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EVP_PKEY_VERIFY(3)		    OpenSSL		    EVP_PKEY_VERIFY(3)

NAME
       EVP_PKEY_verify_init, EVP_PKEY_verify - signature verification using a
       public key algorithm

SYNOPSIS
	#include <openssl/evp.h>

	int EVP_PKEY_verify_init(EVP_PKEY_CTX *ctx);
	int EVP_PKEY_verify(EVP_PKEY_CTX *ctx,
			    const unsigned char	*sig, size_t siglen,
			    const unsigned char	*tbs, size_t tbslen);

DESCRIPTION
       The EVP_PKEY_verify_init() function initializes a public	key algorithm
       context using key pkey for a signature verification operation.

       The EVP_PKEY_verify() function performs a public	key verification
       operation using ctx. The	signature is specified using the sig and
       siglen parameters. The verified data (i.e. the data believed originally
       signed) is specified using the tbs and tbslen parameters.

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

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

RETURN VALUES
       EVP_PKEY_verify_init() and EVP_PKEY_verify() return 1 if	the
       verification was	successful and 0 if it failed. Unlike other functions
       the return value	0 from EVP_PKEY_verify() only indicates	that the
       signature did not verify	successfully (that is tbs did not match	the
       original	data or	the signature was of invalid form) it is not an
       indication of a more serious error.

       A negative value	indicates an error other that signature	verification
       failure.	 In particular a return	value of -2 indicates the operation is
       not supported by	the public key algorithm.

EXAMPLES
       Verify signature	using PKCS#1 and SHA256	digest:

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

	EVP_PKEY_CTX *ctx;
	unsigned char *md, *sig;
	size_t mdlen, siglen;
	EVP_PKEY *verify_key;

	/*
	 * NB: assumes verify_key, sig,	siglen md and mdlen are	already	set up
	 * and that verify_key is an RSA public	key
	 */
	ctx = EVP_PKEY_CTX_new(verify_key, NULL	/* no engine */);
	if (!ctx)
	    /* Error occurred */
	if (EVP_PKEY_verify_init(ctx) <= 0)
	    /* Error */
	if (EVP_PKEY_CTX_set_rsa_padding(ctx, RSA_PKCS1_PADDING) <= 0)
	    /* Error */
	if (EVP_PKEY_CTX_set_signature_md(ctx, EVP_sha256()) <=	0)
	    /* Error */

	/* Perform operation */
	ret = EVP_PKEY_verify(ctx, sig,	siglen,	md, mdlen);

	/*
	 * ret == 1 indicates success, 0 verify	failure	and < 0	for some
	 * other error.
	 */

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

HISTORY
       These functions were added in OpenSSL 1.0.0.

COPYRIGHT
       Copyright 2006-2019 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>.

1.1.1d				  2019-09-10		    EVP_PKEY_VERIFY(3)

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

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