そすうをつくります。

primenumber.rb

module PrimeNumber 
    def self.powmod(base, exp, mod)
        return 1 if exp == 0
        exp.bit_length.times.inject(1) do |buf, i|
            (buf ** 2) * (base ** exp[exp.bit_length - 1 - i]) % mod
        end
    end

    def self.miller_rabin_prime?(num, trial)
        return false if num.even? || num < 3
        odd_factor = num - 1
        exp2 = 0
        while odd_factor.even? do exp2 += 1; odd_factor >>= 1 end

        srand()
        trial.times do 
            witness = rand(2...num)
            m = powmod(witness, odd_factor, num)

            return true if m == 1
            exp2.times do |i|
                return true if m == num - 1
                m = m ** 2 % num
            end
        end

        return false
    end       

    def self.generate_primenumber(len = 1024, miller_rabin_trial = 4)
        rand_max = 1 << (len - 2)

        q = 0

        srand()
        until miller_rabin_prime?(q, miller_rabin_trial)
            q = ((rand(rand_max) + rand_max) << 1) + 1
        end

        return q
    end
end

t = Time.now
prime = PrimeNumber.generate_primenumber.to_s(16)
t = Time.now - t

print prime, "\n\ngenerating time: ", t, "[s]\n\n"

system("echo #{prime}| clip")
system('pause')