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 static byte[] Decode(string data)
{
if (data.Length < 4 || data.Length % 4 != 0)
{
throw new FormatException("FreenetBase64 string needs to be padded to 4 byte align!");
}
var size = 3 * (data.Length / 4);
if (data[data.Length - 1] == '=')
{
--size;
}
if (data[data.Length - 2] == '=')
{
--size;
}
if (data[data.Length - 3] == '=')
{
--size;
}
var result = new byte[size];
if (Codomain == null)
{
Codomain = new int[256];
for (int i = 0; i < 256; ++i)
{
Codomain[i] = -1;
}
for (int i = 0; i < 64; ++i)
{
Codomain[(byte)Domain[i]] = i;
}
Codomain[(byte)'='] = 0;
}
byte v1, v2;
var reader = data.GetEnumerator();
reader.MoveNext();
var writer = new BufRefLen(result);
for (int i = 0; i < data.Length / 4; ++i)
{
v1 = Lookup(reader);
v2 = Lookup(reader);
v1 <<= 2;
v1 |= (byte)(v2 >> 4);
writer.Write8(v1);
if (writer.Length == 0)
{
break;
}
v2 <<= 4;
v1 = Lookup(reader);
v2 |= (byte)(v1 >> 2);
writer.Write8(v2);
if (writer.Length == 0)
{
break;
}
v2 = Lookup(reader);
v2 |= (byte)(v1 << 6);
writer.Write8(v2);
if (writer.Length == 0)
{
break;
}
}
return(result);
}