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EVP_EncryptInit(3)		    OpenSSL		    EVP_EncryptInit(3)

NAME
       EVP_CIPHER_CTX_init, EVP_EncryptInit_ex,	EVP_EncryptUpdate,
       EVP_EncryptFinal_ex, EVP_DecryptInit_ex,	EVP_DecryptUpdate,
       EVP_DecryptFinal_ex, EVP_CipherInit_ex, EVP_CipherUpdate,
       EVP_CipherFinal_ex, EVP_CIPHER_CTX_set_key_length, EVP_CIPHER_CTX_ctrl,
       EVP_CIPHER_CTX_cleanup, EVP_EncryptInit,	EVP_EncryptFinal,
       EVP_DecryptInit,	EVP_DecryptFinal, EVP_CipherInit, EVP_CipherFinal,
       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_CTX_set_padding,  EVP_enc_null,
       EVP_des_cbc, EVP_des_ecb, EVP_des_cfb, EVP_des_ofb, EVP_des_ede_cbc,
       EVP_des_ede, EVP_des_ede_ofb, EVP_des_ede_cfb, EVP_des_ede3_cbc,
       EVP_des_ede3, EVP_des_ede3_ofb, EVP_des_ede3_cfb, EVP_desx_cbc,
       EVP_rc4,	EVP_rc4_40, EVP_rc4_hmac_md5, EVP_idea_cbc, EVP_idea_ecb,
       EVP_idea_cfb, EVP_idea_ofb, EVP_rc2_cbc,	EVP_rc2_ecb, EVP_rc2_cfb,
       EVP_rc2_ofb, EVP_rc2_40_cbc, EVP_rc2_64_cbc, EVP_bf_cbc,	EVP_bf_ecb,
       EVP_bf_cfb, EVP_bf_ofb, EVP_cast5_cbc, EVP_cast5_ecb, EVP_cast5_cfb,
       EVP_cast5_ofb, EVP_rc5_32_12_16_cbc, EVP_rc5_32_12_16_ecb,
       EVP_rc5_32_12_16_cfb, EVP_rc5_32_12_16_ofb, EVP_aes_128_gcm,
       EVP_aes_192_gcm,	EVP_aes_256_gcm, EVP_aes_128_ccm, EVP_aes_192_ccm,
       EVP_aes_256_ccm,	EVP_aes_128_cbc_hmac_sha1, EVP_aes_256_cbc_hmac_sha1,
       EVP_aes_128_cbc_hmac_sha256, EVP_aes_256_cbc_hmac_sha256	- EVP cipher
       routines

SYNOPSIS
	#include <openssl/evp.h>

	void EVP_CIPHER_CTX_init(EVP_CIPHER_CTX	*a);

	int EVP_EncryptInit_ex(EVP_CIPHER_CTX *ctx, const EVP_CIPHER *type,
		ENGINE *impl, const unsigned char *key,	const unsigned char *iv);
	int EVP_EncryptUpdate(EVP_CIPHER_CTX *ctx, unsigned char *out,
		int *outl, const unsigned char *in, int	inl);
	int EVP_EncryptFinal_ex(EVP_CIPHER_CTX *ctx, unsigned char *out,
		int *outl);

	int EVP_DecryptInit_ex(EVP_CIPHER_CTX *ctx, const EVP_CIPHER *type,
		ENGINE *impl, const unsigned char *key,	const unsigned char *iv);
	int EVP_DecryptUpdate(EVP_CIPHER_CTX *ctx, unsigned char *out,
		int *outl, const unsigned char *in, int	inl);
	int EVP_DecryptFinal_ex(EVP_CIPHER_CTX *ctx, unsigned char *outm,
		int *outl);

	int EVP_CipherInit_ex(EVP_CIPHER_CTX *ctx, const EVP_CIPHER *type,
		ENGINE *impl, const unsigned char *key,	const unsigned char *iv, int enc);
	int EVP_CipherUpdate(EVP_CIPHER_CTX *ctx, unsigned char	*out,
		int *outl, const unsigned char *in, int	inl);
	int EVP_CipherFinal_ex(EVP_CIPHER_CTX *ctx, unsigned char *outm,
		int *outl);

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

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

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

	int EVP_CIPHER_CTX_set_padding(EVP_CIPHER_CTX *x, int padding);
	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_CIPHER_CTX_init() initializes cipher	contex ctx.

       EVP_EncryptInit_ex() sets up cipher context ctx for encryption with
       cipher type from	ENGINE impl. ctx must be initialized before calling
       this function. type is normally supplied	by a function such as
       EVP_aes_256_cbc(). If impl is NULL then the default implementation is
       used. 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 out should contain sufficient room. The
       actual number of	bytes written is placed	in outl.

       If padding is enabled (the default) then	EVP_EncryptFinal_ex() 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.

       If padding is disabled then 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.

       EVP_DecryptInit_ex(), EVP_DecryptUpdate() and EVP_DecryptFinal_ex() are
       the corresponding decryption operations.	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 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_ex(), EVP_CipherUpdate() and EVP_CipherFinal_ex()	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
       and free	up any allocated memory	associate with it. It should be	called
       after all operations using a cipher are complete	so sensitive
       information does	not remain in memory.

       EVP_EncryptInit(), EVP_DecryptInit() and	EVP_CipherInit() behave	in a
       similar way to EVP_EncryptInit_ex(), EVP_DecryptInit_ex and
       EVP_CipherInit_ex() except the ctx parameter does not need to be
       initialized and they always use the default cipher implementation.

       EVP_EncryptFinal(), EVP_DecryptFinal() and EVP_CipherFinal() are
       identical to EVP_EncryptFinal_ex(), EVP_DecryptFinal_ex() and
       EVP_CipherFinal_ex(). In	previous releases they also cleaned up the
       ctx, but	this is	no longer done and EVP_CIPHER_CTX_clean() must be
       called to free any context resources.

       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_CTX_set_padding() enables or disables	padding. By default
       encryption operations are padded	using standard block padding and the
       padding is checked and removed when decrypting. If the pad 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.

       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.

RETURN VALUES
       EVP_EncryptInit_ex(), EVP_EncryptUpdate() and EVP_EncryptFinal_ex()
       return 1	for success and	0 for failure.

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

       EVP_CipherInit_ex() and EVP_CipherUpdate() return 1 for success and 0
       for failure.  EVP_CipherFinal_ex() 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_CTX_set_padding() always returns 1.

       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)
	   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.

       EVP_aes_128_gcm(void), EVP_aes_192_gcm(void), EVP_aes_256_gcm(void)
	   AES Galois Counter Mode (GCM) for 128, 192 and 256 bit keys
	   respectively.  These	ciphers	require	additional control operations
	   to function correctly: see "GCM mode" section below for details.

       EVP_aes_128_ccm(void), EVP_aes_192_ccm(void), EVP_aes_256_ccm(void)
	   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.

GCM Mode
       For GCM mode ciphers the	behaviour of the EVP interface is subtly
       altered and several GCM specific	ctrl operations	are supported.

       To specify any additional authenticated data (AAD) a call to
       EVP_CipherUpdate(), EVP_EncryptUpdate() or EVP_DecryptUpdate() should
       be made with the	output parameter out set to NULL.

       When decrypting the return value	of EVP_DecryptFinal() or
       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.

       The following ctrls are supported in GCM	mode:

	EVP_CIPHER_CTX_ctrl(ctx, EVP_CTRL_GCM_SET_IVLEN, ivlen,	NULL);

       Sets the	GCM IV length: this call can only be made before specifying an
       IV. If not called a default IV length is	used (96 bits for AES).

	EVP_CIPHER_CTX_ctrl(ctx, EVP_CTRL_GCM_GET_TAG, taglen, tag);

       Writes taglen bytes of the tag value to the buffer indicated by tag.
       This call can only be made when encrypting data and after all data has
       been processed (e.g. after an EVP_EncryptFinal()	call).

	EVP_CIPHER_CTX_ctrl(ctx, EVP_CTRL_GCM_SET_TAG, taglen, tag);

       Sets the	expected tag to	taglen bytes from tag. This call is only legal
       when decrypting data.

CCM Mode
       The behaviour of	CCM mode ciphers is similar to CCM mode	but with a few
       additional requirements and different ctrl values.

       Like GCM	mode any additional authenticated data (AAD) is	passed by
       calling EVP_CipherUpdate(), EVP_EncryptUpdate() or EVP_DecryptUpdate()
       with the	output parameter out set to NULL. Additionally the total
       plaintext or ciphertext length MUST be passed to	EVP_CipherUpdate(),
       EVP_EncryptUpdate() or EVP_DecryptUpdate() with the output and input
       parameters (in and out) set to NULL and the length passed in the	inl
       parameter.

       The following ctrls are supported in CCM	mode:

	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 tag parameter set to NULL) when
       encrypting.  The	tag length is often referred to	as M. If not set a
       default value is	used (12 for AES).

	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).

	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.

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.
       Additionally, the EVP interface will ensure the use of platform
       specific	cryptographic acceleration such	as AES-NI (the low level
       interfaces do not provide the guarantee).

       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 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.

       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.

       The functions EVP_EncryptInit(),	EVP_EncryptFinal(), EVP_DecryptInit(),
       EVP_CipherInit()	and EVP_CipherFinal() are obsolete but are retained
       for compatibility with existing code. New code should use
       EVP_EncryptInit_ex(), EVP_EncryptFinal_ex(), EVP_DecryptInit_ex(),
       EVP_DecryptFinal_ex(), EVP_CipherInit_ex() and EVP_CipherFinal_ex()
       because they can	reuse an existing context without allocating and
       freeing it up on	each call.

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.

       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
       Encrypt a string	using IDEA:

	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};
	       char intext[] = "Some Crypto Text";
	       EVP_CIPHER_CTX ctx;
	       FILE *out;

	       EVP_CIPHER_CTX_init(&ctx);
	       EVP_EncryptInit_ex(&ctx,	EVP_idea_cbc(),	NULL, key, iv);

	       if(!EVP_EncryptUpdate(&ctx, outbuf, &outlen, intext, strlen(intext)))
		       {
		       /* Error	*/
		       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	*/
		       return 0;
		       }
	       outlen += tmplen;
	       EVP_CIPHER_CTX_cleanup(&ctx);
	       /* Need binary mode for fopen because encrypted data is
		* binary data. Also cannot use strlen()	on it because
		* it wont be null terminated and may contain embedded
		* nulls.
		*/
	       out = fopen(outfile, "wb");
	       fwrite(outbuf, 1, outlen, out);
	       fclose(out);
	       return 1;
	       }

       The ciphertext from the above example can be decrypted using the
       openssl utility with the	command	line (shown on two lines for clarity):

	openssl	idea -d	<filename
		 -K 000102030405060708090A0B0C0D0E0F -iv 0102030405060708

       General encryption and decryption function example using	FILE I/O and
       AES128 with a 128-bit key:

	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";

	       /* Don't	set key	or IV right away; we want to check lengths */
	       EVP_CIPHER_CTX_init(&ctx);
	       EVP_CipherInit_ex(&ctx, EVP_aes_128_cbc(), NULL,	NULL, NULL,
		       do_encrypt);
	       OPENSSL_assert(EVP_CIPHER_CTX_key_length(&ctx) == 16);
	       OPENSSL_assert(EVP_CIPHER_CTX_iv_length(&ctx) ==	16);

	       /* Now we can set key and IV */
	       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_cleanup(&ctx);
			       return 0;
			       }
		       fwrite(outbuf, 1, outlen, out);
		       }
	       if(!EVP_CipherFinal_ex(&ctx, outbuf, &outlen))
		       {
		       /* Error	*/
		       EVP_CIPHER_CTX_cleanup(&ctx);
		       return 0;
		       }
	       fwrite(outbuf, 1, outlen, out);

	       EVP_CIPHER_CTX_cleanup(&ctx);
	       return 1;
	       }

SEE ALSO
       evp(3)

HISTORY
       EVP_CIPHER_CTX_init(), EVP_EncryptInit_ex(), EVP_EncryptFinal_ex(),
       EVP_DecryptInit_ex(), EVP_DecryptFinal_ex(), EVP_CipherInit_ex(),
       EVP_CipherFinal_ex() and	EVP_CIPHER_CTX_set_padding() appeared in
       OpenSSL 0.9.7.

       IDEA appeared in	OpenSSL	0.9.7 but was often disabled due to patent
       concerns; the last patents expired in 2012.

1.0.2p				  2018-08-14		    EVP_EncryptInit(3)

NAME | SYNOPSIS | DESCRIPTION | RETURN VALUES | CIPHER LISTING | GCM Mode | CCM Mode | NOTES | BUGS | EXAMPLES | SEE ALSO | HISTORY

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