 - L> so it is 7 by default
487 Where possible the B<EVP> interface to symmetric ciphers should be used in
488 preference to the low level interfaces. This is because the code then becomes
489 transparent to the cipher used and much more flexible. Additionally, the
490 B<EVP> interface will ensure the use of platform specific cryptographic
491 acceleration such as AES-NI (the low level interfaces do not provide the
494 PKCS padding works by adding B<n> padding bytes of value B<n> to make the total
495 length of the encrypted data a multiple of the block size. Padding is always
496 added so if the data is already a multiple of the block size B<n> will equal
497 the block size. For example if the block size is 8 and 11 bytes are to be
498 encrypted then 5 padding bytes of value 5 will be added.
500 When decrypting the final block is checked to see if it has the correct form.
502 Although the decryption operation can produce an error if padding is enabled,
503 it is not a strong test that the input data or key is correct. A random block
504 has better than 1 in 256 chance of being of the correct format and problems with
505 the input data earlier on will not produce a final decrypt error.
507 If padding is disabled then the decryption operation will always succeed if
508 the total amount of data decrypted is a multiple of the block size.
510 The functions EVP_EncryptInit(), EVP_EncryptFinal(), EVP_DecryptInit(),
511 EVP_CipherInit() and EVP_CipherFinal() are obsolete but are retained for
512 compatibility with existing code. New code should use EVP_EncryptInit_ex(),
513 EVP_EncryptFinal_ex(), EVP_DecryptInit_ex(), EVP_DecryptFinal_ex(),
514 EVP_CipherInit_ex() and EVP_CipherFinal_ex() because they can reuse an
515 existing context without allocating and freeing it up on each call.
517 EVP_get_cipherbynid(), and EVP_get_cipherbyobj() are implemented as macros.
521 For RC5 the number of rounds can currently only be set to 8, 12 or 16. This is
522 a limitation of the current RC5 code rather than the EVP interface.
524 EVP_MAX_KEY_LENGTH and EVP_MAX_IV_LENGTH only refer to the internal ciphers with
525 default key lengths. If custom ciphers exceed these values the results are
526 unpredictable. This is because it has become standard practice to define a
527 generic key as a fixed unsigned char array containing EVP_MAX_KEY_LENGTH bytes.
529 The ASN1 code is incomplete (and sometimes inaccurate) it has only been tested
530 for certain common S/MIME ciphers (RC2, DES, triple DES) in CBC mode.
534 Encrypt a string using IDEA:
536 int do_crypt(char *outfile)
538 unsigned char outbuf[1024];
541 * Bogus key and IV: we'd normally set these from
544 unsigned char key[] = {0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15};
545 unsigned char iv[] = {1,2,3,4,5,6,7,8};
546 char intext[] = "Some Crypto Text";
550 ctx = EVP_CIPHER_CTX_new();
551 EVP_EncryptInit_ex(ctx, EVP_idea_cbc(), NULL, key, iv);
553 if (!EVP_EncryptUpdate(ctx, outbuf, &outlen, intext, strlen(intext))) {
555 EVP_CIPHER_CTX_free(ctx);
559 * Buffer passed to EVP_EncryptFinal() must be after data just
560 * encrypted to avoid overwriting it.
562 if (!EVP_EncryptFinal_ex(ctx, outbuf + outlen, &tmplen)) {
564 EVP_CIPHER_CTX_free(ctx);
568 EVP_CIPHER_CTX_free(ctx);
570 * Need binary mode for fopen because encrypted data is
571 * binary data. Also cannot use strlen() on it because
572 * it won't be NUL terminated and may contain embedded
575 out = fopen(outfile, "wb");
580 fwrite(outbuf, 1, outlen, out);
585 The ciphertext from the above example can be decrypted using the B<openssl>
586 utility with the command line (shown on two lines for clarity):
589 -K 000102030405060708090A0B0C0D0E0F -iv 0102030405060708 <filename
591 General encryption and decryption function example using FILE I/O and AES128
594 int do_crypt(FILE *in, FILE *out, int do_encrypt)
596 /* Allow enough space in output buffer for additional block */
597 unsigned char inbuf[1024], outbuf[1024 + EVP_MAX_BLOCK_LENGTH];
601 * Bogus key and IV: we'd normally set these from
604 unsigned char key[] = "0123456789abcdeF";
605 unsigned char iv[] = "1234567887654321";
607 /* Don't set key or IV right away; we want to check lengths */
608 ctx = EVP_CIPHER_CTX_new();
609 EVP_CipherInit_ex(&ctx, EVP_aes_128_cbc(), NULL, NULL, NULL,
611 OPENSSL_assert(EVP_CIPHER_CTX_key_length(ctx) == 16);
612 OPENSSL_assert(EVP_CIPHER_CTX_iv_length(ctx) == 16);
614 /* Now we can set key and IV */
615 EVP_CipherInit_ex(ctx, NULL, NULL, key, iv, do_encrypt);
618 inlen = fread(inbuf, 1, 1024, in);
621 if (!EVP_CipherUpdate(ctx, outbuf, &outlen, inbuf, inlen)) {
623 EVP_CIPHER_CTX_free(ctx);
626 fwrite(outbuf, 1, outlen, out);
628 if (!EVP_CipherFinal_ex(ctx, outbuf, &outlen)) {
630 EVP_CIPHER_CTX_free(ctx);
633 fwrite(outbuf, 1, outlen, out);
635 EVP_CIPHER_CTX_free(ctx);
646 Support for OCB mode was added in OpenSSL 1.1.0
648 B<EVP_CIPHER_CTX> was made opaque in OpenSSL 1.1.0. As a result,
649 EVP_CIPHER_CTX_reset() appeared and EVP_CIPHER_CTX_cleanup()
650 disappeared. EVP_CIPHER_CTX_init() remains as an alias for
651 EVP_CIPHER_CTX_reset().
655 Copyright 2000-2016 The OpenSSL Project Authors. All Rights Reserved.
657 Licensed under the OpenSSL license (the "License"). You may not use
658 this file except in compliance with the License. You can obtain a copy
659 in the file LICENSE in the source distribution or at
660 L<https://www.openssl.org/source/license.html>.