5 EVP_EncryptInit, EVP_EncryptUpdate, EVP_EncryptFinal - EVP cipher routines
9 #include <openssl/evp.h>
11 int EVP_EncryptInit(EVP_CIPHER_CTX *ctx, const EVP_CIPHER *type,
12 unsigned char *key, unsigned char *iv);
13 int EVP_EncryptUpdate(EVP_CIPHER_CTX *ctx, unsigned char *out,
14 int *outl, unsigned char *in, int inl);
15 int EVP_EncryptFinal(EVP_CIPHER_CTX *ctx, unsigned char *out,
18 int EVP_DecryptInit(EVP_CIPHER_CTX *ctx, const EVP_CIPHER *type,
19 unsigned char *key, unsigned char *iv);
20 int EVP_DecryptUpdate(EVP_CIPHER_CTX *ctx, unsigned char *out,
21 int *outl, unsigned char *in, int inl);
22 int EVP_DecryptFinal(EVP_CIPHER_CTX *ctx, unsigned char *outm,
25 int EVP_CipherInit(EVP_CIPHER_CTX *ctx, const EVP_CIPHER *type,
26 unsigned char *key, unsigned char *iv, int enc);
27 int EVP_CipherUpdate(EVP_CIPHER_CTX *ctx, unsigned char *out,
28 int *outl, unsigned char *in, int inl);
29 int EVP_CipherFinal(EVP_CIPHER_CTX *ctx, unsigned char *outm,
32 int EVP_CIPHER_CTX_set_key_length(EVP_CIPHER_CTX *x, int keylen);
33 int EVP_CIPHER_CTX_ctrl(EVP_CIPHER_CTX *ctx, int type, int arg, void *ptr);
34 int EVP_CIPHER_CTX_cleanup(EVP_CIPHER_CTX *a);
36 const EVP_CIPHER *EVP_get_cipherbyname(const char *name);
37 #define EVP_get_cipherbynid(a) EVP_get_cipherbyname(OBJ_nid2sn(a))
38 #define EVP_get_cipherbyobj(a) EVP_get_cipherbynid(OBJ_obj2nid(a))
40 #define EVP_CIPHER_nid(e) ((e)->nid)
41 #define EVP_CIPHER_block_size(e) ((e)->block_size)
42 #define EVP_CIPHER_key_length(e) ((e)->key_len)
43 #define EVP_CIPHER_iv_length(e) ((e)->iv_len)
44 #define EVP_CIPHER_flags(e) ((e)->flags)
45 #define EVP_CIPHER_mode(e) ((e)->flags) & EVP_CIPH_MODE)
46 int EVP_CIPHER_type(const EVP_CIPHER *ctx);
48 #define EVP_CIPHER_CTX_cipher(e) ((e)->cipher)
49 #define EVP_CIPHER_CTX_nid(e) ((e)->cipher->nid)
50 #define EVP_CIPHER_CTX_block_size(e) ((e)->cipher->block_size)
51 #define EVP_CIPHER_CTX_key_length(e) ((e)->key_len)
52 #define EVP_CIPHER_CTX_iv_length(e) ((e)->cipher->iv_len)
53 #define EVP_CIPHER_CTX_get_app_data(e) ((e)->app_data)
54 #define EVP_CIPHER_CTX_set_app_data(e,d) ((e)->app_data=(char *)(d))
55 #define EVP_CIPHER_CTX_type(c) EVP_CIPHER_type(EVP_CIPHER_CTX_cipher(c))
56 #define EVP_CIPHER_CTX_flags(e) ((e)->cipher->flags)
57 #define EVP_CIPHER_CTX_mode(e) ((e)->cipher->flags & EVP_CIPH_MODE)
59 int EVP_CIPHER_param_to_asn1(EVP_CIPHER_CTX *c, ASN1_TYPE *type);
60 int EVP_CIPHER_asn1_to_param(EVP_CIPHER_CTX *c, ASN1_TYPE *type);
64 The EVP cipher routines are a high level interface to certain
67 EVP_EncryptInit() initialises a cipher context B<ctx> for encryption
68 with cipher B<type>. B<type> is normally supplied by a function such
69 as EVP_des_cbc() . B<key> is the symmetric key to use and B<iv> is the
70 IV to use (if necessary), the actual number of bytes used for the
71 key and IV depends on the cipher. It is possible to set all parameters
72 to NULL except B<type> in an initial call and supply the remaining
73 parameters in subsequent calls, all of which have B<type> set to NULL.
74 This is done when the default cipher parameters are not appropriate.
76 EVP_EncryptUpdate() encrypts B<inl> bytes from the buffer B<in> and
77 writes the encrypted version to B<out>. This function can be called
78 multiple times to encrypt successive blocks of data. The amount
79 of data written depends on the block alignment of the encrypted data:
80 as a result the amount of data written may be anything from zero bytes
81 to (inl + cipher_block_size - 1) so B<outl> should contain sufficient
82 room. The actual number of bytes written is placed in B<outl>.
84 EVP_EncryptFinal() encrypts the "final" data, that is any data that
85 remains in a partial block. It uses L<standard block padding|/NOTES> (aka PKCS
86 padding). The encrypted final data is written to B<out> which should
87 have sufficient space for one cipher block. The number of bytes written
88 is placed in B<outl>. After this function is called the encryption operation
89 is finished and no further calls to EVP_EncryptUpdate() should be made.
91 EVP_DecryptInit(), EVP_DecryptUpdate() and EVP_DecryptFinal() are the
92 corresponding decryption operations. EVP_DecryptFinal() will return an
93 error code if the final block is not correctly formatted. The parameters
94 and restrictions are identical to the encryption operations except that
95 the decrypted data buffer B<out> passed to EVP_DecryptUpdate() should
96 have sufficient room for (B<inl> + cipher_block_size) bytes unless the
97 cipher block size is 1 in which case B<inl> bytes is sufficient.
99 EVP_CipherInit(), EVP_CipherUpdate() and EVP_CipherFinal() are functions
100 that can be used for decryption or encryption. The operation performed
101 depends on the value of the B<enc> parameter. It should be set to 1 for
102 encryption, 0 for decryption and -1 to leave the value unchanged (the
103 actual value of 'enc' being supplied in a previous call).
105 EVP_CIPHER_CTX_cleanup() clears all information from a cipher context.
106 It should be called after all operations using a cipher are complete
107 so sensitive information does not remain in memory.
109 EVP_get_cipherbyname(), EVP_get_cipherbynid() and EVP_get_cipherbyobj()
110 return an EVP_CIPHER structure when passed a cipher name, a NID or an
111 ASN1_OBJECT structure.
113 EVP_CIPHER_nid() and EVP_CIPHER_CTX_nid() return the NID of a cipher when
114 passed an B<EVP_CIPHER> or B<EVP_CIPHER_CTX> structure. The actual NID
115 value is an internal value which may not have a corresponding OBJECT
118 EVP_CIPHER_key_length() and EVP_CIPHER_CTX_key_length() return the key
119 length of a cipher when passed an B<EVP_CIPHER> or B<EVP_CIPHER_CTX>
120 structure. The constant B<EVP_MAX_KEY_LENGTH> is the maximum key length
121 for all ciphers. Note: although EVP_CIPHER_key_length() is fixed for a
122 given cipher, the value of EVP_CIPHER_CTX_key_length() may be different
123 for variable key length ciphers.
125 EVP_CIPHER_CTX_set_key_length() sets the key length of the cipher ctx.
126 If the cipher is a fixed length cipher then attempting to set the key
127 length to any value other than the fixed value is an error.
129 EVP_CIPHER_iv_length() and EVP_CIPHER_CTX_iv_length() return the IV
130 length of a cipher when passed an B<EVP_CIPHER> or B<EVP_CIPHER_CTX>.
131 It will return zero if the cipher does not use an IV. The constant
132 B<EVP_MAX_IV_LENGTH> is the maximum IV length for all ciphers.
134 EVP_CIPHER_block_size() and EVP_CIPHER_CTX_block_size() return the block
135 size of a cipher when passed an B<EVP_CIPHER> or B<EVP_CIPHER_CTX>
136 structure. The constant B<EVP_MAX_IV_LENGTH> is also the maximum block
137 length for all ciphers.
139 EVP_CIPHER_type() and EVP_CIPHER_CTX_type() return the type of the passed
140 cipher or context. This "type" is the actual NID of the cipher OBJECT
141 IDENTIFIER as such it ignores the cipher parameters and 40 bit RC2 and
142 128 bit RC2 have the same NID. If the cipher does not have an object
143 identifier or does not have ASN1 support this function will return
146 EVP_CIPHER_CTX_cipher() returns the B<EVP_CIPHER> structure when passed
147 an B<EVP_CIPHER_CTX> structure.
149 EVP_CIPHER_mode() and EVP_CIPHER_CTX_mode() return the block cipher mode:
150 EVP_CIPH_ECB_MODE, EVP_CIPH_CBC_MODE, EVP_CIPH_CFB_MODE or
151 EVP_CIPH_OFB_MODE. If the cipher is a stream cipher then
152 EVP_CIPH_STREAM_CIPHER is returned.
154 EVP_CIPHER_param_to_asn1() sets the AlgorithmIdentifier "parameter" based
155 on the passed cipher. This will typically include any parameters and an
156 IV. The cipher IV (if any) must be set when this call is made. This call
157 should be made before the cipher is actually "used" (before any
158 EVP_EncryptUpdate(), EVP_DecryptUpdate() calls for example). This function
159 may fail if the cipher does not have any ASN1 support.
161 EVP_CIPHER_asn1_to_param() sets the cipher parameters based on an ASN1
162 AlgorithmIdentifier "parameter". The precise effect depends on the cipher
163 In the case of RC2, for example, it will set the IV and effective key length.
164 This function should be called after the base cipher type is set but before
165 the key is set. For example EVP_CipherInit() will be called with the IV and
166 key set to NULL, EVP_CIPHER_asn1_to_param() will be called and finally
167 EVP_CipherInit() again with all parameters except the key set to NULL. It is
168 possible for this function to fail if the cipher does not have any ASN1 support
169 or the parameters cannot be set (for example the RC2 effective key length
172 EVP_CIPHER_CTX_ctrl() allows various cipher specific parameters to be determined
173 and set. Currently only the RC2 effective key length and the number of rounds of
178 EVP_EncryptInit(), EVP_EncryptUpdate() and EVP_EncryptFinal() return 1 for success
181 EVP_DecryptInit() and EVP_DecryptUpdate() return 1 for success and 0 for failure.
182 EVP_DecryptFinal() returns 0 if the decrypt failed or 1 for success.
184 EVP_CipherInit() and EVP_CipherUpdate() return 1 for success and 0 for failure.
185 EVP_CipherFinal() returns 1 for a decryption failure or 1 for success.
187 EVP_CIPHER_CTX_cleanup() returns 1 for success and 0 for failure.
189 EVP_get_cipherbyname(), EVP_get_cipherbynid() and EVP_get_cipherbyobj()
190 return an B<EVP_CIPHER> structure or NULL on error.
192 EVP_CIPHER_nid() and EVP_CIPHER_CTX_nid() return a NID.
194 EVP_CIPHER_block_size() and EVP_CIPHER_CTX_block_size() return the block
197 EVP_CIPHER_key_length() and EVP_CIPHER_CTX_key_length() return the key
200 EVP_CIPHER_iv_length() and EVP_CIPHER_CTX_iv_length() return the IV
201 length or zero if the cipher does not use an IV.
203 EVP_CIPHER_type() and EVP_CIPHER_CTX_type() return the NID of the cipher's
204 OBJECT IDENTIFIER or NID_undef if it has no defined OBJECT IDENTIFIER.
206 EVP_CIPHER_CTX_cipher() returns an B<EVP_CIPHER> structure.
208 EVP_CIPHER_param_to_asn1() and EVP_CIPHER_asn1_to_param() return 1 for
209 success or zero for failure.
211 =head1 CIPHER LISTING
213 All algorithms have a fixed key length unless otherwise stated.
219 Null cipher: does nothing.
221 =item EVP_des_cbc(void), EVP_des_ecb(void), EVP_des_cfb(void), EVP_des_ofb(void)
223 DES in CBC, ECB, CFB and OFB modes respectively.
225 =item EVP_des_ede_cbc(void), EVP_des_ede(), EVP_des_ede_ofb(void), EVP_des_ede_cfb(void)
227 Two key triple DES in CBC, ECB, CFB and OFB modes respectively.
229 =item EVP_des_ede3_cbc(void), EVP_des_ede3(), EVP_des_ede3_ofb(void), EVP_des_ede3_cfb(void)
231 Three key triple DES in CBC, ECB, CFB and OFB modes respectively.
233 =item EVP_desx_cbc(void)
235 DESX algorithm in CBC mode.
239 RC4 stream cipher. This is a variable key length cipher with default key length 128 bits.
241 =item EVP_rc4_40(void)
243 RC4 stream cipher with 40 bit key length. This is obsolete and new code should use EVP_rc4()
244 and the EVP_CIPHER_CTX_set_key_length() function.
246 =item EVP_idea_cbc() EVP_idea_ecb(void), EVP_idea_cfb(void), EVP_idea_ofb(void), EVP_idea_cbc(void)
248 IDES encryption algorothm in CBC, ECB, CFB and OFB modes respectively.
250 =item EVP_rc2_cbc(void), EVP_rc2_ecb(void), EVP_rc2_cfb(void), EVP_rc2_ofb(void)
252 RC2 encryption algorithm in CBC, ECB, CFB and OFB modes respectively. This is a variable key
253 length cipher with an additional parameter called "effective key bits" or "effective key length".
254 By default both are set to 128 bits.
256 =item EVP_rc2_40_cbc(void), EVP_rc2_64_cbc(void)
258 RC2 algorithm in CBC mode with a default key length and effective key length of 40 and 64 bits.
259 These are obsolete and new code should use EVP_rc2_cbc(), EVP_CIPHER_CTX_set_key_length() and
260 EVP_CIPHER_CTX_ctrl() to set the key length and effective key length.
262 =item EVP_bf_cbc(void), EVP_bf_ecb(void), EVP_bf_cfb(void), EVP_bf_ofb(void);
264 Blowfish encryption algorithm in CBC, ECB, CFB and OFB modes respectively. This is a variable key
267 =item EVP_cast5_cbc(void), EVP_cast5_ecb(void), EVP_cast5_cfb(void), EVP_cast5_ofb(void)
269 CAST encryption algorithm in CBC, ECB, CFB and OFB modes respectively. This is a variable key
272 =item EVP_rc5_32_12_16_cbc(void), EVP_rc5_32_12_16_ecb(void), EVP_rc5_32_12_16_cfb(void), EVP_rc5_32_12_16_ofb(void)
274 RC5 encryption algorithm in CBC, ECB, CFB and OFB modes respectively. This is a variable key length
275 cipher with an additional "number of rounds" parameter. By default the key length is set to 128
282 Where possible the B<EVP> interface to symmetric ciphers should be used in
283 preference to the low level interfaces. This is because the code then becomes
284 transparent to the cipher used and much more flexible.
286 PKCS padding works by adding B<n> padding bytes of value B<n> to make the total
287 length of the encrypted data a multiple of the block size. Padding is always
288 added so if the data is already a multiple of the block size B<n> will equal
289 the block size. For example if the block size is 8 and 11 bytes are to be
290 encrypted then 5 padding bytes of value 5 will be added.
292 When decrypting the final block is checked to see if it has the correct form.
294 Although the decryption operation can produce an error, it is not a strong
295 test that the input data or key is correct. A random block has better than
296 1 in 256 chance of being of the correct format and problems with the
297 input data earlier on will not produce a final decrypt error.
299 The functions EVP_EncryptInit(), EVP_EncryptUpdate(), EVP_EncryptFinal(),
300 EVP_DecryptInit(), EVP_DecryptUpdate(), EVP_CipherInit() and EVP_CipherUpdate()
301 and EVP_CIPHER_CTX_cleanup() did not return errors in OpenSSL version 0.9.5a or
302 earlier. Software only versions of encryption algorithms will never return
303 error codes for these functions, unless there is a programming error (for example
304 and attempt to set the key before the cipher is set in EVP_EncryptInit() ).
308 For RC5 the number of rounds can currently only be set to 8, 12 or 16. This is
309 a limitation of the current RC5 code rather than the EVP interface.
311 It should be possible to disable PKCS padding: currently it isn't.
313 EVP_MAX_KEY_LENGTH and EVP_MAX_IV_LENGTH only refer to the internal ciphers with
314 default key lengths. If custom ciphers exceed these values the results are
315 unpredictable. This is because it has become standard practice to define a
316 generic key as a fixed unsigned char array containing EVP_MAX_KEY_LENGTH bytes.
318 The ASN1 code is incomplete (and sometimes innacurate) it has only been tested
319 for certain common S/MIME ciphers (RC2, DES, triple DES) in CBC mode.
323 Get the number of rounds used in RC5:
326 EVP_CIPHER_CTX_ctrl(ctx, EVP_CTRL_GET_RC5_ROUNDS, 0, &i);
328 Get the RC2 effective key length:
331 EVP_CIPHER_CTX_ctrl(ctx, EVP_CTRL_GET_RC2_KEY_BITS, 0, &i);
333 Set the number of rounds used in RC5:
336 EVP_CIPHER_CTX_ctrl(ctx, EVP_CTRL_SET_RC5_ROUNDS, i, NULL);
338 Set the number of rounds used in RC2:
341 EVP_CIPHER_CTX_ctrl(ctx, EVP_CTRL_SET_RC2_KEY_BITS, i, NULL);