How to resolve the algorithm Chaocipher step by step in the FutureBasic programming language

Published on 12 May 2024 09:40 PM
#Futurebasic

How to resolve the algorithm Chaocipher step by step in the FutureBasic programming language

Table of Contents

Problem Statement

The Chaocipher was invented by J.F.Byrne in 1918 and, although simple by modern cryptographic standards, does not appear to have been broken until the algorithm was finally disclosed by his family in 2010. The algorithm is described in this paper by M.Rubin in 2010 and there is a C# implementation here.

Code the algorithm in your language and test that it works with the plaintext 'WELLDONEISBETTERTHANWELLSAID' used in the paper itself.

Let's start with the solution:

Step by Step solution about How to resolve the algorithm Chaocipher step by step in the FutureBasic programming language

Source code in the futurebasic programming language

begin enum
  _encrypt
  _decrypt
end enum

local fn chaocipher(orig as str255, action as byte, show as bool) as str255
  str255 leftStr, rightStr, out
  short  i, index
  leftStr  = "HXUCZVAMDSLKPEFJRIGTWOBNYQ"
  rightStr = "PTLNBQDEOYSFAVZKGJRIHWXUMC"
  orig     = ucase$(orig)
  out[0]   = orig[0]
  
  if show then print:print,"The left and right alphabets during encryption are:":print
  
  for i = 1 to orig[0]
    if show then print ,leftStr,,rightStr
    if action == _encrypt
      index  = instr$(0, rightStr, mid$(orig, i, 1))
      out[i] = leftStr[index]
    else
      index  = instr$(0, leftStr,  mid$(orig, i, 1))
      out[i] = rightStr[index]
    end if
    
    //leftStr permutation
    leftStr  = mid$(leftStr, index) + left$(leftStr, index-1)
    leftStr  = left$(leftStr, 1) + mid$(leftStr, 3, 12) + mid$(leftStr, 2, 1) + mid$(leftStr, 15)
    
    //rightStr permutation
    rightStr = mid$(rightStr, index+1) + left$(rightStr, index-1) + mid$(rightStr, index, 1)
    rightStr = left$(rightStr, 2) + mid$(rightStr, 4, 11) + mid$(rightStr, 3, 1) + mid$(rightStr, 15)
  next
  
end fn = out


str255 original, encrypted, decrypted
original = "WellDoneIsBetterThanWellSaid"

window 1, @"Chaocipher", ( 0, 0, 475, 550 )
print : print ,"The original text is: """;  original;  """"
encrypted = fn chaocipher(original, _encrypt, yes)
print : print ,"The encrypted text is: """; encrypted; """"
decrypted = fn chaocipher(encrypted, _decrypt, no)
print : print ,"The decrypted text is: """; decrypted; """"
handleevents

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