public static (CryptideKey sec, CryptideKey pub) Generate(int bitSize = 128)
{
var(p, q) = Utils.RandomPrime(bitSize);
var g = Utils.GetPrimitiveRoot(p);
using (var rdmGen = new RandomField(q)) {
var x = rdmGen.Generate(BigInteger.One);
var y = BigInteger.ModPow(g, x, p);
return(new CryptideKey(true, p, g, x), new CryptideKey(false, p, g, y));
}
}
public byte[] EncryptBuffer(string data)
{
var ms = Utils.Decode(data, Bits);
var nums = new List <BigInteger>();
using (var rdm = new RandomField(P)) {
for (var i = 0; i < ms.Count; i++)
{
var r = rdm.Generate();
var c1 = BigInteger.ModPow(G, r, P);
var c2 = BigInteger.Remainder(ms[i] * BigInteger.ModPow(Key, r, P), P);
nums.Add(c1);
nums.Add(c2);
}
}
return(Utils.EncodeByteArray(nums, Bits, true));
}
public static BigInteger getPrimitiveRoot(BigInteger p)
{
if (p == new BigInteger(2))
{
return(BigInteger.One);
}
var min = new BigInteger(3); // Avoid g=2 because of Bleichenbacher's attack
var p1 = new BigInteger(2); // The prime divisors of p-1 are 2 and (p-1)/2
var p2 = (p - 1) / 2; // Because: p = 2q + 1 where q is a prime
using (var rdmGen = new RandomField(p)) {
while (true)
{
var g = rdmGen.Generate(min);
if (BigInteger.ModPow(g, p1, p) != BigInteger.One &&
BigInteger.ModPow(g, p2, p) != BigInteger.One &&
BigInteger.Remainder(p - 1, g) != BigInteger.Zero && // g|p-1
BigInteger.Remainder(p - 1, BigInteger.ModPow(g, p - 2, p)) != BigInteger.Zero) // g^(-1)|p-1 (evades Khadir's attack)
{
return(g);
}
}
}
}
