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);
}
}
}