.\" $OpenBSD: EVP_EncryptInit.3,v 1.21 2018/03/29 21:12:02 schwarze Exp $ .\" full merge up to: OpenSSL 5211e094 Nov 11 14:39:11 2014 -0800 .\" selective merge up to: OpenSSL 16cfc2c9 Mar 8 22:30:28 2018 +0100 .\" .\" This file was written by Dr. Stephen Henson .\" and Richard Levitte . .\" Copyright (c) 2000-2002, 2005, 2012-2016 The OpenSSL Project. .\" All rights reserved. .\" .\" Redistribution and use in source and binary forms, with or without .\" modification, are permitted provided that the following conditions .\" are met: .\" .\" 1. Redistributions of source code must retain the above copyright .\" notice, this list of conditions and the following disclaimer. .\" .\" 2. Redistributions in binary form must reproduce the above copyright .\" notice, this list of conditions and the following disclaimer in .\" the documentation and/or other materials provided with the .\" distribution. .\" .\" 3. All advertising materials mentioning features or use of this .\" software must display the following acknowledgment: .\" "This product includes software developed by the OpenSSL Project .\" for use in the OpenSSL Toolkit. (http://www.openssl.org/)" .\" .\" 4. The names "OpenSSL Toolkit" and "OpenSSL Project" must not be used to .\" endorse or promote products derived from this software without .\" prior written permission. For written permission, please contact .\" openssl-core@openssl.org. .\" .\" 5. Products derived from this software may not be called "OpenSSL" .\" nor may "OpenSSL" appear in their names without prior written .\" permission of the OpenSSL Project. .\" .\" 6. Redistributions of any form whatsoever must retain the following .\" acknowledgment: .\" "This product includes software developed by the OpenSSL Project .\" for use in the OpenSSL Toolkit (http://www.openssl.org/)" .\" .\" THIS SOFTWARE IS PROVIDED BY THE OpenSSL PROJECT ``AS IS'' AND ANY .\" EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE .\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR .\" PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE OpenSSL PROJECT OR .\" ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, .\" SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT .\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; .\" LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) .\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, .\" STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) .\" ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED .\" OF THE POSSIBILITY OF SUCH DAMAGE. .\" .Dd $Mdocdate: March 29 2018 $ .Dt EVP_ENCRYPTINIT 3 .Os .Sh NAME .Nm EVP_CIPHER_CTX_new , .Nm EVP_CIPHER_CTX_reset , .Nm EVP_CIPHER_CTX_cleanup , .Nm EVP_CIPHER_CTX_init , .Nm EVP_CIPHER_CTX_free , .Nm EVP_EncryptInit_ex , .Nm EVP_EncryptUpdate , .Nm EVP_EncryptFinal_ex , .Nm EVP_DecryptInit_ex , .Nm EVP_DecryptUpdate , .Nm EVP_DecryptFinal_ex , .Nm EVP_CipherInit_ex , .Nm EVP_CipherUpdate , .Nm EVP_CipherFinal_ex , .Nm EVP_EncryptInit , .Nm EVP_EncryptFinal , .Nm EVP_DecryptInit , .Nm EVP_DecryptFinal , .Nm EVP_CipherInit , .Nm EVP_CipherFinal , .Nm EVP_CIPHER_CTX_set_padding , .Nm EVP_CIPHER_CTX_set_key_length , .Nm EVP_CIPHER_CTX_ctrl , .Nm EVP_CIPHER_CTX_rand_key , .Nm EVP_get_cipherbyname , .Nm EVP_get_cipherbynid , .Nm EVP_get_cipherbyobj , .Nm EVP_CIPHER_nid , .Nm EVP_CIPHER_block_size , .Nm EVP_CIPHER_key_length , .Nm EVP_CIPHER_iv_length , .Nm EVP_CIPHER_flags , .Nm EVP_CIPHER_mode , .Nm EVP_CIPHER_type , .Nm EVP_CIPHER_CTX_cipher , .Nm EVP_CIPHER_CTX_nid , .Nm EVP_CIPHER_CTX_block_size , .Nm EVP_CIPHER_CTX_key_length , .Nm EVP_CIPHER_CTX_iv_length , .Nm EVP_CIPHER_CTX_get_app_data , .Nm EVP_CIPHER_CTX_set_app_data , .Nm EVP_CIPHER_CTX_type , .Nm EVP_CIPHER_CTX_flags , .Nm EVP_CIPHER_CTX_mode , .Nm EVP_CIPHER_param_to_asn1 , .Nm EVP_CIPHER_asn1_to_param , .Nm EVP_enc_null , .Nm EVP_des_cbc , .Nm EVP_des_ecb , .Nm EVP_des_cfb , .Nm EVP_des_ofb , .Nm EVP_des_ede_cbc , .Nm EVP_des_ede , .Nm EVP_des_ede_ofb , .Nm EVP_des_ede_cfb , .Nm EVP_des_ede3_cbc , .Nm EVP_des_ede3 , .Nm EVP_des_ede3_ofb , .Nm EVP_des_ede3_cfb , .Nm EVP_desx_cbc , .Nm EVP_rc4 , .Nm EVP_rc4_40 , .Nm EVP_rc4_hmac_md5 , .Nm EVP_idea_cbc , .Nm EVP_idea_ecb , .Nm EVP_idea_cfb , .Nm EVP_idea_ofb , .Nm EVP_rc2_cbc , .Nm EVP_rc2_ecb , .Nm EVP_rc2_cfb , .Nm EVP_rc2_ofb , .Nm EVP_rc2_40_cbc , .Nm EVP_rc2_64_cbc , .Nm EVP_bf_cbc , .Nm EVP_bf_ecb , .Nm EVP_bf_cfb , .Nm EVP_bf_ofb , .Nm EVP_cast5_cbc , .Nm EVP_cast5_ecb , .Nm EVP_cast5_cfb , .Nm EVP_cast5_ofb , .Nm EVP_aes_128_cbc , .Nm EVP_aes_128_ecb , .Nm EVP_aes_128_cfb , .Nm EVP_aes_128_ofb , .Nm EVP_aes_192_cbc , .Nm EVP_aes_192_ecb , .Nm EVP_aes_192_cfb , .Nm EVP_aes_192_ofb , .Nm EVP_aes_256_cbc , .Nm EVP_aes_256_ecb , .Nm EVP_aes_256_cfb , .Nm EVP_aes_256_ofb , .Nm EVP_aes_128_gcm , .Nm EVP_aes_192_gcm , .Nm EVP_aes_256_gcm , .Nm EVP_aes_128_ccm , .Nm EVP_aes_192_ccm , .Nm EVP_aes_256_ccm , .Nm EVP_aes_128_cbc_hmac_sha1 , .Nm EVP_aes_256_cbc_hmac_sha1 , .Nm EVP_chacha20 .Nd EVP cipher routines .Sh SYNOPSIS .In openssl/evp.h .Ft EVP_CIPHER_CTX * .Fn EVP_CIPHER_CTX_new void .Ft int .Fo EVP_CIPHER_CTX_reset .Fa "EVP_CIPHER_CTX *ctx" .Fc .Ft int .Fo EVP_CIPHER_CTX_cleanup .Fa "EVP_CIPHER_CTX *ctx" .Fc .Ft void .Fo EVP_CIPHER_CTX_init .Fa "EVP_CIPHER_CTX *ctx" .Fc .Ft void .Fo EVP_CIPHER_CTX_free .Fa "EVP_CIPHER_CTX *ctx" .Fc .Ft int .Fo EVP_EncryptInit_ex .Fa "EVP_CIPHER_CTX *ctx" .Fa "const EVP_CIPHER *type" .Fa "ENGINE *impl" .Fa "const unsigned char *key" .Fa "const unsigned char *iv" .Fc .Ft int .Fo EVP_EncryptUpdate .Fa "EVP_CIPHER_CTX *ctx" .Fa "unsigned char *out" .Fa "int *outl" .Fa "const unsigned char *in" .Fa "int inl" .Fc .Ft int .Fo EVP_EncryptFinal_ex .Fa "EVP_CIPHER_CTX *ctx" .Fa "unsigned char *out" .Fa "int *outl" .Fc .Ft int .Fo EVP_DecryptInit_ex .Fa "EVP_CIPHER_CTX *ctx" .Fa "const EVP_CIPHER *type" .Fa "ENGINE *impl" .Fa "const unsigned char *key" .Fa "const unsigned char *iv" .Fc .Ft int .Fo EVP_DecryptUpdate .Fa "EVP_CIPHER_CTX *ctx" .Fa "unsigned char *out" .Fa "int *outl" .Fa "const unsigned char *in" .Fa "int inl" .Fc .Ft int .Fo EVP_DecryptFinal_ex .Fa "EVP_CIPHER_CTX *ctx" .Fa "unsigned char *outm" .Fa "int *outl" .Fc .Ft int .Fo EVP_CipherInit_ex .Fa "EVP_CIPHER_CTX *ctx" .Fa "const EVP_CIPHER *type" .Fa "ENGINE *impl" .Fa "const unsigned char *key" .Fa "const unsigned char *iv" .Fa "int enc" .Fc .Ft int .Fo EVP_CipherUpdate .Fa "EVP_CIPHER_CTX *ctx" .Fa "unsigned char *out" .Fa "int *outl" .Fa "const unsigned char *in" .Fa "int inl" .Fc .Ft int .Fo EVP_CipherFinal_ex .Fa "EVP_CIPHER_CTX *ctx" .Fa "unsigned char *outm" .Fa "int *outl" .Fc .Ft int .Fo EVP_EncryptInit .Fa "EVP_CIPHER_CTX *ctx" .Fa "const EVP_CIPHER *type" .Fa "const unsigned char *key" .Fa "const unsigned char *iv" .Fc .Ft int .Fo EVP_EncryptFinal .Fa "EVP_CIPHER_CTX *ctx" .Fa "unsigned char *out" .Fa "int *outl" .Fc .Ft int .Fo EVP_DecryptInit .Fa "EVP_CIPHER_CTX *ctx" .Fa "const EVP_CIPHER *type" .Fa "const unsigned char *key" .Fa "const unsigned char *iv" .Fc .Ft int .Fo EVP_DecryptFinal .Fa "EVP_CIPHER_CTX *ctx" .Fa "unsigned char *outm" .Fa "int *outl" .Fc .Ft int .Fo EVP_CipherInit .Fa "EVP_CIPHER_CTX *ctx" .Fa "const EVP_CIPHER *type" .Fa "const unsigned char *key" .Fa "const unsigned char *iv" .Fa "int enc" .Fc .Ft int .Fo EVP_CipherFinal .Fa "EVP_CIPHER_CTX *ctx" .Fa "unsigned char *outm" .Fa "int *outl" .Fc .Ft int .Fo EVP_CIPHER_CTX_set_padding .Fa "EVP_CIPHER_CTX *x" .Fa "int padding" .Fc .Ft int .Fo EVP_CIPHER_CTX_set_key_length .Fa "EVP_CIPHER_CTX *x" .Fa "int keylen" .Fc .Ft int .Fo EVP_CIPHER_CTX_ctrl .Fa "EVP_CIPHER_CTX *ctx" .Fa "int type" .Fa "int arg" .Fa "void *ptr" .Fc .Ft int .Fo EVP_CIPHER_CTX_rand_key .Fa "EVP_CIPHER_CTX *ctx" .Fa "unsigned char *key" .Fc .Ft const EVP_CIPHER * .Fo EVP_get_cipherbyname .Fa "const char *name" .Fc .Ft const EVP_CIPHER * .Fo EVP_get_cipherbynid .Fa "int nid" .Fc .Ft const EVP_CIPHER * .Fo EVP_get_cipherbyobj .Fa "const ASN1_OBJECT *a" .Fc .Ft int .Fo EVP_CIPHER_nid .Fa "const EVP_CIPHER *e" .Fc .Ft int .Fo EVP_CIPHER_block_size .Fa "const EVP_CIPHER *e" .Fc .Ft int .Fo EVP_CIPHER_key_length .Fa "const EVP_CIPHER *e" .Fc .Ft int .Fo EVP_CIPHER_iv_length .Fa "const EVP_CIPHER *e" .Fc .Ft unsigned long .Fo EVP_CIPHER_flags .Fa "const EVP_CIPHER *e" .Fc .Ft unsigned long .Fo EVP_CIPHER_mode .Fa "const EVP_CIPHER *e" .Fc .Ft int .Fo EVP_CIPHER_type .Fa "const EVP_CIPHER *ctx" .Fc .Ft const EVP_CIPHER * .Fo EVP_CIPHER_CTX_cipher .Fa "const EVP_CIPHER_CTX *ctx" .Fc .Ft int .Fo EVP_CIPHER_CTX_nid .Fa "const EVP_CIPHER_CTX *ctx" .Fc .Ft int .Fo EVP_CIPHER_CTX_block_size .Fa "const EVP_CIPHER_CTX *ctx" .Fc .Ft int .Fo EVP_CIPHER_CTX_key_length .Fa "const EVP_CIPHER_CTX *ctx" .Fc .Ft int .Fo EVP_CIPHER_CTX_iv_length .Fa "const EVP_CIPHER_CTX *ctx" .Fc .Ft void * .Fo EVP_CIPHER_CTX_get_app_data .Fa "const EVP_CIPHER_CTX *ctx" .Fc .Ft void .Fo EVP_CIPHER_CTX_set_app_data .Fa "const EVP_CIPHER_CTX *ctx" .Fa "void *data" .Fc .Ft int .Fo EVP_CIPHER_CTX_type .Fa "const EVP_CIPHER_CTX *ctx" .Fc .Ft unsigned long .Fo EVP_CIPHER_CTX_flags .Fa "const EVP_CIPHER_CTX *ctx" .Fc .Ft unsigned long .Fo EVP_CIPHER_CTX_mode .Fa "const EVP_CIPHER_CTX *ctx" .Fc .Ft int .Fo EVP_CIPHER_param_to_asn1 .Fa "EVP_CIPHER_CTX *c" .Fa "ASN1_TYPE *type" .Fc .Ft int .Fo EVP_CIPHER_asn1_to_param .Fa "EVP_CIPHER_CTX *c" .Fa "ASN1_TYPE *type" .Fc .Sh DESCRIPTION The EVP cipher routines are a high level interface to certain symmetric ciphers. .Pp .Fn EVP_CIPHER_CTX_new creates a new, empty cipher context. .Pp .Fn EVP_CIPHER_CTX_reset clears all information from .Fa ctx and frees all allocated memory associated with it, except the .Fa ctx object itself, such that it can be reused for another series of calls to .Fn EVP_CipherInit , .Fn EVP_CipherUpdate , and .Fn EVP_CipherFinal . It is also suitable for cipher contexts on the stack that were used and are no longer needed. .Fn EVP_CIPHER_CTX_cleanup is a deprecated alias for .Fn EVP_CIPHER_CTX_reset . .Pp .Fn EVP_CIPHER_CTX_init is a deprecated function to clear a cipher context on the stack before use. Do not use it on a cipher context returned from .Fn EVP_CIPHER_CTX_new or one one that was already used. .Pp .Fn EVP_CIPHER_CTX_free clears all information from .Fa ctx and frees all allocated memory associated with it, including .Fa ctx itself. This function should be called after all operations using a cipher are complete, so sensitive information does not remain in memory. If .Fa ctx is a .Dv NULL pointer, no action occurs. .Pp .Fn EVP_EncryptInit_ex sets up the cipher context .Fa ctx for encryption with cipher .Fa type from .Vt ENGINE .Fa impl . If .Fa ctx points to an unused object on the stack, it must be initialized with .Fn EVP_MD_CTX_init before calling this function. .Fa type is normally supplied by a function such as .Fn EVP_aes_256_cbc . If .Fa impl is .Dv NULL , then the default implementation is used. .Fa key is the symmetric key to use and .Fa iv is the IV to use (if necessary). The actual number of bytes used for the key and IV depends on the cipher. It is possible to set all parameters to .Dv NULL except .Fa type in an initial call and supply the remaining parameters in subsequent calls, all of which have .Fa type set to .Dv NULL . This is done when the default cipher parameters are not appropriate. .Pp .Fn EVP_EncryptUpdate encrypts .Fa inl bytes from the buffer .Fa in and writes the encrypted version to .Fa out . This function can be called multiple times to encrypt successive blocks of data. The amount of data written depends on the block alignment of the encrypted data: as a result the amount of data written may be anything from zero bytes to (inl + cipher_block_size - 1) so .Fa out should contain sufficient room. The actual number of bytes written is placed in .Fa outl . .Pp If padding is enabled (the default) then .Fn EVP_EncryptFinal_ex encrypts the "final" data, that is any data that remains in a partial block. It uses NOTES (aka PKCS padding). The encrypted final data is written to .Fa out which should have sufficient space for one cipher block. The number of bytes written is placed in .Fa outl . After this function is called the encryption operation is finished and no further calls to .Fn EVP_EncryptUpdate should be made. .Pp If padding is disabled then .Fn EVP_EncryptFinal_ex will not encrypt any more data and it will return an error if any data remains in a partial block: that is if the total data length is not a multiple of the block size. .Pp .Fn EVP_DecryptInit_ex , .Fn EVP_DecryptUpdate , and .Fn EVP_DecryptFinal_ex are the corresponding decryption operations. .Fn EVP_DecryptFinal will return an error code if padding is enabled and the final block is not correctly formatted. The parameters and restrictions are identical to the encryption operations except that if padding is enabled the decrypted data buffer .Fa out passed to .Fn EVP_DecryptUpdate should have sufficient room for (inl + cipher_block_size) bytes unless the cipher block size is 1 in which case .Fa inl bytes is sufficient. .Pp .Fn EVP_CipherInit_ex , .Fn EVP_CipherUpdate , and .Fn EVP_CipherFinal_ex are functions that can be used for decryption or encryption. The operation performed depends on the value of the .Fa enc parameter. It should be set to 1 for encryption, 0 for decryption and -1 to leave the value unchanged (the actual value of .Fa enc being supplied in a previous call). .Pp .Fn EVP_EncryptInit , .Fn EVP_DecryptInit , and .Fn EVP_CipherInit are deprecated functions behaving like .Fn EVP_EncryptInit_ex , .Fn EVP_DecryptInit_ex , and .Fn EVP_CipherInit_ex except that they always use the default cipher implementation and that they require .Fn EVP_CIPHER_CTX_reset before they can be used on a context that was already used. .Pp .Fn EVP_EncryptFinal , .Fn EVP_DecryptFinal , and .Fn EVP_CipherFinal are identical to .Fn EVP_EncryptFinal_ex , .Fn EVP_DecryptFinal_ex , and .Fn EVP_CipherFinal_ex . In previous releases of OpenSSL, they also used to clean up the .Fa ctx , but this is no longer done and .Fn EVP_CIPHER_CTX_reset or .Fn EVP_CIPHER_CTX_free must be called to free any context resources. .Pp .Fn EVP_get_cipherbyname , .Fn EVP_get_cipherbynid , and .Fn EVP_get_cipherbyobj return an .Vt EVP_CIPHER structure when passed a cipher name, a NID or an .Vt ASN1_OBJECT structure. .Pp .Fn EVP_CIPHER_nid and .Fn EVP_CIPHER_CTX_nid return the NID of a cipher when passed an .Vt EVP_CIPHER or .Vt EVP_CIPHER_CTX structure. The actual NID value is an internal value which may not have a corresponding OBJECT IDENTIFIER. .Pp .Fn EVP_CIPHER_CTX_set_padding enables or disables padding. This function should be called after the context is set up for encryption or decryption with .Fn EVP_EncryptInit_ex , .Fn EVP_DecryptInit_ex , or EVP_CipherInit_ex . By default encryption operations are padded using standard block padding and the padding is checked and removed when decrypting. If the .Fa padding parameter is zero, then no padding is performed, the total amount of data encrypted or decrypted must then be a multiple of the block size or an error will occur. .Pp .Fn EVP_CIPHER_key_length and .Fn EVP_CIPHER_CTX_key_length return the key length of a cipher when passed an .Vt EVP_CIPHER or .Vt EVP_CIPHER_CTX structure. The constant .Dv EVP_MAX_KEY_LENGTH is the maximum key length for all ciphers. Note: although .Fn EVP_CIPHER_key_length is fixed for a given cipher, the value of .Fn EVP_CIPHER_CTX_key_length may be different for variable key length ciphers. .Pp .Fn EVP_CIPHER_CTX_set_key_length sets the key length of the cipher ctx. If the cipher is a fixed length cipher, then attempting to set the key length to any value other than the fixed value is an error. .Pp .Fn EVP_CIPHER_iv_length and .Fn EVP_CIPHER_CTX_iv_length return the IV length of a cipher when passed an .Vt EVP_CIPHER or .Vt EVP_CIPHER_CTX . It will return zero if the cipher does not use an IV. The constant .Dv EVP_MAX_IV_LENGTH is the maximum IV length for all ciphers. .Pp .Fn EVP_CIPHER_block_size and .Fn EVP_CIPHER_CTX_block_size return the block size of a cipher when passed an .Vt EVP_CIPHER or .Vt EVP_CIPHER_CTX structure. The constant .Dv EVP_MAX_BLOCK_LENGTH is also the maximum block length for all ciphers. .Pp .Fn EVP_CIPHER_type and .Fn EVP_CIPHER_CTX_type return the type of the passed cipher or context. This "type" is the actual NID of the cipher OBJECT IDENTIFIER as such it ignores the cipher parameters and 40-bit RC2 and 128-bit RC2 have the same NID. If the cipher does not have an object identifier or does not have ASN.1 support this function will return .Dv NID_undef . .Pp .Fn EVP_CIPHER_CTX_cipher returns the .Vt EVP_CIPHER structure when passed an .Vt EVP_CIPHER_CTX structure. .Pp .Fn EVP_CIPHER_mode and .Fn EVP_CIPHER_CTX_mode return the block cipher mode: .Dv EVP_CIPH_ECB_MODE , .Dv EVP_CIPH_CBC_MODE , .Dv EVP_CIPH_CFB_MODE , .Dv EVP_CIPH_OFB_MODE , .Dv EVP_CIPH_CTR_MODE , or .Dv EVP_CIPH_XTS_MODE . If the cipher is a stream cipher then .Dv EVP_CIPH_STREAM_CIPHER is returned. .Pp .Fn EVP_CIPHER_param_to_asn1 sets the ASN.1 .Vt AlgorithmIdentifier parameter based on the passed cipher. This will typically include any parameters and an IV. The cipher IV (if any) must be set when this call is made. This call should be made before the cipher is actually "used" (before any .Fn EVP_EncryptUpdate or .Fn EVP_DecryptUpdate calls, for example). This function may fail if the cipher does not have any ASN.1 support. .Pp .Fn EVP_CIPHER_asn1_to_param sets the cipher parameters based on an ASN.1 .Vt AlgorithmIdentifier parameter. The precise effect depends on the cipher. In the case of RC2, for example, it will set the IV and effective key length. This function should be called after the base cipher type is set but before the key is set. For example .Fn EVP_CipherInit will be called with the IV and key set to .Dv NULL , .Fn EVP_CIPHER_asn1_to_param will be called and finally .Fn EVP_CipherInit again with all parameters except the key set to .Dv NULL . It is possible for this function to fail if the cipher does not have any ASN.1 support or the parameters cannot be set (for example the RC2 effective key length is not supported). .Pp .Fn EVP_CIPHER_CTX_ctrl allows various cipher specific parameters to be determined and set. Currently only the RC2 effective key length can be set. .Pp .Fn EVP_CIPHER_CTX_rand_key generates a random key of the appropriate length based on the cipher context. The .Vt EVP_CIPHER can provide its own random key generation routine to support keys of a specific form. The .Fa key argument must point to a buffer at least as big as the value returned by .Fn EVP_CIPHER_CTX_key_length . .Pp Where possible the EVP interface to symmetric ciphers should be used in preference to the low level interfaces. This is because the code then becomes transparent to the cipher used and much more flexible. .Pp PKCS padding works by adding n padding bytes of value n to make the total length of the encrypted data a multiple of the block size. Padding is always added so if the data is already a multiple of the block size n will equal the block size. For example if the block size is 8 and 11 bytes are to be encrypted then 5 padding bytes of value 5 will be added. .Pp When decrypting the final block is checked to see if it has the correct form. .Pp Although the decryption operation can produce an error if padding is enabled, it is not a strong test that the input data or key is correct. A random block has better than 1 in 256 chance of being of the correct format and problems with the input data earlier on will not produce a final decrypt error. .Pp If padding is disabled then the decryption operation will always succeed if the total amount of data decrypted is a multiple of the block size. .Pp The functions .Fn EVP_EncryptInit , .Fn EVP_EncryptFinal , .Fn EVP_DecryptInit , .Fn EVP_CipherInit , and .Fn EVP_CipherFinal are obsolete but are retained for compatibility with existing code. New code should use .Fn EVP_EncryptInit_ex , .Fn EVP_EncryptFinal_ex , .Fn EVP_DecryptInit_ex , .Fn EVP_DecryptFinal_ex , .Fn EVP_CipherInit_ex , and .Fn EVP_CipherFinal_ex because they can reuse an existing context without allocating and freeing it up on each call. .Pp .Fn EVP_get_cipherbynid and .Fn EVP_get_cipherbyobj are implemented as macros. .Sh RETURN VALUES .Fn EVP_CIPHER_CTX_new returns a pointer to a newly created .Vt EVP_CIPHER_CTX for success or .Dv NULL for failure. .Pp .Fn EVP_CIPHER_CTX_reset , .Fn EVP_CIPHER_CTX_cleanup , .Fn EVP_EncryptInit_ex , .Fn EVP_EncryptUpdate , .Fn EVP_EncryptFinal_ex , .Fn EVP_DecryptInit_ex , .Fn EVP_DecryptUpdate , .Fn EVP_DecryptFinal_ex , .Fn EVP_CipherInit_ex , .Fn EVP_CipherUpdate , .Fn EVP_CipherFinal_ex , .Fn EVP_EncryptInit , .Fn EVP_EncryptFinal , .Fn EVP_DecryptInit , .Fn EVP_DecryptFinal , .Fn EVP_CipherInit , .Fn EVP_CipherFinal , .Fn EVP_CIPHER_CTX_set_key_length , and .Fn EVP_CIPHER_CTX_rand_key return 1 for success or 0 for failure. .Pp .Fn EVP_CIPHER_CTX_set_padding always returns 1. .Pp .Fn EVP_get_cipherbyname , .Fn EVP_get_cipherbynid , and .Fn EVP_get_cipherbyobj return an .Vt EVP_CIPHER structure or .Dv NULL on error. .Pp .Fn EVP_CIPHER_nid and .Fn EVP_CIPHER_CTX_nid return a NID. .Pp .Fn EVP_CIPHER_block_size and .Fn EVP_CIPHER_CTX_block_size return the block size. .Pp .Fn EVP_CIPHER_key_length and .Fn EVP_CIPHER_CTX_key_length return the key length. .Pp .Fn EVP_CIPHER_iv_length and .Fn EVP_CIPHER_CTX_iv_length return the IV length or zero if the cipher does not use an IV. .Pp .Fn EVP_CIPHER_type and .Fn EVP_CIPHER_CTX_type return the NID of the cipher's OBJECT IDENTIFIER or .Dv NID_undef if it has no defined OBJECT IDENTIFIER. .Pp .Fn EVP_CIPHER_CTX_cipher returns an .Vt EVP_CIPHER structure. .Pp .Fn EVP_CIPHER_param_to_asn1 and .Fn EVP_CIPHER_asn1_to_param return greater than zero for success and zero or a negative number for failure. .Sh CIPHER LISTING All algorithms have a fixed key length unless otherwise stated. .Bl -tag -width Ds .It Fn EVP_enc_null Null cipher: does nothing. .It Xo .Fn EVP_aes_128_cbc , .Fn EVP_aes_128_ecb , .Fn EVP_aes_128_cfb , .Fn EVP_aes_128_ofb .Xc AES with a 128-bit key in CBC, ECB, CFB and OFB modes respectively. .It Xo .Fn EVP_aes_192_cbc , .Fn EVP_aes_192_ecb , .Fn EVP_aes_192_cfb , .Fn EVP_aes_192_ofb .Xc AES with a 192-bit key in CBC, ECB, CFB and OFB modes respectively. .It Xo .Fn EVP_aes_256_cbc , .Fn EVP_aes_256_ecb , .Fn EVP_aes_256_cfb , .Fn EVP_aes_256_ofb .Xc AES with a 256-bit key in CBC, ECB, CFB and OFB modes respectively. .It Xo .Fn EVP_des_cbc , .Fn EVP_des_ecb , .Fn EVP_des_cfb , .Fn EVP_des_ofb .Xc DES in CBC, ECB, CFB and OFB modes respectively. .It Xo .Fn EVP_des_ede_cbc , .Fn EVP_des_ede , .Fn EVP_des_ede_ofb , .Fn EVP_des_ede_cfb .Xc Two key triple DES in CBC, ECB, CFB and OFB modes respectively. .It Xo .Fn EVP_des_ede3_cbc , .Fn EVP_des_ede3 , .Fn EVP_des_ede3_ofb , .Fn EVP_des_ede3_cfb .Xc Three key triple DES in CBC, ECB, CFB and OFB modes respectively. .It Fn EVP_desx_cbc DESX algorithm in CBC mode. .It Fn EVP_rc4 RC4 stream cipher. This is a variable key length cipher with default key length 128 bits. .It Fn EVP_rc4_40 RC4 stream cipher with 40-bit key length. This is obsolete and new code should use .Fn EVP_rc4 and the .Fn EVP_CIPHER_CTX_set_key_length function. .It Xo .Fn EVP_idea_cbc , .Fn EVP_idea_ecb , .Fn EVP_idea_cfb , .Fn EVP_idea_ofb .Xc IDEA encryption algorithm in CBC, ECB, CFB and OFB modes respectively. .It Xo .Fn EVP_rc2_cbc , .Fn EVP_rc2_ecb , .Fn EVP_rc2_cfb , .Fn EVP_rc2_ofb .Xc RC2 encryption algorithm in CBC, ECB, CFB and OFB modes respectively. This is a variable key length cipher with an additional parameter called "effective key bits" or "effective key length". By default both are set to 128 bits. .It Xo .Fn EVP_rc2_40_cbc , .Fn EVP_rc2_64_cbc .Xc RC2 algorithm in CBC mode with a default key length and effective key length of 40 and 64 bits. These are obsolete and new code should use .Fn EVP_rc2_cbc , .Fn EVP_CIPHER_CTX_set_key_length , and .Fn EVP_CIPHER_CTX_ctrl to set the key length and effective key length. .It Xo .Fn EVP_bf_cbc , .Fn EVP_bf_ecb , .Fn EVP_bf_cfb , .Fn EVP_bf_ofb .Xc Blowfish encryption algorithm in CBC, ECB, CFB and OFB modes respectively. This is a variable key length cipher. .It Xo .Fn EVP_cast5_cbc , .Fn EVP_cast5_ecb , .Fn EVP_cast5_cfb , .Fn EVP_cast5_ofb .Xc CAST encryption algorithm in CBC, ECB, CFB and OFB modes respectively. This is a variable key length cipher. .It Xo .Fn EVP_aes_128_gcm , .Fn EVP_aes_192_gcm , .Fn EVP_aes_256_gcm .Xc AES Galois Counter Mode (GCM) for 128, 192 and 256 bit keys respectively. These ciphers require additional control operations to function correctly: see the GCM mode section below for details. .It Xo .Fn EVP_aes_128_ccm , .Fn EVP_aes_192_ccm , .Fn EVP_aes_256_ccm .Xc AES Counter with CBC-MAC Mode (CCM) for 128, 192 and 256 bit keys respectively. These ciphers require additional control operations to function correctly: see CCM mode section below for details. .It Fn EVP_chacha20 The ChaCha20 stream cipher. The key length is 256 bits, the IV is 96 bits long. .El .Ss GCM mode For GCM mode ciphers, the behaviour of the EVP interface is subtly altered and several additional ctrl operations are supported. .Pp To specify any additional authenticated data (AAD), a call to .Fn EVP_CipherUpdate , .Fn EVP_EncryptUpdate , or .Fn EVP_DecryptUpdate should be made with the output parameter out set to .Dv NULL . .Pp When decrypting, the return value of .Fn EVP_DecryptFinal or .Fn EVP_CipherFinal indicates if the operation was successful. If it does not indicate success, the authentication operation has failed and any output data MUST NOT be used as it is corrupted. .Pp The following ctrls are supported in GCM mode: .Bl -tag -width Ds .It Fn EVP_CIPHER_CTX_ctrl ctx EVP_CTRL_GCM_SET_IVLEN ivlen NULL Sets the IV length: this call can only be made before specifying an IV. If not called, a default IV length is used. For GCM AES the default is 12, i.e. 96 bits. .It Fn EVP_CIPHER_CTX_ctrl ctx EVP_CTRL_GCM_GET_TAG taglen tag Writes .Fa taglen bytes of the tag value to the buffer indicated by .Fa tag . This call can only be made when encrypting data and after all data has been processed, e.g. after an .Fn EVP_EncryptFinal call. .It Fn EVP_CIPHER_CTX_ctrl ctx EVP_CTRL_GCM_SET_TAG taglen tag Sets the expected tag to .Fa taglen bytes from .Fa tag . This call is only legal when decrypting data and must be made before any data is processed, e.g. before any .Fa EVP_DecryptUpdate call. .El .Ss CCM mode The behaviour of CCM mode ciphers is similar to GCM mode, but with a few additional requirements and different ctrl values. .Pp Like GCM mode any additional authenticated data (AAD) is passed by calling .Fn EVP_CipherUpdate , .Fn EVP_EncryptUpdate , or .Fn EVP_DecryptUpdate with the output parameter out set to .Dv NULL . Additionally, the total plaintext or ciphertext length MUST be passed to .Fn EVP_CipherUpdate , .Fn EVP_EncryptUpdate , or .Fn EVP_DecryptUpdate with the output and input parameters .Pq Fa in No and Fa out set to .Dv NULL and the length passed in the .Fa inl parameter. .Pp The following ctrls are supported in CCM mode: .Bl -tag -width Ds .It Fn EVP_CIPHER_CTX_ctrl ctx EVP_CTRL_CCM_SET_TAG taglen tag This call is made to set the expected CCM tag value when decrypting or the length of the tag (with the .Fa tag parameter set to .Dv NULL ) when encrypting. The tag length is often referred to as M. If not set, a default value is used (12 for AES). .It Fn EVP_CIPHER_CTX_ctrl ctx EVP_CTRL_CCM_SET_L ivlen NULL Sets the CCM L value. If not set, a default is used (8 for AES). .It Fn EVP_CIPHER_CTX_ctrl ctx EVP_CTRL_CCM_SET_IVLEN ivlen NULL Sets the CCM nonce (IV) length: this call can only be made before specifying an nonce value. The nonce length is given by 15 - L so it is 7 by default for AES. .El .Sh EXAMPLES Encrypt a string using blowfish: .Bd -literal -offset 3n int do_crypt(char *outfile) { unsigned char outbuf[1024]; int outlen, tmplen; /* * Bogus key and IV: we'd normally set these from * another source. */ unsigned char key[] = {0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15}; unsigned char iv[] = {1,2,3,4,5,6,7,8}; const char intext[] = "Some Crypto Text"; EVP_CIPHER_CTX *ctx; FILE *out; ctx = EVP_CIPHER_CTX_new(); EVP_EncryptInit_ex(ctx, EVP_bf_cbc(), NULL, key, iv); if (!EVP_EncryptUpdate(ctx, outbuf, &outlen, intext, strlen(intext))) { /* Error */ EVP_CIPHER_CTX_free(ctx); return 0; } /* * Buffer passed to EVP_EncryptFinal() must be after data just * encrypted to avoid overwriting it. */ if (!EVP_EncryptFinal_ex(ctx, outbuf + outlen, &tmplen)) { /* Error */ EVP_CIPHER_CTX_free(ctx); return 0; } outlen += tmplen; EVP_CIPHER_CTX_free(ctx); /* * Need binary mode for fopen because encrypted data is * binary data. Also cannot use strlen() on it because * it won't be NUL terminated and may contain embedded * NULs. */ out = fopen(outfile, "wb"); if (out == NULL) { /* Error */ return 0; } fwrite(outbuf, 1, outlen, out); fclose(out); return 1; } .Ed .Pp The ciphertext from the above example can be decrypted using the .Xr openssl 1 utility with the command line: .Bd -literal -offset indent openssl bf -in cipher.bin -K 000102030405060708090A0B0C0D0E0F \e -iv 0102030405060708 -d .Ed .Pp General encryption, decryption function example using FILE I/O and AES128 with an 128-bit key: .Bd -literal int do_crypt(FILE *in, FILE *out, int do_encrypt) { /* Allow enough space in output buffer for additional block */ unsigned char inbuf[1024], outbuf[1024 + EVP_MAX_BLOCK_LENGTH]; int inlen, outlen; EVP_CIPHER_CTX *ctx; /* * Bogus key and IV: we'd normally set these from * another source. */ unsigned char key[] = "0123456789abcdeF"; unsigned char iv[] = "1234567887654321"; ctx = EVP_CIPHER_CTX_new(); EVP_CipherInit_ex(ctx, EVP_aes_128_cbc(), NULL, NULL, NULL, do_encrypt); EVP_CipherInit_ex(ctx, NULL, NULL, key, iv, do_encrypt); for (;;) { inlen = fread(inbuf, 1, 1024, in); if (inlen <= 0) break; if (!EVP_CipherUpdate(ctx, outbuf, &outlen, inbuf, inlen)) { /* Error */ EVP_CIPHER_CTX_free(ctx); return 0; } fwrite(outbuf, 1, outlen, out); } if (!EVP_CipherFinal_ex(ctx, outbuf, &outlen)) { /* Error */ EVP_CIPHER_CTX_free(ctx); return 0; } fwrite(outbuf, 1, outlen, out); EVP_CIPHER_CTX_free(ctx); return 1; } .Ed .Sh SEE ALSO .Xr evp 3 .Sh HISTORY .Fn EVP_EncryptInit , .Fn EVP_EncryptUpdate , .Fn EVP_EncryptFinal , .Fn EVP_DecryptInit , .Fn EVP_DecryptUpdate , .Fn EVP_DecryptFinal , .Fn EVP_CipherInit , .Fn EVP_CipherUpdate , .Fn EVP_CipherFinal , .Fn EVP_get_cipherbyname , .Fn EVP_des_cbc , .Fn EVP_des_ecb , .Fn EVP_des_cfb , .Fn EVP_des_ofb , .Fn EVP_des_ede_cbc , .Fn EVP_des_ede , .Fn EVP_des_ede_ofb , .Fn EVP_des_ede_cfb , .Fn EVP_des_ede3_cbc , .Fn EVP_des_ede3 , .Fn EVP_des_ede3_ofb , .Fn EVP_des_ede3_cfb , .Fn EVP_rc4 , .Fn EVP_idea_cbc , .Fn EVP_idea_ecb , .Fn EVP_idea_cfb , and .Fn EVP_idea_ofb first appeared in SSLeay 0.5.1. .Fn EVP_rc2_cbc , .Fn EVP_rc2_ecb , .Fn EVP_rc2_cfb , and .Fn EVP_rc2_ofb first appeared in SSLeay 0.5.2. .Fn EVP_desx_cbc first appeared in SSLeay 0.6.2. .Fn EVP_CIPHER_block_size , .Fn EVP_CIPHER_key_length , .Fn EVP_CIPHER_iv_length , .Fn EVP_CIPHER_type , .Fn EVP_CIPHER_CTX_block_size , .Fn EVP_CIPHER_CTX_key_length , .Fn EVP_CIPHER_CTX_iv_length , and .Fn EVP_CIPHER_CTX_type first appeared in SSLeay 0.6.5. .Fn EVP_bf_cbc , .Fn EVP_bf_ecb , .Fn EVP_bf_cfb , and .Fn EVP_bf_ofb first appeared in SSLeay 0.6.6. .Fn EVP_CIPHER_CTX_cleanup , .Fn EVP_get_cipherbyobj , .Fn EVP_CIPHER_nid , .Fn EVP_CIPHER_CTX_cipher , .Fn EVP_CIPHER_CTX_nid , .Fn EVP_CIPHER_CTX_get_app_data , .Fn EVP_CIPHER_CTX_set_app_data , and .Fn EVP_enc_null first appeared in SSLeay 0.8.0. .Fn EVP_get_cipherbynid first appeared in SSLeay 0.8.1. .Fn EVP_CIPHER_CTX_init , .Fn EVP_CIPHER_param_to_asn1 , and .Fn EVP_CIPHER_asn1_to_param first appeared in SSLeay 0.9.0. All these functions have been available since .Ox 2.4 . .Pp .Fn EVP_rc2_64_cbc first appeared in SSL_eay 0.9.1. .Fn EVP_CIPHER_CTX_type first appeared in OpenSSL 0.9.3. These functions and have been available since .Ox 2.6 . .Pp .Fn EVP_CIPHER_CTX_set_key_length , .Fn EVP_CIPHER_CTX_ctrl , .Fn EVP_CIPHER_flags , .Fn EVP_CIPHER_mode , .Fn EVP_CIPHER_CTX_flags , and .Fn EVP_CIPHER_CTX_mode first appeared in OpenSSL 0.9.6 and have been available since .Ox 2.9 . .Pp .Fn EVP_EncryptInit_ex , .Fn EVP_EncryptFinal_ex , .Fn EVP_DecryptInit_ex , .Fn EVP_DecryptFinal_ex , .Fn EVP_CipherInit_ex , .Fn EVP_CipherFinal_ex , and .Fn EVP_CIPHER_CTX_set_padding first appeared in OpenSSL 0.9.7 and have been available since .Ox 3.2 . .Pp .Fn EVP_CIPHER_CTX_rand_key first appeared in OpenSSL 0.9.8. .Fn EVP_CIPHER_CTX_new and .Fn EVP_CIPHER_CTX_free first appeared in OpenSSL 0.9.8b. These functions have been available since .Ox 4.5 . .Pp .Fn EVP_rc4_hmac_md5 , .Fn EVP_aes_128_gcm , .Fn EVP_aes_192_gcm , .Fn EVP_aes_256_gcm , .Fn EVP_aes_128_ccm , .Fn EVP_aes_192_ccm , .Fn EVP_aes_256_ccm , .Fn EVP_aes_128_cbc_hmac_sha1 , and .Fn EVP_aes_256_cbc_hmac_sha1 first appeared in OpenSSL 1.0.1 and have been available since .Ox 5.3 . .Pp .Fn EVP_CIPHER_CTX_reset first appeared in OpenSSL 1.1.0 and has been available since .Ox 6.3 . .Sh BUGS .Dv EVP_MAX_KEY_LENGTH and .Dv EVP_MAX_IV_LENGTH only refer to the internal ciphers with default key lengths. If custom ciphers exceed these values the results are unpredictable. This is because it has become standard practice to define a generic key as a fixed unsigned char array containing .Dv EVP_MAX_KEY_LENGTH bytes. .Pp The ASN.1 code is incomplete (and sometimes inaccurate). It has only been tested for certain common S/MIME ciphers (RC2, DES, triple DES) in CBC mode.