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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 (e-mail address removed)
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#---------------------------------------------------------------------
# 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
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