/// <summary>
/// Signs the passed in data with a private key
/// </summary>
/// <param name="privateKey">the private key used to create the signature</param>
/// <param name="data">The data to sign</param>
/// <returns>the signature as a byte array</returns>
public byte[] Sign(byte[] privateKey, byte[] data)
{
var signer = new Gost3410Signer();
var privKey = (Gost3410PrivateKeyParameters)CreateAsymmetricKeyParameterFromPrivateKeyInfo(privateKey);
try
{
signer.Init(true, privKey);
}
catch (Exception exception)
{
string message = "Private Key Creation Failure!\n" +
$"{exception.Message}.\n" +
$"The private key file is corrupted, verify private key file or try another key.\n" +
$"If all fails create a new key pair.";
throw new CryptoException(message, exception);
}
var bigIntSig = signer.GenerateSignature(data);
var signature = new List <byte>();
signature.AddRange(bigIntSig[0].ToByteArrayUnsigned());
signature.AddRange(bigIntSig[1].ToByteArrayUnsigned());
return(signature.ToArray());
}
/// <summary>
/// Verifies a signature to be authentic
/// </summary>
/// <param name="originalSignature">The signature which is be verified</param>
/// <param name="publicKey">the public key used for the verification</param>
/// <param name="data">the data which is signed</param>
/// <returns>true if signature is authentic, false if not</returns>
public bool Verify(byte[] originalSignature, byte[] publicKey, byte[] data)
{
var signer = new Gost3410Signer();
var pubKey = (Gost3410PublicKeyParameters)CreateAsymmetricKeyParameterFromPublicKeyInfo(publicKey);
signer.Init(false, pubKey);
var r = new byte[originalSignature.Length / 2];
var s = new byte[originalSignature.Length / 2];
Array.Copy(originalSignature, r, r.Length);
Array.Copy(originalSignature, r.Length, s, 0, s.Length);
var R = new BigInteger(1, r);
var S = new BigInteger(1, s);
return(signer.VerifySignature(data, R, S));
}
