18 EVP_CIPHER_CTX_set_key_length,
31 EVP_CIPHER_block_size,
32 EVP_CIPHER_key_length,
37 EVP_CIPHER_CTX_cipher,
40 EVP_CIPHER_CTX_block_size,
41 EVP_CIPHER_CTX_key_length,
42 EVP_CIPHER_CTX_iv_length,
43 EVP_CIPHER_CTX_get_app_data,
44 EVP_CIPHER_CTX_set_app_data,
48 EVP_CIPHER_param_to_asn1,
49 EVP_CIPHER_asn1_to_param,
50 EVP_CIPHER_CTX_set_padding,
58 #include <openssl/evp.h>
60 EVP_CIPHER *EVP_CIPHER_fetch(OPENSSL_CTX *ctx, const char *algorithm,
61 const char *properties);
62 EVP_CIPHER_CTX *EVP_CIPHER_CTX_new(void);
63 int EVP_CIPHER_CTX_reset(EVP_CIPHER_CTX *ctx);
64 void EVP_CIPHER_CTX_free(EVP_CIPHER_CTX *ctx);
66 int EVP_EncryptInit_ex(EVP_CIPHER_CTX *ctx, const EVP_CIPHER *type,
67 ENGINE *impl, const unsigned char *key, const unsigned char *iv);
68 int EVP_EncryptUpdate(EVP_CIPHER_CTX *ctx, unsigned char *out,
69 int *outl, const unsigned char *in, int inl);
70 int EVP_EncryptFinal_ex(EVP_CIPHER_CTX *ctx, unsigned char *out, int *outl);
72 int EVP_DecryptInit_ex(EVP_CIPHER_CTX *ctx, const EVP_CIPHER *type,
73 ENGINE *impl, const unsigned char *key, const unsigned char *iv);
74 int EVP_DecryptUpdate(EVP_CIPHER_CTX *ctx, unsigned char *out,
75 int *outl, const unsigned char *in, int inl);
76 int EVP_DecryptFinal_ex(EVP_CIPHER_CTX *ctx, unsigned char *outm, int *outl);
78 int EVP_CipherInit_ex(EVP_CIPHER_CTX *ctx, const EVP_CIPHER *type,
79 ENGINE *impl, const unsigned char *key, const unsigned char *iv, int enc);
80 int EVP_CipherUpdate(EVP_CIPHER_CTX *ctx, unsigned char *out,
81 int *outl, const unsigned char *in, int inl);
82 int EVP_CipherFinal_ex(EVP_CIPHER_CTX *ctx, unsigned char *outm, int *outl);
84 int EVP_EncryptInit(EVP_CIPHER_CTX *ctx, const EVP_CIPHER *type,
85 const unsigned char *key, const unsigned char *iv);
86 int EVP_EncryptFinal(EVP_CIPHER_CTX *ctx, unsigned char *out, int *outl);
88 int EVP_DecryptInit(EVP_CIPHER_CTX *ctx, const EVP_CIPHER *type,
89 const unsigned char *key, const unsigned char *iv);
90 int EVP_DecryptFinal(EVP_CIPHER_CTX *ctx, unsigned char *outm, int *outl);
92 int EVP_CipherInit(EVP_CIPHER_CTX *ctx, const EVP_CIPHER *type,
93 const unsigned char *key, const unsigned char *iv, int enc);
94 int EVP_CipherFinal(EVP_CIPHER_CTX *ctx, unsigned char *outm, int *outl);
96 int EVP_CIPHER_CTX_set_padding(EVP_CIPHER_CTX *x, int padding);
97 int EVP_CIPHER_CTX_set_key_length(EVP_CIPHER_CTX *x, int keylen);
98 int EVP_CIPHER_CTX_ctrl(EVP_CIPHER_CTX *ctx, int type, int arg, void *ptr);
99 int EVP_CIPHER_CTX_rand_key(EVP_CIPHER_CTX *ctx, unsigned char *key);
101 const EVP_CIPHER *EVP_get_cipherbyname(const char *name);
102 const EVP_CIPHER *EVP_get_cipherbynid(int nid);
103 const EVP_CIPHER *EVP_get_cipherbyobj(const ASN1_OBJECT *a);
105 int EVP_CIPHER_nid(const EVP_CIPHER *e);
106 const char *EVP_CIPHER_name(const EVP_CIPHER *cipher);
107 int EVP_CIPHER_block_size(const EVP_CIPHER *e);
108 int EVP_CIPHER_key_length(const EVP_CIPHER *e);
109 int EVP_CIPHER_iv_length(const EVP_CIPHER *e);
110 unsigned long EVP_CIPHER_flags(const EVP_CIPHER *e);
111 unsigned long EVP_CIPHER_mode(const EVP_CIPHER *e);
112 int EVP_CIPHER_type(const EVP_CIPHER *ctx);
114 const EVP_CIPHER *EVP_CIPHER_CTX_cipher(const EVP_CIPHER_CTX *ctx);
115 int EVP_CIPHER_CTX_nid(const EVP_CIPHER_CTX *ctx);
116 const char *EVP_CIPHER_CTX_name(const EVP_CIPHER_CTX *ctx);
117 int EVP_CIPHER_CTX_block_size(const EVP_CIPHER_CTX *ctx);
118 int EVP_CIPHER_CTX_key_length(const EVP_CIPHER_CTX *ctx);
119 int EVP_CIPHER_CTX_iv_length(const EVP_CIPHER_CTX *ctx);
120 void *EVP_CIPHER_CTX_get_app_data(const EVP_CIPHER_CTX *ctx);
121 void EVP_CIPHER_CTX_set_app_data(const EVP_CIPHER_CTX *ctx, void *data);
122 int EVP_CIPHER_CTX_type(const EVP_CIPHER_CTX *ctx);
123 int EVP_CIPHER_CTX_mode(const EVP_CIPHER_CTX *ctx);
125 int EVP_CIPHER_param_to_asn1(EVP_CIPHER_CTX *c, ASN1_TYPE *type);
126 int EVP_CIPHER_asn1_to_param(EVP_CIPHER_CTX *c, ASN1_TYPE *type);
130 The EVP cipher routines are a high level interface to certain
133 EVP_CIPHER_fetch() fetches the cipher implementation for the given
134 B<algorithm> from any provider offering it, within the criteria given
135 by the B<properties>.
136 See L<provider(7)/Fetching algorithms> for further information.
138 The returned value must eventually be freed with
139 L<EVP_CIPHER_meth_free(3)>.
141 EVP_CIPHER_CTX_new() creates a cipher context.
143 EVP_CIPHER_CTX_free() clears all information from a cipher context
144 and free up any allocated memory associate with it, including B<ctx>
145 itself. This function should be called after all operations using a
146 cipher are complete so sensitive information does not remain in
149 EVP_EncryptInit_ex() sets up cipher context B<ctx> for encryption
150 with cipher B<type>. B<type> is typically supplied by a function such
151 as EVP_aes_256_cbc(), or a value explicitly fetched with
152 EVP_CIPHER_fetch(). If B<impl> is non-NULL, its implementation of the
153 cipher B<type> is used if there is one, and if not, the default
154 implementation is used. B<key> is the symmetric key to use
155 and B<iv> is the IV to use (if necessary), the actual number of bytes
156 used for the key and IV depends on the cipher. It is possible to set
157 all parameters to NULL except B<type> in an initial call and supply
158 the remaining parameters in subsequent calls, all of which have B<type>
159 set to NULL. This is done when the default cipher parameters are not
162 EVP_EncryptUpdate() encrypts B<inl> bytes from the buffer B<in> and
163 writes the encrypted version to B<out>. This function can be called
164 multiple times to encrypt successive blocks of data. The amount
165 of data written depends on the block alignment of the encrypted data:
166 as a result the amount of data written may be anything from zero bytes
167 to (inl + cipher_block_size - 1) so B<out> should contain sufficient
168 room. The actual number of bytes written is placed in B<outl>. It also
169 checks if B<in> and B<out> are partially overlapping, and if they are
170 0 is returned to indicate failure.
172 If padding is enabled (the default) then EVP_EncryptFinal_ex() encrypts
173 the "final" data, that is any data that remains in a partial block.
174 It uses standard block padding (aka PKCS padding) as described in
175 the NOTES section, below. The encrypted
176 final data is written to B<out> which should have sufficient space for
177 one cipher block. The number of bytes written is placed in B<outl>. After
178 this function is called the encryption operation is finished and no further
179 calls to EVP_EncryptUpdate() should be made.
181 If padding is disabled then EVP_EncryptFinal_ex() will not encrypt any more
182 data and it will return an error if any data remains in a partial block:
183 that is if the total data length is not a multiple of the block size.
185 EVP_DecryptInit_ex(), EVP_DecryptUpdate() and EVP_DecryptFinal_ex() are the
186 corresponding decryption operations. EVP_DecryptFinal() will return an
187 error code if padding is enabled and the final block is not correctly
188 formatted. The parameters and restrictions are identical to the encryption
189 operations except that if padding is enabled the decrypted data buffer B<out>
190 passed to EVP_DecryptUpdate() should have sufficient room for
191 (B<inl> + cipher_block_size) bytes unless the cipher block size is 1 in
192 which case B<inl> bytes is sufficient.
194 EVP_CipherInit_ex(), EVP_CipherUpdate() and EVP_CipherFinal_ex() are
195 functions that can be used for decryption or encryption. The operation
196 performed depends on the value of the B<enc> parameter. It should be set
197 to 1 for encryption, 0 for decryption and -1 to leave the value unchanged
198 (the actual value of 'enc' being supplied in a previous call).
200 EVP_CIPHER_CTX_reset() clears all information from a cipher context
201 and free up any allocated memory associate with it, except the B<ctx>
202 itself. This function should be called anytime B<ctx> is to be reused
203 for another EVP_CipherInit() / EVP_CipherUpdate() / EVP_CipherFinal()
206 EVP_EncryptInit(), EVP_DecryptInit() and EVP_CipherInit() behave in a
207 similar way to EVP_EncryptInit_ex(), EVP_DecryptInit_ex() and
208 EVP_CipherInit_ex() except they always use the default cipher implementation.
210 EVP_EncryptFinal(), EVP_DecryptFinal() and EVP_CipherFinal() are
211 identical to EVP_EncryptFinal_ex(), EVP_DecryptFinal_ex() and
212 EVP_CipherFinal_ex(). In previous releases they also cleaned up
213 the B<ctx>, but this is no longer done and EVP_CIPHER_CTX_clean()
214 must be called to free any context resources.
216 EVP_get_cipherbyname(), EVP_get_cipherbynid() and EVP_get_cipherbyobj()
217 return an EVP_CIPHER structure when passed a cipher name, a NID or an
218 ASN1_OBJECT structure.
220 EVP_CIPHER_nid() and EVP_CIPHER_CTX_nid() return the NID of a cipher when
221 passed an B<EVP_CIPHER> or B<EVP_CIPHER_CTX> structure. The actual NID
222 value is an internal value which may not have a corresponding OBJECT
225 EVP_CIPHER_CTX_set_padding() enables or disables padding. This
226 function should be called after the context is set up for encryption
227 or decryption with EVP_EncryptInit_ex(), EVP_DecryptInit_ex() or
228 EVP_CipherInit_ex(). By default encryption operations are padded using
229 standard block padding and the padding is checked and removed when
230 decrypting. If the B<pad> parameter is zero then no padding is
231 performed, the total amount of data encrypted or decrypted must then
232 be a multiple of the block size or an error will occur.
234 EVP_CIPHER_key_length() and EVP_CIPHER_CTX_key_length() return the key
235 length of a cipher when passed an B<EVP_CIPHER> or B<EVP_CIPHER_CTX>
236 structure. The constant B<EVP_MAX_KEY_LENGTH> is the maximum key length
237 for all ciphers. Note: although EVP_CIPHER_key_length() is fixed for a
238 given cipher, the value of EVP_CIPHER_CTX_key_length() may be different
239 for variable key length ciphers.
241 EVP_CIPHER_CTX_set_key_length() sets the key length of the cipher ctx.
242 If the cipher is a fixed length cipher then attempting to set the key
243 length to any value other than the fixed value is an error.
245 EVP_CIPHER_iv_length() and EVP_CIPHER_CTX_iv_length() return the IV
246 length of a cipher when passed an B<EVP_CIPHER> or B<EVP_CIPHER_CTX>.
247 It will return zero if the cipher does not use an IV. The constant
248 B<EVP_MAX_IV_LENGTH> is the maximum IV length for all ciphers.
250 EVP_CIPHER_block_size() and EVP_CIPHER_CTX_block_size() return the block
251 size of a cipher when passed an B<EVP_CIPHER> or B<EVP_CIPHER_CTX>
252 structure. The constant B<EVP_MAX_BLOCK_LENGTH> is also the maximum block
253 length for all ciphers.
255 EVP_CIPHER_type() and EVP_CIPHER_CTX_type() return the type of the passed
256 cipher or context. This "type" is the actual NID of the cipher OBJECT
257 IDENTIFIER as such it ignores the cipher parameters and 40 bit RC2 and
258 128 bit RC2 have the same NID. If the cipher does not have an object
259 identifier or does not have ASN1 support this function will return
262 EVP_CIPHER_name() and EVP_CIPHER_CTX_name() return the name of the passed
265 EVP_CIPHER_CTX_cipher() returns the B<EVP_CIPHER> structure when passed
266 an B<EVP_CIPHER_CTX> structure.
268 EVP_CIPHER_mode() and EVP_CIPHER_CTX_mode() return the block cipher mode:
269 EVP_CIPH_ECB_MODE, EVP_CIPH_CBC_MODE, EVP_CIPH_CFB_MODE, EVP_CIPH_OFB_MODE,
270 EVP_CIPH_CTR_MODE, EVP_CIPH_GCM_MODE, EVP_CIPH_CCM_MODE, EVP_CIPH_XTS_MODE,
271 EVP_CIPH_WRAP_MODE or EVP_CIPH_OCB_MODE. If the cipher is a stream cipher then
272 EVP_CIPH_STREAM_CIPHER is returned.
274 EVP_CIPHER_param_to_asn1() sets the AlgorithmIdentifier "parameter" based
275 on the passed cipher. This will typically include any parameters and an
276 IV. The cipher IV (if any) must be set when this call is made. This call
277 should be made before the cipher is actually "used" (before any
278 EVP_EncryptUpdate(), EVP_DecryptUpdate() calls for example). This function
279 may fail if the cipher does not have any ASN1 support.
281 EVP_CIPHER_asn1_to_param() sets the cipher parameters based on an ASN1
282 AlgorithmIdentifier "parameter". The precise effect depends on the cipher
283 In the case of RC2, for example, it will set the IV and effective key length.
284 This function should be called after the base cipher type is set but before
285 the key is set. For example EVP_CipherInit() will be called with the IV and
286 key set to NULL, EVP_CIPHER_asn1_to_param() will be called and finally
287 EVP_CipherInit() again with all parameters except the key set to NULL. It is
288 possible for this function to fail if the cipher does not have any ASN1 support
289 or the parameters cannot be set (for example the RC2 effective key length
292 EVP_CIPHER_CTX_ctrl() allows various cipher specific parameters to be determined
295 EVP_CIPHER_CTX_rand_key() generates a random key of the appropriate length
296 based on the cipher context. The EVP_CIPHER can provide its own random key
297 generation routine to support keys of a specific form. B<Key> must point to a
298 buffer at least as big as the value returned by EVP_CIPHER_CTX_key_length().
302 EVP_CIPHER_fetch() returns a pointer to a B<EVP_CIPHER> for success
303 and B<NULL> for failure.
305 EVP_CIPHER_CTX_new() returns a pointer to a newly created
306 B<EVP_CIPHER_CTX> for success and B<NULL> for failure.
308 EVP_EncryptInit_ex(), EVP_EncryptUpdate() and EVP_EncryptFinal_ex()
309 return 1 for success and 0 for failure.
311 EVP_DecryptInit_ex() and EVP_DecryptUpdate() return 1 for success and 0 for failure.
312 EVP_DecryptFinal_ex() returns 0 if the decrypt failed or 1 for success.
314 EVP_CipherInit_ex() and EVP_CipherUpdate() return 1 for success and 0 for failure.
315 EVP_CipherFinal_ex() returns 0 for a decryption failure or 1 for success.
317 EVP_CIPHER_CTX_reset() returns 1 for success and 0 for failure.
319 EVP_get_cipherbyname(), EVP_get_cipherbynid() and EVP_get_cipherbyobj()
320 return an B<EVP_CIPHER> structure or NULL on error.
322 EVP_CIPHER_nid() and EVP_CIPHER_CTX_nid() return a NID.
324 EVP_CIPHER_block_size() and EVP_CIPHER_CTX_block_size() return the block
327 EVP_CIPHER_key_length() and EVP_CIPHER_CTX_key_length() return the key
330 EVP_CIPHER_CTX_set_padding() always returns 1.
332 EVP_CIPHER_iv_length() and EVP_CIPHER_CTX_iv_length() return the IV
333 length or zero if the cipher does not use an IV.
335 EVP_CIPHER_type() and EVP_CIPHER_CTX_type() return the NID of the cipher's
336 OBJECT IDENTIFIER or NID_undef if it has no defined OBJECT IDENTIFIER.
338 EVP_CIPHER_CTX_cipher() returns an B<EVP_CIPHER> structure.
340 EVP_CIPHER_param_to_asn1() and EVP_CIPHER_asn1_to_param() return greater
341 than zero for success and zero or a negative number on failure.
343 EVP_CIPHER_CTX_rand_key() returns 1 for success.
345 =head1 CIPHER LISTING
347 All algorithms have a fixed key length unless otherwise stated.
349 Refer to L<SEE ALSO> for the full list of ciphers available through the EVP
356 Null cipher: does nothing.
360 =head1 AEAD Interface
362 The EVP interface for Authenticated Encryption with Associated Data (AEAD)
363 modes are subtly altered and several additional I<ctrl> operations are supported
364 depending on the mode specified.
366 To specify additional authenticated data (AAD), a call to EVP_CipherUpdate(),
367 EVP_EncryptUpdate() or EVP_DecryptUpdate() should be made with the output
368 parameter B<out> set to B<NULL>.
370 When decrypting, the return value of EVP_DecryptFinal() or EVP_CipherFinal()
371 indicates whether the operation was successful. If it does not indicate success,
372 the authentication operation has failed and any output data B<MUST NOT> be used
375 =head2 GCM and OCB Modes
377 The following I<ctrl>s are supported in GCM and OCB modes.
381 =item EVP_CIPHER_CTX_ctrl(ctx, EVP_CTRL_AEAD_SET_IVLEN, ivlen, NULL)
383 Sets the IV length. This call can only be made before specifying an IV. If
384 not called a default IV length is used.
386 For GCM AES and OCB AES the default is 12 (i.e. 96 bits). For OCB mode the
389 =item EVP_CIPHER_CTX_ctrl(ctx, EVP_CTRL_AEAD_GET_TAG, taglen, tag)
391 Writes C<taglen> bytes of the tag value to the buffer indicated by C<tag>.
392 This call can only be made when encrypting data and B<after> all data has been
393 processed (e.g. after an EVP_EncryptFinal() call).
395 For OCB, C<taglen> must either be 16 or the value previously set via
396 B<EVP_CTRL_AEAD_SET_TAG>.
398 =item EVP_CIPHER_CTX_ctrl(ctx, EVP_CTRL_AEAD_SET_TAG, taglen, tag)
400 Sets the expected tag to C<taglen> bytes from C<tag>.
401 The tag length can only be set before specifying an IV.
402 C<taglen> must be between 1 and 16 inclusive.
404 For GCM, this call is only valid when decrypting data.
406 For OCB, this call is valid when decrypting data to set the expected tag,
407 and before encryption to set the desired tag length.
409 In OCB mode, calling this before encryption with C<tag> set to C<NULL> sets the
410 tag length. If this is not called prior to encryption, a default tag length is
413 For OCB AES, the default tag length is 16 (i.e. 128 bits). It is also the
414 maximum tag length for OCB.
420 The EVP interface for CCM mode is similar to that of the GCM mode but with a
421 few additional requirements and different I<ctrl> values.
423 For CCM mode, the total plaintext or ciphertext length B<MUST> be passed to
424 EVP_CipherUpdate(), EVP_EncryptUpdate() or EVP_DecryptUpdate() with the output
425 and input parameters (B<in> and B<out>) set to B<NULL> and the length passed in
426 the B<inl> parameter.
428 The following I<ctrl>s are supported in CCM mode.
432 =item EVP_CIPHER_CTX_ctrl(ctx, EVP_CTRL_AEAD_SET_TAG, taglen, tag)
434 This call is made to set the expected B<CCM> tag value when decrypting or
435 the length of the tag (with the C<tag> parameter set to NULL) when encrypting.
436 The tag length is often referred to as B<M>. If not set a default value is
437 used (12 for AES). When decrypting, the tag needs to be set before passing
438 in data to be decrypted, but as in GCM and OCB mode, it can be set after
439 passing additional authenticated data (see L<AEAD Interface>).
441 =item EVP_CIPHER_CTX_ctrl(ctx, EVP_CTRL_CCM_SET_L, ivlen, NULL)
443 Sets the CCM B<L> value. If not set a default is used (8 for AES).
445 =item EVP_CIPHER_CTX_ctrl(ctx, EVP_CTRL_AEAD_SET_IVLEN, ivlen, NULL)
447 Sets the CCM nonce (IV) length. This call can only be made before specifying an
448 nonce value. The nonce length is given by B<15 - L> so it is 7 by default for
455 For SIV mode ciphers the behaviour of the EVP interface is subtly
456 altered and several additional ctrl operations are supported.
458 To specify any additional authenticated data (AAD) and/or a Nonce, a call to
459 EVP_CipherUpdate(), EVP_EncryptUpdate() or EVP_DecryptUpdate() should be made
460 with the output parameter B<out> set to B<NULL>.
462 RFC5297 states that the Nonce is the last piece of AAD before the actual
463 encrypt/decrypt takes place. The API does not differentiate the Nonce from
466 When decrypting the return value of EVP_DecryptFinal() or EVP_CipherFinal()
467 indicates if the operation was successful. If it does not indicate success
468 the authentication operation has failed and any output data B<MUST NOT>
469 be used as it is corrupted.
471 The following ctrls are supported in both SIV modes.
475 =item EVP_CIPHER_CTX_ctrl(ctx, EVP_CTRL_AEAD_GET_TAG, taglen, tag);
477 Writes B<taglen> bytes of the tag value to the buffer indicated by B<tag>.
478 This call can only be made when encrypting data and B<after> all data has been
479 processed (e.g. after an EVP_EncryptFinal() call). For SIV mode the taglen must
482 =item EVP_CIPHER_CTX_ctrl(ctx, EVP_CTRL_AEAD_SET_TAG, taglen, tag);
484 Sets the expected tag to B<taglen> bytes from B<tag>. This call is only legal
485 when decrypting data and must be made B<before> any data is processed (e.g.
486 before any EVP_DecryptUpdate() call). For SIV mode the taglen must be 16.
490 SIV mode makes two passes over the input data, thus, only one call to
491 EVP_CipherUpdate(), EVP_EncryptUpdate() or EVP_DecryptUpdate() should be made
492 with B<out> set to a non-B<NULL> value. A call to EVP_Decrypt_Final() or
493 EVP_CipherFinal() is not required, but will indicate if the update
496 =head2 ChaCha20-Poly1305
498 The following I<ctrl>s are supported for the ChaCha20-Poly1305 AEAD algorithm.
502 =item EVP_CIPHER_CTX_ctrl(ctx, EVP_CTRL_AEAD_SET_IVLEN, ivlen, NULL)
504 Sets the nonce length. This call can only be made before specifying the nonce.
505 If not called a default nonce length of 12 (i.e. 96 bits) is used. The maximum
506 nonce length is 12 bytes (i.e. 96-bits). If a nonce of less than 12 bytes is set
507 then the nonce is automatically padded with leading 0 bytes to make it 12 bytes
510 =item EVP_CIPHER_CTX_ctrl(ctx, EVP_CTRL_AEAD_GET_TAG, taglen, tag)
512 Writes C<taglen> bytes of the tag value to the buffer indicated by C<tag>.
513 This call can only be made when encrypting data and B<after> all data has been
514 processed (e.g. after an EVP_EncryptFinal() call).
516 C<taglen> specified here must be 16 (B<POLY1305_BLOCK_SIZE>, i.e. 128-bits) or
519 =item EVP_CIPHER_CTX_ctrl(ctx, EVP_CTRL_AEAD_SET_TAG, taglen, tag)
521 Sets the expected tag to C<taglen> bytes from C<tag>.
522 The tag length can only be set before specifying an IV.
523 C<taglen> must be between 1 and 16 (B<POLY1305_BLOCK_SIZE>) inclusive.
524 This call is only valid when decrypting data.
530 Where possible the B<EVP> interface to symmetric ciphers should be used in
531 preference to the low level interfaces. This is because the code then becomes
532 transparent to the cipher used and much more flexible. Additionally, the
533 B<EVP> interface will ensure the use of platform specific cryptographic
534 acceleration such as AES-NI (the low level interfaces do not provide the
537 PKCS padding works by adding B<n> padding bytes of value B<n> to make the total
538 length of the encrypted data a multiple of the block size. Padding is always
539 added so if the data is already a multiple of the block size B<n> will equal
540 the block size. For example if the block size is 8 and 11 bytes are to be
541 encrypted then 5 padding bytes of value 5 will be added.
543 When decrypting the final block is checked to see if it has the correct form.
545 Although the decryption operation can produce an error if padding is enabled,
546 it is not a strong test that the input data or key is correct. A random block
547 has better than 1 in 256 chance of being of the correct format and problems with
548 the input data earlier on will not produce a final decrypt error.
550 If padding is disabled then the decryption operation will always succeed if
551 the total amount of data decrypted is a multiple of the block size.
553 The functions EVP_EncryptInit(), EVP_EncryptFinal(), EVP_DecryptInit(),
554 EVP_CipherInit() and EVP_CipherFinal() are obsolete but are retained for
555 compatibility with existing code. New code should use EVP_EncryptInit_ex(),
556 EVP_EncryptFinal_ex(), EVP_DecryptInit_ex(), EVP_DecryptFinal_ex(),
557 EVP_CipherInit_ex() and EVP_CipherFinal_ex() because they can reuse an
558 existing context without allocating and freeing it up on each call.
560 EVP_get_cipherbynid(), and EVP_get_cipherbyobj() are implemented as macros.
564 B<EVP_MAX_KEY_LENGTH> and B<EVP_MAX_IV_LENGTH> only refer to the internal
565 ciphers with default key lengths. If custom ciphers exceed these values the
566 results are unpredictable. This is because it has become standard practice to
567 define a generic key as a fixed unsigned char array containing
568 B<EVP_MAX_KEY_LENGTH> bytes.
570 The ASN1 code is incomplete (and sometimes inaccurate) it has only been tested
571 for certain common S/MIME ciphers (RC2, DES, triple DES) in CBC mode.
575 Encrypt a string using IDEA:
577 int do_crypt(char *outfile)
579 unsigned char outbuf[1024];
582 * Bogus key and IV: we'd normally set these from
585 unsigned char key[] = {0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15};
586 unsigned char iv[] = {1,2,3,4,5,6,7,8};
587 char intext[] = "Some Crypto Text";
591 ctx = EVP_CIPHER_CTX_new();
592 EVP_EncryptInit_ex(ctx, EVP_idea_cbc(), NULL, key, iv);
594 if (!EVP_EncryptUpdate(ctx, outbuf, &outlen, intext, strlen(intext))) {
596 EVP_CIPHER_CTX_free(ctx);
600 * Buffer passed to EVP_EncryptFinal() must be after data just
601 * encrypted to avoid overwriting it.
603 if (!EVP_EncryptFinal_ex(ctx, outbuf + outlen, &tmplen)) {
605 EVP_CIPHER_CTX_free(ctx);
609 EVP_CIPHER_CTX_free(ctx);
611 * Need binary mode for fopen because encrypted data is
612 * binary data. Also cannot use strlen() on it because
613 * it won't be NUL terminated and may contain embedded
616 out = fopen(outfile, "wb");
621 fwrite(outbuf, 1, outlen, out);
626 The ciphertext from the above example can be decrypted using the B<openssl>
627 utility with the command line (shown on two lines for clarity):
630 -K 000102030405060708090A0B0C0D0E0F -iv 0102030405060708 <filename
632 General encryption and decryption function example using FILE I/O and AES128
635 int do_crypt(FILE *in, FILE *out, int do_encrypt)
637 /* Allow enough space in output buffer for additional block */
638 unsigned char inbuf[1024], outbuf[1024 + EVP_MAX_BLOCK_LENGTH];
642 * Bogus key and IV: we'd normally set these from
645 unsigned char key[] = "0123456789abcdeF";
646 unsigned char iv[] = "1234567887654321";
648 /* Don't set key or IV right away; we want to check lengths */
649 ctx = EVP_CIPHER_CTX_new();
650 EVP_CipherInit_ex(&ctx, EVP_aes_128_cbc(), NULL, NULL, NULL,
652 OPENSSL_assert(EVP_CIPHER_CTX_key_length(ctx) == 16);
653 OPENSSL_assert(EVP_CIPHER_CTX_iv_length(ctx) == 16);
655 /* Now we can set key and IV */
656 EVP_CipherInit_ex(ctx, NULL, NULL, key, iv, do_encrypt);
659 inlen = fread(inbuf, 1, 1024, in);
662 if (!EVP_CipherUpdate(ctx, outbuf, &outlen, inbuf, inlen)) {
664 EVP_CIPHER_CTX_free(ctx);
667 fwrite(outbuf, 1, outlen, out);
669 if (!EVP_CipherFinal_ex(ctx, outbuf, &outlen)) {
671 EVP_CIPHER_CTX_free(ctx);
674 fwrite(outbuf, 1, outlen, out);
676 EVP_CIPHER_CTX_free(ctx);
685 Supported ciphers are listed in:
704 Support for OCB mode was added in OpenSSL 1.1.0.
706 B<EVP_CIPHER_CTX> was made opaque in OpenSSL 1.1.0. As a result,
707 EVP_CIPHER_CTX_reset() appeared and EVP_CIPHER_CTX_cleanup()
708 disappeared. EVP_CIPHER_CTX_init() remains as an alias for
709 EVP_CIPHER_CTX_reset().
713 Copyright 2000-2018 The OpenSSL Project Authors. All Rights Reserved.
715 Licensed under the Apache License 2.0 (the "License"). You may not use
716 this file except in compliance with the License. You can obtain a copy
717 in the file LICENSE in the source distribution or at
718 L<https://www.openssl.org/source/license.html>.