Hi

I am trying to verify a data payload supplied with a RSA signature generated from the SHA256 hash of the data.

The WolfSSL example code seems to work if using the private key but it fails with the following error when using the public key.

MP_EXPTMOD_E -112 mp_exptmod error state

Can anyone explain what this error code means?

Code shown here...
##############################################
    // Create a hash of the payload
    InitSha256(&sha);
    Sha256Update(&sha, payload, sizeof(payload));
    Sha256Final(&sha, hash);

    //ret = CyaSSL_KeyPemToDer(privateKeyPem, sizeof(privateKeyPem), privateKeyDerFromPem,
    //        sizeof(privateKeyDerFromPem), NULL);

    InitRsaKey(&prikey, NULL); // not using heap hint. No custom memory
    ret = RsaPrivateKeyDecode(privateKeyDer, &idx, &prikey, sizeof(privateKeyDer));
    if( ret != 0 )
    {
    // error parsing private key
    }
    idx = 0 ;
    InitRsaKey(&pubkey, NULL); // not using heap hint. No custom memory
    ret = RsaPublicKeyDecode(publicKeyDer, &idx, &pubkey, sizeof(publicKeyDer));
    if( ret != 0 )
    {
    // error parsing public key
    }
    // Sign with private key
    ret = RsaSSL_Sign(hash, sizeof(hash), out, sizeof(out), &prikey, &rng);
    if (ret < 0) {
       return -1;
    }
    // Verify with private key
    memset(plain, 0, sizeof(plain));
    ret = RsaSSL_Verify(out, ret, plain, sizeof(plain), &prikey);
    if (ret < 0) {
       return -1;
    }
    memset(plain, 0, sizeof(plain));
    ret = RsaSSL_Verify(out, ret, plain, sizeof(plain), &pubkey);
    if (ret < 0) {
       return -1;
    }
##############################################

Regards

Jeff White