Diffie-Hellman key exchange in Ruby

ntk () — Mon, 01 Oct 2007 18:39:55 GMT

From: http://labs.musecurity.com/2007/05/09/diffie-hellman-in-ruby/
Author: kowsik





class Integer

    # Compute self ^ e mod m

    def mod_exp e, m

        result = 1

        b = self

        while e > 0

            result = (result * b) % m if e[0] == 1

            e = e >> 1

            b = (b * b) % m

        end

        return result

    end



    # A roundabout, slow but fun way of counting bits.

    def bits_set

        ("%b" % self).count('1')

        #to_s(2).count('1')   # alternative

        #count = 0         # alternative

        #byte = self.abs

        #count += byte & 1 and byte >>= 1 until byte == 0     # cf. http://snippets.dzone.com/posts/show/4233

        #count

    end

end





class DH

    attr_reader :p, :g, :q, :x, :e



    # p is the prime, g the generator and q order of the subgroup

    def initialize p, g, q

        @p = p

        @g = g

        @q = q

    end



    # generate the [secret] random value and the public key

    def generate tries=16

        tries.times do

            @x = rand(@q)

            @e = self.g.mod_exp(@x, self.p)

            return @e if self.valid?

        end

        raise ArgumentError, "can't generate valid e"

    end



    # validate a public key

    def valid? _e = self.e

        _e and _e.between?(2, self.p-2) and _e.bits_set > 1

    end



    # compute the shared secret, given the public key

    def secret f

        f.mod_exp(self.x, self.p)

    end

end



alice = DH.new(53, 5, 23)

bob   = DH.new(53, 5, 15)

alice.generate

bob.generate



alice_s = alice.secret(bob.e)

bob_s   = bob.secret(alice.e)

puts alice_s

puts bob_s

Ruby HMAC verifier

exabrial (Jon) — Sun, 05 Nov 2006 01:54:20 GMT

// Ruby script to verify the HMAC of a file or string.



#!/usr/bin/env ruby

#

#  Created by Jon (exabrial+hmacruby@gmail.com) on 2006-11-04.

#  Copyright (c) 2006. All rights reserved.

#  Released under MIT License



require 'openssl'

require "getopt/std"

include OpenSSL

include Digest



def printhelp

  help=<Purpose: Provides HMAC-SHA1 of a file or string. Text passwords are SHA1 hashed.

Usage: hmac.rb ["string to digest"] [-f (pathtofile)] [-k (pathtokeyfile)]

Options:

  -f (pathtofile) digests a file instead of a string

  -k (pathtokeyfile) does not prompt for key and uses the specified file as a key instead.

end

  puts help

  exit

end



if ARGV.size < 1

  printhelp

elsif ARGV.size==1

  @plaintext=ARGV.shift

else

  begin

    opt = Getopt::Std.getopts("f:k:")

  rescue Getopt::StdError

    printhelp

  end

  

  if opt["f"]

    @plaintext=File.read(opt["f"])

  end

  if opt["k"]

    @key=File.read(opt["k"])

  end

  

  printhelp if (!@plaintext&&!@key)

end



def getkey

  return @key if @key

  print "Please type your key then push enter:"

  return SHA1.new(gets()).to_s

end



def main

  hmacd=HMAC.new(getkey(), SHA1.new)

  hmacd.update(@plaintext)

  puts hmacd.to_s

end



main

DZone Snippets: cryptography code

Diffie-Hellman key exchange in Ruby

Ruby HMAC verifier