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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>;.
1.1.1k                            2021-03-25                EVP_PKEY_VERIFY(3)