From: Jeremy Hinegardner Date: 2005-06-08T16:41:33+09:00 Subject: Re: Ruby version ot TEA (Tiny Encryption Alogrithm)? --vkogqOf2sHV7VnPd Content-Type: text/plain; charset=us-ascii Content-Disposition: inline On Wed, Jun 08, 2005 at 06:10:27AM +0900, James Britt wrote: > Does anyone know of a pure-Ruby lib that implements the Tiny Encryption > Algorithm? I couldn't find one, and I happened to be a bit bored this evening... so will this do? If this code is going to be used to both encrypt and decrypt then it should work. Not sure how it will interact well with other implementations. The conversions of the encrypted longs to printable text could be done in any number of manners. I took the easy route and just converted the longs to hex. I would appreciate it if someone double checked my implementation. And I'm sure there are speed improvements. I went for readability. enjoy, -jeremy -- ======================================================================== Jeremy Hinegardner jeremy@hinegardner.org --vkogqOf2sHV7VnPd Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="tea.rb" #--------------------------------------------------------------------- # This is a pure ruby implementation of the Tiny Encryption Algorithm # (TEA) by David Wheeler and Roger Needham of the Cambridge Computer # Laboratory. # # For more information: # # http://www.simonshepherd.supanet.com/tea.htm # # This is an implementation of the 'New Variant' of the cipher. #--------------------------------------------------------------------- require 'digest/md5' class Crypt class TEA DELTA = 0x9e3779b9 ITERATIONS = 32 #------------------------------------------------------------- # encrypt the given plaintext with the given key, where the key # is a text pass phrase #------------------------------------------------------------- def self.encrypt(plain_text,pass_phrase) tea =TEA.new tea.encrypt(plain_text,pass_phrase) end #------------------------------------------------------------- # decrypt the given ciphertext with the given key, where the key # is a text pass phrase #------------------------------------------------------------- def self.decrypt(cipher_text,pass_phrase) tea = TEA.new tea.decrypt(cipher_text,pass_phrase) end #------------------------------------------------------------- def encrypt(plain_text,pass_phrase) key = passphrase_to_key(pass_phrase) # pad the plaintext to a length modulo 8 # and preface the string with how many padding characters # there where, including itself to_pad = 8 - plain_text.length % 8 plain_text = "#{to_pad}#{plain_text}" 1.upto(to_pad-1) do |i| plain_text = plain_text + rand(0xff).chr end cipher_text = [] # for each 8 char's pack them into 2 ints range = Range.new(0,plain_text.length,true) range.step(8) do |n| num1 = plain_text[n].to_i << 24 num1 += plain_text[n+1].to_i << 16 num1 += plain_text[n+2].to_i << 8 num1 += plain_text[n+3].to_i num2 = plain_text[n+4].to_i << 24 num2 += plain_text[n+5].to_i << 16 num2 += plain_text[n+6].to_i << 8 num2 += plain_text[n+7].to_i enum1,enum2 = encrypt_chunk(num1,num2,key) cipher_text << enum1 cipher_text << enum2 end cipher_text.collect { |c| sprintf("%.8x",c) }.join('') end #------------------------------------------------------------- def decrypt(cipher_text,pass_phrase) key = passphrase_to_key(pass_phrase) plain_text = [] # convert the cipher_text into an array of 2 character # strings cipher_array = cipher_text.scan(/../) # for each 8 char's pack them into 2 ints range = Range.new(0,cipher_array.length,true) range.step(8) do |n| num1 = cipher_array[n].to_i(16) << 24 num1 += cipher_array[n+1].to_i(16) << 16 num1 += cipher_array[n+2].to_i(16) << 8 num1 += cipher_array[n+3].to_i(16) num2 = cipher_array[n+4].to_i(16) << 24 num2 += cipher_array[n+5].to_i(16) << 16 num2 += cipher_array[n+6].to_i(16) << 8 num2 += cipher_array[n+7].to_i(16) enum1,enum2 = decrypt_chunk(num1,num2,key) plain_text << ((enum1 & 0xFF000000) >> 24) plain_text << ((enum1 & 0x00FF0000) >> 16) plain_text << ((enum1 & 0x0000FF00) >> 8) plain_text << ((enum1 & 0x000000FF)) plain_text << ((enum2 & 0xFF000000) >> 24) plain_text << ((enum2 & 0x00FF0000) >> 16) plain_text << ((enum2 & 0x0000FF00) >> 8) plain_text << ((enum2 & 0x000000FF)) end pad_count = plain_text.shift.chr.to_i (pad_count - 1).times { |i| plain_text.pop } plain_text.collect { |c| c.chr }.join("") end ############ private ############ #------------------------------------------------------------- # convert the given passphrase to and MD5 sum and get the 128 # bit key as 4 x 32 bit ints #------------------------------------------------------------- def passphrase_to_key(pass_phrase) Digest::MD5.digest(pass_phrase).unpack('L*') end #------------------------------------------------------------- # encrypt 2 of the integers ( 8 characters ) of the input into # the cipher text output #------------------------------------------------------------- def encrypt_chunk(num1,num2,key) y,z,sum = num1,num2,0 ITERATIONS.times do |i| y += ( z << 4 ^ z >> 5) + z ^ sum + key[sum & 3] y = y & 0xFFFFFFFF; sum += DELTA z += ( y << 4 ^ y >> 5) + y ^ sum + key[sum >> 11 & 3] z = z & 0xFFFFFFFF; # ruby can keep on getting bigger because of Bignum so # you have to and with 0xFFFFFFFF to get the Fixnum # bytes end return [y,z] end #------------------------------------------------------------- # decrypt 2 of the integer cipher texts into the plaintext #------------------------------------------------------------- def decrypt_chunk(num1,num2,key) y,z = num1,num2 sum = DELTA << 5 ITERATIONS.times do |i| z -= ( y << 4 ^ y >> 5) + y ^ sum + key[sum >> 11 & 3] z = z & 0xFFFFFFFF sum -= DELTA y -= ( z << 4 ^ z >> 5) + z ^ sum + key[sum & 3] y = y & 0xFFFFFFFF end return [y,z] end end end if __FILE__ == $0 then plain_text = "Just another Ruby Hacker!" pass_phrase = "I love ruby" puts "encrypting\t[#{plain_text}]" cipher_text = Crypt::TEA.encrypt(plain_text,pass_phrase) puts "decrypting\t[#{cipher_text}]" decrypted_text = Crypt::TEA.decrypt(cipher_text,pass_phrase) puts "decrypted text\t[#{decrypted_text}]" end --vkogqOf2sHV7VnPd--