Diffie-Hellman鍵交換アルゴリズム

diffie_hellman.rb

require 'prime'

N = 100000

def nth_prime(n)
  Prime.each.take(n).last
end

def power(x, n)
  if n <= 1 then
    return (n == 1) ? x : 1
  end
  
  y = power(x, n / 2)
  z = y * y
  
  if (n % 2) == 1 then
    z = z * x	
  end
  
  return z
end

def diffie_hellman_main(g, n, x, y)
  p = power(g, x) % n
  q = power(g, y) % n
  a = power(q, x) % n
  b = power(p, y) % n
  return {:p => p, :q => q, :a => a, :b => b}
end

def diffie_hellman(g, n)
  x = Random.rand(N)
  y = Random.rand(N)
  return diffie_hellman_main(g, n, x, y)
end

def main(argv)
  n = nth_prime(Random.rand(N))
  g = Random.rand(n)
  puts diffie_hellman(g, n).to_s
end

if self.to_s == 'main' then
  main(ARGV)	
end