public override ReadOnlyMemory <byte> PseudoRandomFunction(ReadOnlyMemory <byte> key, ReadOnlyMemory <byte> input)
{
// aes-ecb(trunc128(sha-1(input)))
using (var sha1 = CryptoPal.Platform.Sha1())
{
var checksum = sha1.ComputeHash(input.Span).Slice(0, AesBlockSize);
var kp = this.DK(key, PrfConstant, this.KeySize, this.BlockSize);
return(AESCTS.Encrypt(checksum, kp, AllZerosInitVector));
}
}
public override ReadOnlyMemory <byte> Encrypt(ReadOnlyMemory <byte> data, KerberosKey kerberosKey, KeyUsage usage)
{
var ke = this.GetOrDeriveKey(kerberosKey, usage, KeyDerivationMode.Ke);
ReadOnlyMemory <byte> confounder;
if (this.Confounder.Length > 0)
{
confounder = this.Confounder;
}
else
{
confounder = this.GenerateRandomBytes(this.ConfounderSize);
}
var concatLength = confounder.Length + data.Length;
using (var cleartextPool = CryptoPool.Rent <byte>(concatLength))
{
var cleartext = cleartextPool.Memory.Slice(0, concatLength);
Concat(confounder.Span, data.Span, cleartext);
var encrypted = AESCTS.Encrypt(
cleartext,
ke,
AllZerosInitVector
);
var checksumDataLength = AllZerosInitVector.Length + encrypted.Length;
using (var checksumDataRented = CryptoPool.Rent <byte>(checksumDataLength))
{
var checksumData = checksumDataRented.Memory.Slice(0, checksumDataLength);
Concat(AllZerosInitVector.Span, encrypted.Span, checksumData);
var checksum = this.MakeChecksum(checksumData, kerberosKey, usage, KeyDerivationMode.Ki, this.ChecksumSize);
return(Concat(encrypted.Span, checksum.Span));
}
}
}
public override ReadOnlyMemory <byte> Decrypt(ReadOnlyMemory <byte> cipher, KerberosKey kerberosKey, KeyUsage usage)
{
var cipherLength = cipher.Length - this.ChecksumSize;
var ke = this.GetOrDeriveKey(kerberosKey, usage, KeyDerivationMode.Ke);
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));
}
public void Encrypt(byte[] key, byte[] iv, byte[] tmpEnc)
{
var output = AESCTS.Encrypt(tmpEnc, key, iv);
Buffer.BlockCopy(output, 0, tmpEnc, 0, output.Length);
}
