charcoal.rb

# Copyright 2012 Jesse Zilstorff

module Charcoal
    def self.encrypt(stream, key)
        last = key.first
        stream.bytes.with_index.map do |byte, index|
            key.unshift(last = index ^ key.pop ^ last)
            byte ^ last
        end.pack("C*")
    end
    def self.encrypt_blocks(instream, outstream, key)
        buffer = ""
        blksize = instream.stat.blksize
        while instream.read(blksize, buffer)
            outstream.write(encrypt(buffer, key))
        end
    end
end

Charcoal.encrypt_blocks(
    File.new(ARGV.first),
    File.new(ARGV.last, IO::CREAT|IO::WRONLY),
    "AS<k-_5\y[K`,~aqQrm~8{rI#lw=T|DI".bytes.to_a
    #"rLUQk!uiq5)<4d|7ZURd9k6H~(Mxtd1@".bytes.to_a
)