/usr/man/cat.3/EVP_PKEY_verify_init.3.Z(/usr/man/cat.3/EVP_PKEY_verify_init.3.Z)

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 oper-
       ation 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 verifica-
       tion 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 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.

EXAMPLE

       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);
        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 first added to OpenSSL 1.0.0.

1.0.2t                            2019-09-10                EVP_PKEY_verify(3)
See also EVP_PKEY_verify(3)