18 EVP_CIPHER_CTX_set_key_length,
32 EVP_CIPHER_block_size,
33 EVP_CIPHER_key_length,
38 EVP_CIPHER_CTX_cipher,
41 EVP_CIPHER_CTX_block_size,
42 EVP_CIPHER_CTX_key_length,
43 EVP_CIPHER_CTX_iv_length,
44 EVP_CIPHER_CTX_get_app_data,
45 EVP_CIPHER_CTX_set_app_data,
49 EVP_CIPHER_param_to_asn1,
50 EVP_CIPHER_asn1_to_param,
51 EVP_CIPHER_CTX_set_padding,
60 #include <openssl/evp.h>
62 EVP_CIPHER *EVP_CIPHER_fetch(OPENSSL_CTX *ctx, const char *algorithm,
63 const char *properties);
64 EVP_CIPHER_CTX *EVP_CIPHER_CTX_new(void);
65 int EVP_CIPHER_CTX_reset(EVP_CIPHER_CTX *ctx);
66 void EVP_CIPHER_CTX_free(EVP_CIPHER_CTX *ctx);
68 int EVP_EncryptInit_ex(EVP_CIPHER_CTX *ctx, const EVP_CIPHER *type,
69 ENGINE *impl, const unsigned char *key, const unsigned char *iv);
70 int EVP_EncryptUpdate(EVP_CIPHER_CTX *ctx, unsigned char *out,
71 int *outl, const unsigned char *in, int inl);
72 int EVP_EncryptFinal_ex(EVP_CIPHER_CTX *ctx, unsigned char *out, int *outl);
74 int EVP_DecryptInit_ex(EVP_CIPHER_CTX *ctx, const EVP_CIPHER *type,
75 ENGINE *impl, const unsigned char *key, const unsigned char *iv);
76 int EVP_DecryptUpdate(EVP_CIPHER_CTX *ctx, unsigned char *out,
77 int *outl, const unsigned char *in, int inl);
78 int EVP_DecryptFinal_ex(EVP_CIPHER_CTX *ctx, unsigned char *outm, int *outl);
80 int EVP_CipherInit_ex(EVP_CIPHER_CTX *ctx, const EVP_CIPHER *type,
81 ENGINE *impl, const unsigned char *key, const unsigned char *iv, int enc);
82 int EVP_CipherUpdate(EVP_CIPHER_CTX *ctx, unsigned char *out,
83 int *outl, const unsigned char *in, int inl);
84 int EVP_CipherFinal_ex(EVP_CIPHER_CTX *ctx, unsigned char *outm, int *outl);
86 int EVP_EncryptInit(EVP_CIPHER_CTX *ctx, const EVP_CIPHER *type,
87 const unsigned char *key, const unsigned char *iv);
88 int EVP_EncryptFinal(EVP_CIPHER_CTX *ctx, unsigned char *out, int *outl);
90 int EVP_DecryptInit(EVP_CIPHER_CTX *ctx, const EVP_CIPHER *type,
91 const unsigned char *key, const unsigned char *iv);
92 int EVP_DecryptFinal(EVP_CIPHER_CTX *ctx, unsigned char *outm, int *outl);
94 int EVP_CipherInit(EVP_CIPHER_CTX *ctx, const EVP_CIPHER *type,
95 const unsigned char *key, const unsigned char *iv, int enc);
96 int EVP_CipherFinal(EVP_CIPHER_CTX *ctx, unsigned char *outm, int *outl);
98 int EVP_CIPHER_CTX_set_padding(EVP_CIPHER_CTX *x, int padding);
99 int EVP_CIPHER_CTX_set_key_length(EVP_CIPHER_CTX *x, int keylen);
100 int EVP_CIPHER_CTX_ctrl(EVP_CIPHER_CTX *ctx, int type, int arg, void *ptr);
101 int EVP_CIPHER_CTX_rand_key(EVP_CIPHER_CTX *ctx, unsigned char *key);
103 const EVP_CIPHER *EVP_get_cipherbyname(const char *name);
104 const EVP_CIPHER *EVP_get_cipherbynid(int nid);
105 const EVP_CIPHER *EVP_get_cipherbyobj(const ASN1_OBJECT *a);
107 int EVP_CIPHER_nid(const EVP_CIPHER *e);
108 const char *EVP_CIPHER_name(const EVP_CIPHER *cipher);
109 const OSSL_PROVIDER *EVP_CIPHER_provider(const EVP_CIPHER *cipher);
110 int EVP_CIPHER_block_size(const EVP_CIPHER *e);
111 int EVP_CIPHER_key_length(const EVP_CIPHER *e);
112 int EVP_CIPHER_iv_length(const EVP_CIPHER *e);
113 unsigned long EVP_CIPHER_flags(const EVP_CIPHER *e);
114 unsigned long EVP_CIPHER_mode(const EVP_CIPHER *e);
115 int EVP_CIPHER_type(const EVP_CIPHER *ctx);
117 const EVP_CIPHER *EVP_CIPHER_CTX_cipher(const EVP_CIPHER_CTX *ctx);
118 int EVP_CIPHER_CTX_nid(const EVP_CIPHER_CTX *ctx);
119 const char *EVP_CIPHER_CTX_name(const EVP_CIPHER_CTX *ctx);
120 int EVP_CIPHER_CTX_block_size(const EVP_CIPHER_CTX *ctx);
121 int EVP_CIPHER_CTX_key_length(const EVP_CIPHER_CTX *ctx);
122 int EVP_CIPHER_CTX_iv_length(const EVP_CIPHER_CTX *ctx);
123 void *EVP_CIPHER_CTX_get_app_data(const EVP_CIPHER_CTX *ctx);
124 void EVP_CIPHER_CTX_set_app_data(const EVP_CIPHER_CTX *ctx, void *data);
125 int EVP_CIPHER_CTX_type(const EVP_CIPHER_CTX *ctx);
126 int EVP_CIPHER_CTX_mode(const EVP_CIPHER_CTX *ctx);
128 int EVP_CIPHER_param_to_asn1(EVP_CIPHER_CTX *c, ASN1_TYPE *type);
129 int EVP_CIPHER_asn1_to_param(EVP_CIPHER_CTX *c, ASN1_TYPE *type);
131 void EVP_CIPHER_do_all_ex(OPENSSL_CTX *libctx,
132 void (*fn)(EVP_CIPHER *cipher, void *arg),
137 The EVP cipher routines are a high level interface to certain
140 EVP_CIPHER_fetch() fetches the cipher implementation for the given
141 B<algorithm> from any provider offering it, within the criteria given
142 by the B<properties>.
143 See L<provider(7)/Fetching algorithms> for further information.
145 The returned value must eventually be freed with
146 L<EVP_CIPHER_meth_free(3)>.
148 EVP_CIPHER_CTX_new() creates a cipher context.
150 EVP_CIPHER_CTX_free() clears all information from a cipher context
151 and free up any allocated memory associate with it, including B<ctx>
152 itself. This function should be called after all operations using a
153 cipher are complete so sensitive information does not remain in
156 EVP_EncryptInit_ex() sets up cipher context B<ctx> for encryption
157 with cipher B<type>. B<type> is typically supplied by a function such
158 as EVP_aes_256_cbc(), or a value explicitly fetched with
159 EVP_CIPHER_fetch(). If B<impl> is non-NULL, its implementation of the
160 cipher B<type> is used if there is one, and if not, the default
161 implementation is used. B<key> is the symmetric key to use
162 and B<iv> is the IV to use (if necessary), the actual number of bytes
163 used for the key and IV depends on the cipher. It is possible to set
164 all parameters to NULL except B<type> in an initial call and supply
165 the remaining parameters in subsequent calls, all of which have B<type>
166 set to NULL. This is done when the default cipher parameters are not
169 EVP_EncryptUpdate() encrypts B<inl> bytes from the buffer B<in> and
170 writes the encrypted version to B<out>. This function can be called
171 multiple times to encrypt successive blocks of data. The amount
172 of data written depends on the block alignment of the encrypted data:
173 as a result the amount of data written may be anything from zero bytes
174 to (inl + cipher_block_size - 1) so B<out> should contain sufficient
175 room. The actual number of bytes written is placed in B<outl>. It also
176 checks if B<in> and B<out> are partially overlapping, and if they are
177 0 is returned to indicate failure.
179 If padding is enabled (the default) then EVP_EncryptFinal_ex() encrypts
180 the "final" data, that is any data that remains in a partial block.
181 It uses standard block padding (aka PKCS padding) as described in
182 the NOTES section, below. The encrypted
183 final data is written to B<out> which should have sufficient space for
184 one cipher block. The number of bytes written is placed in B<outl>. After
185 this function is called the encryption operation is finished and no further
186 calls to EVP_EncryptUpdate() should be made.
188 If padding is disabled then EVP_EncryptFinal_ex() will not encrypt any more
189 data and it will return an error if any data remains in a partial block:
190 that is if the total data length is not a multiple of the block size.
192 EVP_DecryptInit_ex(), EVP_DecryptUpdate() and EVP_DecryptFinal_ex() are the
193 corresponding decryption operations. EVP_DecryptFinal() will return an
194 error code if padding is enabled and the final block is not correctly
195 formatted. The parameters and restrictions are identical to the encryption
196 operations except that if padding is enabled the decrypted data buffer B<out>
197 passed to EVP_DecryptUpdate() should have sufficient room for
198 (B<inl> + cipher_block_size) bytes unless the cipher block size is 1 in
199 which case B<inl> bytes is sufficient.
201 EVP_CipherInit_ex(), EVP_CipherUpdate() and EVP_CipherFinal_ex() are
202 functions that can be used for decryption or encryption. The operation
203 performed depends on the value of the B<enc> parameter. It should be set
204 to 1 for encryption, 0 for decryption and -1 to leave the value unchanged
205 (the actual value of 'enc' being supplied in a previous call).
207 EVP_CIPHER_CTX_reset() clears all information from a cipher context
208 and free up any allocated memory associate with it, except the B<ctx>
209 itself. This function should be called anytime B<ctx> is to be reused
210 for another EVP_CipherInit() / EVP_CipherUpdate() / EVP_CipherFinal()
213 EVP_EncryptInit(), EVP_DecryptInit() and EVP_CipherInit() behave in a
214 similar way to EVP_EncryptInit_ex(), EVP_DecryptInit_ex() and
215 EVP_CipherInit_ex() except they always use the default cipher implementation.
217 EVP_EncryptFinal(), EVP_DecryptFinal() and EVP_CipherFinal() are
218 identical to EVP_EncryptFinal_ex(), EVP_DecryptFinal_ex() and
219 EVP_CipherFinal_ex(). In previous releases they also cleaned up
220 the B<ctx>, but this is no longer done and EVP_CIPHER_CTX_clean()
221 must be called to free any context resources.
223 EVP_get_cipherbyname(), EVP_get_cipherbynid() and EVP_get_cipherbyobj()
224 return an EVP_CIPHER structure when passed a cipher name, a NID or an
225 ASN1_OBJECT structure.
227 EVP_CIPHER_nid() and EVP_CIPHER_CTX_nid() return the NID of a cipher when
228 passed an B<EVP_CIPHER> or B<EVP_CIPHER_CTX> structure. The actual NID
229 value is an internal value which may not have a corresponding OBJECT
232 EVP_CIPHER_CTX_set_padding() enables or disables padding. This
233 function should be called after the context is set up for encryption
234 or decryption with EVP_EncryptInit_ex(), EVP_DecryptInit_ex() or
235 EVP_CipherInit_ex(). By default encryption operations are padded using
236 standard block padding and the padding is checked and removed when
237 decrypting. If the B<pad> parameter is zero then no padding is
238 performed, the total amount of data encrypted or decrypted must then
239 be a multiple of the block size or an error will occur.
241 EVP_CIPHER_key_length() and EVP_CIPHER_CTX_key_length() return the key
242 length of a cipher when passed an B<EVP_CIPHER> or B<EVP_CIPHER_CTX>
243 structure. The constant B<EVP_MAX_KEY_LENGTH> is the maximum key length
244 for all ciphers. Note: although EVP_CIPHER_key_length() is fixed for a
245 given cipher, the value of EVP_CIPHER_CTX_key_length() may be different
246 for variable key length ciphers.
248 EVP_CIPHER_CTX_set_key_length() sets the key length of the cipher ctx.
249 If the cipher is a fixed length cipher then attempting to set the key
250 length to any value other than the fixed value is an error.
252 EVP_CIPHER_iv_length() and EVP_CIPHER_CTX_iv_length() return the IV
253 length of a cipher when passed an B<EVP_CIPHER> or B<EVP_CIPHER_CTX>.
254 It will return zero if the cipher does not use an IV. The constant
255 B<EVP_MAX_IV_LENGTH> is the maximum IV length for all ciphers.
257 EVP_CIPHER_block_size() and EVP_CIPHER_CTX_block_size() return the block
258 size of a cipher when passed an B<EVP_CIPHER> or B<EVP_CIPHER_CTX>
259 structure. The constant B<EVP_MAX_BLOCK_LENGTH> is also the maximum block
260 length for all ciphers.
262 EVP_CIPHER_type() and EVP_CIPHER_CTX_type() return the type of the passed
263 cipher or context. This "type" is the actual NID of the cipher OBJECT
264 IDENTIFIER as such it ignores the cipher parameters and 40 bit RC2 and
265 128 bit RC2 have the same NID. If the cipher does not have an object
266 identifier or does not have ASN1 support this function will return
269 EVP_CIPHER_name() and EVP_CIPHER_CTX_name() return the name of the passed
272 EVP_CIPHER_provider() returns an B<OSSL_PROVIDER> pointer to the provider
273 that implements the given B<EVP_CIPHER>.
275 EVP_CIPHER_CTX_cipher() returns the B<EVP_CIPHER> structure when passed
276 an B<EVP_CIPHER_CTX> structure.
278 EVP_CIPHER_mode() and EVP_CIPHER_CTX_mode() return the block cipher mode:
279 EVP_CIPH_ECB_MODE, EVP_CIPH_CBC_MODE, EVP_CIPH_CFB_MODE, EVP_CIPH_OFB_MODE,
280 EVP_CIPH_CTR_MODE, EVP_CIPH_GCM_MODE, EVP_CIPH_CCM_MODE, EVP_CIPH_XTS_MODE,
281 EVP_CIPH_WRAP_MODE, EVP_CIPH_OCB_MODE or EVP_CIPH_SIV_MODE. If the cipher is a
282 stream cipher then EVP_CIPH_STREAM_CIPHER is returned.
284 EVP_CIPHER_flags() returns any flags associated with the cipher. See
285 EVP_CIPHER_meth_set_flags() for a list of currently defined flags.
287 EVP_CIPHER_param_to_asn1() sets the AlgorithmIdentifier "parameter" based
288 on the passed cipher. This will typically include any parameters and an
289 IV. The cipher IV (if any) must be set when this call is made. This call
290 should be made before the cipher is actually "used" (before any
291 EVP_EncryptUpdate(), EVP_DecryptUpdate() calls for example). This function
292 may fail if the cipher does not have any ASN1 support.
294 EVP_CIPHER_asn1_to_param() sets the cipher parameters based on an ASN1
295 AlgorithmIdentifier "parameter". The precise effect depends on the cipher
296 In the case of RC2, for example, it will set the IV and effective key length.
297 This function should be called after the base cipher type is set but before
298 the key is set. For example EVP_CipherInit() will be called with the IV and
299 key set to NULL, EVP_CIPHER_asn1_to_param() will be called and finally
300 EVP_CipherInit() again with all parameters except the key set to NULL. It is
301 possible for this function to fail if the cipher does not have any ASN1 support
302 or the parameters cannot be set (for example the RC2 effective key length
305 EVP_CIPHER_CTX_ctrl() allows various cipher specific parameters to be determined
308 EVP_CIPHER_CTX_rand_key() generates a random key of the appropriate length
309 based on the cipher context. The EVP_CIPHER can provide its own random key
310 generation routine to support keys of a specific form. B<Key> must point to a
311 buffer at least as big as the value returned by EVP_CIPHER_CTX_key_length().
313 EVP_CIPHER_do_all_ex() traverses all ciphers implemented by all activated
314 providers in the given library context I<libctx>, and for each of the
315 implementations, calls the given function I<fn> with the implementation method
316 and the given I<arg> as argument.
320 EVP_CIPHER_fetch() returns a pointer to a B<EVP_CIPHER> for success
321 and B<NULL> for failure.
323 EVP_CIPHER_CTX_new() returns a pointer to a newly created
324 B<EVP_CIPHER_CTX> for success and B<NULL> for failure.
326 EVP_EncryptInit_ex(), EVP_EncryptUpdate() and EVP_EncryptFinal_ex()
327 return 1 for success and 0 for failure.
329 EVP_DecryptInit_ex() and EVP_DecryptUpdate() return 1 for success and 0 for failure.
330 EVP_DecryptFinal_ex() returns 0 if the decrypt failed or 1 for success.
332 EVP_CipherInit_ex() and EVP_CipherUpdate() return 1 for success and 0 for failure.
333 EVP_CipherFinal_ex() returns 0 for a decryption failure or 1 for success.
335 EVP_CIPHER_CTX_reset() returns 1 for success and 0 for failure.
337 EVP_get_cipherbyname(), EVP_get_cipherbynid() and EVP_get_cipherbyobj()
338 return an B<EVP_CIPHER> structure or NULL on error.
340 EVP_CIPHER_nid() and EVP_CIPHER_CTX_nid() return a NID.
342 EVP_CIPHER_block_size() and EVP_CIPHER_CTX_block_size() return the block
345 EVP_CIPHER_key_length() and EVP_CIPHER_CTX_key_length() return the key
348 EVP_CIPHER_CTX_set_padding() always returns 1.
350 EVP_CIPHER_iv_length() and EVP_CIPHER_CTX_iv_length() return the IV
351 length or zero if the cipher does not use an IV.
353 EVP_CIPHER_type() and EVP_CIPHER_CTX_type() return the NID of the cipher's
354 OBJECT IDENTIFIER or NID_undef if it has no defined OBJECT IDENTIFIER.
356 EVP_CIPHER_CTX_cipher() returns an B<EVP_CIPHER> structure.
358 EVP_CIPHER_param_to_asn1() and EVP_CIPHER_asn1_to_param() return greater
359 than zero for success and zero or a negative number on failure.
361 EVP_CIPHER_CTX_rand_key() returns 1 for success.
363 =head1 CIPHER LISTING
365 All algorithms have a fixed key length unless otherwise stated.
367 Refer to L<SEE ALSO> for the full list of ciphers available through the EVP
374 Null cipher: does nothing.
378 =head1 AEAD Interface
380 The EVP interface for Authenticated Encryption with Associated Data (AEAD)
381 modes are subtly altered and several additional I<ctrl> operations are supported
382 depending on the mode specified.
384 To specify additional authenticated data (AAD), a call to EVP_CipherUpdate(),
385 EVP_EncryptUpdate() or EVP_DecryptUpdate() should be made with the output
386 parameter B<out> set to B<NULL>.
388 When decrypting, the return value of EVP_DecryptFinal() or EVP_CipherFinal()
389 indicates whether the operation was successful. If it does not indicate success,
390 the authentication operation has failed and any output data B<MUST NOT> be used
393 =head2 GCM and OCB Modes
395 The following I<ctrl>s are supported in GCM and OCB modes.
399 =item EVP_CIPHER_CTX_ctrl(ctx, EVP_CTRL_AEAD_SET_IVLEN, ivlen, NULL)
401 Sets the IV length. This call can only be made before specifying an IV. If
402 not called a default IV length is used.
404 For GCM AES and OCB AES the default is 12 (i.e. 96 bits). For OCB mode the
407 =item EVP_CIPHER_CTX_ctrl(ctx, EVP_CTRL_AEAD_GET_TAG, taglen, tag)
409 Writes C<taglen> bytes of the tag value to the buffer indicated by C<tag>.
410 This call can only be made when encrypting data and B<after> all data has been
411 processed (e.g. after an EVP_EncryptFinal() call).
413 For OCB, C<taglen> must either be 16 or the value previously set via
414 B<EVP_CTRL_AEAD_SET_TAG>.
416 =item EVP_CIPHER_CTX_ctrl(ctx, EVP_CTRL_AEAD_SET_TAG, taglen, tag)
418 Sets the expected tag to C<taglen> bytes from C<tag>.
419 The tag length can only be set before specifying an IV.
420 C<taglen> must be between 1 and 16 inclusive.
422 For GCM, this call is only valid when decrypting data.
424 For OCB, this call is valid when decrypting data to set the expected tag,
425 and before encryption to set the desired tag length.
427 In OCB mode, calling this before encryption with C<tag> set to C<NULL> sets the
428 tag length. If this is not called prior to encryption, a default tag length is
431 For OCB AES, the default tag length is 16 (i.e. 128 bits). It is also the
432 maximum tag length for OCB.
438 The EVP interface for CCM mode is similar to that of the GCM mode but with a
439 few additional requirements and different I<ctrl> values.
441 For CCM mode, the total plaintext or ciphertext length B<MUST> be passed to
442 EVP_CipherUpdate(), EVP_EncryptUpdate() or EVP_DecryptUpdate() with the output
443 and input parameters (B<in> and B<out>) set to B<NULL> and the length passed in
444 the B<inl> parameter.
446 The following I<ctrl>s are supported in CCM mode.
450 =item EVP_CIPHER_CTX_ctrl(ctx, EVP_CTRL_AEAD_SET_TAG, taglen, tag)
452 This call is made to set the expected B<CCM> tag value when decrypting or
453 the length of the tag (with the C<tag> parameter set to NULL) when encrypting.
454 The tag length is often referred to as B<M>. If not set a default value is
455 used (12 for AES). When decrypting, the tag needs to be set before passing
456 in data to be decrypted, but as in GCM and OCB mode, it can be set after
457 passing additional authenticated data (see L<AEAD Interface>).
459 =item EVP_CIPHER_CTX_ctrl(ctx, EVP_CTRL_CCM_SET_L, ivlen, NULL)
461 Sets the CCM B<L> value. If not set a default is used (8 for AES).
463 =item EVP_CIPHER_CTX_ctrl(ctx, EVP_CTRL_AEAD_SET_IVLEN, ivlen, NULL)
465 Sets the CCM nonce (IV) length. This call can only be made before specifying an
466 nonce value. The nonce length is given by B<15 - L> so it is 7 by default for
473 For SIV mode ciphers the behaviour of the EVP interface is subtly
474 altered and several additional ctrl operations are supported.
476 To specify any additional authenticated data (AAD) and/or a Nonce, a call to
477 EVP_CipherUpdate(), EVP_EncryptUpdate() or EVP_DecryptUpdate() should be made
478 with the output parameter B<out> set to B<NULL>.
480 RFC5297 states that the Nonce is the last piece of AAD before the actual
481 encrypt/decrypt takes place. The API does not differentiate the Nonce from
484 When decrypting the return value of EVP_DecryptFinal() or EVP_CipherFinal()
485 indicates if the operation was successful. If it does not indicate success
486 the authentication operation has failed and any output data B<MUST NOT>
487 be used as it is corrupted.
489 The following ctrls are supported in both SIV modes.
493 =item EVP_CIPHER_CTX_ctrl(ctx, EVP_CTRL_AEAD_GET_TAG, taglen, tag);
495 Writes B<taglen> bytes of the tag value to the buffer indicated by B<tag>.
496 This call can only be made when encrypting data and B<after> all data has been
497 processed (e.g. after an EVP_EncryptFinal() call). For SIV mode the taglen must
500 =item EVP_CIPHER_CTX_ctrl(ctx, EVP_CTRL_AEAD_SET_TAG, taglen, tag);
502 Sets the expected tag to B<taglen> bytes from B<tag>. This call is only legal
503 when decrypting data and must be made B<before> any data is processed (e.g.
504 before any EVP_DecryptUpdate() call). For SIV mode the taglen must be 16.
508 SIV mode makes two passes over the input data, thus, only one call to
509 EVP_CipherUpdate(), EVP_EncryptUpdate() or EVP_DecryptUpdate() should be made
510 with B<out> set to a non-B<NULL> value. A call to EVP_Decrypt_Final() or
511 EVP_CipherFinal() is not required, but will indicate if the update
514 =head2 ChaCha20-Poly1305
516 The following I<ctrl>s are supported for the ChaCha20-Poly1305 AEAD algorithm.
520 =item EVP_CIPHER_CTX_ctrl(ctx, EVP_CTRL_AEAD_SET_IVLEN, ivlen, NULL)
522 Sets the nonce length. This call can only be made before specifying the nonce.
523 If not called a default nonce length of 12 (i.e. 96 bits) is used. The maximum
524 nonce length is 12 bytes (i.e. 96-bits). If a nonce of less than 12 bytes is set
525 then the nonce is automatically padded with leading 0 bytes to make it 12 bytes
528 =item EVP_CIPHER_CTX_ctrl(ctx, EVP_CTRL_AEAD_GET_TAG, taglen, tag)
530 Writes C<taglen> bytes of the tag value to the buffer indicated by C<tag>.
531 This call can only be made when encrypting data and B<after> all data has been
532 processed (e.g. after an EVP_EncryptFinal() call).
534 C<taglen> specified here must be 16 (B<POLY1305_BLOCK_SIZE>, i.e. 128-bits) or
537 =item EVP_CIPHER_CTX_ctrl(ctx, EVP_CTRL_AEAD_SET_TAG, taglen, tag)
539 Sets the expected tag to C<taglen> bytes from C<tag>.
540 The tag length can only be set before specifying an IV.
541 C<taglen> must be between 1 and 16 (B<POLY1305_BLOCK_SIZE>) inclusive.
542 This call is only valid when decrypting data.
548 Where possible the B<EVP> interface to symmetric ciphers should be used in
549 preference to the low level interfaces. This is because the code then becomes
550 transparent to the cipher used and much more flexible. Additionally, the
551 B<EVP> interface will ensure the use of platform specific cryptographic
552 acceleration such as AES-NI (the low level interfaces do not provide the
555 PKCS padding works by adding B<n> padding bytes of value B<n> to make the total
556 length of the encrypted data a multiple of the block size. Padding is always
557 added so if the data is already a multiple of the block size B<n> will equal
558 the block size. For example if the block size is 8 and 11 bytes are to be
559 encrypted then 5 padding bytes of value 5 will be added.
561 When decrypting the final block is checked to see if it has the correct form.
563 Although the decryption operation can produce an error if padding is enabled,
564 it is not a strong test that the input data or key is correct. A random block
565 has better than 1 in 256 chance of being of the correct format and problems with
566 the input data earlier on will not produce a final decrypt error.
568 If padding is disabled then the decryption operation will always succeed if
569 the total amount of data decrypted is a multiple of the block size.
571 The functions EVP_EncryptInit(), EVP_EncryptFinal(), EVP_DecryptInit(),
572 EVP_CipherInit() and EVP_CipherFinal() are obsolete but are retained for
573 compatibility with existing code. New code should use EVP_EncryptInit_ex(),
574 EVP_EncryptFinal_ex(), EVP_DecryptInit_ex(), EVP_DecryptFinal_ex(),
575 EVP_CipherInit_ex() and EVP_CipherFinal_ex() because they can reuse an
576 existing context without allocating and freeing it up on each call.
578 EVP_get_cipherbynid(), and EVP_get_cipherbyobj() are implemented as macros.
582 B<EVP_MAX_KEY_LENGTH> and B<EVP_MAX_IV_LENGTH> only refer to the internal
583 ciphers with default key lengths. If custom ciphers exceed these values the
584 results are unpredictable. This is because it has become standard practice to
585 define a generic key as a fixed unsigned char array containing
586 B<EVP_MAX_KEY_LENGTH> bytes.
588 The ASN1 code is incomplete (and sometimes inaccurate) it has only been tested
589 for certain common S/MIME ciphers (RC2, DES, triple DES) in CBC mode.
593 Encrypt a string using IDEA:
595 int do_crypt(char *outfile)
597 unsigned char outbuf[1024];
600 * Bogus key and IV: we'd normally set these from
603 unsigned char key[] = {0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15};
604 unsigned char iv[] = {1,2,3,4,5,6,7,8};
605 char intext[] = "Some Crypto Text";
609 ctx = EVP_CIPHER_CTX_new();
610 EVP_EncryptInit_ex(ctx, EVP_idea_cbc(), NULL, key, iv);
612 if (!EVP_EncryptUpdate(ctx, outbuf, &outlen, intext, strlen(intext))) {
614 EVP_CIPHER_CTX_free(ctx);
618 * Buffer passed to EVP_EncryptFinal() must be after data just
619 * encrypted to avoid overwriting it.
621 if (!EVP_EncryptFinal_ex(ctx, outbuf + outlen, &tmplen)) {
623 EVP_CIPHER_CTX_free(ctx);
627 EVP_CIPHER_CTX_free(ctx);
629 * Need binary mode for fopen because encrypted data is
630 * binary data. Also cannot use strlen() on it because
631 * it won't be NUL terminated and may contain embedded
634 out = fopen(outfile, "wb");
639 fwrite(outbuf, 1, outlen, out);
644 The ciphertext from the above example can be decrypted using the B<openssl>
645 utility with the command line (shown on two lines for clarity):
648 -K 000102030405060708090A0B0C0D0E0F -iv 0102030405060708 <filename
650 General encryption and decryption function example using FILE I/O and AES128
653 int do_crypt(FILE *in, FILE *out, int do_encrypt)
655 /* Allow enough space in output buffer for additional block */
656 unsigned char inbuf[1024], outbuf[1024 + EVP_MAX_BLOCK_LENGTH];
660 * Bogus key and IV: we'd normally set these from
663 unsigned char key[] = "0123456789abcdeF";
664 unsigned char iv[] = "1234567887654321";
666 /* Don't set key or IV right away; we want to check lengths */
667 ctx = EVP_CIPHER_CTX_new();
668 EVP_CipherInit_ex(&ctx, EVP_aes_128_cbc(), NULL, NULL, NULL,
670 OPENSSL_assert(EVP_CIPHER_CTX_key_length(ctx) == 16);
671 OPENSSL_assert(EVP_CIPHER_CTX_iv_length(ctx) == 16);
673 /* Now we can set key and IV */
674 EVP_CipherInit_ex(ctx, NULL, NULL, key, iv, do_encrypt);
677 inlen = fread(inbuf, 1, 1024, in);
680 if (!EVP_CipherUpdate(ctx, outbuf, &outlen, inbuf, inlen)) {
682 EVP_CIPHER_CTX_free(ctx);
685 fwrite(outbuf, 1, outlen, out);
687 if (!EVP_CipherFinal_ex(ctx, outbuf, &outlen)) {
689 EVP_CIPHER_CTX_free(ctx);
692 fwrite(outbuf, 1, outlen, out);
694 EVP_CIPHER_CTX_free(ctx);
703 Supported ciphers are listed in:
722 Support for OCB mode was added in OpenSSL 1.1.0.
724 B<EVP_CIPHER_CTX> was made opaque in OpenSSL 1.1.0. As a result,
725 EVP_CIPHER_CTX_reset() appeared and EVP_CIPHER_CTX_cleanup()
726 disappeared. EVP_CIPHER_CTX_init() remains as an alias for
727 EVP_CIPHER_CTX_reset().
731 Copyright 2000-2018 The OpenSSL Project Authors. All Rights Reserved.
733 Licensed under the Apache License 2.0 (the "License"). You may not use
734 this file except in compliance with the License. You can obtain a copy
735 in the file LICENSE in the source distribution or at
736 L<https://www.openssl.org/source/license.html>.