private static byte[] XChaCha20Poly1305(bool isEncryption, byte[] key, byte[] nonce, byte[] message, byte[] aad = null)
{
if (key.Length != 32)
{
throw new ArgumentException("Key must be 32 bytes", nameof(key));
}
if (nonce.Length != 24)
{
throw new ArgumentException("Nonce must be 24 bytes", nameof(nonce));
}
// subkey (hchacha20(key, nonce[0:15]))
var subkey = HChaCha20.CreateSubkey(key, nonce); // TODO: parse nonce bytes to pass through here instead
// nonce (chacha20_nonce = "\x00\x00\x00\x00" + nonce[16:23])
var chaChaNonce = new byte[12];
Array.Copy(new byte[] { 0, 0, 0, 0 }, chaChaNonce, 4);
Array.Copy(nonce, 16, chaChaNonce, 4, 8);
// chacha20_encrypt(subkey, chacha20_nonce, plaintext, blk_ctr)
var outputLength = message.Length;
if (isEncryption)
{
outputLength += 16;
}
else
{
outputLength -= 16;
}
var output = new byte[outputLength];
var keyMaterial = new KeyParameter(subkey);
var parameters = new ParametersWithIV(keyMaterial, chaChaNonce);
var chaCha20Poly1305 = new ChaCha20Poly1305();
chaCha20Poly1305.Init(isEncryption, parameters);
// if aditional data present
if (aad != null)
{
chaCha20Poly1305.ProcessAadBytes(aad, 0, aad.Length);
}
var len = chaCha20Poly1305.ProcessBytes(message, 0, message.Length, output, 0);
chaCha20Poly1305.DoFinal(output, len);
return(output);
}
private void CheckTestCase(
ChaCha20Poly1305 encCipher,
ChaCha20Poly1305 decCipher,
string testName,
byte[] SA,
byte[] P,
byte[] C,
byte[] T)
{
byte[] enc = new byte[encCipher.GetOutputSize(P.Length)];
if (SA != null)
{
encCipher.ProcessAadBytes(SA, 0, SA.Length);
}
int len = encCipher.ProcessBytes(P, 0, P.Length, enc, 0);
len += encCipher.DoFinal(enc, len);
if (enc.Length != len)
{
Fail("encryption reported incorrect length: " + testName);
}
byte[] mac = encCipher.GetMac();
byte[] data = new byte[P.Length];
Array.Copy(enc, 0, data, 0, data.Length);
byte[] tail = new byte[enc.Length - P.Length];
Array.Copy(enc, P.Length, tail, 0, tail.Length);
if (!AreEqual(C, data))
{
Fail("incorrect encrypt in: " + testName);
}
if (!AreEqual(T, mac))
{
Fail("getMac() returned wrong mac in: " + testName);
}
if (!AreEqual(T, tail))
{
Fail("stream contained wrong mac in: " + testName);
}
byte[] dec = new byte[decCipher.GetOutputSize(enc.Length)];
if (SA != null)
{
decCipher.ProcessAadBytes(SA, 0, SA.Length);
}
len = decCipher.ProcessBytes(enc, 0, enc.Length, dec, 0);
len += decCipher.DoFinal(dec, len);
mac = decCipher.GetMac();
data = new byte[C.Length];
Array.Copy(dec, 0, data, 0, data.Length);
if (!AreEqual(P, data))
{
Fail("incorrect decrypt in: " + testName);
}
}
private void RandomTest(SecureRandom random)
{
int kLength = 32;
byte[] K = new byte[kLength];
random.NextBytes(K);
int pHead = random.Next(256);
int pLength = random.Next(65536);
int pTail = random.Next(256);
byte[] P = new byte[pHead + pLength + pTail];
random.NextBytes(P);
int aLength = random.Next(256);
byte[] A = new byte[aLength];
random.NextBytes(A);
int saLength = random.Next(256);
byte[] SA = new byte[saLength];
random.NextBytes(SA);
int nonceLength = 12;
byte[] nonce = new byte[nonceLength];
random.NextBytes(nonce);
AeadParameters parameters = new AeadParameters(new KeyParameter(K), 16 * 8, nonce, A);
ChaCha20Poly1305 cipher = InitCipher(true, parameters);
int ctLength = cipher.GetOutputSize(pLength);
byte[] C = new byte[saLength + ctLength];
Array.Copy(SA, 0, C, 0, saLength);
int split = NextInt(random, saLength + 1);
cipher.ProcessAadBytes(C, 0, split);
cipher.ProcessAadBytes(C, split, saLength - split);
int predicted = cipher.GetUpdateOutputSize(pLength);
int len = cipher.ProcessBytes(P, pHead, pLength, C, saLength);
if (predicted != len)
{
Fail("encryption reported incorrect update length in randomised test");
}
len += cipher.DoFinal(C, saLength + len);
if (ctLength != len)
{
Fail("encryption reported incorrect length in randomised test");
}
byte[] encT = cipher.GetMac();
byte[] tail = new byte[ctLength - pLength];
Array.Copy(C, saLength + pLength, tail, 0, tail.Length);
if (!AreEqual(encT, tail))
{
Fail("stream contained wrong mac in randomised test");
}
cipher.Init(false, parameters);
int decPHead = random.Next(256);
int decPLength = cipher.GetOutputSize(ctLength);
int decPTail = random.Next(256);
byte[] decP = new byte[decPHead + decPLength + decPTail];
split = NextInt(random, saLength + 1);
cipher.ProcessAadBytes(C, 0, split);
cipher.ProcessAadBytes(C, split, saLength - split);
predicted = cipher.GetUpdateOutputSize(ctLength);
len = cipher.ProcessBytes(C, saLength, ctLength, decP, decPHead);
if (predicted != len)
{
Fail("decryption reported incorrect update length in randomised test");
}
len += cipher.DoFinal(decP, decPHead + len);
if (!AreEqual(P, pHead, pHead + pLength, decP, decPHead, decPHead + decPLength))
{
Fail("incorrect decrypt in randomised test");
}
byte[] decT = cipher.GetMac();
if (!AreEqual(encT, decT))
{
Fail("decryption produced different mac from encryption");
}
//
// key reuse test
//
cipher.Init(false, AeadTestUtilities.ReuseKey(parameters));
decPHead = random.Next(256);
decPLength = cipher.GetOutputSize(ctLength);
decPTail = random.Next(256);
decP = new byte[decPHead + decPLength + decPTail];
split = NextInt(random, saLength + 1);
cipher.ProcessAadBytes(C, 0, split);
cipher.ProcessAadBytes(C, split, saLength - split);
len = cipher.ProcessBytes(C, saLength, ctLength, decP, decPHead);
len += cipher.DoFinal(decP, decPHead + len);
if (!AreEqual(P, pHead, pHead + pLength, decP, decPHead, decPHead + decPLength))
{
Fail("incorrect decrypt in randomised test");
}
decT = cipher.GetMac();
if (!AreEqual(encT, decT))
{
Fail("decryption produced different mac from encryption");
}
}