public override byte[] Decrypt(ReadOnlyMemory <byte> cipher, KerberosKey kerberosKey, KeyUsage usage)
{
var key = kerberosKey.GetKey(this);
var cipherLength = cipher.Length - ChecksumSize;
var Ke = DK(key, usage, KeyDerivationMode.Ke);
var decrypted = AESCTS.Decrypt(
BlockCopy(cipher, 0, cipherLength),
Ke,
AllZerosInitVector
);
var actualChecksum = MakeChecksum(decrypted, key, usage, KeyDerivationMode.Ki, ChecksumSize);
var expectedChecksum = BlockCopy(cipher, cipherLength, ChecksumSize);
if (!AreEqualSlow(expectedChecksum, actualChecksum))
{
throw new SecurityException("Invalid checksum");
}
return(BlockCopy(decrypted, ConfounderSize, cipherLength - ConfounderSize));
}
public override ReadOnlySpan <byte> Decrypt(ReadOnlyMemory <byte> cipher, KerberosKey kerberosKey, KeyUsage usage)
{
var cipherLength = cipher.Length - ChecksumSize;
var Ke = kerberosKey.GetOrDeriveKey(
this,
$"{usage}|Ke|{KeySize}|{BlockSize}",
key => DK(key.Span, usage, KeyDerivationMode.Ke, KeySize, BlockSize).AsMemory()
);
var decrypted = AESCTS.Decrypt(
cipher.Span.Slice(0, cipherLength),
Ke,
AllZerosInitVector.Span
);
var actualChecksum = MakeChecksum(decrypted, kerberosKey, usage, KeyDerivationMode.Ki, ChecksumSize);
var expectedChecksum = cipher.Slice(cipherLength, ChecksumSize);
if (!AreEqualSlow(expectedChecksum.Span, actualChecksum))
{
throw new SecurityException("Invalid checksum");
}
return(decrypted.Slice(ConfounderSize, cipherLength - ConfounderSize));
}
public override ReadOnlyMemory <byte> Decrypt(ReadOnlyMemory <byte> cipher, KerberosKey kerberosKey, KeyUsage usage)
{
var cipherLength = cipher.Length - this.ChecksumSize;
var ke = this.GetOrDeriveKey(kerberosKey, usage);
var decrypted = AESCTS.Decrypt(
cipher.Slice(0, cipherLength),
ke,
AllZerosInitVector
);
var actualChecksum = this.MakeChecksum(decrypted, kerberosKey, usage, KeyDerivationMode.Ki, this.ChecksumSize);
var expectedChecksum = cipher.Slice(cipherLength, this.ChecksumSize);
if (!AreEqualSlow(expectedChecksum.Span, actualChecksum.Span))
{
throw new SecurityException("Invalid checksum");
}
return(decrypted.Slice(this.ConfounderSize, cipherLength - this.ConfounderSize));
}
