18 EVP_CIPHER_CTX_set_key_length,
30 EVP_CIPHER_block_size,
31 EVP_CIPHER_key_length,
36 EVP_CIPHER_CTX_cipher,
38 EVP_CIPHER_CTX_block_size,
39 EVP_CIPHER_CTX_key_length,
40 EVP_CIPHER_CTX_iv_length,
41 EVP_CIPHER_CTX_get_app_data,
42 EVP_CIPHER_CTX_set_app_data,
46 EVP_CIPHER_param_to_asn1,
47 EVP_CIPHER_asn1_to_param,
48 EVP_CIPHER_CTX_set_padding,
56 #include <openssl/evp.h>
58 EVP_CIPHER *EVP_CIPHER_fetch(OPENSSL_CTX *ctx, const char *algorithm,
59 const char *properties);
60 EVP_CIPHER_CTX *EVP_CIPHER_CTX_new(void);
61 int EVP_CIPHER_CTX_reset(EVP_CIPHER_CTX *ctx);
62 void EVP_CIPHER_CTX_free(EVP_CIPHER_CTX *ctx);
64 int EVP_EncryptInit_ex(EVP_CIPHER_CTX *ctx, const EVP_CIPHER *type,
65 ENGINE *impl, const unsigned char *key, const unsigned char *iv);
66 int EVP_EncryptUpdate(EVP_CIPHER_CTX *ctx, unsigned char *out,
67 int *outl, const unsigned char *in, int inl);
68 int EVP_EncryptFinal_ex(EVP_CIPHER_CTX *ctx, unsigned char *out, int *outl);
70 int EVP_DecryptInit_ex(EVP_CIPHER_CTX *ctx, const EVP_CIPHER *type,
71 ENGINE *impl, const unsigned char *key, const unsigned char *iv);
72 int EVP_DecryptUpdate(EVP_CIPHER_CTX *ctx, unsigned char *out,
73 int *outl, const unsigned char *in, int inl);
74 int EVP_DecryptFinal_ex(EVP_CIPHER_CTX *ctx, unsigned char *outm, int *outl);
76 int EVP_CipherInit_ex(EVP_CIPHER_CTX *ctx, const EVP_CIPHER *type,
77 ENGINE *impl, const unsigned char *key, const unsigned char *iv, int enc);
78 int EVP_CipherUpdate(EVP_CIPHER_CTX *ctx, unsigned char *out,
79 int *outl, const unsigned char *in, int inl);
80 int EVP_CipherFinal_ex(EVP_CIPHER_CTX *ctx, unsigned char *outm, int *outl);
82 int EVP_EncryptInit(EVP_CIPHER_CTX *ctx, const EVP_CIPHER *type,
83 const unsigned char *key, const unsigned char *iv);
84 int EVP_EncryptFinal(EVP_CIPHER_CTX *ctx, unsigned char *out, int *outl);
86 int EVP_DecryptInit(EVP_CIPHER_CTX *ctx, const EVP_CIPHER *type,
87 const unsigned char *key, const unsigned char *iv);
88 int EVP_DecryptFinal(EVP_CIPHER_CTX *ctx, unsigned char *outm, int *outl);
90 int EVP_CipherInit(EVP_CIPHER_CTX *ctx, const EVP_CIPHER *type,
91 const unsigned char *key, const unsigned char *iv, int enc);
92 int EVP_CipherFinal(EVP_CIPHER_CTX *ctx, unsigned char *outm, int *outl);
94 int EVP_CIPHER_CTX_set_padding(EVP_CIPHER_CTX *x, int padding);
95 int EVP_CIPHER_CTX_set_key_length(EVP_CIPHER_CTX *x, int keylen);
96 int EVP_CIPHER_CTX_ctrl(EVP_CIPHER_CTX *ctx, int type, int arg, void *ptr);
97 int EVP_CIPHER_CTX_rand_key(EVP_CIPHER_CTX *ctx, unsigned char *key);
99 const EVP_CIPHER *EVP_get_cipherbyname(const char *name);
100 const EVP_CIPHER *EVP_get_cipherbynid(int nid);
101 const EVP_CIPHER *EVP_get_cipherbyobj(const ASN1_OBJECT *a);
103 int EVP_CIPHER_nid(const EVP_CIPHER *e);
104 int EVP_CIPHER_block_size(const EVP_CIPHER *e);
105 int EVP_CIPHER_key_length(const EVP_CIPHER *e);
106 int EVP_CIPHER_iv_length(const EVP_CIPHER *e);
107 unsigned long EVP_CIPHER_flags(const EVP_CIPHER *e);
108 unsigned long EVP_CIPHER_mode(const EVP_CIPHER *e);
109 int EVP_CIPHER_type(const EVP_CIPHER *ctx);
111 const EVP_CIPHER *EVP_CIPHER_CTX_cipher(const EVP_CIPHER_CTX *ctx);
112 int EVP_CIPHER_CTX_nid(const EVP_CIPHER_CTX *ctx);
113 int EVP_CIPHER_CTX_block_size(const EVP_CIPHER_CTX *ctx);
114 int EVP_CIPHER_CTX_key_length(const EVP_CIPHER_CTX *ctx);
115 int EVP_CIPHER_CTX_iv_length(const EVP_CIPHER_CTX *ctx);
116 void *EVP_CIPHER_CTX_get_app_data(const EVP_CIPHER_CTX *ctx);
117 void EVP_CIPHER_CTX_set_app_data(const EVP_CIPHER_CTX *ctx, void *data);
118 int EVP_CIPHER_CTX_type(const EVP_CIPHER_CTX *ctx);
119 int EVP_CIPHER_CTX_mode(const EVP_CIPHER_CTX *ctx);
121 int EVP_CIPHER_param_to_asn1(EVP_CIPHER_CTX *c, ASN1_TYPE *type);
122 int EVP_CIPHER_asn1_to_param(EVP_CIPHER_CTX *c, ASN1_TYPE *type);
126 The EVP cipher routines are a high level interface to certain
129 EVP_CIPHER_fetch() fetches the cipher implementation for the given
130 B<algorithm> from any provider offering it, within the criteria given
131 by the B<properties>.
132 See L<provider(7)/Fetching algorithms> for further information.
134 The returned value must eventually be freed with
135 L<EVP_CIPHER_meth_free(3)>.
137 EVP_CIPHER_CTX_new() creates a cipher context.
139 EVP_CIPHER_CTX_free() clears all information from a cipher context
140 and free up any allocated memory associate with it, including B<ctx>
141 itself. This function should be called after all operations using a
142 cipher are complete so sensitive information does not remain in
145 EVP_EncryptInit_ex() sets up cipher context B<ctx> for encryption
146 with cipher B<type>. B<type> is typically supplied by a function such
147 as EVP_aes_256_cbc(), or a value explicitly fetched with
148 EVP_CIPHER_fetch(). If B<impl> is non-NULL, its implementation of the
149 cipher B<type> is used if there is one, and if not, the default
150 implementation is used. B<key> is the symmetric key to use
151 and B<iv> is the IV to use (if necessary), the actual number of bytes
152 used for the key and IV depends on the cipher. It is possible to set
153 all parameters to NULL except B<type> in an initial call and supply
154 the remaining parameters in subsequent calls, all of which have B<type>
155 set to NULL. This is done when the default cipher parameters are not
158 EVP_EncryptUpdate() encrypts B<inl> bytes from the buffer B<in> and
159 writes the encrypted version to B<out>. This function can be called
160 multiple times to encrypt successive blocks of data. The amount
161 of data written depends on the block alignment of the encrypted data:
162 as a result the amount of data written may be anything from zero bytes
163 to (inl + cipher_block_size - 1) so B<out> should contain sufficient
164 room. The actual number of bytes written is placed in B<outl>. It also
165 checks if B<in> and B<out> are partially overlapping, and if they are
166 0 is returned to indicate failure.
168 If padding is enabled (the default) then EVP_EncryptFinal_ex() encrypts
169 the "final" data, that is any data that remains in a partial block.
170 It uses standard block padding (aka PKCS padding) as described in
171 the NOTES section, below. The encrypted
172 final data is written to B<out> which should have sufficient space for
173 one cipher block. The number of bytes written is placed in B<outl>. After
174 this function is called the encryption operation is finished and no further
175 calls to EVP_EncryptUpdate() should be made.
177 If padding is disabled then EVP_EncryptFinal_ex() will not encrypt any more
178 data and it will return an error if any data remains in a partial block:
179 that is if the total data length is not a multiple of the block size.
181 EVP_DecryptInit_ex(), EVP_DecryptUpdate() and EVP_DecryptFinal_ex() are the
182 corresponding decryption operations. EVP_DecryptFinal() will return an
183 error code if padding is enabled and the final block is not correctly
184 formatted. The parameters and restrictions are identical to the encryption
185 operations except that if padding is enabled the decrypted data buffer B<out>
186 passed to EVP_DecryptUpdate() should have sufficient room for
187 (B<inl> + cipher_block_size) bytes unless the cipher block size is 1 in
188 which case B<inl> bytes is sufficient.
190 EVP_CipherInit_ex(), EVP_CipherUpdate() and EVP_CipherFinal_ex() are
191 functions that can be used for decryption or encryption. The operation
192 performed depends on the value of the B<enc> parameter. It should be set
193 to 1 for encryption, 0 for decryption and -1 to leave the value unchanged
194 (the actual value of 'enc' being supplied in a previous call).
196 EVP_CIPHER_CTX_reset() clears all information from a cipher context
197 and free up any allocated memory associate with it, except the B<ctx>
198 itself. This function should be called anytime B<ctx> is to be reused
199 for another EVP_CipherInit() / EVP_CipherUpdate() / EVP_CipherFinal()
202 EVP_EncryptInit(), EVP_DecryptInit() and EVP_CipherInit() behave in a
203 similar way to EVP_EncryptInit_ex(), EVP_DecryptInit_ex() and
204 EVP_CipherInit_ex() except they always use the default cipher implementation.
206 EVP_EncryptFinal(), EVP_DecryptFinal() and EVP_CipherFinal() are
207 identical to EVP_EncryptFinal_ex(), EVP_DecryptFinal_ex() and
208 EVP_CipherFinal_ex(). In previous releases they also cleaned up
209 the B<ctx>, but this is no longer done and EVP_CIPHER_CTX_clean()
210 must be called to free any context resources.
212 EVP_get_cipherbyname(), EVP_get_cipherbynid() and EVP_get_cipherbyobj()
213 return an EVP_CIPHER structure when passed a cipher name, a NID or an
214 ASN1_OBJECT structure.
216 EVP_CIPHER_nid() and EVP_CIPHER_CTX_nid() return the NID of a cipher when
217 passed an B<EVP_CIPHER> or B<EVP_CIPHER_CTX> structure. The actual NID
218 value is an internal value which may not have a corresponding OBJECT
221 EVP_CIPHER_CTX_set_padding() enables or disables padding. This
222 function should be called after the context is set up for encryption
223 or decryption with EVP_EncryptInit_ex(), EVP_DecryptInit_ex() or
224 EVP_CipherInit_ex(). By default encryption operations are padded using
225 standard block padding and the padding is checked and removed when
226 decrypting. If the B<pad> parameter is zero then no padding is
227 performed, the total amount of data encrypted or decrypted must then
228 be a multiple of the block size or an error will occur.
230 EVP_CIPHER_key_length() and EVP_CIPHER_CTX_key_length() return the key
231 length of a cipher when passed an B<EVP_CIPHER> or B<EVP_CIPHER_CTX>
232 structure. The constant B<EVP_MAX_KEY_LENGTH> is the maximum key length
233 for all ciphers. Note: although EVP_CIPHER_key_length() is fixed for a
234 given cipher, the value of EVP_CIPHER_CTX_key_length() may be different
235 for variable key length ciphers.
237 EVP_CIPHER_CTX_set_key_length() sets the key length of the cipher ctx.
238 If the cipher is a fixed length cipher then attempting to set the key
239 length to any value other than the fixed value is an error.
241 EVP_CIPHER_iv_length() and EVP_CIPHER_CTX_iv_length() return the IV
242 length of a cipher when passed an B<EVP_CIPHER> or B<EVP_CIPHER_CTX>.
243 It will return zero if the cipher does not use an IV. The constant
244 B<EVP_MAX_IV_LENGTH> is the maximum IV length for all ciphers.
246 EVP_CIPHER_block_size() and EVP_CIPHER_CTX_block_size() return the block
247 size of a cipher when passed an B<EVP_CIPHER> or B<EVP_CIPHER_CTX>
248 structure. The constant B<EVP_MAX_BLOCK_LENGTH> is also the maximum block
249 length for all ciphers.
251 EVP_CIPHER_type() and EVP_CIPHER_CTX_type() return the type of the passed
252 cipher or context. This "type" is the actual NID of the cipher OBJECT
253 IDENTIFIER as such it ignores the cipher parameters and 40 bit RC2 and
254 128 bit RC2 have the same NID. If the cipher does not have an object
255 identifier or does not have ASN1 support this function will return
258 EVP_CIPHER_CTX_cipher() returns the B<EVP_CIPHER> structure when passed
259 an B<EVP_CIPHER_CTX> structure.
261 EVP_CIPHER_mode() and EVP_CIPHER_CTX_mode() return the block cipher mode:
262 EVP_CIPH_ECB_MODE, EVP_CIPH_CBC_MODE, EVP_CIPH_CFB_MODE, EVP_CIPH_OFB_MODE,
263 EVP_CIPH_CTR_MODE, EVP_CIPH_GCM_MODE, EVP_CIPH_CCM_MODE, EVP_CIPH_XTS_MODE,
264 EVP_CIPH_WRAP_MODE or EVP_CIPH_OCB_MODE. If the cipher is a stream cipher then
265 EVP_CIPH_STREAM_CIPHER is returned.
267 EVP_CIPHER_param_to_asn1() sets the AlgorithmIdentifier "parameter" based
268 on the passed cipher. This will typically include any parameters and an
269 IV. The cipher IV (if any) must be set when this call is made. This call
270 should be made before the cipher is actually "used" (before any
271 EVP_EncryptUpdate(), EVP_DecryptUpdate() calls for example). This function
272 may fail if the cipher does not have any ASN1 support.
274 EVP_CIPHER_asn1_to_param() sets the cipher parameters based on an ASN1
275 AlgorithmIdentifier "parameter". The precise effect depends on the cipher
276 In the case of RC2, for example, it will set the IV and effective key length.
277 This function should be called after the base cipher type is set but before
278 the key is set. For example EVP_CipherInit() will be called with the IV and
279 key set to NULL, EVP_CIPHER_asn1_to_param() will be called and finally
280 EVP_CipherInit() again with all parameters except the key set to NULL. It is
281 possible for this function to fail if the cipher does not have any ASN1 support
282 or the parameters cannot be set (for example the RC2 effective key length
285 EVP_CIPHER_CTX_ctrl() allows various cipher specific parameters to be determined
288 EVP_CIPHER_CTX_rand_key() generates a random key of the appropriate length
289 based on the cipher context. The EVP_CIPHER can provide its own random key
290 generation routine to support keys of a specific form. B<Key> must point to a
291 buffer at least as big as the value returned by EVP_CIPHER_CTX_key_length().
295 EVP_CIPHER_fetch() returns a pointer to a B<EVP_CIPHER> for success
296 and B<NULL> for failure.
298 EVP_CIPHER_CTX_new() returns a pointer to a newly created
299 B<EVP_CIPHER_CTX> for success and B<NULL> for failure.
301 EVP_EncryptInit_ex(), EVP_EncryptUpdate() and EVP_EncryptFinal_ex()
302 return 1 for success and 0 for failure.
304 EVP_DecryptInit_ex() and EVP_DecryptUpdate() return 1 for success and 0 for failure.
305 EVP_DecryptFinal_ex() returns 0 if the decrypt failed or 1 for success.
307 EVP_CipherInit_ex() and EVP_CipherUpdate() return 1 for success and 0 for failure.
308 EVP_CipherFinal_ex() returns 0 for a decryption failure or 1 for success.
310 EVP_CIPHER_CTX_reset() returns 1 for success and 0 for failure.
312 EVP_get_cipherbyname(), EVP_get_cipherbynid() and EVP_get_cipherbyobj()
313 return an B<EVP_CIPHER> structure or NULL on error.
315 EVP_CIPHER_nid() and EVP_CIPHER_CTX_nid() return a NID.
317 EVP_CIPHER_block_size() and EVP_CIPHER_CTX_block_size() return the block
320 EVP_CIPHER_key_length() and EVP_CIPHER_CTX_key_length() return the key
323 EVP_CIPHER_CTX_set_padding() always returns 1.
325 EVP_CIPHER_iv_length() and EVP_CIPHER_CTX_iv_length() return the IV
326 length or zero if the cipher does not use an IV.
328 EVP_CIPHER_type() and EVP_CIPHER_CTX_type() return the NID of the cipher's
329 OBJECT IDENTIFIER or NID_undef if it has no defined OBJECT IDENTIFIER.
331 EVP_CIPHER_CTX_cipher() returns an B<EVP_CIPHER> structure.
333 EVP_CIPHER_param_to_asn1() and EVP_CIPHER_asn1_to_param() return greater
334 than zero for success and zero or a negative number on failure.
336 EVP_CIPHER_CTX_rand_key() returns 1 for success.
338 =head1 CIPHER LISTING
340 All algorithms have a fixed key length unless otherwise stated.
342 Refer to L<SEE ALSO> for the full list of ciphers available through the EVP
349 Null cipher: does nothing.
353 =head1 AEAD Interface
355 The EVP interface for Authenticated Encryption with Associated Data (AEAD)
356 modes are subtly altered and several additional I<ctrl> operations are supported
357 depending on the mode specified.
359 To specify additional authenticated data (AAD), a call to EVP_CipherUpdate(),
360 EVP_EncryptUpdate() or EVP_DecryptUpdate() should be made with the output
361 parameter B<out> set to B<NULL>.
363 When decrypting, the return value of EVP_DecryptFinal() or EVP_CipherFinal()
364 indicates whether the operation was successful. If it does not indicate success,
365 the authentication operation has failed and any output data B<MUST NOT> be used
368 =head2 GCM and OCB Modes
370 The following I<ctrl>s are supported in GCM and OCB modes.
374 =item EVP_CIPHER_CTX_ctrl(ctx, EVP_CTRL_AEAD_SET_IVLEN, ivlen, NULL)
376 Sets the IV length. This call can only be made before specifying an IV. If
377 not called a default IV length is used.
379 For GCM AES and OCB AES the default is 12 (i.e. 96 bits). For OCB mode the
382 =item EVP_CIPHER_CTX_ctrl(ctx, EVP_CTRL_AEAD_GET_TAG, taglen, tag)
384 Writes C<taglen> bytes of the tag value to the buffer indicated by C<tag>.
385 This call can only be made when encrypting data and B<after> all data has been
386 processed (e.g. after an EVP_EncryptFinal() call).
388 For OCB, C<taglen> must either be 16 or the value previously set via
389 B<EVP_CTRL_AEAD_SET_TAG>.
391 =item EVP_CIPHER_CTX_ctrl(ctx, EVP_CTRL_AEAD_SET_TAG, taglen, tag)
393 Sets the expected tag to C<taglen> bytes from C<tag>.
394 The tag length can only be set before specifying an IV.
395 C<taglen> must be between 1 and 16 inclusive.
397 For GCM, this call is only valid when decrypting data.
399 For OCB, this call is valid when decrypting data to set the expected tag,
400 and before encryption to set the desired tag length.
402 In OCB mode, calling this before encryption with C<tag> set to C<NULL> sets the
403 tag length. If this is not called prior to encryption, a default tag length is
406 For OCB AES, the default tag length is 16 (i.e. 128 bits). It is also the
407 maximum tag length for OCB.
413 The EVP interface for CCM mode is similar to that of the GCM mode but with a
414 few additional requirements and different I<ctrl> values.
416 For CCM mode, the total plaintext or ciphertext length B<MUST> be passed to
417 EVP_CipherUpdate(), EVP_EncryptUpdate() or EVP_DecryptUpdate() with the output
418 and input parameters (B<in> and B<out>) set to B<NULL> and the length passed in
419 the B<inl> parameter.
421 The following I<ctrl>s are supported in CCM mode.
425 =item EVP_CIPHER_CTX_ctrl(ctx, EVP_CTRL_AEAD_SET_TAG, taglen, tag)
427 This call is made to set the expected B<CCM> tag value when decrypting or
428 the length of the tag (with the C<tag> parameter set to NULL) when encrypting.
429 The tag length is often referred to as B<M>. If not set a default value is
430 used (12 for AES). When decrypting, the tag needs to be set before passing
431 in data to be decrypted, but as in GCM and OCB mode, it can be set after
432 passing additional authenticated data (see L<AEAD Interface>).
434 =item EVP_CIPHER_CTX_ctrl(ctx, EVP_CTRL_CCM_SET_L, ivlen, NULL)
436 Sets the CCM B<L> value. If not set a default is used (8 for AES).
438 =item EVP_CIPHER_CTX_ctrl(ctx, EVP_CTRL_AEAD_SET_IVLEN, ivlen, NULL)
440 Sets the CCM nonce (IV) length. This call can only be made before specifying an
441 nonce value. The nonce length is given by B<15 - L> so it is 7 by default for
448 For SIV mode ciphers the behaviour of the EVP interface is subtly
449 altered and several additional ctrl operations are supported.
451 To specify any additional authenticated data (AAD) and/or a Nonce, a call to
452 EVP_CipherUpdate(), EVP_EncryptUpdate() or EVP_DecryptUpdate() should be made
453 with the output parameter B<out> set to B<NULL>.
455 RFC5297 states that the Nonce is the last piece of AAD before the actual
456 encrypt/decrypt takes place. The API does not differentiate the Nonce from
459 When decrypting the return value of EVP_DecryptFinal() or EVP_CipherFinal()
460 indicates if the operation was successful. If it does not indicate success
461 the authentication operation has failed and any output data B<MUST NOT>
462 be used as it is corrupted.
464 The following ctrls are supported in both SIV modes.
468 =item EVP_CIPHER_CTX_ctrl(ctx, EVP_CTRL_AEAD_GET_TAG, taglen, tag);
470 Writes B<taglen> bytes of the tag value to the buffer indicated by B<tag>.
471 This call can only be made when encrypting data and B<after> all data has been
472 processed (e.g. after an EVP_EncryptFinal() call). For SIV mode the taglen must
475 =item EVP_CIPHER_CTX_ctrl(ctx, EVP_CTRL_AEAD_SET_TAG, taglen, tag);
477 Sets the expected tag to B<taglen> bytes from B<tag>. This call is only legal
478 when decrypting data and must be made B<before> any data is processed (e.g.
479 before any EVP_DecryptUpdate() call). For SIV mode the taglen must be 16.
483 SIV mode makes two passes over the input data, thus, only one call to
484 EVP_CipherUpdate(), EVP_EncryptUpdate() or EVP_DecryptUpdate() should be made
485 with B<out> set to a non-B<NULL> value. A call to EVP_Decrypt_Final() or
486 EVP_CipherFinal() is not required, but will indicate if the update
489 =head2 ChaCha20-Poly1305
491 The following I<ctrl>s are supported for the ChaCha20-Poly1305 AEAD algorithm.
495 =item EVP_CIPHER_CTX_ctrl(ctx, EVP_CTRL_AEAD_SET_IVLEN, ivlen, NULL)
497 Sets the nonce length. This call can only be made before specifying the nonce.
498 If not called a default nonce length of 12 (i.e. 96 bits) is used. The maximum
499 nonce length is 12 bytes (i.e. 96-bits). If a nonce of less than 12 bytes is set
500 then the nonce is automatically padded with leading 0 bytes to make it 12 bytes
503 =item EVP_CIPHER_CTX_ctrl(ctx, EVP_CTRL_AEAD_GET_TAG, taglen, tag)
505 Writes C<taglen> bytes of the tag value to the buffer indicated by C<tag>.
506 This call can only be made when encrypting data and B<after> all data has been
507 processed (e.g. after an EVP_EncryptFinal() call).
509 C<taglen> specified here must be 16 (B<POLY1305_BLOCK_SIZE>, i.e. 128-bits) or
512 =item EVP_CIPHER_CTX_ctrl(ctx, EVP_CTRL_AEAD_SET_TAG, taglen, tag)
514 Sets the expected tag to C<taglen> bytes from C<tag>.
515 The tag length can only be set before specifying an IV.
516 C<taglen> must be between 1 and 16 (B<POLY1305_BLOCK_SIZE>) inclusive.
517 This call is only valid when decrypting data.
523 Where possible the B<EVP> interface to symmetric ciphers should be used in
524 preference to the low level interfaces. This is because the code then becomes
525 transparent to the cipher used and much more flexible. Additionally, the
526 B<EVP> interface will ensure the use of platform specific cryptographic
527 acceleration such as AES-NI (the low level interfaces do not provide the
530 PKCS padding works by adding B<n> padding bytes of value B<n> to make the total
531 length of the encrypted data a multiple of the block size. Padding is always
532 added so if the data is already a multiple of the block size B<n> will equal
533 the block size. For example if the block size is 8 and 11 bytes are to be
534 encrypted then 5 padding bytes of value 5 will be added.
536 When decrypting the final block is checked to see if it has the correct form.
538 Although the decryption operation can produce an error if padding is enabled,
539 it is not a strong test that the input data or key is correct. A random block
540 has better than 1 in 256 chance of being of the correct format and problems with
541 the input data earlier on will not produce a final decrypt error.
543 If padding is disabled then the decryption operation will always succeed if
544 the total amount of data decrypted is a multiple of the block size.
546 The functions EVP_EncryptInit(), EVP_EncryptFinal(), EVP_DecryptInit(),
547 EVP_CipherInit() and EVP_CipherFinal() are obsolete but are retained for
548 compatibility with existing code. New code should use EVP_EncryptInit_ex(),
549 EVP_EncryptFinal_ex(), EVP_DecryptInit_ex(), EVP_DecryptFinal_ex(),
550 EVP_CipherInit_ex() and EVP_CipherFinal_ex() because they can reuse an
551 existing context without allocating and freeing it up on each call.
553 EVP_get_cipherbynid(), and EVP_get_cipherbyobj() are implemented as macros.
557 B<EVP_MAX_KEY_LENGTH> and B<EVP_MAX_IV_LENGTH> only refer to the internal
558 ciphers with default key lengths. If custom ciphers exceed these values the
559 results are unpredictable. This is because it has become standard practice to
560 define a generic key as a fixed unsigned char array containing
561 B<EVP_MAX_KEY_LENGTH> bytes.
563 The ASN1 code is incomplete (and sometimes inaccurate) it has only been tested
564 for certain common S/MIME ciphers (RC2, DES, triple DES) in CBC mode.
568 Encrypt a string using IDEA:
570 int do_crypt(char *outfile)
572 unsigned char outbuf[1024];
575 * Bogus key and IV: we'd normally set these from
578 unsigned char key[] = {0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15};
579 unsigned char iv[] = {1,2,3,4,5,6,7,8};
580 char intext[] = "Some Crypto Text";
584 ctx = EVP_CIPHER_CTX_new();
585 EVP_EncryptInit_ex(ctx, EVP_idea_cbc(), NULL, key, iv);
587 if (!EVP_EncryptUpdate(ctx, outbuf, &outlen, intext, strlen(intext))) {
589 EVP_CIPHER_CTX_free(ctx);
593 * Buffer passed to EVP_EncryptFinal() must be after data just
594 * encrypted to avoid overwriting it.
596 if (!EVP_EncryptFinal_ex(ctx, outbuf + outlen, &tmplen)) {
598 EVP_CIPHER_CTX_free(ctx);
602 EVP_CIPHER_CTX_free(ctx);
604 * Need binary mode for fopen because encrypted data is
605 * binary data. Also cannot use strlen() on it because
606 * it won't be NUL terminated and may contain embedded
609 out = fopen(outfile, "wb");
614 fwrite(outbuf, 1, outlen, out);
619 The ciphertext from the above example can be decrypted using the B<openssl>
620 utility with the command line (shown on two lines for clarity):
623 -K 000102030405060708090A0B0C0D0E0F -iv 0102030405060708 <filename
625 General encryption and decryption function example using FILE I/O and AES128
628 int do_crypt(FILE *in, FILE *out, int do_encrypt)
630 /* Allow enough space in output buffer for additional block */
631 unsigned char inbuf[1024], outbuf[1024 + EVP_MAX_BLOCK_LENGTH];
635 * Bogus key and IV: we'd normally set these from
638 unsigned char key[] = "0123456789abcdeF";
639 unsigned char iv[] = "1234567887654321";
641 /* Don't set key or IV right away; we want to check lengths */
642 ctx = EVP_CIPHER_CTX_new();
643 EVP_CipherInit_ex(&ctx, EVP_aes_128_cbc(), NULL, NULL, NULL,
645 OPENSSL_assert(EVP_CIPHER_CTX_key_length(ctx) == 16);
646 OPENSSL_assert(EVP_CIPHER_CTX_iv_length(ctx) == 16);
648 /* Now we can set key and IV */
649 EVP_CipherInit_ex(ctx, NULL, NULL, key, iv, do_encrypt);
652 inlen = fread(inbuf, 1, 1024, in);
655 if (!EVP_CipherUpdate(ctx, outbuf, &outlen, inbuf, inlen)) {
657 EVP_CIPHER_CTX_free(ctx);
660 fwrite(outbuf, 1, outlen, out);
662 if (!EVP_CipherFinal_ex(ctx, outbuf, &outlen)) {
664 EVP_CIPHER_CTX_free(ctx);
667 fwrite(outbuf, 1, outlen, out);
669 EVP_CIPHER_CTX_free(ctx);
678 Supported ciphers are listed in:
697 Support for OCB mode was added in OpenSSL 1.1.0.
699 B<EVP_CIPHER_CTX> was made opaque in OpenSSL 1.1.0. As a result,
700 EVP_CIPHER_CTX_reset() appeared and EVP_CIPHER_CTX_cleanup()
701 disappeared. EVP_CIPHER_CTX_init() remains as an alias for
702 EVP_CIPHER_CTX_reset().
706 Copyright 2000-2018 The OpenSSL Project Authors. All Rights Reserved.
708 Licensed under the Apache License 2.0 (the "License"). You may not use
709 this file except in compliance with the License. You can obtain a copy
710 in the file LICENSE in the source distribution or at
711 L<https://www.openssl.org/source/license.html>.