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EVP_ENCRYPTINIT(3)		    OpenSSL		    EVP_ENCRYPTINIT(3)

NAME
       EVP_CIPHER_CTX_new, EVP_CIPHER_CTX_reset, EVP_CIPHER_CTX_free,
       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_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 cipher routines

SYNOPSIS
	#include <openssl/evp.h>

	EVP_CIPHER_CTX *EVP_CIPHER_CTX_new(void);
	int EVP_CIPHER_CTX_reset(EVP_CIPHER_CTX	*ctx);
	void EVP_CIPHER_CTX_free(EVP_CIPHER_CTX	*ctx);

	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_rand_key(EVP_CIPHER_CTX *ctx, unsigned char *key);

	const EVP_CIPHER *EVP_get_cipherbyname(const char *name);
	const EVP_CIPHER *EVP_get_cipherbynid(int nid);
	const EVP_CIPHER *EVP_get_cipherbyobj(const ASN1_OBJECT	*a);

	int EVP_CIPHER_nid(const EVP_CIPHER *e);
	int EVP_CIPHER_block_size(const	EVP_CIPHER *e);
	int EVP_CIPHER_key_length(const	EVP_CIPHER *e);
	int EVP_CIPHER_iv_length(const EVP_CIPHER *e);
	unsigned long EVP_CIPHER_flags(const EVP_CIPHER	*e);
	unsigned long EVP_CIPHER_mode(const EVP_CIPHER *e);
	int EVP_CIPHER_type(const EVP_CIPHER *ctx);

	const EVP_CIPHER *EVP_CIPHER_CTX_cipher(const EVP_CIPHER_CTX *ctx);
	int EVP_CIPHER_CTX_nid(const EVP_CIPHER_CTX *ctx);
	int EVP_CIPHER_CTX_block_size(const EVP_CIPHER_CTX *ctx);
	int EVP_CIPHER_CTX_key_length(const EVP_CIPHER_CTX *ctx);
	int EVP_CIPHER_CTX_iv_length(const EVP_CIPHER_CTX *ctx);
	void *EVP_CIPHER_CTX_get_app_data(const	EVP_CIPHER_CTX *ctx);
	void EVP_CIPHER_CTX_set_app_data(const EVP_CIPHER_CTX *ctx, void *data);
	int EVP_CIPHER_CTX_type(const EVP_CIPHER_CTX *ctx);
	int EVP_CIPHER_CTX_mode(const EVP_CIPHER_CTX *ctx);

	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_new() creates a cipher context.

       EVP_CIPHER_CTX_free() clears all	information from a cipher context and
       free up any allocated memory associate with it, including ctx itself.
       This function should be called after all	operations using a cipher are
       complete	so sensitive information does not remain in memory.

       EVP_EncryptInit_ex() sets up cipher context ctx for encryption with
       cipher type from	ENGINE impl. ctx must be created 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. It also checks	if in
       and out are partially overlapping, and if they are 0 is returned	to
       indicate	failure.

       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) as described in the
       NOTES section, below. 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_reset() clears all information from a cipher context and
       free up any allocated memory associate with it, except the ctx itself.
       This function should be called anytime ctx is to	be reused for another
       EVP_CipherInit()	/ EVP_CipherUpdate() / EVP_CipherFinal() series	of
       calls.

       EVP_EncryptInit(), EVP_DecryptInit() and	EVP_CipherInit() behave	in a
       similar way to EVP_EncryptInit_ex(), EVP_DecryptInit_ex() and
       EVP_CipherInit_ex() except 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. This function
       should be called	after the context is set up for	encryption or
       decryption with EVP_EncryptInit_ex(), 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 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_BLOCK_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,
       EVP_CIPH_OFB_MODE, EVP_CIPH_CTR_MODE, EVP_CIPH_GCM_MODE,
       EVP_CIPH_CCM_MODE, EVP_CIPH_XTS_MODE, EVP_CIPH_WRAP_MODE	or
       EVP_CIPH_OCB_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.

       EVP_CIPHER_CTX_rand_key() generates a random key	of the appropriate
       length based on the cipher context. The EVP_CIPHER can provide its own
       random key generation routine to	support	keys of	a specific form. Key
       must point to a buffer at least as big as the value returned by
       EVP_CIPHER_CTX_key_length().

RETURN VALUES
       EVP_CIPHER_CTX_new() returns a pointer to a newly created
       EVP_CIPHER_CTX for success and NULL for failure.

       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_reset() 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
       greater than zero for success and zero or a negative number on failure.

       EVP_CIPHER_CTX_rand_key() returns 1 for success.

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

       Refer to	"SEE ALSO" for the full	list of	ciphers	available through the
       EVP interface.

       EVP_enc_null()
	   Null	cipher:	does nothing.

AEAD Interface
       The EVP interface for Authenticated Encryption with Associated Data
       (AEAD) modes are	subtly altered and several additional ctrl operations
       are supported depending on the mode specified.

       To specify 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 whether 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.

   GCM and OCB Modes
       The following ctrls are supported in GCM	and OCB	modes.

       EVP_CIPHER_CTX_ctrl(ctx,	EVP_CTRL_AEAD_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 and OCB AES the default is 12 (i.e. 96 bits). For OCB
	   mode	the maximum is 15.

       EVP_CIPHER_CTX_ctrl(ctx,	EVP_CTRL_AEAD_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).

	   For OCB, "taglen" must either be 16 or the value previously set via
	   EVP_CTRL_AEAD_SET_TAG.

       EVP_CIPHER_CTX_ctrl(ctx,	EVP_CTRL_AEAD_SET_TAG, taglen, tag)
	   Sets	the expected tag to "taglen" bytes from	"tag".	The tag	length
	   can only be set before specifying an	IV.  "taglen" must be between
	   1 and 16 inclusive.

	   For GCM, this call is only valid when decrypting data.

	   For OCB, this call is valid when decrypting data to set the
	   expected tag, and before encryption to set the desired tag length.

	   In OCB mode,	calling	this before encryption with "tag" set to
	   "NULL" sets the tag length.	If this	is not called prior to
	   encryption, a default tag length is used.

	   For OCB AES,	the default tag	length is 16 (i.e. 128 bits).  It is
	   also	the maximum tag	length for OCB.

   CCM Mode
       The EVP interface for CCM mode is similar to that of the	GCM mode but
       with a few additional requirements and different	ctrl values.

       For CCM mode, 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_AEAD_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_AEAD_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.

   ChaCha20-Poly1305
       The following ctrls are supported for the ChaCha20-Poly1305 AEAD
       algorithm.

       EVP_CIPHER_CTX_ctrl(ctx,	EVP_CTRL_AEAD_SET_IVLEN, ivlen,	NULL)
	   Sets	the nonce length. This call can	only be	made before specifying
	   the nonce.  If not called a default nonce length of 12 (i.e.	96
	   bits) is used. The maximum nonce length is 16 (CHACHA_CTR_SIZE,
	   i.e.	128-bits).

       EVP_CIPHER_CTX_ctrl(ctx,	EVP_CTRL_AEAD_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).

	   "taglen" specified here must	be 16 (POLY1305_BLOCK_SIZE, i.e.
	   128-bits) or	less.

       EVP_CIPHER_CTX_ctrl(ctx,	EVP_CTRL_AEAD_SET_TAG, taglen, tag)
	   Sets	the expected tag to "taglen" bytes from	"tag".	The tag	length
	   can only be set before specifying an	IV.  "taglen" must be between
	   1 and 16 (POLY1305_BLOCK_SIZE) inclusive.  This call	is only	valid
	   when	decrypting data.

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.

       EVP_get_cipherbynid(), and EVP_get_cipherbyobj()	are implemented	as
       macros.

BUGS
       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;

	    ctx	= EVP_CIPHER_CTX_new();
	    EVP_EncryptInit_ex(ctx, EVP_idea_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;
	}

       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	\
	    -K 000102030405060708090A0B0C0D0E0F	-iv 0102030405060708 <filename

       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	*/
	    ctx	= EVP_CIPHER_CTX_new();
	    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_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;
	}

SEE ALSO
       evp(7)

       Supported ciphers are listed in:

       EVP_aes(3), EVP_aria(3),	EVP_bf(3), EVP_camellia(3), EVP_cast5(3),
       EVP_chacha20(3),	EVP_des(3), EVP_desx(3), EVP_idea(3), EVP_rc2(3),
       EVP_rc4(3), EVP_rc5(3), EVP_seed(3), EVP_sm4(3)

HISTORY
       Support for OCB mode was	added in OpenSSL 1.1.0

       EVP_CIPHER_CTX was made opaque in OpenSSL 1.1.0.	 As a result,
       EVP_CIPHER_CTX_reset() appeared and EVP_CIPHER_CTX_cleanup()
       disappeared.  EVP_CIPHER_CTX_init() remains as an alias for
       EVP_CIPHER_CTX_reset().

COPYRIGHT
       Copyright 2000-2018 The OpenSSL Project Authors.	All Rights Reserved.

       Licensed	under the OpenSSL license (the "License").  You	may not	use
       this file except	in compliance with the License.	 You can obtain	a copy
       in the file LICENSE in the source distribution or at
       <https://www.openssl.org/source/license.html>.

1.1.1a				  2018-11-20		    EVP_ENCRYPTINIT(3)

NAME | SYNOPSIS | DESCRIPTION | RETURN VALUES | CIPHER LISTING | AEAD Interface | NOTES | BUGS | EXAMPLES | SEE ALSO | HISTORY | COPYRIGHT

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