Chaocipher

From Rosetta Code
Chaocipher is a draft programming task. It is not yet considered ready to be promoted as a complete task, for reasons that should be found in its talk page.

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[edit]

Translation of: Kotlin
#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;
}
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[edit]

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 ] [email protected] ;
 
: 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 ] [email protected] ;
 
MAIN: main
Output:
OAHQHCNYNXTSZJRRHJBYHQKSOUJY
WELLDONEISBETTERTHANWELLSAID

Go[edit]

Translation of: Kotlin
package main
 
import(
"fmt"
"strings"
"unicode/utf8"
)
 
type Mode int
 
const(
Encrypt Mode = iota
Decrypt
)
 
const(
lAlphabet = "HXUCZVAMDSLKPEFJRIGTWOBNYQ"
rAlphabet = "PTLNBQDEOYSFAVZKGJRIHWXUMC"
)
 
func Chao(text string, mode Mode, showSteps bool) string {
len := len(text)
if utf8.RuneCountInString(text) != len {
fmt.Println("Text contains non-ASCII characters")
return ""
}
left := lAlphabet
right := rAlphabet
eText := make([]byte, len)
temp := make([]byte, 26)
 
for i := 0; i < len; i++ {
if showSteps {
fmt.Println(left, " ", right)
}
var index int
if mode == Encrypt {
index = strings.IndexByte(right, text[i])
eText[i] = left[index]
} else {
index = strings.IndexByte(left, text[i])
eText[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
left = string(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
right = string(temp[:])
}
 
return string(eText[:])
}
 
func main() {
plainText := "WELLDONEISBETTERTHANWELLSAID"
fmt.Println("The original plaintext is :", plainText)
fmt.Print("\nThe left and right alphabets after each permutation ")
fmt.Println("during encryption are :\n")
cipherText := Chao(plainText, Encrypt, true)
fmt.Println("\nThe ciphertext is :", cipherText)
plainText2 := Chao(cipherText, Decrypt, false)
fmt.Println("\nThe recovered plaintext is :", plainText2)
}
Output:
Same as Kotlin entry.

Kotlin[edit]

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.

// 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")
}
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[edit]

Translation of: Perl 6

Since rotate is not a built-in in Perl, using a custom one, not general-purpose but sufficient for this task.

sub init {
@left = split '', 'HXUCZVAMDSLKPEFJRIGTWOBNYQ';
@right = split '', 'PTLNBQDEOYSFAVZKGJRIHWXUMC';
}
 
sub encode {
my($letter) = @_;
my $index = index join('', @right), $letter;
my $enc = $left[$index];
left_permute($index);
right_permute($index);
$enc
}
 
sub decode {
my($letter) = @_;
my $index = index join('', @left), $letter;
my $dec = $right[$index];
left_permute($index);
right_permute($index);
$dec
}
 
sub right_permute {
my($index) = @_;
rotate(\@right, $index + 1);
rotate(\@right, 1, 2, 13);
}
 
sub left_permute {
my($index) = @_;
rotate(\@left, $index);
rotate(\@left, 1, 1, 13);
}
 
sub rotate {
our @list; local *list = shift;
my($n,$s,$e) = @_;
@list = $s ? @list[0..$s-1, $s+$n..$e+$n-1, $s..$s+$n-1, $e+1..$#list]
: @list[$n..$#list, 0..$n-1]
}
 
init; $e_msg .= encode($_) for split '', 'WELLDONEISBETTERTHANWELLSAID';
init; $d_msg .= decode($_) for split '', $e_msg;
 
print "$e_msg\n";
print "$d_msg\n";
Output:
OAHQHCNYNXTSZJRRHJBYHQKSOUJY
WELLDONEISBETTERTHANWELLSAID

Perl 6[edit]

Works with: Rakudo version 2018.03
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;
Output:
OAHQHCNYNXTSZJRRHJBYHQKSOUJY
WELLDONEISBETTERTHANWELLSAID

zkl[edit]

Translation of: perl6
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){
left.append(left.pop(0,index)); // rotate index times
left.insert(13,left.pop(1)); // rotate [1..13] once
 
right.append(right.pop(0,index+1)); # rotate index+1 times, idx==25==noop
right.insert(13,right.pop(2)); // rotate [2..13] once
}
}
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);
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