private BigInteger RandomPrimeMSBSet(int bits)
{
if (bits <= 1)
{
throw new ArithmeticException("No primes with this bitcount");
}
BigInteger limit = ((BigInteger)1) << bits;
while (true)
{
var p = this.NextProbablePrime(BigIntegerHelper.SetBit(BigIntegerHelper.RandomIntBits(bits - 1), bits - 1));
if (p < limit)
{
return(p);
}
}
}
/*
* Re-randomization.
*/
BigInteger reRandomize(BigInteger cipher)
{
BigInteger r = BigIntegerHelper.RandomIntBits(DGK_BLINDING_T);
return(cipherAdd(cipher, cipherMul(h, r)));
}