Class: Cipher::StraddlingCheckerboard

Inherits:
Substitution show all
Defined in:
lib/cipher.rb

Overview

StraddlingCheckerboard

This is the Straddling Checkerboard system (intended as a first pass to the Nihilist cipher and possibly others).

Instance Attribute Summary

Attributes inherited from Substitution

#key

Instance Method Summary (collapse)

Constructor Details

- (StraddlingCheckerboard) initialize(key)

Returns a new instance of StraddlingCheckerboard



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# File 'lib/cipher.rb', line 203

def initialize(key)
  @key = Key::SCKey.new(key)
end

Instance Method Details

- (Object) decode(cipher_text)

decode



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# File 'lib/cipher.rb', line 222

def decode(cipher_text)
  plain_text = ""

  ct = cipher_text.dup
  in_numbers = false
  while ct.length != 0 do
    c = ct.slice!(0,1)
    #
    # XXX US-ASCII hack
    #
    d = c.ord - 48
    if @key.is_long?(d)
      c << ct.slice!(0,1)
    end
    pt = @key.decode(c)
    #
    # Number shift
    #
    if pt == '/' then
      if in_numbers then
        in_numbers = false
      else
        in_numbers = true
      end
    else
      if in_numbers then
        pt = ct.slice!(0,1)[0]
      end
      plain_text << pt
    end
  end
  return plain_text
end

- (Object) encode(plain_text)

encode



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# File 'lib/cipher.rb', line 209

def encode(plain_text)
  cipher_text = plain_text.each_char.inject('') do |text, c|
    if c >= '0' and c <= '9' then
      text << @key.encode('/') << c + c << @key.encode('/')
    else
      text << @key.encode(c)
    end
  end
  return cipher_text
end