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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))

26/Feb/2001		      0.9.6				1

EVP_EncryptInit(3)	     OpenSSL	       EVP_EncryptInit(3)

	#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

26/Feb/2001		      0.9.6				2

EVP_EncryptInit(3)	     OpenSSL	       EVP_EncryptInit(3)

       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

26/Feb/2001		      0.9.6				3

EVP_EncryptInit(3)	     OpenSSL	       EVP_EncryptInit(3)

       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

26/Feb/2001		      0.9.6				4

EVP_EncryptInit(3)	     OpenSSL	       EVP_EncryptInit(3)

       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 1
       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.

26/Feb/2001		      0.9.6				5

EVP_EncryptInit(3)	     OpenSSL	       EVP_EncryptInit(3)

       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

26/Feb/2001		      0.9.6				6

EVP_EncryptInit(3)	     OpenSSL	       EVP_EncryptInit(3)

	   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

26/Feb/2001		      0.9.6				7

EVP_EncryptInit(3)	     OpenSSL	       EVP_EncryptInit(3)

       (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
       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"

26/Feb/2001		      0.9.6				8

EVP_EncryptInit(3)	     OpenSSL	       EVP_EncryptInit(3)

26/Feb/2001		      0.9.6				9

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