/usr/man/cat.3/EVP_PKEY_verify_init.3

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 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>

1.0.2t               Last change: 2019-09-10                    1

EVP_PKEY_verify(3)           OpenSSL           EVP_PKEY_verify(3)

      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               Last change: 2019-09-10                    2

See also EVP_PKEY_verify(3)