/// <summary>
/// Verifies that a digital signature is valid by determining the hash value
/// in the signature using the provided public key and comparing it to the hash
/// value of the provided data.
/// </summary>
/// <param name="inputStream">The data that was signed.</param>
/// <param name="signature">The signature data to be verified.</param>
/// <param name="rsaProvider">The RSA crypto service provider.</param>
/// <param name="hashAlgorithm">The hash algorithm to use to create the hash value.</param>
/// <returns>True if the signature is valid; otherwise, false.</returns>
public bool VerifyData(Stream inputStream, byte[] signature, RSACryptoServiceProvider rsaProvider, Nequeo.Cryptography.HashcodeType hashAlgorithm = HashcodeType.SHA512)
{
Stream signatureInput = null;
try
{
// Export the signer public key parameters.
RSAParameters rsaPublicKeySignerParam = rsaProvider.ExportParameters(false);
Key.Crypto.Parameters.RsaKeyParameters rsaPublicKeySigner =
new Key.Crypto.Parameters.RsaKeyParameters(
false,
new Key.Math.BigInteger(1, rsaPublicKeySignerParam.Modulus),
new Key.Math.BigInteger(1, rsaPublicKeySignerParam.Exponent)
);
signatureInput = new MemoryStream(signature);
signatureInput = Key.Bcpg.OpenPgp.PgpUtilities.GetDecoderStream(signatureInput);
// Get the public key.
Key.Bcpg.OpenPgp.PgpPublicKey publicKey = new Key.Bcpg.OpenPgp.PgpPublicKey(Key.Bcpg.PublicKeyAlgorithmTag.RsaGeneral, rsaPublicKeySigner, DateTime.UtcNow);
Key.Bcpg.OpenPgp.PgpObjectFactory pgpFact = new Key.Bcpg.OpenPgp.PgpObjectFactory(signatureInput);
Key.Bcpg.OpenPgp.PgpSignatureList signatureList = null;
Key.Bcpg.OpenPgp.PgpObject pgpObject = pgpFact.NextPgpObject();
// If the message is compressed.
if (pgpObject is Key.Bcpg.OpenPgp.PgpCompressedData)
{
// Get the compression object.
Key.Bcpg.OpenPgp.PgpCompressedData compressedData = (Key.Bcpg.OpenPgp.PgpCompressedData)pgpObject;
pgpFact = new Key.Bcpg.OpenPgp.PgpObjectFactory(compressedData.GetDataStream());
signatureList = (Key.Bcpg.OpenPgp.PgpSignatureList)pgpFact.NextPgpObject();
}
else
{
// Get the message list.
signatureList = (Key.Bcpg.OpenPgp.PgpSignatureList)pgpObject;
}
// Load the public key into the pgp signer.
Key.Bcpg.OpenPgp.PgpSignature pgpSignature = signatureList[0];
pgpSignature.InitVerify(publicKey);
int ch;
while ((ch = inputStream.ReadByte()) >= 0)
{
// Update the generator.
pgpSignature.Update((byte)ch);
}
// Verify the signature.
if (pgpSignature.Verify())
{
// signature verified.
return(true);
}
else
{
// signature verification failed.
return(false);
}
}
catch (Exception)
{
throw;
}
finally
{
if (signatureInput != null)
{
signatureInput.Close();
}
}
}
