public void Encrypt_KnownKey()
{
// Arrange
Secret kdk = new Secret(Encoding.UTF8.GetBytes("master key"));
CngGcmAuthenticatedEncryptor encryptor = new CngGcmAuthenticatedEncryptor(kdk, CachedAlgorithmHandles.AES_GCM, symmetricAlgorithmKeySizeInBytes: 128 / 8, genRandom: new SequentialGenRandom());
ArraySegment <byte> plaintext = new ArraySegment <byte>(new byte[] { 0, 1, 2, 3, 4, 5, 6, 7 }, 2, 3);
ArraySegment <byte> aad = new ArraySegment <byte>(new byte[] { 7, 6, 5, 4, 3, 2, 1, 0 }, 1, 4);
// Act
byte[] retVal = encryptor.Encrypt(
plaintext: plaintext,
additionalAuthenticatedData: aad,
preBufferSize: 3,
postBufferSize: 4);
// Assert
// retVal := 00 00 00 (preBuffer)
// | 00 01 02 03 04 05 06 07 08 09 0A 0B 0C 0D 0E 0F (keyModifier)
// | 10 11 12 13 14 15 16 17 18 19 1A 1B (nonce)
// | 43 B6 91 (encryptedData)
// | 8D 0D 66 D9 A1 D9 44 2D 5D 8E 41 DA 39 60 9C E8 (authTag)
// | 00 00 00 00 (postBuffer)
string retValAsString = Convert.ToBase64String(retVal);
Assert.Equal("AAAAAAECAwQFBgcICQoLDA0ODxAREhMUFRYXGBkaG0O2kY0NZtmh2UQtXY5B2jlgnOgAAAAA", retValAsString);
}
public void Encrypt_Decrypt_RoundTrips()
{
// Arrange
Secret kdk = new Secret(new byte[512 / 8]);
CngGcmAuthenticatedEncryptor encryptor = new CngGcmAuthenticatedEncryptor(kdk, CachedAlgorithmHandles.AES_GCM, symmetricAlgorithmKeySizeInBytes: 256 / 8);
ArraySegment <byte> plaintext = new ArraySegment <byte>(Encoding.UTF8.GetBytes("plaintext"));
ArraySegment <byte> aad = new ArraySegment <byte>(Encoding.UTF8.GetBytes("aad"));
// Act
byte[] ciphertext = encryptor.Encrypt(plaintext, aad);
byte[] decipheredtext = encryptor.Decrypt(new ArraySegment <byte>(ciphertext), aad);
// Assert
Assert.Equal(plaintext, decipheredtext);
}
public void Encrypt_Decrypt_Tampering_Fails()
{
// Arrange
Secret kdk = new Secret(new byte[512 / 8]);
CngGcmAuthenticatedEncryptor encryptor = new CngGcmAuthenticatedEncryptor(kdk, CachedAlgorithmHandles.AES_GCM, symmetricAlgorithmKeySizeInBytes: 256 / 8);
ArraySegment <byte> plaintext = new ArraySegment <byte>(Encoding.UTF8.GetBytes("plaintext"));
ArraySegment <byte> aad = new ArraySegment <byte>(Encoding.UTF8.GetBytes("aad"));
byte[] validCiphertext = encryptor.Encrypt(plaintext, aad);
// Act & assert - 1
// Ciphertext is too short to be a valid payload
byte[] invalidCiphertext_tooShort = new byte[10];
Assert.Throws <CryptographicException>(() =>
{
encryptor.Decrypt(new ArraySegment <byte>(invalidCiphertext_tooShort), aad);
});
// Act & assert - 2
// Ciphertext has been manipulated
byte[] invalidCiphertext_manipulated = (byte[])validCiphertext.Clone();
invalidCiphertext_manipulated[0] ^= 0x01;
Assert.Throws <CryptographicException>(() =>
{
encryptor.Decrypt(new ArraySegment <byte>(invalidCiphertext_manipulated), aad);
});
// Act & assert - 3
// Ciphertext is too long
byte[] invalidCiphertext_tooLong = validCiphertext.Concat(new byte[] { 0 }).ToArray();
Assert.Throws <CryptographicException>(() =>
{
encryptor.Decrypt(new ArraySegment <byte>(invalidCiphertext_tooLong), aad);
});
// Act & assert - 4
// AAD is incorrect
Assert.Throws <CryptographicException>(() =>
{
encryptor.Decrypt(new ArraySegment <byte>(validCiphertext), new ArraySegment <byte>(Encoding.UTF8.GetBytes("different aad")));
});
}