public virtual void Init(
bool forEncryption,
ICipherParameters parameters)
{
_forEncryption = forEncryption;
KeyParameter keyParam;
if (parameters is AeadParameters)
{
AeadParameters param = (AeadParameters)parameters;
_nonce = param.GetNonce();
_initialAssociatedText = param.GetAssociatedText();
keyParam = param.Key;
}
else if (parameters is ParametersWithIV)
{
ParametersWithIV param = (ParametersWithIV)parameters;
_nonce = param.GetIV();
_initialAssociatedText = null;
keyParam = (KeyParameter)param.Parameters;
}
else
{
throw new ArgumentException("invalid parameters passed to ChaCha20Poly1305");
}
if (_nonce == null || _nonce.Length < 1)
{
throw new ArgumentException("IV must be at least 1 byte");
}
// Geneate the key
ChaCha7539Engine tmpCypher = new ChaCha7539Engine();
byte[] zero = new byte[32];
byte[] polyKey = new byte[32];
ParametersWithIV tmpKey = new ParametersWithIV(keyParam, _nonce);
tmpCypher.Init(true, tmpKey);
tmpCypher.ProcessBytes(zero, 0, zero.Length, polyKey, 0);
_poly = new Poly1305();
KeyParameter tmpKey2 = new KeyParameter(polyKey);
_poly.Init(tmpKey2);
_chacha20 = new ChaChaX();
_chacha20.Init(forEncryption, tmpKey);
InitCipher();
}
public byte[] Decrypt(byte[] cipher, byte[] key, byte[] iv, byte[] aad = null, byte[] associated = null)
{
if (key.Length * 8 != this.KeySize)
{
throw new InvalidOperationException($"the given key has invalid size {key.Length * 8}, expect {this.KeySize}");
}
if (iv.Length != 12)
{
throw new InvalidOperationException($"chacha20 requires 96 bits IV, got {iv.Length * 8}");
}
if (cipher.Length <= 16)
{
throw new ArgumentException($"incorrect argument [cipher] size");
}
// split cipher and mac
var cipherText = cipher.Take(cipher.Length - 16).ToArray();
var macText = cipher.Skip(cipher.Length - 16).ToArray();
var engine = new Engines.ChaCha7539Engine();
engine.Init(false, new Parameters.ParametersWithIV(new Parameters.KeyParameter(key), iv));
// calculate mac key
var mackeyBlock = new byte[64];
engine.ProcessBytes(mackeyBlock, 0, mackeyBlock.Length, mackeyBlock, 0);
var mackey = mackeyBlock.Take(32).ToArray();
// calculate mac
var poly = new Macs.Poly1305();
poly.Init(new Parameters.KeyParameter(mackey));
PolyUpdateMacText(poly, aad);
PolyUpdateMacText(poly, cipherText);
PolyUpdateMacLength(poly, aad.Length);
PolyUpdateMacLength(poly, cipherText.Length);
var myMac = PolyDoFinal(poly);
if (!Utils.BytesEqual(myMac, macText))
{
throw new ArgumentException("bad record mac");
}
// decrypt
var plain = new byte[cipherText.Length];
engine.ProcessBytes(cipherText, 0, cipherText.Length, plain, 0);
return(plain);
}
public byte[] Encrypt(byte[] plain, byte[] key, byte[] iv, byte[] aad = null, byte[] associated = null)
{
if (key.Length * 8 != this.KeySize)
{
throw new InvalidOperationException($"the given key has invalid size {key.Length * 8}, expect {this.KeySize}");
}
if (iv.Length != 12)
{
throw new InvalidOperationException($"chacha20 requires 96 bits IV, got {iv.Length * 8}");
}
var engine = new Engines.ChaCha7539Engine();
engine.Init(true, new Parameters.ParametersWithIV(new Parameters.KeyParameter(key), iv));
// calculate mac key
var mackeyBlock = new byte[64];
engine.ProcessBytes(mackeyBlock, 0, mackeyBlock.Length, mackeyBlock, 0);
var mackey = mackeyBlock.Take(32).ToArray();
// encrypt
var cipher = new byte[plain.Length];
engine.ProcessBytes(plain, 0, plain.Length, cipher, 0);
// calculate mac
var poly = new Macs.Poly1305();
poly.Init(new Parameters.KeyParameter(mackey));
PolyUpdateMacText(poly, aad);
PolyUpdateMacText(poly, cipher);
PolyUpdateMacLength(poly, aad.Length);
PolyUpdateMacLength(poly, cipher.Length);
var myMac = PolyDoFinal(poly);
var cipherBlock = new byte[cipher.Length + myMac.Length];
Buffer.BlockCopy(cipher, 0, cipherBlock, 0, cipher.Length);
Buffer.BlockCopy(myMac, 0, cipherBlock, cipher.Length, myMac.Length);
return(cipherBlock);
}