public static void Encrypt(BufRef dest, BufLen data, I2PPublicKey key, bool zeropad)
{
if (data == null || data.Length > ClearTextLength)
{
throw new InvalidParameterException($"ElGamal data must be {ClearTextLength} bytes or less!");
}
var k = new BigInteger(I2PConstants.ElGamalFullExponentBits, Rnd);
var a = I2PConstants.ElGamalG.ModPow(k, I2PConstants.ElGamalP);
var b1 = key.ToBigInteger().ModPow(k, I2PConstants.ElGamalP);
var start = new BufLen(new byte[EGBlockLength]);
var writer = new BufRefLen(start, 1);
start[0] = 0xFF;
writer.Write(I2PHashSHA256.GetHash(data));
writer.Write(data);
var egblock = new BufLen(start, 0, writer - start);
var egint = egblock.ToBigInteger();
var b = b1.Multiply(egint).Mod(I2PConstants.ElGamalP);
var targetlen = zeropad
? EncryptedPaddedLength / 2
: EncryptedShortLength / 2;
WriteToDest(dest, a, targetlen);
WriteToDest(dest, b, targetlen);
}
public void Encrypt(BufRef dest, BufLen data, bool zeropad)
{
if (data == null || data.Length > 222)
{
throw new InvalidParameterException("ElGamal data length can max be 222 bytes!");
}
var hashbuf = new BufRefLen(new byte[255]);
hashbuf.Write8(0xFF);
hashbuf.Write(I2PHashSHA256.GetHash(data));
hashbuf.Write(data);
hashbuf.Reset();
var b = b1.Multiply(new BigInteger(1, hashbuf.ToByteArray())).Mod(I2PConstants.ElGamalP);
if (zeropad)
{
dest.Write8(0);
dest.Write(a.ToByteArray(256));
dest.Write8(0);
dest.Write(b.ToByteArray(256));
}
else
{
dest.Write(a.ToByteArray(256));
dest.Write(b.ToByteArray(256));
}
}
public BufRef ReadBufRef(int length)
{
PreReadCheck(length);
var result = new BufRef(this, 0);
Seek(length);
return(result);
}
private static void WriteToDest(BufRef dest, BigInteger v, int targetlen)
{
var vba = v.ToByteArray();
if (vba.Length < targetlen)
{
dest.Write(new byte[targetlen - vba.Length]);
}
if (vba.Length > targetlen)
{
dest.Write(new BufLen(vba, vba.Length - targetlen));
}
else
{
dest.Write(vba);
}
}
