public async Task <string> DecryptDataBlock(byte[] privateKey, EncryptedDataBlock dataBlock)
{
ValidateDigitalSignature(privateKey, dataBlock);
return(await SymmetricallyDecrypt(Convert.FromBase64String(dataBlock.AesKey), Convert.FromBase64String(dataBlock.InitialisationVector),
dataBlock.EncryptedData).ConfigureAwait(false));
}
private static void ValidateDigitalSignature(byte[] privateKey, EncryptedDataBlock dataBlock)
{
try
{
var decryptedDigitalSignature = AsymmetricallyDecrypt(privateKey, dataBlock.DigitalSignature);
var hash = GenerateHash(dataBlock.EncryptedData);
if (string.Compare(decryptedDigitalSignature, hash, StringComparison.OrdinalIgnoreCase) != 0)
{
throw new InvalidOperationException("The computed digital signature for the data block does not match the original digital signature.");
}
}
catch (CryptographicException ex)
{
throw new InvalidOperationException("There was a problem decrypting the data block. Potential data corruption or packet tampering has occurred.", ex);
}
}