Class: Cipher::DisruptedTransposition

Inherits:

SimpleCipher

• Object
• SimpleCipher
• Cipher::DisruptedTransposition

show all

Includes:

Crypto

Defined in:

lib/cipher.rb

Overview

http://users.telenet.be/d.rijmenants/en/handciphers.htm

Constant Summary

Constant Summary

Constants included from Crypto

Crypto::BASE

Instance Attribute Summary (collapse)

• - (Object) key readonly

  Returns the value of attribute key.

• - (Object) lkey readonly

  Returns the value of attribute lkey.

• - (Object) nkey readonly

  Returns the value of attribute nkey.

Instance Method Summary (collapse)

• - (Object) compute_holes(len)

  compute_holes.

• - (Object) decode

  decode.

• - (Object) encode(plain_text)

  encode.

• - (DisruptedTransposition) initialize(key) constructor

  A new instance of DisruptedTransposition.

Methods included from Crypto

#addmod10, #chainadd, #expand5to10, #find_hole, #keyshuffle, #normalize, #p1_encode, #str_to_numeric, #submod10

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# File 'lib/cipher.rb', line 108

def initialize(key)
  @key = Key::TKey.new(key)
  @nkey = @key.to_numeric
  @lkey = @nkey.size
end

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# File 'lib/cipher.rb', line 106

def key
  @key
end

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# File 'lib/cipher.rb', line 106

def lkey
  @lkey
end

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# File 'lib/cipher.rb', line 106

def nkey
  @nkey
end

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# File 'lib/cipher.rb', line 172

def compute_holes(len)
  #
  # We have potentially as many holes as we have key letters
  # but we have a much more simple stop condition, that is, the last
  # hole is incomplete
  #
  # Return the list of unavailable [x,y] (i.e. all areas merged)
  #
  holes = Array.new
  start_row = 0
  start_x = 0
  loop do
    pos = @nkey.index(start_x)
    hole = HoleArea.new(start_row, pos, @lkey - pos, len)
    holes << hole.a
    break unless hole.complete?
    start_x += 1
    start_row = start_row + hole.ylen
  end
  holes.flatten(1)
end

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# File 'lib/cipher.rb', line 162

def decode
  @msglen = plain_text.length
  holes = compute_holes(@msglen)

end

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# File 'lib/cipher.rb', line 116

def encode(plain_text)
  @msglen = plain_text.length
  holes = compute_holes(@msglen)

  j = 0
  t_len = @key.length
  table = Array.new(t_len) { '' }
  cipher_text = ''

  # 1st phase: fill in everything else than a hole
  #
  plain = plain_text.each_char.to_a
  for i in 0..(@msglen - 1) do
    pt = plain.shift
    #print "pt: #{pt} #{[i / t_len,j]} @nkey[#{j}]: #{@nkey[j]} "
    if holes.include?([i / t_len,j])
      table[@nkey[j]] << '.'
      plain.unshift(pt)
    else
      table[@nkey[j]] << pt
    end
    #puts " table[#{@nkey[j]}]: #{table[@nkey[j]]}"
    j = (j + 1) % t_len
  end

  # 2nd phase: fill in all holes
  #
  holes.each do |e|
    row = e[0]
    col = @nkey[e[1]]

    p = plain.shift
    curcol = table[col]
    curcol[row] = p
    #puts("holes: #{row},#{col} -> #{p} curcol: #{curcol}")
  end

  # Now take every column based upon key ordering
  #
  cipher_text = @nkey.sort.each.inject('') do |text, t|
    text +  table[t]
  end
end