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EVP_EncryptInit(3)		    OpenSSL		    EVP_EncryptInit(3)

NAME
       EVP_EncryptInit, EVP_EncryptUpdate, EVP_EncryptFinal, EVP_DecryptInit,
       EVP_DecryptUpdate, EVP_DecryptFinal, EVP_CipherInit, EVP_CipherUpdate,
       EVP_CipherFinal, EVP_CIPHER_CTX_set_key_length, EVP_CIPHER_CTX_ctrl,
       EVP_CIPHER_CTX_cleanup, EVP_get_cipherbyname, EVP_get_cipherbynid,
       EVP_get_cipherbyobj, EVP_CIPHER_nid, EVP_CIPHER_block_size,
       EVP_CIPHER_key_length, EVP_CIPHER_iv_length, EVP_CIPHER_flags,
       EVP_CIPHER_mode, EVP_CIPHER_type, EVP_CIPHER_CTX_cipher,
       EVP_CIPHER_CTX_nid, EVP_CIPHER_CTX_block_size,
       EVP_CIPHER_CTX_key_length, EVP_CIPHER_CTX_iv_length,
       EVP_CIPHER_CTX_get_app_data, EVP_CIPHER_CTX_set_app_data,
       EVP_CIPHER_CTX_type, EVP_CIPHER_CTX_flags, EVP_CIPHER_CTX_mode,
       EVP_CIPHER_param_to_asn1, EVP_CIPHER_asn1_to_param - EVP cipher
       routines

SYNOPSIS
	#include <openssl/evp.h>

	int EVP_EncryptInit(EVP_CIPHER_CTX *ctx, const EVP_CIPHER *type,
		unsigned char *key, unsigned char *iv);
	int EVP_EncryptUpdate(EVP_CIPHER_CTX *ctx, unsigned char *out,
		int *outl, unsigned char *in, int inl);
	int EVP_EncryptFinal(EVP_CIPHER_CTX *ctx, unsigned char *out,
		int *outl);

	int EVP_DecryptInit(EVP_CIPHER_CTX *ctx, const EVP_CIPHER *type,
		unsigned char *key, unsigned char *iv);
	int EVP_DecryptUpdate(EVP_CIPHER_CTX *ctx, unsigned char *out,
		int *outl, unsigned char *in, int inl);
	int EVP_DecryptFinal(EVP_CIPHER_CTX *ctx, unsigned char *outm,
		int *outl);

	int EVP_CipherInit(EVP_CIPHER_CTX *ctx, const EVP_CIPHER *type,
		unsigned char *key, unsigned char *iv, int enc);
	int EVP_CipherUpdate(EVP_CIPHER_CTX *ctx, unsigned char *out,
		int *outl, unsigned char *in, int inl);
	int EVP_CipherFinal(EVP_CIPHER_CTX *ctx, unsigned char *outm,
		int *outl);

	int EVP_CIPHER_CTX_set_key_length(EVP_CIPHER_CTX *x, int keylen);
	int EVP_CIPHER_CTX_ctrl(EVP_CIPHER_CTX *ctx, int type, int arg, void *ptr);
	int EVP_CIPHER_CTX_cleanup(EVP_CIPHER_CTX *a);

	const EVP_CIPHER *EVP_get_cipherbyname(const char *name);
	#define EVP_get_cipherbynid(a) EVP_get_cipherbyname(OBJ_nid2sn(a))
	#define EVP_get_cipherbyobj(a) EVP_get_cipherbynid(OBJ_obj2nid(a))

	#define EVP_CIPHER_nid(e)	       ((e)->nid)
	#define EVP_CIPHER_block_size(e)       ((e)->block_size)
	#define EVP_CIPHER_key_length(e)       ((e)->key_len)
	#define EVP_CIPHER_iv_length(e)		       ((e)->iv_len)
	#define EVP_CIPHER_flags(e)	       ((e)->flags)
	#define EVP_CIPHER_mode(e)	       ((e)->flags) & EVP_CIPH_MODE)
	int EVP_CIPHER_type(const EVP_CIPHER *ctx);

	#define EVP_CIPHER_CTX_cipher(e)       ((e)->cipher)
	#define EVP_CIPHER_CTX_nid(e)	       ((e)->cipher->nid)
	#define EVP_CIPHER_CTX_block_size(e)   ((e)->cipher->block_size)
	#define EVP_CIPHER_CTX_key_length(e)   ((e)->key_len)
	#define EVP_CIPHER_CTX_iv_length(e)    ((e)->cipher->iv_len)
	#define EVP_CIPHER_CTX_get_app_data(e) ((e)->app_data)
	#define EVP_CIPHER_CTX_set_app_data(e,d) ((e)->app_data=(char *)(d))
	#define EVP_CIPHER_CTX_type(c)	       EVP_CIPHER_type(EVP_CIPHER_CTX_cipher(c))
	#define EVP_CIPHER_CTX_flags(e)		       ((e)->cipher->flags)
	#define EVP_CIPHER_CTX_mode(e)	       ((e)->cipher->flags & EVP_CIPH_MODE)

	int EVP_CIPHER_param_to_asn1(EVP_CIPHER_CTX *c, ASN1_TYPE *type);
	int EVP_CIPHER_asn1_to_param(EVP_CIPHER_CTX *c, ASN1_TYPE *type);

DESCRIPTION
       The EVP cipher routines are a high level interface to certain symmetric
       ciphers.

       EVP_EncryptInit() initializes a cipher context ctx for encryption with
       cipher type. type is normally supplied by a function such as
       EVP_des_cbc() . key is the symmetric key to use and 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 NULL
       except type in an initial call and supply the remaining parameters in
       subsequent calls, all of which have type set to NULL.  This is done
       when the default cipher parameters are not appropriate.

       EVP_EncryptUpdate() encrypts inl bytes from the buffer in and writes
       the encrypted version to 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 outl should contain sufficient room.  The
       actual number of bytes written is placed in outl.

       EVP_EncryptFinal() encrypts the "final" data, that is any data that
       remains in a partial block. It uses standard block padding (aka PKCS
       padding). The encrypted final data is written to out which should have
       sufficient space for one cipher block. The number of bytes written is
       placed in outl. After this function is called the encryption operation
       is finished and no further calls to EVP_EncryptUpdate() should be made.

       EVP_DecryptInit(), EVP_DecryptUpdate() and EVP_DecryptFinal() are the
       corresponding decryption operations. EVP_DecryptFinal() will return an
       error code if the final block is not correctly formatted. The
       parameters and restrictions are identical to the encryption operations
       except that the decrypted data buffer out passed to EVP_DecryptUpdate()
       should have sufficient room for (inl + cipher_block_size) bytes unless
       the cipher block size is 1 in which case inl bytes is sufficient.

       EVP_CipherInit(), EVP_CipherUpdate() and EVP_CipherFinal() are
       functions that can be used for decryption or encryption. The operation
       performed depends on the value of the enc parameter. It should be set
       to 1 for encryption, 0 for decryption and -1 to leave the value
       unchanged (the actual value of 'enc' being supplied in a previous
       call).

       EVP_CIPHER_CTX_cleanup() clears all information from a cipher context.
       It should be called after all operations using a cipher are complete so
       sensitive information does not remain in memory.

       EVP_get_cipherbyname(), EVP_get_cipherbynid() and EVP_get_cipherbyobj()
       return an EVP_CIPHER structure when passed a cipher name, a NID or an
       ASN1_OBJECT structure.

       EVP_CIPHER_nid() and EVP_CIPHER_CTX_nid() return the NID of a cipher
       when passed an EVP_CIPHER or EVP_CIPHER_CTX structure.  The actual NID
       value is an internal value which may not have a corresponding OBJECT
       IDENTIFIER.

       EVP_CIPHER_key_length() and EVP_CIPHER_CTX_key_length() return the key
       length of a cipher when passed an EVP_CIPHER or EVP_CIPHER_CTX
       structure. The constant EVP_MAX_KEY_LENGTH is the maximum key length
       for all ciphers. Note: although EVP_CIPHER_key_length() is fixed for a
       given cipher, the value of EVP_CIPHER_CTX_key_length() may be different
       for variable key length ciphers.

       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.

       EVP_CIPHER_iv_length() and EVP_CIPHER_CTX_iv_length() return the IV
       length of a cipher when passed an EVP_CIPHER or EVP_CIPHER_CTX.	It
       will return zero if the cipher does not use an IV.  The constant
       EVP_MAX_IV_LENGTH is the maximum IV length for all ciphers.

       EVP_CIPHER_block_size() and EVP_CIPHER_CTX_block_size() return the
       block size of a cipher when passed an EVP_CIPHER or EVP_CIPHER_CTX
       structure. The constant EVP_MAX_IV_LENGTH is also the maximum block
       length for all ciphers.

       EVP_CIPHER_type() and 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 ASN1 support this function will
       return NID_undef.

       EVP_CIPHER_CTX_cipher() returns the EVP_CIPHER structure when passed an
       EVP_CIPHER_CTX structure.

       EVP_CIPHER_mode() and EVP_CIPHER_CTX_mode() return the block cipher
       mode: EVP_CIPH_ECB_MODE, EVP_CIPH_CBC_MODE, EVP_CIPH_CFB_MODE or
       EVP_CIPH_OFB_MODE. If the cipher is a stream cipher then
       EVP_CIPH_STREAM_CIPHER is returned.

       EVP_CIPHER_param_to_asn1() sets the 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 EVP_EncryptUpdate(), EVP_DecryptUpdate() calls for example). This
       function may fail if the cipher does not have any ASN1 support.

       EVP_CIPHER_asn1_to_param() sets the cipher parameters based on an ASN1
       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
       EVP_CipherInit() will be called with the IV and key set to NULL,
       EVP_CIPHER_asn1_to_param() will be called and finally EVP_CipherInit()
       again with all parameters except the key set to NULL. It is possible
       for this function to fail if the cipher does not have any ASN1 support
       or the parameters cannot be set (for example the RC2 effective key
       length is not supported.

       EVP_CIPHER_CTX_ctrl() allows various cipher specific parameters to be
       determined and set. Currently only the RC2 effective key length and the
       number of rounds of RC5 can be set.

RETURN VALUES
       EVP_EncryptInit(), EVP_EncryptUpdate() and EVP_EncryptFinal() return 1
       for success and 0 for failure.

       EVP_DecryptInit() and EVP_DecryptUpdate() return 1 for success and 0
       for failure.  EVP_DecryptFinal() returns 0 if the decrypt failed or 1
       for success.

       EVP_CipherInit() and EVP_CipherUpdate() return 1 for success and 0 for
       failure.	 EVP_CipherFinal() returns 0 for a decryption failure or 1 for
       success.

       EVP_CIPHER_CTX_cleanup() returns 1 for success and 0 for failure.

       EVP_get_cipherbyname(), EVP_get_cipherbynid() and EVP_get_cipherbyobj()
       return an EVP_CIPHER structure or NULL on error.

       EVP_CIPHER_nid() and EVP_CIPHER_CTX_nid() return a NID.

       EVP_CIPHER_block_size() and EVP_CIPHER_CTX_block_size() return the
       block size.

       EVP_CIPHER_key_length() and EVP_CIPHER_CTX_key_length() return the key
       length.

       EVP_CIPHER_iv_length() and EVP_CIPHER_CTX_iv_length() return the IV
       length or zero if the cipher does not use an IV.

       EVP_CIPHER_type() and EVP_CIPHER_CTX_type() return the NID of the
       cipher's OBJECT IDENTIFIER or NID_undef if it has no defined OBJECT
       IDENTIFIER.

       EVP_CIPHER_CTX_cipher() returns an EVP_CIPHER structure.

       EVP_CIPHER_param_to_asn1() and EVP_CIPHER_asn1_to_param() return 1 for
       success or zero for failure.

CIPHER LISTING
       All algorithms have a fixed key length unless otherwise stated.

       EVP_enc_null()
	   Null cipher: does nothing.

       EVP_des_cbc(void), EVP_des_ecb(void), EVP_des_cfb(void),
       EVP_des_ofb(void)
	   DES in CBC, ECB, CFB and OFB modes respectively.

       EVP_des_ede_cbc(void), EVP_des_ede(), EVP_des_ede_ofb(void),
       EVP_des_ede_cfb(void)
	   Two key triple DES in CBC, ECB, CFB and OFB modes respectively.

       EVP_des_ede3_cbc(void), EVP_des_ede3(), EVP_des_ede3_ofb(void),
       EVP_des_ede3_cfb(void)
	   Three key triple DES in CBC, ECB, CFB and OFB modes respectively.

       EVP_desx_cbc(void)
	   DESX algorithm in CBC mode.

       EVP_rc4(void)
	   RC4 stream cipher. This is a variable key length cipher with
	   default key length 128 bits.

       EVP_rc4_40(void)
	   RC4 stream cipher with 40 bit key length. This is obsolete and new
	   code should use EVP_rc4() and the EVP_CIPHER_CTX_set_key_length()
	   function.

       EVP_idea_cbc() EVP_idea_ecb(void), EVP_idea_cfb(void),
       EVP_idea_ofb(void), EVP_idea_cbc(void)
	   IDEA encryption algorithm in CBC, ECB, CFB and OFB modes
	   respectively.

       EVP_rc2_cbc(void), EVP_rc2_ecb(void), EVP_rc2_cfb(void),
       EVP_rc2_ofb(void)
	   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.

       EVP_rc2_40_cbc(void), EVP_rc2_64_cbc(void)
	   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 EVP_rc2_cbc(), EVP_CIPHER_CTX_set_key_length() and
	   EVP_CIPHER_CTX_ctrl() to set the key length and effective key
	   length.

       EVP_bf_cbc(void), EVP_bf_ecb(void), EVP_bf_cfb(void), EVP_bf_ofb(void);
	   Blowfish encryption algorithm in CBC, ECB, CFB and OFB modes
	   respectively. This is a variable key length cipher.

       EVP_cast5_cbc(void), EVP_cast5_ecb(void), EVP_cast5_cfb(void),
       EVP_cast5_ofb(void)
	   CAST encryption algorithm in CBC, ECB, CFB and OFB modes
	   respectively. This is a variable key length cipher.

       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)
	   RC5 encryption algorithm in CBC, ECB, CFB and OFB modes
	   respectively. This is a variable key length cipher with an
	   additional "number of rounds" parameter. By default the key length
	   is set to 128 bits and 12 rounds.

NOTES
       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.

       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.

       When decrypting the final block is checked to see if it has the correct
       form.

       Although the decryption operation can produce an error, 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.

       The functions EVP_EncryptInit(), EVP_EncryptUpdate(),
       EVP_EncryptFinal(), EVP_DecryptInit(), EVP_DecryptUpdate(),
       EVP_CipherInit() and EVP_CipherUpdate() and EVP_CIPHER_CTX_cleanup()
       did not return errors in OpenSSL version 0.9.5a or earlier. Software
       only versions of encryption algorithms will never return error codes
       for these functions, unless there is a programming error (for example
       and attempt to set the key before the cipher is set in
       EVP_EncryptInit() ).

BUGS
       For RC5 the number of rounds can currently only be set to 8, 12 or 16.
       This is a limitation of the current RC5 code rather than the EVP
       interface.

       It should be possible to disable PKCS padding: currently it isn't.

       EVP_MAX_KEY_LENGTH and 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 EVP_MAX_KEY_LENGTH bytes.

       The ASN1 code is incomplete (and sometimes inaccurate) it has only been
       tested for certain common S/MIME ciphers (RC2, DES, triple DES) in CBC
       mode.

EXAMPLES
       Get the number of rounds used in RC5:

	int nrounds;
	EVP_CIPHER_CTX_ctrl(ctx, EVP_CTRL_GET_RC5_ROUNDS, 0, &i);

       Get the RC2 effective key length:

	int key_bits;
	EVP_CIPHER_CTX_ctrl(ctx, EVP_CTRL_GET_RC2_KEY_BITS, 0, &i);

       Set the number of rounds used in RC5:

	int nrounds;
	EVP_CIPHER_CTX_ctrl(ctx, EVP_CTRL_SET_RC5_ROUNDS, i, NULL);

       Set the number of rounds used in RC2:

	int nrounds;
	EVP_CIPHER_CTX_ctrl(ctx, EVP_CTRL_SET_RC2_KEY_BITS, i, NULL);

SEE ALSO
       evp(3)

HISTORY
3rd Berkeley Distribution	    0.9.6m		    EVP_EncryptInit(3)
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