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
168 For EVP_CIPH_GCM_MODE the IV will be generated internally if it is not
171 EVP_EncryptUpdate() encrypts B<inl> bytes from the buffer B<in> and
172 writes the encrypted version to B<out>. This function can be called
173 multiple times to encrypt successive blocks of data. The amount
174 of data written depends on the block alignment of the encrypted data:
175 as a result the amount of data written may be anything from zero bytes
176 to (inl + cipher_block_size - 1) so B<out> should contain sufficient
177 room. The actual number of bytes written is placed in B<outl>. It also
178 checks if B<in> and B<out> are partially overlapping, and if they are
179 0 is returned to indicate failure.
181 If padding is enabled (the default) then EVP_EncryptFinal_ex() encrypts
182 the "final" data, that is any data that remains in a partial block.
183 It uses standard block padding (aka PKCS padding) as described in
184 the NOTES section, below. The encrypted
185 final data is written to B<out> which should have sufficient space for
186 one cipher block. The number of bytes written is placed in B<outl>. After
187 this function is called the encryption operation is finished and no further
188 calls to EVP_EncryptUpdate() should be made.
190 If padding is disabled then EVP_EncryptFinal_ex() will not encrypt any more
191 data and it will return an error if any data remains in a partial block:
192 that is if the total data length is not a multiple of the block size.
194 EVP_DecryptInit_ex(), EVP_DecryptUpdate() and EVP_DecryptFinal_ex() are the
195 corresponding decryption operations. EVP_DecryptFinal() will return an
196 error code if padding is enabled and the final block is not correctly
197 formatted. The parameters and restrictions are identical to the encryption
198 operations except that if padding is enabled the decrypted data buffer B<out>
199 passed to EVP_DecryptUpdate() should have sufficient room for
200 (B<inl> + cipher_block_size) bytes unless the cipher block size is 1 in
201 which case B<inl> bytes is sufficient.
203 EVP_CipherInit_ex(), EVP_CipherUpdate() and EVP_CipherFinal_ex() are
204 functions that can be used for decryption or encryption. The operation
205 performed depends on the value of the B<enc> parameter. It should be set
206 to 1 for encryption, 0 for decryption and -1 to leave the value unchanged
207 (the actual value of 'enc' being supplied in a previous call).
209 EVP_CIPHER_CTX_reset() clears all information from a cipher context
210 and free up any allocated memory associate with it, except the B<ctx>
211 itself. This function should be called anytime B<ctx> is to be reused
212 for another EVP_CipherInit() / EVP_CipherUpdate() / EVP_CipherFinal()
215 EVP_EncryptInit(), EVP_DecryptInit() and EVP_CipherInit() behave in a
216 similar way to EVP_EncryptInit_ex(), EVP_DecryptInit_ex() and
217 EVP_CipherInit_ex() except they always use the default cipher implementation.
219 EVP_EncryptFinal(), EVP_DecryptFinal() and EVP_CipherFinal() are
220 identical to EVP_EncryptFinal_ex(), EVP_DecryptFinal_ex() and
221 EVP_CipherFinal_ex(). In previous releases they also cleaned up
222 the B<ctx>, but this is no longer done and EVP_CIPHER_CTX_clean()
223 must be called to free any context resources.
225 EVP_get_cipherbyname(), EVP_get_cipherbynid() and EVP_get_cipherbyobj()
226 return an EVP_CIPHER structure when passed a cipher name, a NID or an
227 ASN1_OBJECT structure.
229 EVP_CIPHER_nid() and EVP_CIPHER_CTX_nid() return the NID of a cipher when
230 passed an B<EVP_CIPHER> or B<EVP_CIPHER_CTX> structure. The actual NID
231 value is an internal value which may not have a corresponding OBJECT
234 EVP_CIPHER_CTX_set_padding() enables or disables padding. This
235 function should be called after the context is set up for encryption
236 or decryption with EVP_EncryptInit_ex(), EVP_DecryptInit_ex() or
237 EVP_CipherInit_ex(). By default encryption operations are padded using
238 standard block padding and the padding is checked and removed when
239 decrypting. If the B<pad> parameter is zero then no padding is
240 performed, the total amount of data encrypted or decrypted must then
241 be a multiple of the block size or an error will occur.
243 EVP_CIPHER_key_length() and EVP_CIPHER_CTX_key_length() return the key
244 length of a cipher when passed an B<EVP_CIPHER> or B<EVP_CIPHER_CTX>
245 structure. The constant B<EVP_MAX_KEY_LENGTH> is the maximum key length
246 for all ciphers. Note: although EVP_CIPHER_key_length() is fixed for a
247 given cipher, the value of EVP_CIPHER_CTX_key_length() may be different
248 for variable key length ciphers.
250 EVP_CIPHER_CTX_set_key_length() sets the key length of the cipher ctx.
251 If the cipher is a fixed length cipher then attempting to set the key
252 length to any value other than the fixed value is an error.
254 EVP_CIPHER_iv_length() and EVP_CIPHER_CTX_iv_length() return the IV
255 length of a cipher when passed an B<EVP_CIPHER> or B<EVP_CIPHER_CTX>.
256 It will return zero if the cipher does not use an IV. The constant
257 B<EVP_MAX_IV_LENGTH> is the maximum IV length for all ciphers.
259 EVP_CIPHER_block_size() and EVP_CIPHER_CTX_block_size() return the block
260 size of a cipher when passed an B<EVP_CIPHER> or B<EVP_CIPHER_CTX>
261 structure. The constant B<EVP_MAX_BLOCK_LENGTH> is also the maximum block
262 length for all ciphers.
264 EVP_CIPHER_type() and EVP_CIPHER_CTX_type() return the type of the passed
265 cipher or context. This "type" is the actual NID of the cipher OBJECT
266 IDENTIFIER as such it ignores the cipher parameters and 40 bit RC2 and
267 128 bit RC2 have the same NID. If the cipher does not have an object
268 identifier or does not have ASN1 support this function will return
271 EVP_CIPHER_name() and EVP_CIPHER_CTX_name() return the name of the passed
274 EVP_CIPHER_provider() returns an B<OSSL_PROVIDER> pointer to the provider
275 that implements the given B<EVP_CIPHER>.
277 EVP_CIPHER_CTX_cipher() returns the B<EVP_CIPHER> structure when passed
278 an B<EVP_CIPHER_CTX> structure.
280 EVP_CIPHER_mode() and EVP_CIPHER_CTX_mode() return the block cipher mode:
281 EVP_CIPH_ECB_MODE, EVP_CIPH_CBC_MODE, EVP_CIPH_CFB_MODE, EVP_CIPH_OFB_MODE,
282 EVP_CIPH_CTR_MODE, EVP_CIPH_GCM_MODE, EVP_CIPH_CCM_MODE, EVP_CIPH_XTS_MODE,
283 EVP_CIPH_WRAP_MODE, EVP_CIPH_OCB_MODE or EVP_CIPH_SIV_MODE. If the cipher is a
284 stream cipher then EVP_CIPH_STREAM_CIPHER is returned.
286 EVP_CIPHER_flags() returns any flags associated with the cipher. See
287 EVP_CIPHER_meth_set_flags() for a list of currently defined flags.
289 EVP_CIPHER_param_to_asn1() sets the AlgorithmIdentifier "parameter" based
290 on the passed cipher. This will typically include any parameters and an
291 IV. The cipher IV (if any) must be set when this call is made. This call
292 should be made before the cipher is actually "used" (before any
293 EVP_EncryptUpdate(), EVP_DecryptUpdate() calls for example). This function
294 may fail if the cipher does not have any ASN1 support.
296 EVP_CIPHER_asn1_to_param() sets the cipher parameters based on an ASN1
297 AlgorithmIdentifier "parameter". The precise effect depends on the cipher
298 In the case of RC2, for example, it will set the IV and effective key length.
299 This function should be called after the base cipher type is set but before
300 the key is set. For example EVP_CipherInit() will be called with the IV and
301 key set to NULL, EVP_CIPHER_asn1_to_param() will be called and finally
302 EVP_CipherInit() again with all parameters except the key set to NULL. It is
303 possible for this function to fail if the cipher does not have any ASN1 support
304 or the parameters cannot be set (for example the RC2 effective key length
307 EVP_CIPHER_CTX_ctrl() allows various cipher specific parameters to be determined
310 EVP_CIPHER_CTX_rand_key() generates a random key of the appropriate length
311 based on the cipher context. The EVP_CIPHER can provide its own random key
312 generation routine to support keys of a specific form. B<Key> must point to a
313 buffer at least as big as the value returned by EVP_CIPHER_CTX_key_length().
315 EVP_CIPHER_do_all_ex() traverses all ciphers implemented by all activated
316 providers in the given library context I<libctx>, and for each of the
317 implementations, calls the given function I<fn> with the implementation method
318 and the given I<arg> as argument.
322 EVP_CIPHER_fetch() returns a pointer to a B<EVP_CIPHER> for success
323 and B<NULL> for failure.
325 EVP_CIPHER_CTX_new() returns a pointer to a newly created
326 B<EVP_CIPHER_CTX> for success and B<NULL> for failure.
328 EVP_EncryptInit_ex(), EVP_EncryptUpdate() and EVP_EncryptFinal_ex()
329 return 1 for success and 0 for failure.
331 EVP_DecryptInit_ex() and EVP_DecryptUpdate() return 1 for success and 0 for failure.
332 EVP_DecryptFinal_ex() returns 0 if the decrypt failed or 1 for success.
334 EVP_CipherInit_ex() and EVP_CipherUpdate() return 1 for success and 0 for failure.
335 EVP_CipherFinal_ex() returns 0 for a decryption failure or 1 for success.
337 EVP_CIPHER_CTX_reset() returns 1 for success and 0 for failure.
339 EVP_get_cipherbyname(), EVP_get_cipherbynid() and EVP_get_cipherbyobj()
340 return an B<EVP_CIPHER> structure or NULL on error.
342 EVP_CIPHER_nid() and EVP_CIPHER_CTX_nid() return a NID.
344 EVP_CIPHER_block_size() and EVP_CIPHER_CTX_block_size() return the block
347 EVP_CIPHER_key_length() and EVP_CIPHER_CTX_key_length() return the key
350 EVP_CIPHER_CTX_set_padding() always returns 1.
352 EVP_CIPHER_iv_length() and EVP_CIPHER_CTX_iv_length() return the IV
353 length or zero if the cipher does not use an IV.
355 EVP_CIPHER_type() and EVP_CIPHER_CTX_type() return the NID of the cipher's
356 OBJECT IDENTIFIER or NID_undef if it has no defined OBJECT IDENTIFIER.
358 EVP_CIPHER_CTX_cipher() returns an B<EVP_CIPHER> structure.
360 EVP_CIPHER_param_to_asn1() and EVP_CIPHER_asn1_to_param() return greater
361 than zero for success and zero or a negative number on failure.
363 EVP_CIPHER_CTX_rand_key() returns 1 for success.
365 =head1 CIPHER LISTING
367 All algorithms have a fixed key length unless otherwise stated.
369 Refer to L<SEE ALSO> for the full list of ciphers available through the EVP
376 Null cipher: does nothing.
380 =head1 AEAD Interface
382 The EVP interface for Authenticated Encryption with Associated Data (AEAD)
383 modes are subtly altered and several additional I<ctrl> operations are supported
384 depending on the mode specified.
386 To specify additional authenticated data (AAD), a call to EVP_CipherUpdate(),
387 EVP_EncryptUpdate() or EVP_DecryptUpdate() should be made with the output
388 parameter B<out> set to B<NULL>.
390 When decrypting, the return value of EVP_DecryptFinal() or EVP_CipherFinal()
391 indicates whether the operation was successful. If it does not indicate success,
392 the authentication operation has failed and any output data B<MUST NOT> be used
395 =head2 GCM and OCB Modes
397 The following I<ctrl>s are supported in GCM and OCB modes.
401 =item EVP_CIPHER_CTX_ctrl(ctx, EVP_CTRL_AEAD_SET_IVLEN, ivlen, NULL)
403 Sets the IV length. This call can only be made before specifying an IV. If
404 not called a default IV length is used.
406 For GCM AES and OCB AES the default is 12 (i.e. 96 bits). For OCB mode the
409 =item EVP_CIPHER_CTX_ctrl(ctx, EVP_CTRL_AEAD_GET_TAG, taglen, tag)
411 Writes C<taglen> bytes of the tag value to the buffer indicated by C<tag>.
412 This call can only be made when encrypting data and B<after> all data has been
413 processed (e.g. after an EVP_EncryptFinal() call).
415 For OCB, C<taglen> must either be 16 or the value previously set via
416 B<EVP_CTRL_AEAD_SET_TAG>.
418 =item EVP_CIPHER_CTX_ctrl(ctx, EVP_CTRL_AEAD_SET_TAG, taglen, tag)
420 Sets the expected tag to C<taglen> bytes from C<tag>.
421 The tag length can only be set before specifying an IV.
422 C<taglen> must be between 1 and 16 inclusive.
424 For GCM, this call is only valid when decrypting data.
426 For OCB, this call is valid when decrypting data to set the expected tag,
427 and before encryption to set the desired tag length.
429 In OCB mode, calling this before encryption with C<tag> set to C<NULL> sets the
430 tag length. If this is not called prior to encryption, a default tag length is
433 For OCB AES, the default tag length is 16 (i.e. 128 bits). It is also the
434 maximum tag length for OCB.
440 The EVP interface for CCM mode is similar to that of the GCM mode but with a
441 few additional requirements and different I<ctrl> values.
443 For CCM mode, the total plaintext or ciphertext length B<MUST> be passed to
444 EVP_CipherUpdate(), EVP_EncryptUpdate() or EVP_DecryptUpdate() with the output
445 and input parameters (B<in> and B<out>) set to B<NULL> and the length passed in
446 the B<inl> parameter.
448 The following I<ctrl>s are supported in CCM mode.
452 =item EVP_CIPHER_CTX_ctrl(ctx, EVP_CTRL_AEAD_SET_TAG, taglen, tag)
454 This call is made to set the expected B<CCM> tag value when decrypting or
455 the length of the tag (with the C<tag> parameter set to NULL) when encrypting.
456 The tag length is often referred to as B<M>. If not set a default value is
457 used (12 for AES). When decrypting, the tag needs to be set before passing
458 in data to be decrypted, but as in GCM and OCB mode, it can be set after
459 passing additional authenticated data (see L<AEAD Interface>).
461 =item EVP_CIPHER_CTX_ctrl(ctx, EVP_CTRL_CCM_SET_L, ivlen, NULL)
463 Sets the CCM B<L> value. If not set a default is used (8 for AES).
465 =item EVP_CIPHER_CTX_ctrl(ctx, EVP_CTRL_AEAD_SET_IVLEN, ivlen, NULL)
467 Sets the CCM nonce (IV) length. This call can only be made before specifying an
468 nonce value. The nonce length is given by B<15 - L> so it is 7 by default for
475 For SIV mode ciphers the behaviour of the EVP interface is subtly
476 altered and several additional ctrl operations are supported.
478 To specify any additional authenticated data (AAD) and/or a Nonce, a call to
479 EVP_CipherUpdate(), EVP_EncryptUpdate() or EVP_DecryptUpdate() should be made
480 with the output parameter B<out> set to B<NULL>.
482 RFC5297 states that the Nonce is the last piece of AAD before the actual
483 encrypt/decrypt takes place. The API does not differentiate the Nonce from
486 When decrypting the return value of EVP_DecryptFinal() or EVP_CipherFinal()
487 indicates if the operation was successful. If it does not indicate success
488 the authentication operation has failed and any output data B<MUST NOT>
489 be used as it is corrupted.
491 The following ctrls are supported in both SIV modes.
495 =item EVP_CIPHER_CTX_ctrl(ctx, EVP_CTRL_AEAD_GET_TAG, taglen, tag);
497 Writes B<taglen> bytes of the tag value to the buffer indicated by B<tag>.
498 This call can only be made when encrypting data and B<after> all data has been
499 processed (e.g. after an EVP_EncryptFinal() call). For SIV mode the taglen must
502 =item EVP_CIPHER_CTX_ctrl(ctx, EVP_CTRL_AEAD_SET_TAG, taglen, tag);
504 Sets the expected tag to B<taglen> bytes from B<tag>. This call is only legal
505 when decrypting data and must be made B<before> any data is processed (e.g.
506 before any EVP_DecryptUpdate() call). For SIV mode the taglen must be 16.
510 SIV mode makes two passes over the input data, thus, only one call to
511 EVP_CipherUpdate(), EVP_EncryptUpdate() or EVP_DecryptUpdate() should be made
512 with B<out> set to a non-B<NULL> value. A call to EVP_Decrypt_Final() or
513 EVP_CipherFinal() is not required, but will indicate if the update
516 =head2 ChaCha20-Poly1305
518 The following I<ctrl>s are supported for the ChaCha20-Poly1305 AEAD algorithm.
522 =item EVP_CIPHER_CTX_ctrl(ctx, EVP_CTRL_AEAD_SET_IVLEN, ivlen, NULL)
524 Sets the nonce length. This call can only be made before specifying the nonce.
525 If not called a default nonce length of 12 (i.e. 96 bits) is used. The maximum
526 nonce length is 12 bytes (i.e. 96-bits). If a nonce of less than 12 bytes is set
527 then the nonce is automatically padded with leading 0 bytes to make it 12 bytes
530 =item EVP_CIPHER_CTX_ctrl(ctx, EVP_CTRL_AEAD_GET_TAG, taglen, tag)
532 Writes C<taglen> bytes of the tag value to the buffer indicated by C<tag>.
533 This call can only be made when encrypting data and B<after> all data has been
534 processed (e.g. after an EVP_EncryptFinal() call).
536 C<taglen> specified here must be 16 (B<POLY1305_BLOCK_SIZE>, i.e. 128-bits) or
539 =item EVP_CIPHER_CTX_ctrl(ctx, EVP_CTRL_AEAD_SET_TAG, taglen, tag)
541 Sets the expected tag to C<taglen> bytes from C<tag>.
542 The tag length can only be set before specifying an IV.
543 C<taglen> must be between 1 and 16 (B<POLY1305_BLOCK_SIZE>) inclusive.
544 This call is only valid when decrypting data.
550 Where possible the B<EVP> interface to symmetric ciphers should be used in
551 preference to the low level interfaces. This is because the code then becomes
552 transparent to the cipher used and much more flexible. Additionally, the
553 B<EVP> interface will ensure the use of platform specific cryptographic
554 acceleration such as AES-NI (the low level interfaces do not provide the
557 PKCS padding works by adding B<n> padding bytes of value B<n> to make the total
558 length of the encrypted data a multiple of the block size. Padding is always
559 added so if the data is already a multiple of the block size B<n> will equal
560 the block size. For example if the block size is 8 and 11 bytes are to be
561 encrypted then 5 padding bytes of value 5 will be added.
563 When decrypting the final block is checked to see if it has the correct form.
565 Although the decryption operation can produce an error if padding is enabled,
566 it is not a strong test that the input data or key is correct. A random block
567 has better than 1 in 256 chance of being of the correct format and problems with
568 the input data earlier on will not produce a final decrypt error.
570 If padding is disabled then the decryption operation will always succeed if
571 the total amount of data decrypted is a multiple of the block size.
573 The functions EVP_EncryptInit(), EVP_EncryptFinal(), EVP_DecryptInit(),
574 EVP_CipherInit() and EVP_CipherFinal() are obsolete but are retained for
575 compatibility with existing code. New code should use EVP_EncryptInit_ex(),
576 EVP_EncryptFinal_ex(), EVP_DecryptInit_ex(), EVP_DecryptFinal_ex(),
577 EVP_CipherInit_ex() and EVP_CipherFinal_ex() because they can reuse an
578 existing context without allocating and freeing it up on each call.
580 EVP_get_cipherbynid(), and EVP_get_cipherbyobj() are implemented as macros.
584 B<EVP_MAX_KEY_LENGTH> and B<EVP_MAX_IV_LENGTH> only refer to the internal
585 ciphers with default key lengths. If custom ciphers exceed these values the
586 results are unpredictable. This is because it has become standard practice to
587 define a generic key as a fixed unsigned char array containing
588 B<EVP_MAX_KEY_LENGTH> bytes.
590 The ASN1 code is incomplete (and sometimes inaccurate) it has only been tested
591 for certain common S/MIME ciphers (RC2, DES, triple DES) in CBC mode.
595 Encrypt a string using IDEA:
597 int do_crypt(char *outfile)
599 unsigned char outbuf[1024];
602 * Bogus key and IV: we'd normally set these from
605 unsigned char key[] = {0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15};
606 unsigned char iv[] = {1,2,3,4,5,6,7,8};
607 char intext[] = "Some Crypto Text";
611 ctx = EVP_CIPHER_CTX_new();
612 EVP_EncryptInit_ex(ctx, EVP_idea_cbc(), NULL, key, iv);
614 if (!EVP_EncryptUpdate(ctx, outbuf, &outlen, intext, strlen(intext))) {
616 EVP_CIPHER_CTX_free(ctx);
620 * Buffer passed to EVP_EncryptFinal() must be after data just
621 * encrypted to avoid overwriting it.
623 if (!EVP_EncryptFinal_ex(ctx, outbuf + outlen, &tmplen)) {
625 EVP_CIPHER_CTX_free(ctx);
629 EVP_CIPHER_CTX_free(ctx);
631 * Need binary mode for fopen because encrypted data is
632 * binary data. Also cannot use strlen() on it because
633 * it won't be NUL terminated and may contain embedded
636 out = fopen(outfile, "wb");
641 fwrite(outbuf, 1, outlen, out);
646 The ciphertext from the above example can be decrypted using the B<openssl>
647 utility with the command line (shown on two lines for clarity):
650 -K 000102030405060708090A0B0C0D0E0F -iv 0102030405060708 <filename
652 General encryption and decryption function example using FILE I/O and AES128
655 int do_crypt(FILE *in, FILE *out, int do_encrypt)
657 /* Allow enough space in output buffer for additional block */
658 unsigned char inbuf[1024], outbuf[1024 + EVP_MAX_BLOCK_LENGTH];
662 * Bogus key and IV: we'd normally set these from
665 unsigned char key[] = "0123456789abcdeF";
666 unsigned char iv[] = "1234567887654321";
668 /* Don't set key or IV right away; we want to check lengths */
669 ctx = EVP_CIPHER_CTX_new();
670 EVP_CipherInit_ex(&ctx, EVP_aes_128_cbc(), NULL, NULL, NULL,
672 OPENSSL_assert(EVP_CIPHER_CTX_key_length(ctx) == 16);
673 OPENSSL_assert(EVP_CIPHER_CTX_iv_length(ctx) == 16);
675 /* Now we can set key and IV */
676 EVP_CipherInit_ex(ctx, NULL, NULL, key, iv, do_encrypt);
679 inlen = fread(inbuf, 1, 1024, in);
682 if (!EVP_CipherUpdate(ctx, outbuf, &outlen, inbuf, inlen)) {
684 EVP_CIPHER_CTX_free(ctx);
687 fwrite(outbuf, 1, outlen, out);
689 if (!EVP_CipherFinal_ex(ctx, outbuf, &outlen)) {
691 EVP_CIPHER_CTX_free(ctx);
694 fwrite(outbuf, 1, outlen, out);
696 EVP_CIPHER_CTX_free(ctx);
705 Supported ciphers are listed in:
724 Support for OCB mode was added in OpenSSL 1.1.0.
726 B<EVP_CIPHER_CTX> was made opaque in OpenSSL 1.1.0. As a result,
727 EVP_CIPHER_CTX_reset() appeared and EVP_CIPHER_CTX_cleanup()
728 disappeared. EVP_CIPHER_CTX_init() remains as an alias for
729 EVP_CIPHER_CTX_reset().
733 Copyright 2000-2018 The OpenSSL Project Authors. All Rights Reserved.
735 Licensed under the Apache License 2.0 (the "License"). You may not use
736 this file except in compliance with the License. You can obtain a copy
737 in the file LICENSE in the source distribution or at
738 L<https://www.openssl.org/source/license.html>.