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EVP_PKEY_DECRYPT(3)		    OpenSSL		   EVP_PKEY_DECRYPT(3)

NAME
       EVP_PKEY_decrypt_init, EVP_PKEY_decrypt - decrypt using a public	key
       algorithm

SYNOPSIS
	#include <openssl/evp.h>

	int EVP_PKEY_decrypt_init(EVP_PKEY_CTX *ctx);
	int EVP_PKEY_decrypt(EVP_PKEY_CTX *ctx,
			     unsigned char *out, size_t	*outlen,
			     const unsigned char *in, size_t inlen);

DESCRIPTION
       The EVP_PKEY_decrypt_init() function initializes	a public key algorithm
       context using key pkey for a decryption operation.

       The EVP_PKEY_decrypt() function performs	a public key decryption
       operation using ctx. The	data to	be decrypted is	specified using	the in
       and inlen parameters. If	out is NULL then the maximum size of the
       output buffer is	written	to the outlen parameter. If out	is not NULL
       then before the call the	outlen parameter should	contain	the length of
       the out buffer, if the call is successful the decrypted data is written
       to out and the amount of	data written to	outlen.

NOTES
       After the call to EVP_PKEY_decrypt_init() algorithm specific control
       operations can be performed to set any appropriate parameters for the
       operation.

       The function EVP_PKEY_decrypt() can be called more than once on the
       same context if several operations are performed	using the same
       parameters.

RETURN VALUES
       EVP_PKEY_decrypt_init() and EVP_PKEY_decrypt() return 1 for success and
       0 or a negative value for failure. In particular	a return value of -2
       indicates the operation is not supported	by the public key algorithm.

EXAMPLE
       Decrypt data using OAEP (for RSA	keys):

	#include <openssl/evp.h>
	#include <openssl/rsa.h>

	EVP_PKEY_CTX *ctx;
	ENGINE *eng;
	unsigned char *out, *in;
	size_t outlen, inlen;
	EVP_PKEY *key;

	/*
	 * NB: assumes key, eng, in, inlen are already set up
	 * and that key	is an RSA private key
	 */
	ctx = EVP_PKEY_CTX_new(key, eng);
	if (!ctx)
	    /* Error occurred */
	if (EVP_PKEY_decrypt_init(ctx) <= 0)
	    /* Error */
	if (EVP_PKEY_CTX_set_rsa_padding(ctx, RSA_OAEP_PADDING)	<= 0)
	    /* Error */

	/* Determine buffer length */
	if (EVP_PKEY_decrypt(ctx, NULL,	&outlen, in, inlen) <= 0)
	    /* Error */

	out = OPENSSL_malloc(outlen);

	if (!out)
	    /* malloc failure */

	if (EVP_PKEY_decrypt(ctx, out, &outlen,	in, inlen) <= 0)
	    /* Error */

	/* Decrypted data is outlen bytes written to buffer out	*/

SEE ALSO
       EVP_PKEY_CTX_new(3), EVP_PKEY_encrypt(3), EVP_PKEY_sign(3),
       EVP_PKEY_verify(3), EVP_PKEY_verify_recover(3), EVP_PKEY_derive(3)

HISTORY
       These functions were first added	to OpenSSL 1.0.0.

COPYRIGHT
       Copyright 2006-2018 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_PKEY_DECRYPT(3)

NAME | SYNOPSIS | DESCRIPTION | NOTES | RETURN VALUES | EXAMPLE | SEE ALSO | HISTORY | COPYRIGHT

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