aes.rb

=begin
Copyright 2018 strict-flower

Permission is hereby granted, free of charge, to any person obtaining a
copy of this software and associated documentation files (the "Software"),
to deal in the Software without restriction, including without limitation
the rights to use, copy, modify, merge, publish, distribute, sublicense,
and/or sell copies of the Software, and to permit persons to whom the
Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in
all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
IN THE SOFTWARE.
=end

require_relative './aes_table' # https://pastebin.com/UWLstSg8
require 'matrix'

# Galois field implementation (simple ver)
class Fixnum
  alias_method :integer_add, :+
  alias_method :integer_sub, :-
  alias_method :integer_mul, :*
  alias_method :integer_div, :/

  def +(other)
    self ^ other.to_i
  end

  def -(other)
    self + other
  end

  def -@
    self
  end

  def /(other)
    raise 1 # assertion
  end

  def *(other)
    if self == 0
      0
    elsif self == 1
      other
    else
      other = other.to_i
      if other == 0
        0
      elsif other == 1
        self
      else
        if $mult_table.keys.include?(other)
          $mult_table[other][self]
        elsif $mult_table.keys.include?(self)
          $mult_table[self][other]
        else
          raise "Invalid Argument"
        end
      end
    end
  end
end

class AESMatrix < Matrix
  def self.to_mat(data)
    data = data.to_a
    raise unless data.length == 16
    AESMatrix.columns(data.each_slice(4).to_a)
  end

  def to_a
    t.rows.flatten
  end
end

def SubBytes(t)
  t.map{|x| $sbox[x]}
end

def SubBytesInv(t)
  t.map{|x| $sboxinv[x]}
end

$P = AESMatrix.to_mat([2, 1, 1, 3, 3, 2, 1, 1, 1, 3, 2, 1, 1, 1, 3, 2])
$PInv = AESMatrix.to_mat([14, 9, 13, 11, 11, 14, 9, 13, 13, 11, 14, 9, 9, 13, 11, 14])

def MixColumns(t)
  t * $P
end

def MixColumnsInv(t)
  t * $PInv
end

def ShiftRows(t)
  m = t[0, 0..3]
  m << t[1, 1..3]
  m << t[1, 0]
  m << t[2, 2..3]
  m << t[2, 0..1]
  m << t[3, 3..3]
  m << t[3, 0..2]
  m.flatten!
  AESMatrix.rows(m.each_slice(4).to_a)
end

def ShiftRowsInv(t)
  m = t[0, 0..3]
  m << t[1, 3]
  m << t[1, 0..2]
  m << t[2, 2..3]
  m << t[2, 0..1]
  m << t[3, 1..3]
  m << t[3, 0]
  m.flatten!
  AESMatrix.rows(m.each_slice(4).to_a)
end

def AddRoundKey(t, key)
  t + key
end

alias AddRoundKeyInv AddRoundKey

def RoundFunc(r, state, key)
  state = SubBytes(state)
  state = ShiftRows(state)
  if r != $r - 1
    state = MixColumns(state)
  end
  AddRoundKey(state, key)
end

def RoundFuncInv(r, state, key)
  AddRoundKeyInv(state, key)
  if r != $r - 1
    state = MixColumnsInv(state)
  end
  state = SubBytesInv(state)
  ShiftRowsInv(state)
end

def encrypt(m, key)
  state = AESMatrix.to_mat(m)
  key = AESMatrix.to_mat(key)

  state = AddRoundKey(state, key)
  $r.times { |r|
    state = RoundFunc(r, state, key)
    puts r
  }
  state.to_a
end

def decrypt(c, key)
  state = AESMatrix.to_mat(c)
  key = AESMatrix.to_mat(key)

  $r.times { |_r|
    r = $r.integer_sub(_r).integer_sub(1)
    state = RoundFuncInv(r, state, key)
  }
  AddRoundKeyInv(state, key).to_a
end

$r = 10
m = [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15]
k = [0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0]

p encrypt(m, k)
p decrypt(encrypt(m, k), k)

raise unless 1 + 1 == 0
raise unless $PInv * $P == AESMatrix.I(4)
raise unless $P * $PInv == AESMatrix.I(4)
raise unless $P + $P == AESMatrix.zero(4)