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138.\" ======================================================================
140.IX Title "EVP_EncryptInit 3"
141.TH EVP_EncryptInit 3 "0.9.7a" "2003-02-19" "OpenSSL"
143.SH "NAME"
144EVP_CIPHER_CTX_init, EVP_EncryptInit_ex, EVP_EncryptUpdate,
145EVP_EncryptFinal_ex, EVP_DecryptInit_ex, EVP_DecryptUpdate,
146EVP_DecryptFinal_ex, EVP_CipherInit_ex, EVP_CipherUpdate,
147EVP_CipherFinal_ex, EVP_CIPHER_CTX_set_key_length,
148EVP_CIPHER_CTX_ctrl, EVP_CIPHER_CTX_cleanup, EVP_EncryptInit,
149EVP_EncryptFinal, EVP_DecryptInit, EVP_DecryptFinal,
150EVP_CipherInit, EVP_CipherFinal, EVP_get_cipherbyname,
151EVP_get_cipherbynid, EVP_get_cipherbyobj, EVP_CIPHER_nid,
152EVP_CIPHER_block_size, EVP_CIPHER_key_length, EVP_CIPHER_iv_length,
154EVP_CIPHER_CTX_nid, EVP_CIPHER_CTX_block_size, EVP_CIPHER_CTX_key_length,
155EVP_CIPHER_CTX_iv_length, EVP_CIPHER_CTX_get_app_data,
156EVP_CIPHER_CTX_set_app_data, EVP_CIPHER_CTX_type, EVP_CIPHER_CTX_flags,
157EVP_CIPHER_CTX_mode, EVP_CIPHER_param_to_asn1, EVP_CIPHER_asn1_to_param,
158EVP_CIPHER_CTX_set_padding \- \s-1EVP\s0 cipher routines
160.IX Header "SYNOPSIS"
161.Vb 1
162\& #include <openssl/evp.h>
164.Vb 1
165\& int EVP_CIPHER_CTX_init(EVP_CIPHER_CTX *a);
167.Vb 6
168\& int EVP_EncryptInit_ex(EVP_CIPHER_CTX *ctx, const EVP_CIPHER *type,
169\& ENGINE *impl, unsigned char *key, unsigned char *iv);
170\& int EVP_EncryptUpdate(EVP_CIPHER_CTX *ctx, unsigned char *out,
171\& int *outl, unsigned char *in, int inl);
172\& int EVP_EncryptFinal_ex(EVP_CIPHER_CTX *ctx, unsigned char *out,
173\& int *outl);
175.Vb 6
176\& int EVP_DecryptInit_ex(EVP_CIPHER_CTX *ctx, const EVP_CIPHER *type,
177\& ENGINE *impl, unsigned char *key, unsigned char *iv);
178\& int EVP_DecryptUpdate(EVP_CIPHER_CTX *ctx, unsigned char *out,
179\& int *outl, unsigned char *in, int inl);
180\& int EVP_DecryptFinal_ex(EVP_CIPHER_CTX *ctx, unsigned char *outm,
181\& int *outl);
183.Vb 6
184\& int EVP_CipherInit_ex(EVP_CIPHER_CTX *ctx, const EVP_CIPHER *type,
185\& ENGINE *impl, unsigned char *key, unsigned char *iv, int enc);
186\& int EVP_CipherUpdate(EVP_CIPHER_CTX *ctx, unsigned char *out,
187\& int *outl, unsigned char *in, int inl);
188\& int EVP_CipherFinal_ex(EVP_CIPHER_CTX *ctx, unsigned char *outm,
189\& int *outl);
191.Vb 4
192\& int EVP_EncryptInit(EVP_CIPHER_CTX *ctx, const EVP_CIPHER *type,
193\& unsigned char *key, unsigned char *iv);
194\& int EVP_EncryptFinal(EVP_CIPHER_CTX *ctx, unsigned char *out,
195\& int *outl);
197.Vb 4
198\& int EVP_DecryptInit(EVP_CIPHER_CTX *ctx, const EVP_CIPHER *type,
199\& unsigned char *key, unsigned char *iv);
200\& int EVP_DecryptFinal(EVP_CIPHER_CTX *ctx, unsigned char *outm,
201\& int *outl);
203.Vb 4
204\& int EVP_CipherInit(EVP_CIPHER_CTX *ctx, const EVP_CIPHER *type,
205\& unsigned char *key, unsigned char *iv, int enc);
206\& int EVP_CipherFinal(EVP_CIPHER_CTX *ctx, unsigned char *outm,
207\& int *outl);
209.Vb 4
210\& int EVP_CIPHER_CTX_set_padding(EVP_CIPHER_CTX *x, int padding);
211\& int EVP_CIPHER_CTX_set_key_length(EVP_CIPHER_CTX *x, int keylen);
212\& int EVP_CIPHER_CTX_ctrl(EVP_CIPHER_CTX *ctx, int type, int arg, void *ptr);
213\& int EVP_CIPHER_CTX_cleanup(EVP_CIPHER_CTX *a);
215.Vb 3
216\& const EVP_CIPHER *EVP_get_cipherbyname(const char *name);
217\& #define EVP_get_cipherbynid(a) EVP_get_cipherbyname(OBJ_nid2sn(a))
218\& #define EVP_get_cipherbyobj(a) EVP_get_cipherbynid(OBJ_obj2nid(a))
220.Vb 7
221\& #define EVP_CIPHER_nid(e) ((e)->nid)
222\& #define EVP_CIPHER_block_size(e) ((e)->block_size)
223\& #define EVP_CIPHER_key_length(e) ((e)->key_len)
224\& #define EVP_CIPHER_iv_length(e) ((e)->iv_len)
225\& #define EVP_CIPHER_flags(e) ((e)->flags)
226\& #define EVP_CIPHER_mode(e) ((e)->flags) & EVP_CIPH_MODE)
227\& int EVP_CIPHER_type(const EVP_CIPHER *ctx);
229.Vb 10
230\& #define EVP_CIPHER_CTX_cipher(e) ((e)->cipher)
231\& #define EVP_CIPHER_CTX_nid(e) ((e)->cipher->nid)
232\& #define EVP_CIPHER_CTX_block_size(e) ((e)->cipher->block_size)
233\& #define EVP_CIPHER_CTX_key_length(e) ((e)->key_len)
234\& #define EVP_CIPHER_CTX_iv_length(e) ((e)->cipher->iv_len)
235\& #define EVP_CIPHER_CTX_get_app_data(e) ((e)->app_data)
236\& #define EVP_CIPHER_CTX_set_app_data(e,d) ((e)->app_data=(char *)(d))
237\& #define EVP_CIPHER_CTX_type(c) EVP_CIPHER_type(EVP_CIPHER_CTX_cipher(c))
238\& #define EVP_CIPHER_CTX_flags(e) ((e)->cipher->flags)
239\& #define EVP_CIPHER_CTX_mode(e) ((e)->cipher->flags & EVP_CIPH_MODE)
241.Vb 2
242\& int EVP_CIPHER_param_to_asn1(EVP_CIPHER_CTX *c, ASN1_TYPE *type);
243\& int EVP_CIPHER_asn1_to_param(EVP_CIPHER_CTX *c, ASN1_TYPE *type);
247The \s-1EVP\s0 cipher routines are a high level interface to certain
248symmetric ciphers.
250\&\fIEVP_CIPHER_CTX_init()\fR initializes cipher contex \fBctx\fR.
252\&\fIEVP_EncryptInit_ex()\fR sets up cipher context \fBctx\fR for encryption
253with cipher \fBtype\fR from \s-1ENGINE\s0 \fBimpl\fR. \fBctx\fR must be initialized
254before calling this function. \fBtype\fR is normally supplied
255by a function such as \fIEVP_des_cbc()\fR. If \fBimpl\fR is \s-1NULL\s0 then the
256default implementation is used. \fBkey\fR is the symmetric key to use
257and \fBiv\fR is the \s-1IV\s0 to use (if necessary), the actual number of bytes
258used for the key and \s-1IV\s0 depends on the cipher. It is possible to set
259all parameters to \s-1NULL\s0 except \fBtype\fR in an initial call and supply
260the remaining parameters in subsequent calls, all of which have \fBtype\fR
261set to \s-1NULL\s0. This is done when the default cipher parameters are not
264\&\fIEVP_EncryptUpdate()\fR encrypts \fBinl\fR bytes from the buffer \fBin\fR and
265writes the encrypted version to \fBout\fR. This function can be called
266multiple times to encrypt successive blocks of data. The amount
267of data written depends on the block alignment of the encrypted data:
268as a result the amount of data written may be anything from zero bytes
269to (inl + cipher_block_size \- 1) so \fBoutl\fR should contain sufficient
270room. The actual number of bytes written is placed in \fBoutl\fR.
272If padding is enabled (the default) then \fIEVP_EncryptFinal_ex()\fR encrypts
273the \*(L"final\*(R" data, that is any data that remains in a partial block.
274It uses standard block padding (aka \s-1PKCS\s0 padding). The encrypted
275final data is written to \fBout\fR which should have sufficient space for
276one cipher block. The number of bytes written is placed in \fBoutl\fR. After
277this function is called the encryption operation is finished and no further
278calls to \fIEVP_EncryptUpdate()\fR should be made.
280If padding is disabled then \fIEVP_EncryptFinal_ex()\fR will not encrypt any more
281data and it will return an error if any data remains in a partial block:
282that is if the total data length is not a multiple of the block size.
284\&\fIEVP_DecryptInit_ex()\fR, \fIEVP_DecryptUpdate()\fR and \fIEVP_DecryptFinal_ex()\fR are the
285corresponding decryption operations. \fIEVP_DecryptFinal()\fR will return an
286error code if padding is enabled and the final block is not correctly
287formatted. The parameters and restrictions are identical to the encryption
288operations except that if padding is enabled the decrypted data buffer \fBout\fR
289passed to \fIEVP_DecryptUpdate()\fR should have sufficient room for
290(\fBinl\fR + cipher_block_size) bytes unless the cipher block size is 1 in
291which case \fBinl\fR bytes is sufficient.
293\&\fIEVP_CipherInit_ex()\fR, \fIEVP_CipherUpdate()\fR and \fIEVP_CipherFinal_ex()\fR are
294functions that can be used for decryption or encryption. The operation
295performed depends on the value of the \fBenc\fR parameter. It should be set
296to 1 for encryption, 0 for decryption and \-1 to leave the value unchanged
297(the actual value of 'enc' being supplied in a previous call).
299\&\fIEVP_CIPHER_CTX_cleanup()\fR clears all information from a cipher context
300and free up any allocated memory associate with it. It should be called
301after all operations using a cipher are complete so sensitive information
302does not remain in memory.
304\&\fIEVP_EncryptInit()\fR, \fIEVP_DecryptInit()\fR and \fIEVP_CipherInit()\fR behave in a
305similar way to \fIEVP_EncryptInit_ex()\fR, EVP_DecryptInit_ex and
306\&\fIEVP_CipherInit_ex()\fR except the \fBctx\fR paramter does not need to be
307initialized and they always use the default cipher implementation.
309\&\fIEVP_EncryptFinal()\fR, \fIEVP_DecryptFinal()\fR and \fIEVP_CipherFinal()\fR behave in a
310similar way to \fIEVP_EncryptFinal_ex()\fR, \fIEVP_DecryptFinal_ex()\fR and
311\&\fIEVP_CipherFinal_ex()\fR except \fBctx\fR is automatically cleaned up
312after the call.
314\&\fIEVP_get_cipherbyname()\fR, \fIEVP_get_cipherbynid()\fR and \fIEVP_get_cipherbyobj()\fR
315return an \s-1EVP_CIPHER\s0 structure when passed a cipher name, a \s-1NID\s0 or an
316\&\s-1ASN1_OBJECT\s0 structure.
318\&\fIEVP_CIPHER_nid()\fR and \fIEVP_CIPHER_CTX_nid()\fR return the \s-1NID\s0 of a cipher when
319passed an \fB\s-1EVP_CIPHER\s0\fR or \fB\s-1EVP_CIPHER_CTX\s0\fR structure. The actual \s-1NID\s0
320value is an internal value which may not have a corresponding \s-1OBJECT\s0
323\&\fIEVP_CIPHER_CTX_set_padding()\fR enables or disables padding. By default
324encryption operations are padded using standard block padding and the
325padding is checked and removed when decrypting. If the \fBpad\fR parameter
326is zero then no padding is performed, the total amount of data encrypted
327or decrypted must then be a multiple of the block size or an error will
330\&\fIEVP_CIPHER_key_length()\fR and \fIEVP_CIPHER_CTX_key_length()\fR return the key
331length of a cipher when passed an \fB\s-1EVP_CIPHER\s0\fR or \fB\s-1EVP_CIPHER_CTX\s0\fR
332structure. The constant \fB\s-1EVP_MAX_KEY_LENGTH\s0\fR is the maximum key length
333for all ciphers. Note: although \fIEVP_CIPHER_key_length()\fR is fixed for a
334given cipher, the value of \fIEVP_CIPHER_CTX_key_length()\fR may be different
335for variable key length ciphers.
337\&\fIEVP_CIPHER_CTX_set_key_length()\fR sets the key length of the cipher ctx.
338If the cipher is a fixed length cipher then attempting to set the key
339length to any value other than the fixed value is an error.
341\&\fIEVP_CIPHER_iv_length()\fR and \fIEVP_CIPHER_CTX_iv_length()\fR return the \s-1IV\s0
342length of a cipher when passed an \fB\s-1EVP_CIPHER\s0\fR or \fB\s-1EVP_CIPHER_CTX\s0\fR.
343It will return zero if the cipher does not use an \s-1IV\s0. The constant
344\&\fB\s-1EVP_MAX_IV_LENGTH\s0\fR is the maximum \s-1IV\s0 length for all ciphers.
346\&\fIEVP_CIPHER_block_size()\fR and \fIEVP_CIPHER_CTX_block_size()\fR return the block
347size of a cipher when passed an \fB\s-1EVP_CIPHER\s0\fR or \fB\s-1EVP_CIPHER_CTX\s0\fR
348structure. The constant \fB\s-1EVP_MAX_IV_LENGTH\s0\fR is also the maximum block
349length for all ciphers.
351\&\fIEVP_CIPHER_type()\fR and \fIEVP_CIPHER_CTX_type()\fR return the type of the passed
352cipher or context. This \*(L"type\*(R" is the actual \s-1NID\s0 of the cipher \s-1OBJECT\s0
353\&\s-1IDENTIFIER\s0 as such it ignores the cipher parameters and 40 bit \s-1RC2\s0 and
354128 bit \s-1RC2\s0 have the same \s-1NID\s0. If the cipher does not have an object
355identifier or does not have \s-1ASN1\s0 support this function will return
358\&\fIEVP_CIPHER_CTX_cipher()\fR returns the \fB\s-1EVP_CIPHER\s0\fR structure when passed
359an \fB\s-1EVP_CIPHER_CTX\s0\fR structure.
361\&\fIEVP_CIPHER_mode()\fR and \fIEVP_CIPHER_CTX_mode()\fR return the block cipher mode:
362\&\s-1EVP_CIPH_ECB_MODE\s0, \s-1EVP_CIPH_CBC_MODE\s0, \s-1EVP_CIPH_CFB_MODE\s0 or
363\&\s-1EVP_CIPH_OFB_MODE\s0. If the cipher is a stream cipher then
364\&\s-1EVP_CIPH_STREAM_CIPHER\s0 is returned.
366\&\fIEVP_CIPHER_param_to_asn1()\fR sets the AlgorithmIdentifier \*(L"parameter\*(R" based
367on the passed cipher. This will typically include any parameters and an
368\&\s-1IV\s0. The cipher \s-1IV\s0 (if any) must be set when this call is made. This call
369should be made before the cipher is actually \*(L"used\*(R" (before any
370\&\fIEVP_EncryptUpdate()\fR, \fIEVP_DecryptUpdate()\fR calls for example). This function
371may fail if the cipher does not have any \s-1ASN1\s0 support.
373\&\fIEVP_CIPHER_asn1_to_param()\fR sets the cipher parameters based on an \s-1ASN1\s0
374AlgorithmIdentifier \*(L"parameter\*(R". The precise effect depends on the cipher
375In the case of \s-1RC2\s0, for example, it will set the \s-1IV\s0 and effective key length.
376This function should be called after the base cipher type is set but before
377the key is set. For example \fIEVP_CipherInit()\fR will be called with the \s-1IV\s0 and
378key set to \s-1NULL\s0, \fIEVP_CIPHER_asn1_to_param()\fR will be called and finally
379\&\fIEVP_CipherInit()\fR again with all parameters except the key set to \s-1NULL\s0. It is
380possible for this function to fail if the cipher does not have any \s-1ASN1\s0 support
381or the parameters cannot be set (for example the \s-1RC2\s0 effective key length
382is not supported.
384\&\fIEVP_CIPHER_CTX_ctrl()\fR allows various cipher specific parameters to be determined
385and set. Currently only the \s-1RC2\s0 effective key length and the number of rounds of
386\&\s-1RC5\s0 can be set.
389EVP_CIPHER_CTX_init, \fIEVP_EncryptInit_ex()\fR, \fIEVP_EncryptUpdate()\fR and
390\&\fIEVP_EncryptFinal_ex()\fR return 1 for success and 0 for failure.
392\&\fIEVP_DecryptInit_ex()\fR and \fIEVP_DecryptUpdate()\fR return 1 for success and 0 for failure.
393\&\fIEVP_DecryptFinal_ex()\fR returns 0 if the decrypt failed or 1 for success.
395\&\fIEVP_CipherInit_ex()\fR and \fIEVP_CipherUpdate()\fR return 1 for success and 0 for failure.
396\&\fIEVP_CipherFinal_ex()\fR returns 0 for a decryption failure or 1 for success.
398\&\fIEVP_CIPHER_CTX_cleanup()\fR returns 1 for success and 0 for failure.
400\&\fIEVP_get_cipherbyname()\fR, \fIEVP_get_cipherbynid()\fR and \fIEVP_get_cipherbyobj()\fR
401return an \fB\s-1EVP_CIPHER\s0\fR structure or \s-1NULL\s0 on error.
403\&\fIEVP_CIPHER_nid()\fR and \fIEVP_CIPHER_CTX_nid()\fR return a \s-1NID\s0.
405\&\fIEVP_CIPHER_block_size()\fR and \fIEVP_CIPHER_CTX_block_size()\fR return the block
408\&\fIEVP_CIPHER_key_length()\fR and \fIEVP_CIPHER_CTX_key_length()\fR return the key
411\&\fIEVP_CIPHER_CTX_set_padding()\fR always returns 1.
413\&\fIEVP_CIPHER_iv_length()\fR and \fIEVP_CIPHER_CTX_iv_length()\fR return the \s-1IV\s0
414length or zero if the cipher does not use an \s-1IV\s0.
416\&\fIEVP_CIPHER_type()\fR and \fIEVP_CIPHER_CTX_type()\fR return the \s-1NID\s0 of the cipher's
417\&\s-1OBJECT\s0 \s-1IDENTIFIER\s0 or NID_undef if it has no defined \s-1OBJECT\s0 \s-1IDENTIFIER\s0.
419\&\fIEVP_CIPHER_CTX_cipher()\fR returns an \fB\s-1EVP_CIPHER\s0\fR structure.
421\&\fIEVP_CIPHER_param_to_asn1()\fR and \fIEVP_CIPHER_asn1_to_param()\fR return 1 for
422success or zero for failure.
425All algorithms have a fixed key length unless otherwise stated.
426.Ip "\fIEVP_enc_null()\fR" 4
427.IX Item "EVP_enc_null()"
428Null cipher: does nothing.
429.Ip "EVP_des_cbc(void), EVP_des_ecb(void), EVP_des_cfb(void), EVP_des_ofb(void)" 4
430.IX Item "EVP_des_cbc(void), EVP_des_ecb(void), EVP_des_cfb(void), EVP_des_ofb(void)"
431\&\s-1DES\s0 in \s-1CBC\s0, \s-1ECB\s0, \s-1CFB\s0 and \s-1OFB\s0 modes respectively.
432.Ip "EVP_des_ede_cbc(void), \fIEVP_des_ede()\fR, EVP_des_ede_ofb(void), EVP_des_ede_cfb(void)" 4
433.IX Item "EVP_des_ede_cbc(void), EVP_des_ede(), EVP_des_ede_ofb(void), EVP_des_ede_cfb(void)"
434Two key triple \s-1DES\s0 in \s-1CBC\s0, \s-1ECB\s0, \s-1CFB\s0 and \s-1OFB\s0 modes respectively.
435.Ip "EVP_des_ede3_cbc(void), \fIEVP_des_ede3()\fR, EVP_des_ede3_ofb(void), EVP_des_ede3_cfb(void)" 4
436.IX Item "EVP_des_ede3_cbc(void), EVP_des_ede3(), EVP_des_ede3_ofb(void), EVP_des_ede3_cfb(void)"
437Three key triple \s-1DES\s0 in \s-1CBC\s0, \s-1ECB\s0, \s-1CFB\s0 and \s-1OFB\s0 modes respectively.
438.Ip "EVP_desx_cbc(void)" 4
439.IX Item "EVP_desx_cbc(void)"
440\&\s-1DESX\s0 algorithm in \s-1CBC\s0 mode.
441.Ip "EVP_rc4(void)" 4
442.IX Item "EVP_rc4(void)"
443\&\s-1RC4\s0 stream cipher. This is a variable key length cipher with default key length 128 bits.
444.Ip "EVP_rc4_40(void)" 4
445.IX Item "EVP_rc4_40(void)"
446\&\s-1RC4\s0 stream cipher with 40 bit key length. This is obsolete and new code should use \fIEVP_rc4()\fR
447and the \fIEVP_CIPHER_CTX_set_key_length()\fR function.
448.Ip "\fIEVP_idea_cbc()\fR EVP_idea_ecb(void), EVP_idea_cfb(void), EVP_idea_ofb(void), EVP_idea_cbc(void)" 4
449.IX Item "EVP_idea_cbc() EVP_idea_ecb(void), EVP_idea_cfb(void), EVP_idea_ofb(void), EVP_idea_cbc(void)"
450\&\s-1IDEA\s0 encryption algorithm in \s-1CBC\s0, \s-1ECB\s0, \s-1CFB\s0 and \s-1OFB\s0 modes respectively.
451.Ip "EVP_rc2_cbc(void), EVP_rc2_ecb(void), EVP_rc2_cfb(void), EVP_rc2_ofb(void)" 4
452.IX Item "EVP_rc2_cbc(void), EVP_rc2_ecb(void), EVP_rc2_cfb(void), EVP_rc2_ofb(void)"
453\&\s-1RC2\s0 encryption algorithm in \s-1CBC\s0, \s-1ECB\s0, \s-1CFB\s0 and \s-1OFB\s0 modes respectively. This is a variable key
454length cipher with an additional parameter called \*(L"effective key bits\*(R" or \*(L"effective key length\*(R".
455By default both are set to 128 bits.
456.Ip "EVP_rc2_40_cbc(void), EVP_rc2_64_cbc(void)" 4
457.IX Item "EVP_rc2_40_cbc(void), EVP_rc2_64_cbc(void)"
458\&\s-1RC2\s0 algorithm in \s-1CBC\s0 mode with a default key length and effective key length of 40 and 64 bits.
459These are obsolete and new code should use \fIEVP_rc2_cbc()\fR, \fIEVP_CIPHER_CTX_set_key_length()\fR and
460\&\fIEVP_CIPHER_CTX_ctrl()\fR to set the key length and effective key length.
461.Ip "EVP_bf_cbc(void), EVP_bf_ecb(void), EVP_bf_cfb(void), EVP_bf_ofb(void);" 4
462.IX Item "EVP_bf_cbc(void), EVP_bf_ecb(void), EVP_bf_cfb(void), EVP_bf_ofb(void);"
463Blowfish encryption algorithm in \s-1CBC\s0, \s-1ECB\s0, \s-1CFB\s0 and \s-1OFB\s0 modes respectively. This is a variable key
464length cipher.
465.Ip "EVP_cast5_cbc(void), EVP_cast5_ecb(void), EVP_cast5_cfb(void), EVP_cast5_ofb(void)" 4
466.IX Item "EVP_cast5_cbc(void), EVP_cast5_ecb(void), EVP_cast5_cfb(void), EVP_cast5_ofb(void)"
467\&\s-1CAST\s0 encryption algorithm in \s-1CBC\s0, \s-1ECB\s0, \s-1CFB\s0 and \s-1OFB\s0 modes respectively. This is a variable key
468length cipher.
469.Ip "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)" 4
470.IX 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)"
471\&\s-1RC5\s0 encryption algorithm in \s-1CBC\s0, \s-1ECB\s0, \s-1CFB\s0 and \s-1OFB\s0 modes respectively. This is a variable key length
472cipher with an additional \*(L"number of rounds\*(R" parameter. By default the key length is set to 128
473bits and 12 rounds.
474.SH "NOTES"
475.IX Header "NOTES"
476Where possible the \fB\s-1EVP\s0\fR interface to symmetric ciphers should be used in
477preference to the low level interfaces. This is because the code then becomes
478transparent to the cipher used and much more flexible.
480\&\s-1PKCS\s0 padding works by adding \fBn\fR padding bytes of value \fBn\fR to make the total
481length of the encrypted data a multiple of the block size. Padding is always
482added so if the data is already a multiple of the block size \fBn\fR will equal
483the block size. For example if the block size is 8 and 11 bytes are to be
484encrypted then 5 padding bytes of value 5 will be added.
486When decrypting the final block is checked to see if it has the correct form.
488Although the decryption operation can produce an error if padding is enabled,
489it is not a strong test that the input data or key is correct. A random block
490has better than 1 in 256 chance of being of the correct format and problems with
491the input data earlier on will not produce a final decrypt error.
493If padding is disabled then the decryption operation will always succeed if
494the total amount of data decrypted is a multiple of the block size.
496The functions \fIEVP_EncryptInit()\fR, \fIEVP_EncryptFinal()\fR, \fIEVP_DecryptInit()\fR,
497\&\fIEVP_CipherInit()\fR and \fIEVP_CipherFinal()\fR are obsolete but are retained for
498compatibility with existing code. New code should use \fIEVP_EncryptInit_ex()\fR,
499\&\fIEVP_EncryptFinal_ex()\fR, \fIEVP_DecryptInit_ex()\fR, \fIEVP_DecryptFinal_ex()\fR,
500\&\fIEVP_CipherInit_ex()\fR and \fIEVP_CipherFinal_ex()\fR because they can reuse an
501existing context without allocating and freeing it up on each call.
502.SH "BUGS"
503.IX Header "BUGS"
504For \s-1RC5\s0 the number of rounds can currently only be set to 8, 12 or 16. This is
505a limitation of the current \s-1RC5\s0 code rather than the \s-1EVP\s0 interface.
507\&\s-1EVP_MAX_KEY_LENGTH\s0 and \s-1EVP_MAX_IV_LENGTH\s0 only refer to the internal ciphers with
508default key lengths. If custom ciphers exceed these values the results are
509unpredictable. This is because it has become standard practice to define a
510generic key as a fixed unsigned char array containing \s-1EVP_MAX_KEY_LENGTH\s0 bytes.
512The \s-1ASN1\s0 code is incomplete (and sometimes inaccurate) it has only been tested
513for certain common S/MIME ciphers (\s-1RC2\s0, \s-1DES\s0, triple \s-1DES\s0) in \s-1CBC\s0 mode.
515.IX Header "EXAMPLES"
516Get the number of rounds used in \s-1RC5:\s0
518.Vb 2
519\& int nrounds;
520\& EVP_CIPHER_CTX_ctrl(ctx, EVP_CTRL_GET_RC5_ROUNDS, 0, &nrounds);
522Get the \s-1RC2\s0 effective key length:
524.Vb 2
525\& int key_bits;
526\& EVP_CIPHER_CTX_ctrl(ctx, EVP_CTRL_GET_RC2_KEY_BITS, 0, &key_bits);
528Set the number of rounds used in \s-1RC5:\s0
530.Vb 2
531\& int nrounds;
532\& EVP_CIPHER_CTX_ctrl(ctx, EVP_CTRL_SET_RC5_ROUNDS, nrounds, NULL);
534Set the effective key length used in \s-1RC2:\s0
536.Vb 2
537\& int key_bits;
538\& EVP_CIPHER_CTX_ctrl(ctx, EVP_CTRL_SET_RC2_KEY_BITS, key_bits, NULL);
540Encrypt a string using blowfish:
542.Vb 14
543\& int do_crypt(char *outfile)
544\& {
545\& unsigned char outbuf[1024];
546\& int outlen, tmplen;
547\& /* Bogus key and IV: we'd normally set these from
548\& * another source.
549\& */
550\& unsigned char key[] = {0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15};
551\& unsigned char iv[] = {1,2,3,4,5,6,7,8};
552\& char intext[] = "Some Crypto Text";
553\& EVP_CIPHER_CTX ctx;
554\& FILE *out;
555\& EVP_CIPHER_CTX_init(&ctx);
556\& EVP_EncryptInit_ex(&ctx, EVP_bf_cbc(), NULL, key, iv);
558.Vb 25
559\& if(!EVP_EncryptUpdate(&ctx, outbuf, &outlen, intext, strlen(intext)))
560\& {
561\& /* Error */
562\& return 0;
563\& }
564\& /* Buffer passed to EVP_EncryptFinal() must be after data just
565\& * encrypted to avoid overwriting it.
566\& */
567\& if(!EVP_EncryptFinal_ex(&ctx, outbuf + outlen, &tmplen))
568\& {
569\& /* Error */
570\& return 0;
571\& }
572\& outlen += tmplen;
573\& EVP_CIPHER_CTX_cleanup(&ctx);
574\& /* Need binary mode for fopen because encrypted data is
575\& * binary data. Also cannot use strlen() on it because
576\& * it wont be null terminated and may contain embedded
577\& * nulls.
578\& */
579\& out = fopen(outfile, "wb");
580\& fwrite(outbuf, 1, outlen, out);
581\& fclose(out);
582\& return 1;
583\& }
585The ciphertext from the above example can be decrypted using the \fBopenssl\fR
586utility with the command line:
588.Vb 1
589\& S<openssl bf -in cipher.bin -K 000102030405060708090A0B0C0D0E0F -iv 0102030405060708 -d>
591General encryption, decryption function example using \s-1FILE\s0 I/O and \s-1RC2\s0 with an
59280 bit key:
594.Vb 16
595\& int do_crypt(FILE *in, FILE *out, int do_encrypt)
596\& {
597\& /* Allow enough space in output buffer for additional block */
598\& inbuf[1024], outbuf[1024 + EVP_MAX_BLOCK_LENGTH];
599\& int inlen, outlen;
600\& /* Bogus key and IV: we'd normally set these from
601\& * another source.
602\& */
603\& unsigned char key[] = "0123456789";
604\& unsigned char iv[] = "12345678";
605\& /* Don't set key or IV because we will modify the parameters */
606\& EVP_CIPHER_CTX_init(&ctx);
607\& EVP_CipherInit_ex(&ctx, EVP_rc2(), NULL, NULL, NULL, do_encrypt);
608\& EVP_CIPHER_CTX_set_key_length(&ctx, 10);
609\& /* We finished modifying parameters so now we can set key and IV */
610\& EVP_CipherInit_ex(&ctx, NULL, NULL, key, iv, do_encrypt);
612.Vb 17
613\& for(;;)
614\& {
615\& inlen = fread(inbuf, 1, 1024, in);
616\& if(inlen <= 0) break;
617\& if(!EVP_CipherUpdate(&ctx, outbuf, &outlen, inbuf, inlen))
618\& {
619\& /* Error */
620\& return 0;
621\& }
622\& fwrite(outbuf, 1, outlen, out);
623\& }
624\& if(!EVP_CipherFinal_ex(&ctx, outbuf, &outlen))
625\& {
626\& /* Error */
627\& return 0;
628\& }
629\& fwrite(outbuf, 1, outlen, out);
631.Vb 3
632\& EVP_CIPHER_CTX_cleanup(&ctx);
633\& return 1;
634\& }
637.IX Header "SEE ALSO"
640.IX Header "HISTORY"
641\&\fIEVP_CIPHER_CTX_init()\fR, \fIEVP_EncryptInit_ex()\fR, \fIEVP_EncryptFinal_ex()\fR,
642\&\fIEVP_DecryptInit_ex()\fR, \fIEVP_DecryptFinal_ex()\fR, \fIEVP_CipherInit_ex()\fR,
643\&\fIEVP_CipherFinal_ex()\fR and \fIEVP_CIPHER_CTX_set_padding()\fR appeared in
644OpenSSL 0.9.7.