Module: SubstitutionCipher

Defined in:
lib/accu-cipher.rb

Overview

Module containing the classes and methods of the library.

Constant Summary collapse

ALPHA_RANGE = 
97..122

Class Method Summary collapse

Class Method Details

.crack_offset(string) ⇒ Object

A method to crack (with the users help) a string that has been “encrypted” with SubstitutionCipher#encrypt.



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# File 'lib/accu-cipher.rb', line 90

def self.crack_offset(string)
  first = Time.now
  range = 1..25
  complete = false
  range.to_a.each do |value|
    puts "\n-------------\n\n"
    puts self.decrypt(string,value)
    puts "\n-------------\n\n"
    puts "Valid? |Y N|"
    result = gets.chomp.downcase
    if result == "y" then
      complete = value
      break
    end
  end
  puts "\n-------------\n\n"
  if not complete then
    puts "Crack failed."
  else
    puts "Offset: #{complete}\nTime taken: #{Time.now-first}"
  end
  return complete
end

.decrypt(string, offset = 3) ⇒ Object

“Decrypt” a string via a substitution cipher.



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# File 'lib/accu-cipher.rb', line 70

def self.decrypt(string,offset=3)
  string = self.purge_nonalpha string
  final = ""
  string.split("").each_with_index do |source,index|
    if (not source.ord == 10 and not source.ord == 32) then
      result = source.ord - offset
      if not SubstitutionCipher::ALPHA_RANGE.include? source.ord then
        result += 25
      end
    else
      result = source.ord
    end
    final << result.chr
  end
  return final
end

.encrypt(string, offset = 3) ⇒ Object

“Encrypt” a string via a substitution cipher.



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# File 'lib/accu-cipher.rb', line 51

def self.encrypt(string,offset=3)
  string = self.purge_nonalpha string
  final = ""
  string.split("").each_with_index do |source,index|
    if (not source.ord == 10 and not source.ord == 32) then
      result = source.ord + offset
      if not SubstitutionCipher::ALPHA_RANGE.include? source.ord then
        result -= 25
      end
    else
      result = source.ord
    end
    final << result.chr
  end
  return final
end

.purge_nonalpha(text) ⇒ Object

Remove non-alphabetical letters from plaintext (bar spaces and newlines)



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# File 'lib/accu-cipher.rb', line 35

def self.purge_nonalpha(text)
  text = text.dup.downcase
  table = []
  text.split("").each_with_index do |source,index|
    if not SubstitutionCipher::ALPHA_RANGE.include? source.ord and (not source.ord == 10 and not source.ord == 32) then
      table << index
    end
  end
  table.reverse.each do |index|
    text[index] = ""
  end
  return text
end