public void Encrypt(ReadOnlySpan <byte> nonce, ReadOnlySpan <byte> source,
Span <byte> destination, Span <byte> tag, ReadOnlySpan <byte> associatedData = default)
{
var input = ArrayPool <byte> .Shared.Rent(source.Length);
var output = ArrayPool <byte> .Shared.Rent(destination.Length + tag.Length);
try
{
_engine = new BufferedAeadBlockCipher(new GcmBlockCipher(_aes));
_engine.Init(true, new AeadParameters(_key, 128, nonce.ToArray(), associatedData.ToArray()));
source.CopyTo(input);
_engine.DoFinal(input, 0, source.Length, output, 0);
output.AsSpan(0, destination.Length).CopyTo(destination);
output.AsSpan(destination.Length, tag.Length).CopyTo(tag);
}
finally
{
ArrayPool <byte> .Shared.Return(input);
ArrayPool <byte> .Shared.Return(output);
}
}
public void Decrypt(ReadOnlySpan <byte> nonce, ReadOnlySpan <byte> source, ReadOnlySpan <byte> tag,
Span <byte> destination, ReadOnlySpan <byte> associatedData = default)
{
var input = ArrayPool <byte> .Shared.Rent(source.Length + tag.Length);
var output = ArrayPool <byte> .Shared.Rent(destination.Length);
try
{
_engine.Init(false, new AeadParameters(_key, 128, nonce.ToArray(), associatedData.ToArray()));
source.CopyTo(input);
tag.CopyTo(input.AsSpan(source.Length));
_engine.DoFinal(input, 0, source.Length + tag.Length, output, 0);
output.AsSpan(0, destination.Length).CopyTo(destination);
}
finally
{
ArrayPool <byte> .Shared.Return(input);
ArrayPool <byte> .Shared.Return(output);
}
}
/// <summary>
/// Create a buffered cipher to encrypt or decrypt a stream as it is being read
/// </summary>
/// <param name="forEncryption">forEncryption if true the cipher is initialised for encryption, if false for decryption</param>
/// <param name="key">Key to be used for encryption</param>
/// <param name="nonce">Nonce to be used for encryption</param>
/// <param name="tagSize">Tag size in bits for the tag appended in the end of the stream</param>
/// <param name="associatedText">Additional associated data</param>
/// <returns></returns>
internal static IBufferedCipher CreateCipher(bool forEncryption, byte[] key, int tagSize, byte[] nonce, byte[] associatedText)
{
var aesEngine = new AesEngine();
var blockCipher = new GcmBlockCipher(aesEngine);
var aeadBlockCipher = new BufferedAeadBlockCipher(blockCipher);
var parameters = new AeadParameters(new KeyParameter(key), tagSize, nonce, associatedText);
aeadBlockCipher.Init(forEncryption, parameters);
return(aeadBlockCipher);
}