Chaocipher

Description

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.

Task

The task is to code the algorithm in your language and to test that it works with the plaintext 'WELLDONEISBETTERTHANWELLSAID' used in the paper itself.

C

Translation of: Kotlin

<lang c>#include <stdio.h>

include <string.h>
include <stdlib.h>

define TRUE 1
define FALSE 0

typedef int bool; typedef enum { ENCRYPT, DECRYPT } cmode;

const char *l_alphabet = "HXUCZVAMDSLKPEFJRIGTWOBNYQ"; const char *r_alphabet = "PTLNBQDEOYSFAVZKGJRIHWXUMC";

void chao(const char *in, char *out, cmode mode, bool show_steps) {

   int i, j, index;
   char store;
   size_t len = strlen(in);
   char left[27], right[27], temp[27];
   strcpy(left, l_alphabet);
   strcpy(right, r_alphabet);
   temp[26] = '\0';

   for (i = 0; i < len; ++i ) {
       if (show_steps) printf("%s  %s\n", left, right);
       if (mode == ENCRYPT) {
           index = strchr(right, in[i]) - right;
           out[i] = left[index];
       }
       else {
           index = strchr(left, in[i]) - left;
           out[i] = right[index];
       }
       if (i == len - 1) break;

       /* permute left */

       for (j = index; j < 26; ++j) temp[j - index] = left[j];
       for (j = 0; j < index; ++j) temp[26 - index + j] = left[j];
       store = temp[1];
       for (j = 2; j < 14; ++j) temp[j - 1] = temp[j];
       temp[13] = store;
       strcpy(left, temp);

       /* permute right */

       for (j = index; j < 26; ++j) temp[j - index] = right[j];
       for (j = 0; j < index; ++j) temp[26 - index + j] = right[j];
       store = temp[0];
       for (j = 1; j < 26; ++j) temp[j - 1] = temp[j];
       temp[25] = store;
       store = temp[2];
       for (j = 3; j < 14; ++j) temp[j - 1] = temp[j];
       temp[13] = store;
       strcpy(right, temp);
   }

}

int main() {

   const char *plain_text = "WELLDONEISBETTERTHANWELLSAID";
   char *cipher_text = malloc(strlen(plain_text) + 1);
   char *plain_text2 = malloc(strlen(plain_text) + 1);
   printf("The original plaintext is : %s\n", plain_text);
   printf("\nThe left and right alphabets after each permutation"
          " during encryption are :\n\n");
   chao(plain_text, cipher_text, ENCRYPT, TRUE);
   printf("\nThe ciphertext is : %s\n", cipher_text);
   chao(cipher_text, plain_text2, DECRYPT, FALSE);
   printf("\nThe recovered plaintext is : %s\n", plain_text2);
   free(cipher_text);
   free(plain_text2);
   return 0;

}</lang>

Output:

The original plaintext is : WELLDONEISBETTERTHANWELLSAID

The left and right alphabets after each permutation during encryption are :

HXUCZVAMDSLKPEFJRIGTWOBNYQ  PTLNBQDEOYSFAVZKGJRIHWXUMC
ONYQHXUCZVAMDBSLKPEFJRIGTW  XUCPTLNBQDEOYMSFAVZKGJRIHW
ADBSLKPEFJRIGMTWONYQHXUCZV  OYSFAVZKGJRIHMWXUCPTLNBQDE
HUCZVADBSLKPEXFJRIGMTWONYQ  NBDEOYSFAVZKGQJRIHMWXUCPTL
QUCZVADBSLKPEHXFJRIGMTWONY  NBEOYSFAVZKGQDJRIHMWXUCPTL
HFJRIGMTWONYQXUCZVADBSLKPE  JRHMWXUCPTLNBIEOYSFAVZKGQD
CVADBSLKPEHFJZRIGMTWONYQXU  YSAVZKGQDJRHMFWXUCPTLNBIEO
NQXUCVADBSLKPYEHFJZRIGMTWO  BIOYSAVZKGQDJERHMFWXUCPTLN
YHFJZRIGMTWONEQXUCVADBSLKP  RHFWXUCPTLNBIMOYSAVZKGQDJE
NQXUCVADBSLKPEYHFJZRIGMTWO  MOSAVZKGQDJERYHFWXUCPTLNBI
XCVADBSLKPEYHUFJZRIGMTWONQ  AVKGQDJERYHFWZXUCPTLNBIMOS
TONQXCVADBSLKWPEYHUFJZRIGM  IMSAVKGQDJERYOHFWZXUCPTLNB
SKWPEYHUFJZRILGMTONQXCVADB  RYHFWZXUCPTLNOBIMSAVKGQDJE
ZILGMTONQXCVARDBSKWPEYHUFJ  LNBIMSAVKGQDJOERYHFWZXUCPT
JILGMTONQXCVAZRDBSKWPEYHUF  LNIMSAVKGQDJOBERYHFWZXUCPT
RBSKWPEYHUFJIDLGMTONQXCVAZ  RYFWZXUCPTLNIHMSAVKGQDJOBE
RSKWPEYHUFJIDBLGMTONQXCVAZ  YFZXUCPTLNIHMWSAVKGQDJOBER
HFJIDBLGMTONQUXCVAZRSKWPEY  LNHMWSAVKGQDJIOBERYFZXUCPT
JDBLGMTONQUXCIVAZRSKWPEYHF  MWAVKGQDJIOBESRYFZXUCPTLNH
BGMTONQUXCIVALZRSKWPEYHFJD  VKQDJIOBESRYFGZXUCPTLNHMWA
YFJDBGMTONQUXHCIVALZRSKWPE  HMAVKQDJIOBESWRYFGZXUCPTLN
HIVALZRSKWPEYCFJDBGMTONQUX  RYGZXUCPTLNHMFAVKQDJIOBESW
QXHIVALZRSKWPUEYCFJDBGMTON  SWYGZXUCPTLNHRMFAVKQDJIOBE
KPUEYCFJDBGMTWONQXHIVALZRS  NHMFAVKQDJIOBRESWYGZXUCPTL
SPUEYCFJDBGMTKWONQXHIVALZR  NHFAVKQDJIOBRMESWYGZXUCPTL
OQXHIVALZRSPUNEYCFJDBGMTKW  WYZXUCPTLNHFAGVKQDJIOBRMES
UEYCFJDBGMTKWNOQXHIVALZRSP  GVQDJIOBRMESWKYZXUCPTLNHFA
JBGMTKWNOQXHIDVALZRSPUEYCF  OBMESWKYZXUCPRTLNHFAGVQDJI

The ciphertext is : OAHQHCNYNXTSZJRRHJBYHQKSOUJY

The recovered plaintext is : WELLDONEISBETTERTHANWELLSAID

Factor

<lang factor>USING: arrays combinators fry io kernel locals math namespaces prettyprint sequences sequences.extras strings ; IN: rosetta-code.chaocipher

CONSTANT: zenith 0 CONSTANT: nadir 13

SYMBOLS: l-alphabet r-alphabet last-index ;

init-alphabets ( -- )

   "HXUCZVAMDSLKPEFJRIGTWOBNYQ" l-alphabet
   "PTLNBQDEOYSFAVZKGJRIHWXUMC" r-alphabet [ set ] 2bi@ ;

zero-alphabet ( seq -- seq' )

   last-index get rotate ;

3append ( a b c d -- abcd )

   append append append ;

permute-l-alphabet ( -- )

   l-alphabet get zero-alphabet dup
   zenith 1 + swap nth :> extracted-char
   {
       [ 1 head ]
       [ nadir 1 + head 2 tail ]
       [ drop extracted-char 1string ]
       [ nadir 1 + tail ]
   } cleave
   3append l-alphabet set ;

permute-r-alphabet ( -- )

   r-alphabet get zero-alphabet
   1 rotate dup
   zenith 2 + swap nth :> extracted-char
   {
       [ 2 head ]
       [ nadir 1 + head 3 tail ]
       [ drop extracted-char 1string ]
       [ nadir 1 + tail ]
   } cleave
   3append r-alphabet set ;

encipher-char ( char alpha1 alpha2 -- char' )

   '[ _ get index dup last-index set _ get nth ] call ;

encipher ( str quot -- str' )

   [ permute-l-alphabet permute-r-alphabet ] compose map
   init-alphabets ; inline

encrypt ( str -- str' )

   [ r-alphabet l-alphabet encipher-char ] encipher ;

decrypt ( str -- str' )

   [ l-alphabet r-alphabet encipher-char ] encipher ;

main ( -- )

   init-alphabets
   "WELLDONEISBETTERTHANWELLSAID" encrypt dup decrypt
   [ print ] bi@ ;

MAIN: main</lang>

Output:

WELLDONEISBETTERTHANWELLSAID
OAHQHCNYNXTSZJRRHJBYHQKSOUJY

Kotlin

This is based on the C# implementation referred to in the task description, except that the encrypt and decrypt operations are combined into a single method. <lang scala>// Version 1.2.40

enum class Mode { ENCRYPT, DECRYPT }

object Chao {

   private val lAlphabet = "HXUCZVAMDSLKPEFJRIGTWOBNYQ"
   private val rAlphabet = "PTLNBQDEOYSFAVZKGJRIHWXUMC"

   fun exec(text: String, mode: Mode, showSteps: Boolean = false): String {
       var left  = lAlphabet
       var right = rAlphabet
       val eText = CharArray(text.length)
       val temp  = CharArray(26)

       for (i in 0 until text.length) {
           if (showSteps) println("$left  $right")
           var index: Int
           if (mode == Mode.ENCRYPT) {
               index = right.indexOf(text[i])
               eText[i] = left[index]
           }
           else {
               index = left.indexOf(text[i])
               eText[i] = right[index]
           }
           if (i == text.length - 1) break

           // permute left

           for (j in index..25) temp[j - index] = left[j]
           for (j in 0 until index) temp[26 - index + j] = left[j]
           var store = temp[1]
           for (j in 2..13) temp[j - 1] = temp[j]
           temp[13] = store
           left = String(temp)

           // permute right

           for (j in index..25) temp[j - index] = right[j]
           for (j in 0 until index) temp[26 - index + j] = right[j]
           store = temp[0]
           for (j in 1..25) temp[j - 1] = temp[j]
           temp[25] = store
           store = temp[2]
           for (j in 3..13) temp[j - 1] = temp[j]
           temp[13] = store
           right = String(temp)
       }

       return String(eText)
   }

}

fun main(args: Array<String>) {

   val plainText = "WELLDONEISBETTERTHANWELLSAID"
   println("The original plaintext is : $plainText")
   println("\nThe left and right alphabets after each permutation" +
            " during encryption are :\n")
   val cipherText = Chao.exec(plainText, Mode.ENCRYPT, true)
   println("\nThe ciphertext is : $cipherText")
   val plainText2 = Chao.exec(cipherText, Mode.DECRYPT)
   println("\nThe recovered plaintext is : $plainText2")

}</lang>

Output:

The original plaintext is : WELLDONEISBETTERTHANWELLSAID

The left and right alphabets after each permutation during encryption are :

HXUCZVAMDSLKPEFJRIGTWOBNYQ  PTLNBQDEOYSFAVZKGJRIHWXUMC
ONYQHXUCZVAMDBSLKPEFJRIGTW  XUCPTLNBQDEOYMSFAVZKGJRIHW
ADBSLKPEFJRIGMTWONYQHXUCZV  OYSFAVZKGJRIHMWXUCPTLNBQDE
HUCZVADBSLKPEXFJRIGMTWONYQ  NBDEOYSFAVZKGQJRIHMWXUCPTL
QUCZVADBSLKPEHXFJRIGMTWONY  NBEOYSFAVZKGQDJRIHMWXUCPTL
HFJRIGMTWONYQXUCZVADBSLKPE  JRHMWXUCPTLNBIEOYSFAVZKGQD
CVADBSLKPEHFJZRIGMTWONYQXU  YSAVZKGQDJRHMFWXUCPTLNBIEO
NQXUCVADBSLKPYEHFJZRIGMTWO  BIOYSAVZKGQDJERHMFWXUCPTLN
YHFJZRIGMTWONEQXUCVADBSLKP  RHFWXUCPTLNBIMOYSAVZKGQDJE
NQXUCVADBSLKPEYHFJZRIGMTWO  MOSAVZKGQDJERYHFWXUCPTLNBI
XCVADBSLKPEYHUFJZRIGMTWONQ  AVKGQDJERYHFWZXUCPTLNBIMOS
TONQXCVADBSLKWPEYHUFJZRIGM  IMSAVKGQDJERYOHFWZXUCPTLNB
SKWPEYHUFJZRILGMTONQXCVADB  RYHFWZXUCPTLNOBIMSAVKGQDJE
ZILGMTONQXCVARDBSKWPEYHUFJ  LNBIMSAVKGQDJOERYHFWZXUCPT
JILGMTONQXCVAZRDBSKWPEYHUF  LNIMSAVKGQDJOBERYHFWZXUCPT
RBSKWPEYHUFJIDLGMTONQXCVAZ  RYFWZXUCPTLNIHMSAVKGQDJOBE
RSKWPEYHUFJIDBLGMTONQXCVAZ  YFZXUCPTLNIHMWSAVKGQDJOBER
HFJIDBLGMTONQUXCVAZRSKWPEY  LNHMWSAVKGQDJIOBERYFZXUCPT
JDBLGMTONQUXCIVAZRSKWPEYHF  MWAVKGQDJIOBESRYFZXUCPTLNH
BGMTONQUXCIVALZRSKWPEYHFJD  VKQDJIOBESRYFGZXUCPTLNHMWA
YFJDBGMTONQUXHCIVALZRSKWPE  HMAVKQDJIOBESWRYFGZXUCPTLN
HIVALZRSKWPEYCFJDBGMTONQUX  RYGZXUCPTLNHMFAVKQDJIOBESW
QXHIVALZRSKWPUEYCFJDBGMTON  SWYGZXUCPTLNHRMFAVKQDJIOBE
KPUEYCFJDBGMTWONQXHIVALZRS  NHMFAVKQDJIOBRESWYGZXUCPTL
SPUEYCFJDBGMTKWONQXHIVALZR  NHFAVKQDJIOBRMESWYGZXUCPTL
OQXHIVALZRSPUNEYCFJDBGMTKW  WYZXUCPTLNHFAGVKQDJIOBRMES
UEYCFJDBGMTKWNOQXHIVALZRSP  GVQDJIOBRMESWKYZXUCPTLNHFA
JBGMTKWNOQXHIDVALZRSPUEYCF  OBMESWKYZXUCPRTLNHFAGVQDJI

The ciphertext is : OAHQHCNYNXTSZJRRHJBYHQKSOUJY

The recovered plaintext is : WELLDONEISBETTERTHANWELLSAID

Perl 6

Works with: Rakudo version 2018.03

<lang perl6>my @left; my @right;

sub reset {

   @left  = <HXUCZVAMDSLKPEFJRIGTWOBNYQ>.comb;
   @right = <PTLNBQDEOYSFAVZKGJRIHWXUMC>.comb;

}

sub encode ($letter) {

   my $index = @right.first: $letter.uc, :k;
   my $enc   = @left[$index];
   $index.&permute;
   $enc

}

sub decode ($letter) {

   my $index = @left.first: $letter.uc, :k;
   my $dec   = @right[$index];
   $index.&permute;
   $dec

}

sub permute ($index) {

   @left.=rotate: $index;
   @left[1..13].=rotate;
   @right.=rotate: $index + 1;
   @right[2..13].=rotate;

}

reset; say 'WELLDONEISBETTERTHANWELLSAID'.comb».&encode.join; reset; say 'OAHQHCNYNXTSZJRRHJBYHQKSOUJY'.comb».&decode.join;</lang>

Output:

OAHQHCNYNXTSZJRRHJBYHQKSOUJY
WELLDONEISBETTERTHANWELLSAID

zkl

Translation of: perl6

<lang zkl>class Chao{

  var [const private] lAlphabet = "HXUCZVAMDSLKPEFJRIGTWOBNYQ",

rAlphabet = "PTLNBQDEOYSFAVZKGJRIHWXUMC";

  fcn encode(text){ code(text,encodeL); }
  fcn decode(text){ code(text,decodeL); }
  // reset alphabets each [en|de]code and maintain re-entrancy
  fcn code(text,f){ text.apply(f,Data(Void,lAlphabet),Data(Void,rAlphabet)) }
  fcn [private] encodeL(letter,left,right){  // encode a letter
     index:=right.index(letter);
     enc  :=left[index].toChar();
     permute(left,right,index);
     println(left.text," ",right.text,"  ",index);
     enc
  }
  fcn [private] decodeL(letter,left,right){  // decode a letter
     index:=left.index(letter);
     dec  :=right[index].toChar();
     permute(left,right,index);
     dec
  }
  fcn [private] permute(left,right,index){
     do(index){ left.append(left.pop(0)) }	// rotate index times
     left.insert(13,left.pop(1));		// rotate [1..13] once

     do(index+1){ right.append(right.pop(0)) }	// rotate index+1 times
     right.insert(13,right.pop(2));		// rotate [2..13] once
  }

}</lang> <lang zkl>plainText:="WELLDONEISBETTERTHANWELLSAID"; println("The original plaintext is : ",plainText); println("\nThe left and right alphabets after each permutation"

        " during encryption are:");

cipherText:=Chao.encode(plainText); println("\nThe ciphertext is : ",cipherText);

plainText2:=Chao.decode(cipherText); println("\nThe recovered plaintext is : ",plainText2);</lang>

Output:

The original plaintext is : WELLDONEISBETTERTHANWELLSAID

The left and right alphabets after each permutation during encryption are:
ONYQHXUCZVAMDBSLKPEFJRIGTW XUCPTLNBQDEOYMSFAVZKGJRIHW  21
ADBSLKPEFJRIGMTWONYQHXUCZV OYSFAVZKGJRIHMWXUCPTLNBQDE  10
HUCZVADBSLKPEXFJRIGMTWONYQ NBDEOYSFAVZKGQJRIHMWXUCPTL  20
QUCZVADBSLKPEHXFJRIGMTWONY NBEOYSFAVZKGQDJRIHMWXUCPTL  25
HFJRIGMTWONYQXUCZVADBSLKPE JRHMWXUCPTLNBIEOYSFAVZKGQD  13
CVADBSLKPEHFJZRIGMTWONYQXU YSAVZKGQDJRHMFWXUCPTLNBIEO  15
NQXUCVADBSLKPYEHFJZRIGMTWO BIOYSAVZKGQDJERHMFWXUCPTLN  21
YHFJZRIGMTWONEQXUCVADBSLKP RHFWXUCPTLNBIMOYSAVZKGQDJE  13
NQXUCVADBSLKPEYHFJZRIGMTWO MOSAVZKGQDJERYHFWXUCPTLNBI  12
XCVADBSLKPEYHUFJZRIGMTWONQ AVKGQDJERYHFWZXUCPTLNBIMOS  2
TONQXCVADBSLKWPEYHUFJZRIGM IMSAVKGQDJERYOHFWZXUCPTLNB  21
SKWPEYHUFJZRILGMTONQXCVADB RYHFWZXUCPTLNOBIMSAVKGQDJE  10
ZILGMTONQXCVARDBSKWPEYHUFJ LNBIMSAVKGQDJOERYHFWZXUCPT  10
JILGMTONQXCVAZRDBSKWPEYHUF LNIMSAVKGQDJOBERYHFWZXUCPT  25
RBSKWPEYHUFJIDLGMTONQXCVAZ RYFWZXUCPTLNIHMSAVKGQDJOBE  14
RSKWPEYHUFJIDBLGMTONQXCVAZ YFZXUCPTLNIHMWSAVKGQDJOBER  0
HFJIDBLGMTONQUXCVAZRSKWPEY LNHMWSAVKGQDJIOBERYFZXUCPT  7
JDBLGMTONQUXCIVAZRSKWPEYHF MWAVKGQDJIOBESRYFZXUCPTLNH  2
BGMTONQUXCIVALZRSKWPEYHFJD VKQDJIOBESRYFGZXUCPTLNHMWA  2
YFJDBGMTONQUXHCIVALZRSKWPE HMAVKQDJIOBESWRYFGZXUCPTLN  21
HIVALZRSKWPEYCFJDBGMTONQUX RYGZXUCPTLNHMFAVKQDJIOBESW  13
QXHIVALZRSKWPUEYCFJDBGMTON SWYGZXUCPTLNHRMFAVKQDJIOBE  23
KPUEYCFJDBGMTWONQXHIVALZRS NHMFAVKQDJIOBRESWYGZXUCPTL  10
SPUEYCFJDBGMTKWONQXHIVALZR NHFAVKQDJIOBRMESWYGZXUCPTL  25
OQXHIVALZRSPUNEYCFJDBGMTKW WYZXUCPTLNHFAGVKQDJIOBRMES  15
UEYCFJDBGMTKWNOQXHIVALZRSP GVQDJIOBRMESWKYZXUCPTLNHFA  12
JBGMTKWNOQXHIDVALZRSPUEYCF OBMESWKYZXUCPRTLNHFAGVQDJI  5
YFJBGMTKWNOQXCHIDVALZRSPUE JIBMESWKYZXUCOPRTLNHFAGVQD  23

The ciphertext is : OAHQHCNYNXTSZJRRHJBYHQKSOUJY

The recovered plaintext is : WELLDONEISBETTERTHANWELLSAID