public bool Authenticate(KeyPair authenticationKeyPair, string signedText)
{
_rsaCryptoServiceProvider.FromXmlString(authenticationKeyPair.Public.Key);
string signature = CryptoHelpers.ExtractSignature(signedText);
string message = CryptoHelpers.StripSignature(signedText);
if (string.IsNullOrEmpty(signature))
{
throw new Exception("Digital signature is missing or not formatted properly.");
}
var bytes = TextHelpers.ClearTextToClearBytes(message);
var sigbytes = TextHelpers.CipherTextToCipherBytes(signature);
return(_rsaCryptoServiceProvider.VerifyData(bytes, HashAlgorithm.Create(), sigbytes));
}
public string Decrypt(KeyPair decryptionKeyPair, string cipherText)
{
//they use THEIR private key to decrypt
_rsaCryptoServiceProvider.FromXmlString(decryptionKeyPair.Private.Key);
var blockSize = GetModulusSize();
var plainStream = new MemoryStream();
var cipherStream = new MemoryStream(TextHelpers.CipherTextToCipherBytes(cipherText));
var buffer = new byte[blockSize];
int r;
while ((r = cipherStream.Read(buffer, 0, buffer.Length)) > 0)
{
var p = _rsaCryptoServiceProvider.Decrypt(buffer, false);
plainStream.Write(p, 0, p.Length);
}
//TODO: getting extra data here. not sure why
var clearBytes = plainStream.ToArray();
return(TextHelpers.ClearBytesToClearString(clearBytes));
}
