17 EVP_CIPHER_CTX_set_key_length,
29 EVP_CIPHER_block_size,
30 EVP_CIPHER_key_length,
35 EVP_CIPHER_CTX_cipher,
37 EVP_CIPHER_CTX_block_size,
38 EVP_CIPHER_CTX_key_length,
39 EVP_CIPHER_CTX_iv_length,
40 EVP_CIPHER_CTX_get_app_data,
41 EVP_CIPHER_CTX_set_app_data,
45 EVP_CIPHER_param_to_asn1,
46 EVP_CIPHER_asn1_to_param,
47 EVP_CIPHER_CTX_set_padding,
55 #include <openssl/evp.h>
57 EVP_CIPHER_CTX *EVP_CIPHER_CTX_new(void);
58 int EVP_CIPHER_CTX_reset(EVP_CIPHER_CTX *ctx);
59 void EVP_CIPHER_CTX_free(EVP_CIPHER_CTX *ctx);
61 int EVP_EncryptInit_ex(EVP_CIPHER_CTX *ctx, const EVP_CIPHER *type,
62 ENGINE *impl, const unsigned char *key, const unsigned char *iv);
63 int EVP_EncryptUpdate(EVP_CIPHER_CTX *ctx, unsigned char *out,
64 int *outl, const unsigned char *in, int inl);
65 int EVP_EncryptFinal_ex(EVP_CIPHER_CTX *ctx, unsigned char *out, int *outl);
67 int EVP_DecryptInit_ex(EVP_CIPHER_CTX *ctx, const EVP_CIPHER *type,
68 ENGINE *impl, const unsigned char *key, const unsigned char *iv);
69 int EVP_DecryptUpdate(EVP_CIPHER_CTX *ctx, unsigned char *out,
70 int *outl, const unsigned char *in, int inl);
71 int EVP_DecryptFinal_ex(EVP_CIPHER_CTX *ctx, unsigned char *outm, int *outl);
73 int EVP_CipherInit_ex(EVP_CIPHER_CTX *ctx, const EVP_CIPHER *type,
74 ENGINE *impl, const unsigned char *key, const unsigned char *iv, int enc);
75 int EVP_CipherUpdate(EVP_CIPHER_CTX *ctx, unsigned char *out,
76 int *outl, const unsigned char *in, int inl);
77 int EVP_CipherFinal_ex(EVP_CIPHER_CTX *ctx, unsigned char *outm, int *outl);
79 int EVP_EncryptInit(EVP_CIPHER_CTX *ctx, const EVP_CIPHER *type,
80 const unsigned char *key, const unsigned char *iv);
81 int EVP_EncryptFinal(EVP_CIPHER_CTX *ctx, unsigned char *out, int *outl);
83 int EVP_DecryptInit(EVP_CIPHER_CTX *ctx, const EVP_CIPHER *type,
84 const unsigned char *key, const unsigned char *iv);
85 int EVP_DecryptFinal(EVP_CIPHER_CTX *ctx, unsigned char *outm, int *outl);
87 int EVP_CipherInit(EVP_CIPHER_CTX *ctx, const EVP_CIPHER *type,
88 const unsigned char *key, const unsigned char *iv, int enc);
89 int EVP_CipherFinal(EVP_CIPHER_CTX *ctx, unsigned char *outm, int *outl);
91 int EVP_CIPHER_CTX_set_padding(EVP_CIPHER_CTX *x, int padding);
92 int EVP_CIPHER_CTX_set_key_length(EVP_CIPHER_CTX *x, int keylen);
93 int EVP_CIPHER_CTX_ctrl(EVP_CIPHER_CTX *ctx, int type, int arg, void *ptr);
94 int EVP_CIPHER_CTX_rand_key(EVP_CIPHER_CTX *ctx, unsigned char *key);
96 const EVP_CIPHER *EVP_get_cipherbyname(const char *name);
97 const EVP_CIPHER *EVP_get_cipherbynid(int nid);
98 const EVP_CIPHER *EVP_get_cipherbyobj(const ASN1_OBJECT *a);
100 int EVP_CIPHER_nid(const EVP_CIPHER *e);
101 int EVP_CIPHER_block_size(const EVP_CIPHER *e);
102 int EVP_CIPHER_key_length(const EVP_CIPHER *e);
103 int EVP_CIPHER_iv_length(const EVP_CIPHER *e);
104 unsigned long EVP_CIPHER_flags(const EVP_CIPHER *e);
105 unsigned long EVP_CIPHER_mode(const EVP_CIPHER *e);
106 int EVP_CIPHER_type(const EVP_CIPHER *ctx);
108 const EVP_CIPHER *EVP_CIPHER_CTX_cipher(const EVP_CIPHER_CTX *ctx);
109 int EVP_CIPHER_CTX_nid(const EVP_CIPHER_CTX *ctx);
110 int EVP_CIPHER_CTX_block_size(const EVP_CIPHER_CTX *ctx);
111 int EVP_CIPHER_CTX_key_length(const EVP_CIPHER_CTX *ctx);
112 int EVP_CIPHER_CTX_iv_length(const EVP_CIPHER_CTX *ctx);
113 void *EVP_CIPHER_CTX_get_app_data(const EVP_CIPHER_CTX *ctx);
114 void EVP_CIPHER_CTX_set_app_data(const EVP_CIPHER_CTX *ctx, void *data);
115 int EVP_CIPHER_CTX_type(const EVP_CIPHER_CTX *ctx);
116 int EVP_CIPHER_CTX_mode(const EVP_CIPHER_CTX *ctx);
118 int EVP_CIPHER_param_to_asn1(EVP_CIPHER_CTX *c, ASN1_TYPE *type);
119 int EVP_CIPHER_asn1_to_param(EVP_CIPHER_CTX *c, ASN1_TYPE *type);
123 The EVP cipher routines are a high level interface to certain
126 EVP_CIPHER_CTX_new() creates a cipher context.
128 EVP_CIPHER_CTX_free() clears all information from a cipher context
129 and free up any allocated memory associate with it, including B<ctx>
130 itself. This function should be called after all operations using a
131 cipher are complete so sensitive information does not remain in
134 EVP_EncryptInit_ex() sets up cipher context B<ctx> for encryption
135 with cipher B<type> from ENGINE B<impl>. B<ctx> must be created
136 before calling this function. B<type> is normally supplied
137 by a function such as EVP_aes_256_cbc(). If B<impl> is NULL then the
138 default implementation is used. B<key> is the symmetric key to use
139 and B<iv> is the IV to use (if necessary), the actual number of bytes
140 used for the key and IV depends on the cipher. It is possible to set
141 all parameters to NULL except B<type> in an initial call and supply
142 the remaining parameters in subsequent calls, all of which have B<type>
143 set to NULL. This is done when the default cipher parameters are not
146 EVP_EncryptUpdate() encrypts B<inl> bytes from the buffer B<in> and
147 writes the encrypted version to B<out>. This function can be called
148 multiple times to encrypt successive blocks of data. The amount
149 of data written depends on the block alignment of the encrypted data:
150 as a result the amount of data written may be anything from zero bytes
151 to (inl + cipher_block_size - 1) so B<out> should contain sufficient
152 room. The actual number of bytes written is placed in B<outl>. It also
153 checks if B<in> and B<out> are partially overlapping, and if they are
154 0 is returned to indicate failure.
156 If padding is enabled (the default) then EVP_EncryptFinal_ex() encrypts
157 the "final" data, that is any data that remains in a partial block.
158 It uses standard block padding (aka PKCS padding) as described in
159 the NOTES section, below. The encrypted
160 final data is written to B<out> which should have sufficient space for
161 one cipher block. The number of bytes written is placed in B<outl>. After
162 this function is called the encryption operation is finished and no further
163 calls to EVP_EncryptUpdate() should be made.
165 If padding is disabled then EVP_EncryptFinal_ex() will not encrypt any more
166 data and it will return an error if any data remains in a partial block:
167 that is if the total data length is not a multiple of the block size.
169 EVP_DecryptInit_ex(), EVP_DecryptUpdate() and EVP_DecryptFinal_ex() are the
170 corresponding decryption operations. EVP_DecryptFinal() will return an
171 error code if padding is enabled and the final block is not correctly
172 formatted. The parameters and restrictions are identical to the encryption
173 operations except that if padding is enabled the decrypted data buffer B<out>
174 passed to EVP_DecryptUpdate() should have sufficient room for
175 (B<inl> + cipher_block_size) bytes unless the cipher block size is 1 in
176 which case B<inl> bytes is sufficient.
178 EVP_CipherInit_ex(), EVP_CipherUpdate() and EVP_CipherFinal_ex() are
179 functions that can be used for decryption or encryption. The operation
180 performed depends on the value of the B<enc> parameter. It should be set
181 to 1 for encryption, 0 for decryption and -1 to leave the value unchanged
182 (the actual value of 'enc' being supplied in a previous call).
184 EVP_CIPHER_CTX_reset() clears all information from a cipher context
185 and free up any allocated memory associate with it, except the B<ctx>
186 itself. This function should be called anytime B<ctx> is to be reused
187 for another EVP_CipherInit() / EVP_CipherUpdate() / EVP_CipherFinal()
190 EVP_EncryptInit(), EVP_DecryptInit() and EVP_CipherInit() behave in a
191 similar way to EVP_EncryptInit_ex(), EVP_DecryptInit_ex() and
192 EVP_CipherInit_ex() except they always use the default cipher implementation.
194 EVP_EncryptFinal(), EVP_DecryptFinal() and EVP_CipherFinal() are
195 identical to EVP_EncryptFinal_ex(), EVP_DecryptFinal_ex() and
196 EVP_CipherFinal_ex(). In previous releases they also cleaned up
197 the B<ctx>, but this is no longer done and EVP_CIPHER_CTX_clean()
198 must be called to free any context resources.
200 EVP_get_cipherbyname(), EVP_get_cipherbynid() and EVP_get_cipherbyobj()
201 return an EVP_CIPHER structure when passed a cipher name, a NID or an
202 ASN1_OBJECT structure.
204 EVP_CIPHER_nid() and EVP_CIPHER_CTX_nid() return the NID of a cipher when
205 passed an B<EVP_CIPHER> or B<EVP_CIPHER_CTX> structure. The actual NID
206 value is an internal value which may not have a corresponding OBJECT
209 EVP_CIPHER_CTX_set_padding() enables or disables padding. This
210 function should be called after the context is set up for encryption
211 or decryption with EVP_EncryptInit_ex(), EVP_DecryptInit_ex() or
212 EVP_CipherInit_ex(). By default encryption operations are padded using
213 standard block padding and the padding is checked and removed when
214 decrypting. If the B<pad> parameter is zero then no padding is
215 performed, the total amount of data encrypted or decrypted must then
216 be a multiple of the block size or an error will occur.
218 EVP_CIPHER_key_length() and EVP_CIPHER_CTX_key_length() return the key
219 length of a cipher when passed an B<EVP_CIPHER> or B<EVP_CIPHER_CTX>
220 structure. The constant B<EVP_MAX_KEY_LENGTH> is the maximum key length
221 for all ciphers. Note: although EVP_CIPHER_key_length() is fixed for a
222 given cipher, the value of EVP_CIPHER_CTX_key_length() may be different
223 for variable key length ciphers.
225 EVP_CIPHER_CTX_set_key_length() sets the key length of the cipher ctx.
226 If the cipher is a fixed length cipher then attempting to set the key
227 length to any value other than the fixed value is an error.
229 EVP_CIPHER_iv_length() and EVP_CIPHER_CTX_iv_length() return the IV
230 length of a cipher when passed an B<EVP_CIPHER> or B<EVP_CIPHER_CTX>.
231 It will return zero if the cipher does not use an IV. The constant
232 B<EVP_MAX_IV_LENGTH> is the maximum IV length for all ciphers.
234 EVP_CIPHER_block_size() and EVP_CIPHER_CTX_block_size() return the block
235 size of a cipher when passed an B<EVP_CIPHER> or B<EVP_CIPHER_CTX>
236 structure. The constant B<EVP_MAX_BLOCK_LENGTH> is also the maximum block
237 length for all ciphers.
239 EVP_CIPHER_type() and EVP_CIPHER_CTX_type() return the type of the passed
240 cipher or context. This "type" is the actual NID of the cipher OBJECT
241 IDENTIFIER as such it ignores the cipher parameters and 40 bit RC2 and
242 128 bit RC2 have the same NID. If the cipher does not have an object
243 identifier or does not have ASN1 support this function will return
246 EVP_CIPHER_CTX_cipher() returns the B<EVP_CIPHER> structure when passed
247 an B<EVP_CIPHER_CTX> structure.
249 EVP_CIPHER_mode() and EVP_CIPHER_CTX_mode() return the block cipher mode:
250 EVP_CIPH_ECB_MODE, EVP_CIPH_CBC_MODE, EVP_CIPH_CFB_MODE, EVP_CIPH_OFB_MODE,
251 EVP_CIPH_CTR_MODE, EVP_CIPH_GCM_MODE, EVP_CIPH_CCM_MODE, EVP_CIPH_XTS_MODE,
252 EVP_CIPH_WRAP_MODE or EVP_CIPH_OCB_MODE. If the cipher is a stream cipher then
253 EVP_CIPH_STREAM_CIPHER is returned.
255 EVP_CIPHER_param_to_asn1() sets the AlgorithmIdentifier "parameter" based
256 on the passed cipher. This will typically include any parameters and an
257 IV. The cipher IV (if any) must be set when this call is made. This call
258 should be made before the cipher is actually "used" (before any
259 EVP_EncryptUpdate(), EVP_DecryptUpdate() calls for example). This function
260 may fail if the cipher does not have any ASN1 support.
262 EVP_CIPHER_asn1_to_param() sets the cipher parameters based on an ASN1
263 AlgorithmIdentifier "parameter". The precise effect depends on the cipher
264 In the case of RC2, for example, it will set the IV and effective key length.
265 This function should be called after the base cipher type is set but before
266 the key is set. For example EVP_CipherInit() will be called with the IV and
267 key set to NULL, EVP_CIPHER_asn1_to_param() will be called and finally
268 EVP_CipherInit() again with all parameters except the key set to NULL. It is
269 possible for this function to fail if the cipher does not have any ASN1 support
270 or the parameters cannot be set (for example the RC2 effective key length
273 EVP_CIPHER_CTX_ctrl() allows various cipher specific parameters to be determined
276 EVP_CIPHER_CTX_rand_key() generates a random key of the appropriate length
277 based on the cipher context. The EVP_CIPHER can provide its own random key
278 generation routine to support keys of a specific form. B<Key> must point to a
279 buffer at least as big as the value returned by EVP_CIPHER_CTX_key_length().
283 EVP_CIPHER_CTX_new() returns a pointer to a newly created
284 B<EVP_CIPHER_CTX> for success and B<NULL> for failure.
286 EVP_EncryptInit_ex(), EVP_EncryptUpdate() and EVP_EncryptFinal_ex()
287 return 1 for success and 0 for failure.
289 EVP_DecryptInit_ex() and EVP_DecryptUpdate() return 1 for success and 0 for failure.
290 EVP_DecryptFinal_ex() returns 0 if the decrypt failed or 1 for success.
292 EVP_CipherInit_ex() and EVP_CipherUpdate() return 1 for success and 0 for failure.
293 EVP_CipherFinal_ex() returns 0 for a decryption failure or 1 for success.
295 EVP_CIPHER_CTX_reset() returns 1 for success and 0 for failure.
297 EVP_get_cipherbyname(), EVP_get_cipherbynid() and EVP_get_cipherbyobj()
298 return an B<EVP_CIPHER> structure or NULL on error.
300 EVP_CIPHER_nid() and EVP_CIPHER_CTX_nid() return a NID.
302 EVP_CIPHER_block_size() and EVP_CIPHER_CTX_block_size() return the block
305 EVP_CIPHER_key_length() and EVP_CIPHER_CTX_key_length() return the key
308 EVP_CIPHER_CTX_set_padding() always returns 1.
310 EVP_CIPHER_iv_length() and EVP_CIPHER_CTX_iv_length() return the IV
311 length or zero if the cipher does not use an IV.
313 EVP_CIPHER_type() and EVP_CIPHER_CTX_type() return the NID of the cipher's
314 OBJECT IDENTIFIER or NID_undef if it has no defined OBJECT IDENTIFIER.
316 EVP_CIPHER_CTX_cipher() returns an B<EVP_CIPHER> structure.
318 EVP_CIPHER_param_to_asn1() and EVP_CIPHER_asn1_to_param() return greater
319 than zero for success and zero or a negative number on failure.
321 EVP_CIPHER_CTX_rand_key() returns 1 for success.
323 =head1 CIPHER LISTING
325 All algorithms have a fixed key length unless otherwise stated.
327 Refer to L<SEE ALSO> for the full list of ciphers available through the EVP
334 Null cipher: does nothing.
338 =head1 AEAD Interface
340 The EVP interface for Authenticated Encryption with Associated Data (AEAD)
341 modes are subtly altered and several additional I<ctrl> operations are supported
342 depending on the mode specified.
344 To specify additional authenticated data (AAD), a call to EVP_CipherUpdate(),
345 EVP_EncryptUpdate() or EVP_DecryptUpdate() should be made with the output
346 parameter B<out> set to B<NULL>.
348 When decrypting, the return value of EVP_DecryptFinal() or EVP_CipherFinal()
349 indicates whether the operation was successful. If it does not indicate success,
350 the authentication operation has failed and any output data B<MUST NOT> be used
353 =head2 GCM and OCB Modes
355 The following I<ctrl>s are supported in GCM and OCB modes.
359 =item EVP_CIPHER_CTX_ctrl(ctx, EVP_CTRL_AEAD_SET_IVLEN, ivlen, NULL)
361 Sets the IV length. This call can only be made before specifying an IV. If
362 not called a default IV length is used.
364 For GCM AES and OCB AES the default is 12 (i.e. 96 bits). For OCB mode the
367 =item EVP_CIPHER_CTX_ctrl(ctx, EVP_CTRL_AEAD_GET_TAG, taglen, tag)
369 Writes C<taglen> bytes of the tag value to the buffer indicated by C<tag>.
370 This call can only be made when encrypting data and B<after> all data has been
371 processed (e.g. after an EVP_EncryptFinal() call).
373 For OCB, C<taglen> must either be 16 or the value previously set via
374 B<EVP_CTRL_AEAD_SET_TAG>.
376 =item EVP_CIPHER_CTX_ctrl(ctx, EVP_CTRL_AEAD_SET_TAG, taglen, tag)
378 Sets the expected tag to C<taglen> bytes from C<tag>.
379 The tag length can only be set before specifying an IV.
380 C<taglen> must be between 1 and 16 inclusive.
382 For GCM, this call is only valid when decrypting data.
384 For OCB, this call is valid when decrypting data to set the expected tag,
385 and before encryption to set the desired tag length.
387 In OCB mode, calling this before encryption with C<tag> set to C<NULL> sets the
388 tag length. If this is not called prior to encryption, a default tag length is
391 For OCB AES, the default tag length is 16 (i.e. 128 bits). It is also the
392 maximum tag length for OCB.
398 The EVP interface for CCM mode is similar to that of the GCM mode but with a
399 few additional requirements and different I<ctrl> values.
401 For CCM mode, the total plaintext or ciphertext length B<MUST> be passed to
402 EVP_CipherUpdate(), EVP_EncryptUpdate() or EVP_DecryptUpdate() with the output
403 and input parameters (B<in> and B<out>) set to B<NULL> and the length passed in
404 the B<inl> parameter.
406 The following I<ctrl>s are supported in CCM mode.
410 =item EVP_CIPHER_CTX_ctrl(ctx, EVP_CTRL_AEAD_SET_TAG, taglen, tag)
412 This call is made to set the expected B<CCM> tag value when decrypting or
413 the length of the tag (with the C<tag> parameter set to NULL) when encrypting.
414 The tag length is often referred to as B<M>. If not set a default value is
417 =item EVP_CIPHER_CTX_ctrl(ctx, EVP_CTRL_CCM_SET_L, ivlen, NULL)
419 Sets the CCM B<L> value. If not set a default is used (8 for AES).
421 =item EVP_CIPHER_CTX_ctrl(ctx, EVP_CTRL_AEAD_SET_IVLEN, ivlen, NULL)
423 Sets the CCM nonce (IV) length. This call can only be made before specifying an
424 nonce value. The nonce length is given by B<15 - L> so it is 7 by default for
431 For SIV mode ciphers the behaviour of the EVP interface is subtly
432 altered and several additional ctrl operations are supported.
434 To specify any additional authenticated data (AAD) and/or a Nonce, a call to
435 EVP_CipherUpdate(), EVP_EncryptUpdate() or EVP_DecryptUpdate() should be made
436 with the output parameter B<out> set to B<NULL>.
438 RFC5297 states that the Nonce is the last piece of AAD before the actual
439 encrypt/decrypt takes place. The API does not differentiate the Nonce from
442 When decrypting the return value of EVP_DecryptFinal() or EVP_CipherFinal()
443 indicates if the operation was successful. If it does not indicate success
444 the authentication operation has failed and any output data B<MUST NOT>
445 be used as it is corrupted.
447 The following ctrls are supported in both SIV modes.
451 =item EVP_CIPHER_CTX_ctrl(ctx, EVP_CTRL_AEAD_GET_TAG, taglen, tag);
453 Writes B<taglen> bytes of the tag value to the buffer indicated by B<tag>.
454 This call can only be made when encrypting data and B<after> all data has been
455 processed (e.g. after an EVP_EncryptFinal() call). For SIV mode the taglen must
458 =item EVP_CIPHER_CTX_ctrl(ctx, EVP_CTRL_AEAD_SET_TAG, taglen, tag);
460 Sets the expected tag to B<taglen> bytes from B<tag>. This call is only legal
461 when decrypting data and must be made B<before> any data is processed (e.g.
462 before any EVP_DecryptUpdate() call). For SIV mode the taglen must be 16.
466 SIV mode makes two passes over the input data, thus, only one call to
467 EVP_CipherUpdate(), EVP_EncryptUpdate() or EVP_DecryptUpdate() should be made
468 with B<out> set to a non-B<NULL> value. A call to EVP_Decrypt_Final() or
469 EVP_CipherFinal() is not required, but will indicate if the update
472 =head2 ChaCha20-Poly1305
474 The following I<ctrl>s are supported for the ChaCha20-Poly1305 AEAD algorithm.
478 =item EVP_CIPHER_CTX_ctrl(ctx, EVP_CTRL_AEAD_SET_IVLEN, ivlen, NULL)
480 Sets the nonce length. This call can only be made before specifying the nonce.
481 If not called a default nonce length of 12 (i.e. 96 bits) is used. The maximum
482 nonce length is 16 (B<CHACHA_CTR_SIZE>, i.e. 128-bits).
484 =item EVP_CIPHER_CTX_ctrl(ctx, EVP_CTRL_AEAD_GET_TAG, taglen, tag)
486 Writes C<taglen> bytes of the tag value to the buffer indicated by C<tag>.
487 This call can only be made when encrypting data and B<after> all data has been
488 processed (e.g. after an EVP_EncryptFinal() call).
490 C<taglen> specified here must be 16 (B<POLY1305_BLOCK_SIZE>, i.e. 128-bits) or
493 =item EVP_CIPHER_CTX_ctrl(ctx, EVP_CTRL_AEAD_SET_TAG, taglen, tag)
495 Sets the expected tag to C<taglen> bytes from C<tag>.
496 The tag length can only be set before specifying an IV.
497 C<taglen> must be between 1 and 16 (B<POLY1305_BLOCK_SIZE>) inclusive.
498 This call is only valid when decrypting data.
504 Where possible the B<EVP> interface to symmetric ciphers should be used in
505 preference to the low level interfaces. This is because the code then becomes
506 transparent to the cipher used and much more flexible. Additionally, the
507 B<EVP> interface will ensure the use of platform specific cryptographic
508 acceleration such as AES-NI (the low level interfaces do not provide the
511 PKCS padding works by adding B<n> padding bytes of value B<n> to make the total
512 length of the encrypted data a multiple of the block size. Padding is always
513 added so if the data is already a multiple of the block size B<n> will equal
514 the block size. For example if the block size is 8 and 11 bytes are to be
515 encrypted then 5 padding bytes of value 5 will be added.
517 When decrypting the final block is checked to see if it has the correct form.
519 Although the decryption operation can produce an error if padding is enabled,
520 it is not a strong test that the input data or key is correct. A random block
521 has better than 1 in 256 chance of being of the correct format and problems with
522 the input data earlier on will not produce a final decrypt error.
524 If padding is disabled then the decryption operation will always succeed if
525 the total amount of data decrypted is a multiple of the block size.
527 The functions EVP_EncryptInit(), EVP_EncryptFinal(), EVP_DecryptInit(),
528 EVP_CipherInit() and EVP_CipherFinal() are obsolete but are retained for
529 compatibility with existing code. New code should use EVP_EncryptInit_ex(),
530 EVP_EncryptFinal_ex(), EVP_DecryptInit_ex(), EVP_DecryptFinal_ex(),
531 EVP_CipherInit_ex() and EVP_CipherFinal_ex() because they can reuse an
532 existing context without allocating and freeing it up on each call.
534 EVP_get_cipherbynid(), and EVP_get_cipherbyobj() are implemented as macros.
538 B<EVP_MAX_KEY_LENGTH> and B<EVP_MAX_IV_LENGTH> only refer to the internal
539 ciphers with default key lengths. If custom ciphers exceed these values the
540 results are unpredictable. This is because it has become standard practice to
541 define a generic key as a fixed unsigned char array containing
542 B<EVP_MAX_KEY_LENGTH> bytes.
544 The ASN1 code is incomplete (and sometimes inaccurate) it has only been tested
545 for certain common S/MIME ciphers (RC2, DES, triple DES) in CBC mode.
549 Encrypt a string using IDEA:
551 int do_crypt(char *outfile)
553 unsigned char outbuf[1024];
556 * Bogus key and IV: we'd normally set these from
559 unsigned char key[] = {0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15};
560 unsigned char iv[] = {1,2,3,4,5,6,7,8};
561 char intext[] = "Some Crypto Text";
565 ctx = EVP_CIPHER_CTX_new();
566 EVP_EncryptInit_ex(ctx, EVP_idea_cbc(), NULL, key, iv);
568 if (!EVP_EncryptUpdate(ctx, outbuf, &outlen, intext, strlen(intext))) {
570 EVP_CIPHER_CTX_free(ctx);
574 * Buffer passed to EVP_EncryptFinal() must be after data just
575 * encrypted to avoid overwriting it.
577 if (!EVP_EncryptFinal_ex(ctx, outbuf + outlen, &tmplen)) {
579 EVP_CIPHER_CTX_free(ctx);
583 EVP_CIPHER_CTX_free(ctx);
585 * Need binary mode for fopen because encrypted data is
586 * binary data. Also cannot use strlen() on it because
587 * it won't be NUL terminated and may contain embedded
590 out = fopen(outfile, "wb");
595 fwrite(outbuf, 1, outlen, out);
600 The ciphertext from the above example can be decrypted using the B<openssl>
601 utility with the command line (shown on two lines for clarity):
604 -K 000102030405060708090A0B0C0D0E0F -iv 0102030405060708 <filename
606 General encryption and decryption function example using FILE I/O and AES128
609 int do_crypt(FILE *in, FILE *out, int do_encrypt)
611 /* Allow enough space in output buffer for additional block */
612 unsigned char inbuf[1024], outbuf[1024 + EVP_MAX_BLOCK_LENGTH];
616 * Bogus key and IV: we'd normally set these from
619 unsigned char key[] = "0123456789abcdeF";
620 unsigned char iv[] = "1234567887654321";
622 /* Don't set key or IV right away; we want to check lengths */
623 ctx = EVP_CIPHER_CTX_new();
624 EVP_CipherInit_ex(&ctx, EVP_aes_128_cbc(), NULL, NULL, NULL,
626 OPENSSL_assert(EVP_CIPHER_CTX_key_length(ctx) == 16);
627 OPENSSL_assert(EVP_CIPHER_CTX_iv_length(ctx) == 16);
629 /* Now we can set key and IV */
630 EVP_CipherInit_ex(ctx, NULL, NULL, key, iv, do_encrypt);
633 inlen = fread(inbuf, 1, 1024, in);
636 if (!EVP_CipherUpdate(ctx, outbuf, &outlen, inbuf, inlen)) {
638 EVP_CIPHER_CTX_free(ctx);
641 fwrite(outbuf, 1, outlen, out);
643 if (!EVP_CipherFinal_ex(ctx, outbuf, &outlen)) {
645 EVP_CIPHER_CTX_free(ctx);
648 fwrite(outbuf, 1, outlen, out);
650 EVP_CIPHER_CTX_free(ctx);
659 Supported ciphers are listed in:
678 Support for OCB mode was added in OpenSSL 1.1.0.
680 B<EVP_CIPHER_CTX> was made opaque in OpenSSL 1.1.0. As a result,
681 EVP_CIPHER_CTX_reset() appeared and EVP_CIPHER_CTX_cleanup()
682 disappeared. EVP_CIPHER_CTX_init() remains as an alias for
683 EVP_CIPHER_CTX_reset().
687 Copyright 2000-2018 The OpenSSL Project Authors. All Rights Reserved.
689 Licensed under the Apache License 2.0 (the "License"). You may not use
690 this file except in compliance with the License. You can obtain a copy
691 in the file LICENSE in the source distribution or at
692 L<https://www.openssl.org/source/license.html>.