private EG_Secret_Key GenerateKey(int nBits)
{
BigInteger q = new BigInteger();
BigInteger p;
BigInteger g;
BigInteger gPowTwo;
BigInteger gPowQ;
EG_Secret_Key eskKey = new EG_Secret_Key();
/*
// construct a prime p = 2q + 1
do {
q = BigInteger.genRandom(nBits - 1);
System.Windows.Forms.Application.DoEvents();
p = (2*q) + 1;
} while ((!p.isProbablePrime()) || (!q.isProbablePrime()));
*/
q = BigInteger.genPseudoPrime(nBits - 1);
p = BigInteger.genPseudoPrime(nBits);
// find a generator
do {
g = new BigInteger();
g = BigInteger.genRandom(nBits - 1);
gPowTwo = g.modPow(new BigInteger(2), p);
gPowQ = g.modPow(q, p);
} while ((gPowTwo == 1) || (gPowQ == 1));
BigInteger x;
do {
x = new BigInteger();
x = BigInteger.genRandom(nBits);
} while (x >= p-1);
BigInteger y = g.modPow(x, p);
eskKey.p = p;
eskKey.g = g;
eskKey.x = x;
eskKey.y = y;
return eskKey;
}
private DSA_Secret_Key GenerateParams(int keyLength)
{
byte[] seed = new byte[20];
byte[] part1 = new byte[20];
byte[] part2 = new byte[20];
byte[] u = new byte[20];
RandomNumberGenerator rng = RandomNumberGenerator.Create();
BigInteger p = new BigInteger(); // prime
BigInteger q = new BigInteger(); // group order
BigInteger g; // group generator
DSA_Secret_Key dskKey = new DSA_Secret_Key();
SHA1 sha = SHA1.Create();
int n = (keyLength - 1) / 160;
byte[] w = new byte [keyLength / 8];
bool primesFound = false;
while (!primesFound) {
do {
rng.GetBytes(seed);
part1 = sha.ComputeHash(seed);
Array.Copy(seed, 0, part2, 0, seed.Length);
add(part2, seed, 1);
part2 = sha.ComputeHash(part2);
for (int i = 0; i != u.Length; i++)
u[i] = (byte)(part1[i] ^ part2[i]);
// first bit must be set (to respect key length)
u[0] |= (byte)0x80;
// last bit must be set (prime are all odds - except 2)
u[19] |= (byte)0x01;
q = new BigInteger(u);
} while (!q.isProbablePrime());
int counter = 0;
int offset = 2;
while (counter < 4096) {
for (int k = 0; k < n; k++) {
add(part1, seed, offset + k);
part1 = sha.ComputeHash(part1);
Array.Copy(part1, 0, w, w.Length - (k + 1) * part1.Length, part1.Length);
}
add(part1, seed, offset + n);
part1 = sha.ComputeHash(part1);
Array.Copy(part1, part1.Length - ((w.Length - (n) * part1.Length)), w, 0, w.Length - n * part1.Length);
w[0] |= (byte)0x80;
BigInteger xx = new BigInteger (w);
BigInteger c = xx % (q * 2);
p = xx - (c - 1);
if (p.testBit((uint)(keyLength - 1))) {
if (p.isProbablePrime()) {
primesFound = true;
break;
}
}
counter += 1;
offset += n + 1;
}
}
// calculate the generator g
BigInteger pMinusOneOverQ = (p - 1) / q;
for (;;) {
BigInteger h = new BigInteger();
h = BigInteger.genRandom(keyLength);
if ((h <= 1) || (h >= (p - 1)))
continue;
g = h.modPow(pMinusOneOverQ, p);
if (g <= 1)
continue;
break;
}
dskKey.p = p;
dskKey.q = q;
dskKey.g = g;
return dskKey;
}
private BigInteger[] Encrypt(BigInteger biPlain, RSA_Public_Key rpkKey)
{
if ((rpkKey.e == 0) || (rpkKey.n == 0))
throw new System.ArgumentException("This is not a valid public key");
BigInteger biCipher = biPlain.modPow(rpkKey.e, rpkKey.n);
BigInteger[] biOutput = new BigInteger[1];
biOutput[0] = biCipher;
return biOutput;
}
