fish.rb

require 'rubygems'
require "crypt/blowfish"

if RUBY_VERSION.to_f >= 1.9
  module ::Crypt
    class Blowfish
      def setup_blowfish
        @sBoxes = Array.new(4) { |i| INITIALSBOXES[i].clone }
        @pArray = INITIALPARRAY.clone
        keypos = 0
        0.upto(17) { |i|
          data = 0
          4.times {
            data = ((data << 8) | @key[keypos].ord) % ULONG
            keypos = (keypos.next) % @key.length
          }
          @pArray[i] = (@pArray[i] ^ data) % ULONG
        }
        l = 0
        r = 0
        0.step(17, 2) { |i|
          l, r = encrypt_pair(l, r)
          @pArray[i]   = l
          @pArray[i+1] = r
        }
        0.upto(3) { |i|
          0.step(255, 2) { |j|
            l, r = encrypt_pair(l, r)
            @sBoxes[i][j]   = l
            @sBoxes[i][j+1] = r
          }
        }
      end
    end
  end
end

module IRC
  class BadInputError < StandardError; end
  
  class MBase64
    B64 = "./0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ"
    
    def self.decode encoded
      return nil if not encoded.length % 12 == 0
      
      decoded = String.new
      
      k = -1
      while (k < encoded.length - 1) do
        right = 0
        left = 0
        
        (0..5).each do |i|
          k = k + 1
          right |= B64.index(encoded[k]) << (i * 6)
        end
        
        (0..5).each do |i|
          k = k + 1
          left |= B64.index(encoded[k]) << (i * 6)
        end
        
        (0..3).each do |i|
          decoded += ((left & (0xFF << ((3 - i) * 8))) >> ((3 - i) * 8)).chr
        end
        
        (0..3).each do |i|
          decoded += ((right & (0xFF << ((3 - i) * 8))) >> ((3 - i) * 8)).chr
        end
      end
      
      return decoded
    end
    
    def self.encode decoded
      if not decoded.length % 8 == 0
        raise IRC::BadInputError,
          "can only encode strings which are a multiple of 8 characters."
      end
      
      encoded = String.new
      
      k = -1
      
      while (k < decoded.length - 1) do
        k = k.next
        left = (decoded[k].ord << 24)
        k = k.next
        left += (decoded[k].ord << 16)
        k = k.next
        left += (decoded[k].ord << 8)
        k = k.next
        left += decoded[k].ord
        
        k = k.next
        right = (decoded[k].ord << 24)
        k = k.next
        right += (decoded[k].ord << 16)
        k = k.next
        right += (decoded[k].ord << 8)
        k = k.next
        right += decoded[k].ord
        
        (0..5).each do
          encoded += B64[right & 0x3F].chr
          right = right >> 6
        end
        (0..5).each do
          encoded += B64[left & 0x3F].chr
          left = left >> 6
        end
      end
      
      return encoded
    end
  end
  
  class FiSH

      @blowfish = Crypt::Blowfish.new("some nice key here")
    
    def encrypt text
      text = pad(text, 8)
      result = ""
      
      num_block = text.length / 8
      num_block.times do |n|
        block = text[n*8..(n+1)*8-1]
        enc = @blowfish.encrypt_block(block)
        result += MBase64.encode(enc)
      end
      
      return result
    end
    
    def decrypt text
      return nil if not text.length % 12 == 0
      
      result = ""
      
      num_block = (text.length / 12).to_i
      num_block.times do |n|
        block = MBase64.decode( text[n*12..(n+1)*12-1] )
        result += @blowfish.decrypt_block(block)
      end
      
      return result.gsub /\0*$/, ""
    end
    
    private
    
    def pad text, n=8
      pad_num = n - (text.length % n)
      if pad_num > 0 and pad_num != n
        pad_num.times { text += 0.chr }
      end
      return text
    end
  end

end