dh.rb
89 lines
| 2.7 KiB
| text/x-ruby
|
RubyLexer
Eric Davis
|
r2376 | require "openid/util" | ||
| require "openid/cryptutil" | ||||
| module OpenID | ||||
| # Encapsulates a Diffie-Hellman key exchange. This class is used | ||||
| # internally by both the consumer and server objects. | ||||
| # | ||||
| # Read more about Diffie-Hellman on wikipedia: | ||||
| # http://en.wikipedia.org/wiki/Diffie-Hellman | ||||
| class DiffieHellman | ||||
| # From the OpenID specification | ||||
| @@default_mod = 155172898181473697471232257763715539915724801966915404479707795314057629378541917580651227423698188993727816152646631438561595825688188889951272158842675419950341258706556549803580104870537681476726513255747040765857479291291572334510643245094715007229621094194349783925984760375594985848253359305585439638443 | ||||
| @@default_gen = 2 | ||||
| attr_reader :modulus, :generator, :public | ||||
| # A new DiffieHellman object, using the modulus and generator from | ||||
| # the OpenID specification | ||||
| def DiffieHellman.from_defaults | ||||
| DiffieHellman.new(@@default_mod, @@default_gen) | ||||
| end | ||||
| def initialize(modulus=nil, generator=nil, priv=nil) | ||||
| @modulus = modulus.nil? ? @@default_mod : modulus | ||||
| @generator = generator.nil? ? @@default_gen : generator | ||||
| set_private(priv.nil? ? OpenID::CryptUtil.rand(@modulus-2) + 1 : priv) | ||||
| end | ||||
| def get_shared_secret(composite) | ||||
| DiffieHellman.powermod(composite, @private, @modulus) | ||||
| end | ||||
| def xor_secret(algorithm, composite, secret) | ||||
| dh_shared = get_shared_secret(composite) | ||||
| packed_dh_shared = OpenID::CryptUtil.num_to_binary(dh_shared) | ||||
| hashed_dh_shared = algorithm.call(packed_dh_shared) | ||||
| return DiffieHellman.strxor(secret, hashed_dh_shared) | ||||
| end | ||||
| def using_default_values? | ||||
| @generator == @@default_gen && @modulus == @@default_mod | ||||
| end | ||||
| private | ||||
| def set_private(priv) | ||||
| @private = priv | ||||
| @public = DiffieHellman.powermod(@generator, @private, @modulus) | ||||
| end | ||||
| def DiffieHellman.strxor(s, t) | ||||
| if s.length != t.length | ||||
| raise ArgumentError, "strxor: lengths don't match. " + | ||||
| "Inputs were #{s.inspect} and #{t.inspect}" | ||||
| end | ||||
| if String.method_defined? :bytes | ||||
| s.bytes.zip(t.bytes).map{|sb,tb| sb^tb}.pack('C*') | ||||
| else | ||||
| indices = 0...(s.length) | ||||
| chrs = indices.collect {|i| (s[i]^t[i]).chr} | ||||
| chrs.join("") | ||||
| end | ||||
| end | ||||
| # This code is taken from this post: | ||||
| # <http://blade.nagaokaut.ac.jp/cgi-bin/scat.\rb/ruby/ruby-talk/19098> | ||||
| # by Eric Lee Green. | ||||
| def DiffieHellman.powermod(x, n, q) | ||||
| counter=0 | ||||
| n_p=n | ||||
| y_p=1 | ||||
| z_p=x | ||||
| while n_p != 0 | ||||
| if n_p[0]==1 | ||||
| y_p=(y_p*z_p) % q | ||||
| end | ||||
| n_p = n_p >> 1 | ||||
| z_p = (z_p * z_p) % q | ||||
| counter += 1 | ||||
| end | ||||
| return y_p | ||||
| end | ||||
| end | ||||
| end | ||||