Caesar cipher: Difference between revisions
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Decrypted: The five boxing wizards jump quickly |
Decrypted: The five boxing wizards jump quickly |
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</pre> |
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=={{header|Smalltalk}}== |
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{{works with|Smalltalk/X}} |
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well, I'm lucky: the standard library already contains a rot:n method! |
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<lang Smalltalk>'THE QUICK BROWN FOX' rot:3 -> 'WKH TXLFN EURZQ IRA' </lang> |
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but if it wasn't, here is an implementation: |
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{{works with|Smalltalk}} |
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<lang smalltalk> |
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!CharacterArray methodsFor:'encoding'! |
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rot:n |
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^ self class |
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streamContents:[:aStream | |
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self do:[:char | |
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aStream nextPut:(char rot:n) ]] |
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!Character methodsFor:'encoding'! |
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rot:n |
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(self isLetter) ifTrue:[ |
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self isLowercase ifTrue:[ |
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^ 'abcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwxyz' at:(self-$a+1+n) |
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] ifFalse:[ |
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^ 'ABCDEFGHIJKLMNOPQRSTUVWXYZABCDEFGHIJKLMNOPQRSTUVWXYZ' at:(self-$A+1+n) |
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] |
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]. |
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^ self |
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</lang> |
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=={{header|Tcl}}== |
=={{header|Tcl}}== |
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Revision as of 21:27, 20 January 2013
You are encouraged to solve this task according to the task description, using any language you may know.
Implement a Caesar cipher, both encryption and decryption. The key is an integer from 1 to 25. This cipher rotates the letters of the alphabet (A to Z). The encryption replaces each letter with the 1st to 25th next letter in the alphabet (wrapping Z to A). So key 2 encrypts "HI" to "JK", but key 20 encrypts "HI" to "BC". This simple "monoalphabetic substitution cipher" provides almost no security, because an attacker who has the encrypted message can either use frequency analysis to guess the key, or just try all 25 keys.
Caesar cipher is identical to Vigenère cipher with key of length 1. Also, Rot-13 is identical to Caesar cipher with key 13.
Ada
<lang Ada>with Ada.Text_IO;
procedure Caesar is
type M26 is mod 26;
function To_M26(C: Character; Offset: Character) return M26 is
begin
return M26(Character'Pos(C)-Character'Pos(Offset));
end To_M26;
function To_Character(Value: in M26; Offset: Character)
return Character is
begin
return Character'Val(Integer(Value)+Character'Pos(Offset));
end To_Character;
function Encrypt (Plain: String; Key: M26) return String is
Ciph: String(Plain'Range);
begin
for I in Plain'Range loop
case Plain(I) is
when 'A' .. 'Z' =>
Ciph(I) := To_Character(To_M26(Plain(I), 'A')+Key, 'A');
when 'a' .. 'z' =>
Ciph(I) := To_Character(To_M26(Plain(I), 'a')+Key, 'a');
when others =>
Ciph(I) := Plain(I);
end case;
end loop;
return Ciph;
end Encrypt;
Text: String := Ada.Text_IO.Get_Line; Key: M26 := 3; -- Default key from "Commentarii de Bello Gallico"
begin -- Caesar main program
Ada.Text_IO.Put_Line("Plaintext ------------>" & Text);
Text := Encrypt(Text, Key);
Ada.Text_IO.Put_Line("Ciphertext ----------->" & Text);
Ada.Text_IO.Put_Line("Decrypted Ciphertext ->" & Encrypt(Text, -Key));
end Caesar;</lang> Output
> ./caesar The five boxing wizards jump quickly Plaintext ------------>The five boxing wizards jump quickly Ciphertext ----------->Wkh ilyh eralqj zlcdugv mxps txlfnob Decrypted Ciphertext ->The five boxing wizards jump quickly
ALGOL 68
Note: This specimen retains the original Ada coding style.
<lang algol68>#!/usr/local/bin/a68g --script #
program caesar: BEGIN
MODE MODXXVI = SHORT SHORT INT; # MOD26 #
PROC to m26 = (CHAR c, offset)MODXXVI:
BEGIN
ABS c - ABS offset
END #to m26#;
PROC to char = (MODXXVI value, CHAR offset)CHAR:
BEGIN
REPR ( ABS offset + value MOD 26 )
END #to char#;
PROC encrypt = (STRING plain, MODXXVI key)STRING:
BEGIN
[UPB plain]CHAR ciph;
FOR i TO UPB plain DO
CHAR c = plain[i];
ciph[i]:=
IF "A" <= c AND c <= "Z" THEN
to char(to m26(c, "A")+key, "A")
ELIF "a" <= c AND c <= "z" THEN
to char(to m26(c, "a")+key, "a")
ELSE
c
FI
OD;
ciph
END #encrypt#;
- caesar main program #
STRING text := "The five boxing wizards jump quickly" # OR read string #; MODXXVI key := 3; # Default key from "Bello Gallico" #
printf(($gl$, "Plaintext ------------>" + text)); text := encrypt(text, key); printf(($gl$, "Ciphertext ----------->" + text)); printf(($gl$, "Decrypted Ciphertext ->" + encrypt(text, -key)))
END #caesar#</lang> Output:
Plaintext ------------>The five boxing wizards jump quickly Ciphertext ----------->Wkh ilyh eralqj zlcdugv mxps txlfnob Decrypted Ciphertext ->The five boxing wizards jump quickly
AutoHotkey
This ungodly solution is an attempt at code-golf. It requires input to be all-caps alphabetic, only works on AutoHotkey_L Unicode, and might not run on x64 <lang AutoHotkey>n=2 s=HI t:=&s While *t o.=Chr(Mod(*t-65+n,26)+65),t+=2 MsgBox % o</lang> This next one is much more sane and handles input very well, including case. <lang AutoHotkey>Caesar(string, n){ Loop Parse, string { If (Asc(A_LoopField) >= Asc("A") and Asc(A_LoopField) <= Asc("Z")) out .= Chr(Mod(Asc(A_LoopField)-Asc("A")+n,26)+Asc("A")) Else If (Asc(A_LoopField) >= Asc("a") and Asc(A_LoopField) <= Asc("z")) out .= Chr(Mod(Asc(A_LoopField)-Asc("a")+n,26)+Asc("a")) Else out .= A_LoopField } return out }
MsgBox % Caesar("h i", 2) "`n" Caesar("Hi", 20)</lang>
It outputs
j k Bc
AutoIt
The Ceasar Funktion can enrcypt and decrypt, standart is Encryption, to Decrypt set third parameter to False <lang autoit> $Caesar = Caesar("Hi", 2, True) MsgBox(0, "Caesar", $Caesar) Func Caesar($String, $int, $encrypt = True) If Not IsNumber($int) Or Not StringIsDigit($int) Then Return SetError(1, 0, 0) If $int < 1 Or $int > 25 Then Return SetError(2, 0, 0) Local $sLetters, $x $String = StringUpper($String) $split = StringSplit($String, "") For $i = 1 To $split[0] If Asc($split[$i]) - 64 > 26 Or Asc($split[$i]) - 64 < 1 Then $sLetters &= $split[$i] ContinueLoop EndIf If $encrypt = True Then $move = Asc($split[$i]) - 64 + $int Else $move = Asc($split[$i]) - 64 - $int EndIf If $move > 26 Then $move -= 26 ElseIf $move < 1 Then $move += 26 EndIf While $move $x = Mod($move, 26) If $x = 0 Then $x = 26 $sLetters &= Chr($x + 64) $move = ($move - $x) / 26 WEnd Next Return $sLetters EndFunc ;==>Caesar </lang>
AWK
<lang awk>
- !/usr/bin/awk -f
BEGIN {
message = "My hovercraft is full of eels." key = 1
cypher = caesarEncode(key, message) clear = caesarDecode(key, cypher)
print "message: " message print " cypher: " cypher print " clear: " clear exit
}
function caesarEncode(key, message) {
return caesarXlat(key, message, "encode")
}
function caesarDecode(key, message) {
return caesarXlat(key, message, "decode")
}
function caesarXlat(key, message, dir, plain, cypher, i, num, s) {
plain = "ABCDEFGHIJKLMNOPQRSTUVWXYZ" cypher = substr(plain, key+1) substr(plain, 1, key)
if (toupper(substr(dir, 1, 1)) == "D") {
s = plain
plain = cypher
cypher = s
}
s = ""
message = toupper(message)
for (i = 1; i <= length(message); i++) {
num = index(plain, substr(message, i, 1))
if (num) s = s substr(cypher, num, 1)
else s = s substr(message, i, 1)
}
return s
} </lang>
Example output:
message: My hovercraft is full of eels. cypher: NZ IPWFSDSBGU JT GVMM PG FFMT. clear: MY HOVERCRAFT IS FULL OF EELS.
BBC BASIC
<lang bbcbasic> plaintext$ = "Pack my box with five dozen liquor jugs"
PRINT plaintext$
key% = RND(25)
cyphertext$ = FNcaesar(plaintext$, key%)
PRINT cyphertext$
decyphered$ = FNcaesar(cyphertext$, 26-key%)
PRINT decyphered$
END
DEF FNcaesar(text$, key%)
LOCAL I%, C%
FOR I% = 1 TO LEN(text$)
C% = ASC(MID$(text$,I%))
IF (C% AND &1F) >= 1 AND (C% AND &1F) <= 26 THEN
C% = (C% AND &E0) OR (((C% AND &1F) + key% - 1) MOD 26 + 1)
MID$(text$, I%, 1) = CHR$(C%)
ENDIF
NEXT
= text$
</lang> Output:
Pack my box with five dozen liquor jugs Zkmu wi lyh gsdr psfo nyjox vsaeyb teqc Pack my box with five dozen liquor jugs
C
<lang c>#include <stdio.h>
- include <stdlib.h>
- include <string.h>
- define caesar(x) rot(13, x)
- define decaesar(x) rot(13, x)
- define decrypt_rot(x, y) rot((26-x), y)
void rot(int c, char *str) { int l = strlen(str); const char *alpha[2] = { "abcdefghijklmnopqrstuvwxyz", "ABCDEFGHIJKLMNOPQRSTUVWXYZ"};
int i; for (i = 0; i < l; i++) { if (!isalpha(str[i])) continue;
str[i] = alpha[isupper(str[i])][((int)(tolower(str[i])-'a')+c)%26]; } }
int main()
{
char str[] = "This is a top secret text message!";
printf("Original: %s\n", str); caesar(str); printf("Encrypted: %s\n", str); decaesar(str); printf("Decrypted: %s\n", str);
return 0; }</lang>
C++
<lang C++>#include <string>
- include <iostream>
- include <algorithm>
- include <cctype>
class MyTransform { private :
int shift ;
public :
MyTransform( int s ) : shift( s ) { }
char operator( )( char c ) {
if ( isspace( c ) )
return ' ' ;
else {
static std::string letters( "abcdefghijklmnopqrstuvwxyz" ) ; std::string::size_type found = letters.find(tolower( c )) ; int shiftedpos = ( static_cast<int>( found ) + shift ) % 26 ; if ( shiftedpos < 0 ) //in case of decryption possibly shiftedpos = 26 + shiftedpos ; char shifted = letters[shiftedpos] ; return shifted ;
} }
} ;
int main( ) {
std::string input ; std::cout << "Which text is to be encrypted ?\n" ; getline( std::cin , input ) ; std::cout << "shift ?\n" ; int myshift = 0 ; std::cin >> myshift ; std::cout << "Before encryption:\n" << input << std::endl ; std::transform ( input.begin( ) , input.end( ) , input.begin( ) ,
MyTransform( myshift ) ) ;
std::cout << "encrypted:\n" ; std::cout << input << std::endl ; myshift *= -1 ; //decrypting again std::transform ( input.begin( ) , input.end( ) , input.begin( ) ,
MyTransform( myshift ) ) ;
std::cout << "Decrypted again:\n" ; std::cout << input << std::endl ; return 0 ;
}</lang> Output:
Which text is to be encrypted ? this is an interesting text shift ? 3 Before encryption: this is an interesting text encrypted: wklv lv dq lqwhuhvwlqj whaw Decrypted again: this is an interesting text
C#
<lang csharp>using System; using System.Linq;
namespace CaesarCypher {
class Program
{
static char Encrypt(char ch, int code)
{
if (!char.IsLetter(ch))
{
return ch;
}
char offset = char.IsUpper(ch) ? 'A' : 'a';
return (char)(((ch + code - offset) % 26) + offset);
}
static string Encrypt(string input, int code)
{
return new string(input.ToCharArray().Select(ch => Encrypt(ch, code)).ToArray());
}
static string Decrypt(string input, int code)
{
return Encrypt(input, 26 - code);
}
const string TestCase = "Pack my box with five dozen liquor jugs.";
static void Main()
{
string str = TestCase;
Console.WriteLine(str);
str = Encrypt(str, 5);
Console.WriteLine("Encrypted: {0}", str);
str = Decrypt(str, 5);
Console.WriteLine("Decrypted: {0}", str);
Console.ReadKey();
}
}
}</lang> Output:
Pack my box with five dozen liquor jugs. Encrypted: Ufhp rd gtc bnym knaj itejs qnvztw ozlx. Decrypted: Pack my box with five dozen liquor jugs.
Clojure
<lang Clojure>(defn encrypt-character [offset c]
(if (Character/isLetter c)
(let [v (int c)
base (if (>= v (int \a))
(int \a)
(int \A))
offset (mod offset 26)] ;works with negative offsets too!
(char (+ (mod (+ (- v base) offset) 26)
base)))
c))
(defn encrypt [offset text]
(apply str (map #(encrypt-character offset %) text)))
(defn decrypt [offset text]
(encrypt (- 26 offset) text))
(let [text "The Quick Brown Fox Jumps Over The Lazy Dog."
enc (encrypt -1 text)] (print "Original text:" text "\n") (print "Encryption:" enc "\n") (print "Decryption:" (decrypt -1 enc) "\n"))</lang>
output
Original text: The Quick Brown Fox Jumps Over The Lazy Dog. Encryption: Sgd Pthbj Aqnvm Enw Itlor Nudq Sgd Kzyx Cnf. Decryption: The Quick Brown Fox Jumps Over The Lazy Dog.
CoffeeScript
<lang coffeescript>cipher = (msg, rot) ->
msg.replace /([a-z|A-Z])/g, ($1) ->
c = $1.charCodeAt(0)
String.fromCharCode \
if c >= 97
then (c + rot + 26 - 97) % 26 + 97
else (c + rot + 26 - 65) % 26 + 65
console.log cipher "Hello World", 2 console.log cipher "azAz %^&*()", 3</lang> output
> coffee foo.coffee Jgnnq Yqtnf dcDc %^&*()
Common Lisp
<lang lisp>(defun encipher-char (ch key)
(let*
((c (char-code ch))
(la (char-code #\a)) (lz (char-code #\z))
(ua (char-code #\A)) (uz (char-code #\Z))
(base (cond
((and (>= c la) (<= c lz)) la)
((and (>= c ua) (<= c uz)) ua)
(t nil))))
(if base (code-char (+ (mod (+ (- c base) key) 26) base)) ch)))
(defun caesar-cipher (str key)
(map 'string #'(lambda (c) (encipher-char c key)) str))
(defun caesar-decipher (str key) (caesar-cipher str (- key)))
(let* ((original-text "The five boxing wizards jump quickly")
(key 3)
(cipher-text (caesar-cipher original-text key))
(recovered-text (caesar-decipher cipher-text key)))
(format t " Original: ~a ~%" original-text)
(format t "Encrypted: ~a ~%" cipher-text)
(format t "Decrypted: ~a ~%" recovered-text))</lang>
Output:
Original: The five boxing wizards jump quickly Encrypted: Wkh ilyh eralqj zlcdugv mxps txlfnob Decrypted: The five boxing wizards jump quickly
Cubescript
<lang cubescript>alias modn [ mod (+ (mod $arg1 $arg2) $arg2) $arg2 ] //Cubescript's built-in mod will fail on negative numbers
alias cipher [ push alpha [ "A B C D E F G H I J K L M N O P Q R S T U V W X Y Z" "a b c d e f g h i j k l m n o p q r s t u v w x y z" ] [ push chars [] [ loop i (strlen $arg1) [ looplist n $alpha [ if (! (listlen $chars)) [ alias chars (? (> (listindex $n (substr $arg1 $i 1)) -1) $n []) ] ] alias arg1 ( concatword (substr $arg1 0 $i) ( ? (> (listindex $chars (substr $arg1 $i 1)) -1) ( at $chars ( modn (+ ( listindex $chars (substr $arg1 $i 1) ) $arg2) (listlen $chars) ) ) (substr $arg1 $i 1) ) (substr $arg1 (+ $i 1) (strlen $arg1)) ) alias chars [] ] ] ] result $arg1 ]
alias decipher [ push alpha [ "A B C D E F G H I J K L M N O P Q R S T U V W X Y Z" "a b c d e f g h i j k l m n o p q r s t u v w x y z" ] [ push chars [] [ loop i (strlen $arg1) [ looplist n $alpha [ if (! (listlen $chars)) [ alias chars (? (> (listindex $n (substr $arg1 $i 1)) -1) $n []) ] ] alias arg1 ( concatword (substr $arg1 0 $i) ( ? (> (listindex $chars (substr $arg1 $i 1)) -1) ( at $chars ( modn (- ( listindex $chars (substr $arg1 $i 1) ) $arg2 ) (listlen $chars) ) ) (substr $arg1 $i 1) ) (substr $arg1 (+ $i 1) (strlen $arg1)) ) alias chars [] ] ] ] result $arg1 ]</lang>
Usage: <lang>>>> cipher "The Quick Brown Fox Jumps Over The Lazy Dog." 5 > Ymj Vznhp Gwtbs Ktc Ozrux Tajw Ymj Qfed Itl. >>> decipher "Ymj Vznhp Gwtbs Ktc Ozrux Tajw Ymj Qfed Itl." 5 > The Quick Brown Fox Jumps Over The Lazy Dog.</lang>
D
<lang d>import std.stdio, std.traits;
pure S rot(S)(in S s, in int key) if (isSomeString!S) {
auto res = s.dup;
foreach (i, ref c; res) {
if ('a' <= c && c <= 'z')
c = ((c - 'a' + key) % 26 + 'a');
else if ('A' <= c && c <= 'Z')
c = ((c - 'A' + key) % 26 + 'A');
}
return cast(S) res;
}
void main() {
int key = 3;
auto txt = "The five boxing wizards jump quickly";
writeln("Original: ", txt);
writeln("Encrypted: ", txt.rot(key));
writeln("Decrypted: ", txt.rot(key).rot(26 - key));
}</lang>
Original: The five boxing wizards jump quickly Encrypted: Wkh ilyh eralqj zlcdugv mxps txlfnob Decrypted: The five boxing wizards jump quickly
Simpler in-place version (same output): <lang d>import std.stdio, std.ascii;
void inplaceRot(char[] txt, in int key) pure nothrow {
foreach (ref c; txt) {
if (isLower(c))
c = (c - 'a' + key) % 26 + 'a';
else if (isUpper(c))
c = (c - 'A' + key) % 26 + 'A';
}
}
void main() {
enum key = 3;
auto txt = "The five boxing wizards jump quickly".dup;
writeln("Original: ", txt);
txt.inplaceRot(key);
writeln("Encrypted: ", txt);
txt.inplaceRot(26 - key);
writeln("Decrypted: ", txt);
}</lang>
Dart
<lang dart>class Caesar {
int _key;
Caesar(this._key);
int _toCharCode(String s) {
return s.charCodeAt(0);
}
String _fromCharCode(int ch) {
return new String.fromCharCodes([ch]);
}
String _process(String msg, int offset) {
StringBuffer sb=new StringBuffer();
for(int i=0;i<msg.length;i++) {
int ch=msg.charCodeAt(i);
if(ch>=_toCharCode('A')&&ch<=_toCharCode('Z')) {
sb.add(_fromCharCode(_toCharCode("A")+(ch-_toCharCode("A")+offset)%26));
}
else if(ch>=_toCharCode('a')&&ch<=_toCharCode('z')) {
sb.add(_fromCharCode(_toCharCode("a")+(ch-_toCharCode("a")+offset)%26));
} else {
sb.add(msg[i]);
}
}
return sb.toString();
}
String encrypt(String msg) {
return _process(msg, _key);
}
String decrypt(String msg) {
return _process(msg, 26-_key);
}
}
void trip(String msg) {
Caesar cipher=new Caesar(10);
String enc=cipher.encrypt(msg);
String dec=cipher.decrypt(enc);
print("\"$msg\" encrypts to:");
print("\"$enc\" decrypts to:");
print("\"$dec\"");
Expect.equals(msg,dec);
}
main() {
Caesar c2=new Caesar(2);
print(c2.encrypt("HI"));
Caesar c20=new Caesar(20);
print(c20.encrypt("HI"));
// try a few roundtrips
trip("");
trip("A");
trip("z");
trip("Caesar cipher");
trip(".-:/\"\\!");
trip("The Quick Brown Fox Jumps Over The Lazy Dog.");
}</lang> Output:
JK BC "" encrypts to: "" decrypts to: "" "A" encrypts to: "K" decrypts to: "A" "z" encrypts to: "j" decrypts to: "z" "Caesar cipher" encrypts to: "Mkockb mszrob" decrypts to: "Caesar cipher" ".-:/"\!" encrypts to: ".-:/"\!" decrypts to: ".-:/"\!" "The Quick Brown Fox Jumps Over The Lazy Dog." encrypts to: "Dro Aesmu Lbygx Pyh Tewzc Yfob Dro Vkji Nyq." decrypts to: "The Quick Brown Fox Jumps Over The Lazy Dog."
Elena
<lang elena>#define std'dictionary'*.
- define std'basic'*.
- define std'patterns'*.
- define std'routines'strings'*.
- define math'* = std'math'*.
// --- subjects ---
- subject cipher_key.
- symbol Letters = "abcdefghijklmnopqrstuvwxyz".
- symbol BigLetters = "ABCDEFGHIJKLMNOPQRSTUVWXYZ".
- symbol TestText = "Pack my box with five dozen liquor jugs.".
- symbol Key = 12.
- symbol EEncrypt : aKey =
{
eval : aChar
[
#var anIndex := Letters~eliteralop first_occ'find:aChar.
#if (-1) ifless:anIndex
[
$next eval:(Letters @ (aKey + anIndex)~math'eops math'modulus:26).
]
| [
anIndex := BigLetters~eliteralop first_occ'find:aChar.
#if (-1) ifless:anIndex
[
$next eval:(BigLetters @ (aKey + anIndex)~math'eops math'modulus:26).
]
| [
$next eval:aChar.
].
].
]
}.
- symbol Encrypted &literal:aLiteral &cipher_key:aKey
= __group(EEncrypt::aKey, Summing::String) start:Scan::aLiteral.
- symbol Decrypted &literal:aLiteral &cipher_key:aKey
= __group(EEncrypt::(26 - aKey), Summing::String) start:Scan::aLiteral.
- symbol Program =
[
#var anS := TestText.
'program'output << "Original text :" << anS << "%n".
anS := Encrypted &&literal:anS &cipher_key:Key.
'program'output << "Encrypted text:" << anS << "%n".
anS := Decrypted &&literal:anS &cipher_key:Key.
'program'output << "Decrypted text:" << anS << "%n".
'program'input get.
].</lang>
Erlang
<lang Erlang> %% Ceasar cypher in Erlang for the rosetta code wiki. %% Implemented by J.W. Luiten
-module(ceasar). -export([main/2]).
%% rot: rotate Char by Key places rot(Char,Key) when (Char >= $A) and (Char =< $Z) or
(Char >= $a) and (Char =< $z) -> Offset = $A + Char band 32, N = Char - Offset, Offset + (N + Key) rem 26;
rot(Char, _Key) ->
Char.
%% key: normalize key. key(Key) when Key < 0 ->
26 + Key rem 26;
key(Key) when Key > 25 ->
Key rem 26;
key(Key) ->
Key.
main(PlainText, Key) ->
Encode = key(Key),
Decode = key(-Key),
io:format("Plaintext ----> ~s~n", [PlainText]),
CypherText = lists:map(fun(Char) -> rot(Char, Encode) end, PlainText),
io:format("Cyphertext ---> ~s~n", [CypherText]),
PlainText = lists:map(fun(Char) -> rot(Char, Decode) end, CypherText).
</lang> Command: <lang Erlang>ceasar:main("The five boxing wizards jump quickly", 3).</lang> Output:
Plaintext ----> The five boxing wizards jump quickly Cyphertext ---> Wkh ilyh eralqj zlcdugv mxps txlfnob "The five boxing wizards jump quickly"
Euphoria
<lang Euphoria> --caesar cipher for Rosetta Code wiki --User:Lnettnay
--usage eui caesar ->default text, key and encode flag --usage eui caesar 'Text with spaces and punctuation!' 5 D --If text has imbedded spaces must use apostophes instead of quotes so all punctuation works --key = integer from 1 to 25, defaults to 13 --flag = E (Encode) or D (Decode), defaults to E --no error checking is done on key or flag
include std/get.e include std/types.e
sequence cmd = command_line()
sequence val
-- default text for encryption
sequence text = "The Quick Brown Fox Jumps Over The Lazy Dog."
atom key = 13 -- default to Rot-13
sequence flag = "E" -- default to Encrypt
atom offset
atom num_letters = 26 -- number of characters in alphabet
--get text if length(cmd) >= 3 then text = cmd[3] end if
--get key value if length(cmd) >= 4 then val = value(cmd[4]) key = val[2] end if
--get Encrypt/Decrypt flag if length(cmd) = 5 then flag = cmd[5] if compare(flag, "D") = 0 then key = 26 - key end if end if
for i = 1 to length(text) do if t_alpha(text[i]) then if t_lower(text[i]) then offset = 'a' else offset = 'A' end if text[i] = remainder(text[i] - offset + key, num_letters) + offset end if end for
printf(1,"%s\n",{text})
</lang> Output
"The Quick Brown Fox Jumps Over The Lazy Dog." encrypts to: "Gur Dhvpx Oebja Sbk Whzcf Bire Gur Ynml Qbt." decrypts to: "The Quick Brown Fox Jumps Over The Lazy Dog."
F#
<lang fsharp>module caesar =
open System
let private cipher n s =
let shift c =
if Char.IsLetter c then
let a = (if Char.IsLower c then 'a' else 'A') |> int
(int c - a + n) % 26 + a |> char
else c
String.map shift s
let encrypt n = cipher n let decrypt n = cipher (26 - n)</lang>
> caesar.encrypt 2 "HI";; val it : string = "JK" > caesar.encrypt 20 "HI";; val it : string = "BC" > let c = caesar.encrypt 13 "The quick brown fox jumps over the lazy dog.";; val c : string = "Gur dhvpx oebja sbk whzcf bire gur ynml qbt." > caesar.decrypt 13 c;; val it : string = "The quick brown fox jumps over the lazy dog."
Fantom
Shifts upper/lower case letters, leaves other characters as they are.
<lang fantom> class Main {
static Int shift (Int char, Int key)
{
newChar := char + key
if (char >= 'a' && char <= 'z')
{
if (newChar - 'a' < 0) { newChar += 26 }
if (newChar - 'a' >= 26) { newChar -= 26 }
}
else if (char >= 'A' && char <= 'Z')
{
if (newChar - 'A' < 0) { newChar += 26 }
if (newChar - 'A' >= 26) { newChar -= 26 }
}
else // not alphabetic, so keep as is
{
newChar = char
}
return newChar
}
static Str shiftStr (Str msg, Int key)
{
res := StrBuf()
msg.each { res.addChar (shift(it, key)) }
return res.toStr
}
static Str encode (Str msg, Int key)
{
return shiftStr (msg, key)
}
static Str decode (Str msg, Int key)
{
return shiftStr (msg, -key)
}
static Void main (Str[] args)
{
if (args.size == 2)
{
msg := args[0]
key := Int(args[1])
echo ("$msg with key $key")
echo ("Encode: ${encode(msg, key)}")
echo ("Decode: ${decode(encode(msg, key), key)}")
}
}
} </lang>
Example:
$ fan caesar.fan "Encrypt - With ! Case," 1 Encrypt - With ! Case, with key 1 Encode: Fodszqu - Xjui ! Dbtf, Decode: Encrypt - With ! Case, $ fan caesar.fan "Encrypt - With ! Case," 5 Encrypt - With ! Case, with key 5 Encode: Jshwduy - Bnym ! Hfxj, Decode: Encrypt - With ! Case, $ fan caesar.fan "Encrypt - With ! Case," 10 Encrypt - With ! Case, with key 10 Encode: Oxmbizd - Gsdr ! Mkco, Decode: Encrypt - With ! Case,
Forth
<lang forth>: ceasar ( c n -- c )
over 32 or [char] a - dup 0 26 within if over + 25 > if 26 - then + else 2drop then ;
- ceasar-string ( n str len -- )
over + swap do i c@ over ceasar i c! loop drop ;
- ceasar-inverse ( n -- 'n ) 26 swap - 26 mod ;
2variable test s" The five boxing wizards jump quickly!" test 2!
3 test 2@ ceasar-string test 2@ cr type
3 ceasar-inverse test 2@ ceasar-string test 2@ cr type</lang>
Fortran
<lang fortran>program Caesar_Cipher
implicit none
integer, parameter :: key = 3 character(43) :: message = "The five boxing wizards jump quickly"
write(*, "(2a)") "Original message = ", message call encrypt(message) write(*, "(2a)") "Encrypted message = ", message call decrypt(message) write(*, "(2a)") "Decrypted message = ", message
contains
subroutine encrypt(text)
character(*), intent(inout) :: text
integer :: i
do i = 1, len(text)
select case(text(i:i))
case ('A':'Z')
text(i:i) = achar(modulo(iachar(text(i:i)) - 65 + key, 26) + 65)
case ('a':'z')
text(i:i) = achar(modulo(iachar(text(i:i)) - 97 + key, 26) + 97)
end select
end do
end subroutine
subroutine decrypt(text)
character(*), intent(inout) :: text
integer :: i
do i = 1, len(text)
select case(text(i:i))
case ('A':'Z')
text(i:i) = achar(modulo(iachar(text(i:i)) - 65 - key, 26) + 65)
case ('a':'z')
text(i:i) = achar(modulo(iachar(text(i:i)) - 97 - key, 26) + 97)
end select
end do
end subroutine
end program Caesar_Cipher</lang> Output
Original message = The five boxing wizards jump quickly Encrypted message = Wkh ilyh eralgj zlcdugv mxps txlfnob Decrypted message = The five boxing wizards jump quickly
GAP
<lang gap>CaesarCipher := function(s, n) local r, c, i, lower, upper; lower := "abcdefghijklmnopqrstuvwxyz"; upper := "ABCDEFGHIJKLMNOPQRSTUVWXYZ"; r := ""; for c in s do i := Position(lower, c); if i <> fail then Add(r, lower[RemInt(i + n - 1, 26) + 1]); else i := Position(upper, c); if i <> fail then Add(r, upper[RemInt(i + n - 1, 26) + 1]); else Add(r, c); fi; fi; od; return r; end;
CaesarCipher("IBM", 25);
- "HAL"
CaesarCipher("Vgg cphvi wzdibn vmz wjmi amzz viy zlpvg di ydbidot viy mdbcon.", 5);
- "All human beings are born free and equal in dignity and rights."</lang>
Go
Obvious solution with explicit testing for character ranges: <lang go>package main
import (
"fmt" "strings"
)
type ckey struct {
enc, dec func(rune) rune
}
func newCaesar(k int) (*ckey, bool) {
if k < 1 || k > 25 {
return nil, false
}
rk := rune(k)
return &ckey{
enc: func(c rune) rune {
if c >= 'a' && c <= 'z'-rk || c >= 'A' && c <= 'Z'-rk {
return c + rk
} else if c > 'z'-rk && c <= 'z' || c > 'Z'-rk && c <= 'Z' {
return c + rk - 26
}
return c
},
dec: func(c rune) rune {
if c >= 'a'+rk && c <= 'z' || c >= 'A'+rk && c <= 'Z' {
return c - rk
} else if c >= 'a' && c < 'a'+rk || c >= 'A' && c < 'A'+rk {
return c - rk + 26
}
return c
},
}, true
}
func (ck ckey) encipher(pt string) string {
return strings.Map(ck.enc, pt)
}
func (ck ckey) decipher(ct string) string {
return strings.Map(ck.dec, ct)
}
func main() {
pt := "The five boxing wizards jump quickly"
fmt.Println("Plaintext:", pt)
for _, key := range []int{0, 1, 7, 25, 26} {
ck, ok := newCaesar(key)
if !ok {
fmt.Println("Key", key, "invalid")
continue
}
ct := ck.encipher(pt)
fmt.Println("Key", key)
fmt.Println(" Enciphered:", ct)
fmt.Println(" Deciphered:", ck.decipher(ct))
}
}</lang> Data driven version using functions designed for case conversion. (And for method using % operator, see Vigenère_cipher#Go.) <lang go>package main
import (
"fmt" "strings" "unicode"
)
type ckey struct {
enc, dec unicode.SpecialCase
}
func newCaesar(k int) (*ckey, bool) {
if k < 1 || k > 25 {
return nil, false
}
i := uint32(k)
r := rune(k)
return &ckey{
unicode.SpecialCase{
{'A', 'Z' - i, [3]rune{r}},
{'Z' - i + 1, 'Z', [3]rune{r - 26}},
{'a', 'z' - i, [3]rune{r}},
{'z' - i + 1, 'z', [3]rune{r - 26}},
},
unicode.SpecialCase{
{'A', 'A' + i - 1, [3]rune{26 - r}},
{'A' + i, 'Z', [3]rune{-r}},
{'a', 'a' + i - 1, [3]rune{26 - r}},
{'a' + i, 'z', [3]rune{-r}},
},
}, true
}
func (ck ckey) encipher(pt string) string {
return strings.ToUpperSpecial(ck.enc, pt)
}
func (ck ckey) decipher(ct string) string {
return strings.ToUpperSpecial(ck.dec, ct)
}
func main() {
pt := "The five boxing wizards jump quickly"
fmt.Println("Plaintext:", pt)
for _, key := range []int{0, 1, 7, 25, 26} {
ck, ok := newCaesar(key)
if !ok {
fmt.Println("Key", key, "invalid")
continue
}
ct := ck.encipher(pt)
fmt.Println("Key", key)
fmt.Println(" Enciphered:", ct)
fmt.Println(" Deciphered:", ck.decipher(ct))
}
}</lang> Output of either version:
Plaintext: The five boxing wizards jump quickly Key 0 invalid Key 1 Enciphered: Uif gjwf cpyjoh xjabset kvnq rvjdlmz Deciphered: The five boxing wizards jump quickly Key 7 Enciphered: Aol mpcl ivepun dpghykz qbtw xbpjrsf Deciphered: The five boxing wizards jump quickly Key 25 Enciphered: Sgd ehud anwhmf vhyzqcr itlo pthbjkx Deciphered: The five boxing wizards jump quickly Key 26 invalid
Groovy
<lang groovy>def caeserEncode(int cipherKey, String text) {
def builder = new StringBuilder()
text.each { character ->
int ch = character[0] as char
switch(ch) {
case 'a'..'z': ch = ((ch - 97 + cipherKey) % 26 + 97); break
case 'A'..'Z': ch = ((ch - 65 + cipherKey) % 26 + 65); break
}
builder.append(ch as char)
}
builder.toString()
} def caeserDecode(int cipherKey, String text) { caeserEncode(26 - cipherKey, text) }
def plainText = "The Quick Brown Fox jumped over the lazy dog" def cipherKey = 12 def cipherText = caeserEncode(cipherKey, plainText) def decodedText = caeserDecode(cipherKey, cipherText)
println "plainText: $plainText" println "cypherText($cipherKey): $cipherText" println "decodedText($cipherKey): $decodedText"
assert plainText == decodedText</lang> Output:
plainText: The Quick Brown Fox jumped over the lazy dog cypherText(12): Ftq Cguow Ndaiz Raj vgybqp ahqd ftq xmlk pas decodedText(12): The Quick Brown Fox jumped over the lazy dog
Haskell
<lang haskell>import Data.Char (ord, chr) import Data.Ix (inRange)
caesar :: Int -> String -> String caesar k = map f
where
f c
| inRange ('a','z') c = tr 'a' k c
| inRange ('A','Z') c = tr 'A' k c
| otherwise = c
unCaesar :: Int -> String -> String unCaesar k = caesar (-k)
-- char addition tr :: Char -> Int -> Char -> Char tr base offset char = chr $ ord base + (ord char - ord base + offset) `mod` 26</lang> And trying it out in GHCi:
*Main> caesar 1 "hal" "ibm" *Main> unCaesar 1 "ibm" "hal"
Icon and Unicon
Strictly speaking a Ceasar Cipher is a shift of 3 (the default in this case). <lang Icon>procedure main() ctext := caesar(ptext := map("The quick brown fox jumped over the lazy dog")) dtext := caesar(ctext,,"decrypt") write("Plain text = ",image(ptext)) write("Encphered text = ",image(ctext)) write("Decphered text = ",image(dtext)) end
procedure caesar(text,k,mode) #: mono-alphabetic shift cipher /k := 3 k := (((k % *&lcase) + *&lcase) % *&lcase) + 1 case mode of {
&null|"e"|"encrypt": return map(text,&lcase,(&lcase||&lcase)[k+:*&lcase]) "d"|"decrypt" : return map(text,(&lcase||&lcase)[k+:*&lcase],&lcase) }
end</lang>
Output:
Plain text = "the quick brown fox jumped over the lazy dog" Encphered text = "wkh txlfn eurzq ira mxpshg ryhu wkh odcb grj" Decphered text = "the quick brown fox jumped over the lazy dog"
J
If we assume that the task also requires us to leave non-alphabetic characters alone: <lang j>cndx=: [: , 65 97 +/ 26 | (i.26)&+ caesar=: (cndx 0)}&a.@u:@cndx@[ {~ a.i.]</lang> Example use:<lang j> 2 caesar 'This simple "monoalphabetic substitution cipher" provides almost no security, ...' Vjku ukorng "oqpqcnrjcdgvke uwduvkvwvkqp ekrjgt" rtqxkfgu cnoquv pq ugewtkva, ...</lang> If we instead assume the task only requires we treat upper case characters: <lang j>CAESAR=:1 :'(26|m&+)&.((26{.64}.a.)&i.)'</lang> Example use:<lang j> 20 CAESAR 'HI' BC</lang>
Java
<lang java5>public class Cipher { public static void main(String[] args) { String enc = Cipher.encode( "The quick brown fox Jumped over the lazy Dog", 12); System.out.println(enc); System.out.println(Cipher.decode(enc, 12)); }
public static String decode(String enc, int offset) { return encode(enc, -offset); }
public static String encode(String enc, int offset) { offset = offset % 26 + 26; StringBuilder encoded = new StringBuilder(); for (char i : enc.toLowerCase().toCharArray()) { if (Character.isLetter(i)) { int j = (i - 'a' + offset) % 26; encoded.append((char) (j + 'a')); } else { encoded.append(i); } } return encoded.toString(); } }</lang> Output:
ftq cguow ndaiz raj vgybqp ahqd ftq xmlk pas the quick brown fox jumped over the lazy dog
JavaScript
<lang javascript><html><head><title>Caesar</title></head>
<body>
<script type="application/javascript"> function disp(x) { var e = document.createTextNode(x + '\n'); document.getElementById('x').appendChild(e); }
function trans(msg, rot) { return msg.replace(/([a-z])/ig, function($1) { var c = $1.charCodeAt(0); return String.fromCharCode( c >= 97 ? (c + rot + 26 - 97) % 26 + 97 : (c + rot + 26 - 65) % 26 + 65); }); }
var msg = "The quick brown f0x Jumped over the lazy Dog 123"; var enc = trans(msg, 3); var dec = trans(enc, -3);
disp("Original:" + msg + "\nEncoded: " + enc + "\nDecoded: " + dec); </script></body></html></lang>
LabVIEW
For readability, input is in all caps.
This image is a VI Snippet, an executable image of LabVIEW code. The LabVIEW version is shown on the top-right hand corner. You can download it, then drag-and-drop it onto the LabVIEW block diagram from a file browser, and it will appear as runnable, editable code.
Liberty BASIC
<lang lb>key = 7
Print "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz"
'Encrypt the text Print CaesarCypher$("ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz", key)
'Decrypt the text by changing the key to (26 - key) Print CaesarCypher$(CaesarCypher$("ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz", key), (26 - key))
Function CaesarCypher$(string$, key)
If (key < 0) Or (key > 25) Then _
CaesarCypher$ = "Key is Ouside of Bounds" : Exit Function
For i = 1 To Len(string$)
rotate = Asc(Mid$(string$, i, 1))
rotate = (rotate + key)
If Asc(Mid$(string$, i, 1)) > Asc("Z") Then
If rotate > Asc("z") Then rotate = (Asc("a") + (rotate - Asc("z")) - 1)
Else
If rotate > Asc("Z") Then rotate = (Asc("A") + (rotate - Asc("Z")) - 1)
End If
CaesarCypher$ = (CaesarCypher$ + Chr$(rotate))
Next i
End Function</lang>
Logo
<lang logo>; some useful constants make "lower_a ascii "a make "lower_z ascii "z make "upper_a ascii "A make "upper_z ascii "Z
- encipher a single character
to encipher_char :char :key
local "code make "code ascii :char
local "base make "base 0
ifelse [and (:code >= :lower_a) (:code <= :lower_z)] [make "base :lower_a] [
if [and (:code >= :upper_a) (:code <= :upper_z)] [make "base :upper_a] ]
ifelse [:base > 0] [
output char (:base + (modulo ( :code - :base + :key ) 26 ))
] [
output :char
]
end
- encipher a whole string
to caesar_cipher :string :key
output map [encipher_char ? :key] :string
end
- Demo
make "plaintext "|The five boxing wizards jump quickly| make "key 3 make "ciphertext caesar_cipher :plaintext :key make "recovered caesar_cipher :ciphertext -:key
print sentence "| Original:| :plaintext print sentence "|Encrypted:| :ciphertext print sentence "|Recovered:| :recovered bye</lang>
Output:
Original: The five boxing wizards jump quickly Encrypted: Wkh ilyh eralqj zlcdugv mxps txlfnob Recovered: The five boxing wizards jump quickly
Maple
<lang Maple> > StringTools:-Encode( "The five boxing wizards jump quickly", encoding = alpharot[3] );
"Wkh ilyh eralqj zlcdugv mxps txlfnob"
> StringTools:-Encode( %, encoding = alpharot[ 23 ] );
"The five boxing wizards jump quickly"
</lang> (The symbol % refers the the last (non-NULL) value computed.)
Mathematica
<lang Mathematica>cypher[mesg_String,n_Integer]:=StringReplace[mesg,Flatten[Thread[Rule[#,RotateLeft[#,3]]]&/@CharacterRange@@@{{"a","z"},{"A","Z"}}]]</lang> example output:
cypher["The five boxing wizards jump quickly",3] -> Wkh ilyh eralqj zlcdugv mxps txlfnob
MATLAB / Octave
<lang Matlab> function s = cipherCaesar(s, key)
s = char( mod(s - 'A' + key, 25 ) + 'A');
end;
function s = decipherCaesar(s, key)
s = char( mod(s - 'A' - key, 25 ) + 'A');
end; </lang>
Here is a test: <lang Matlab> decipherCaesar(cipherCaesar('ABC',4),4)
ans = ABC </lang>
NetRexx
The cipher code in this sample is also used in the Rot-13 – NetRexx task. <lang NetRexx>/* NetRexx */
options replace format comments java crossref savelog symbols nobinary
messages = [ -
'The five boxing wizards jump quickly', - 'Attack at dawn!', - 'HI']
keys = [1, 2, 20, 25, 13]
loop m_ = 0 to messages.length - 1
in = messages[m_] loop k_ = 0 to keys.length - 1 say 'Caesar cipher, key:' keys[k_].right(3) ec = caesar_encipher(in, keys[k_]) dc = caesar_decipher(ec, keys[k_]) say in say ec say dc say end k_ say 'Rot-13:' ec = rot13(in) dc = rot13(ec) say in say ec say dc say end m_
return
method rot13(input) public static signals IllegalArgumentException
return caesar(input, 13, isFalse)
method caesar(input = Rexx, idx = int, caps = boolean) public static signals IllegalArgumentException
if idx < 1 | idx > 25 then signal IllegalArgumentException()
-- 12345678901234567890123456 itab = 'ABCDEFGHIJKLMNOPQRSTUVWXYZ' shift = itab.length - idx parse itab tl +(shift) tr otab = tr || tl
if caps then input = input.upper
cipher = input.translate(itab || itab.lower, otab || otab.lower)
return cipher
method caesar_encipher(input = Rexx, idx = int, caps = boolean) public static signals IllegalArgumentException
return caesar(input, idx, caps)
method caesar_decipher(input = Rexx, idx = int, caps = boolean) public static signals IllegalArgumentException
return caesar(input, int(26) - idx, isFalse)
method caesar_encipher(input = Rexx, idx = int) public static signals IllegalArgumentException
return caesar(input, idx, isFalse)
method caesar_decipher(input = Rexx, idx = int) public static signals IllegalArgumentException
return caesar(input, int(26) - idx, isFalse)
method caesar_encipher(input = Rexx, idx = int, opt = Rexx) public static signals IllegalArgumentException
return caesar(input, idx, opt)
method caesar_decipher(input = Rexx, idx = int, opt = Rexx) public static signals IllegalArgumentException
return caesar(input, int(26) - idx, opt)
method caesar(input = Rexx, idx = int, opt = Rexx) public static signals IllegalArgumentException
if opt.upper.abbrev('U') >= 1 then caps = isTrue
else caps = isFalse
return caesar(input, idx, caps)
method caesar(input = Rexx, idx = int) public static signals IllegalArgumentException
return caesar(input, idx, isFalse)
method isTrue public static returns boolean
return (1 == 1)
method isFalse public static returns boolean
return \isTrue</lang>
Caesar cipher, key: 1 The five boxing wizards jump quickly Uif gjwf cpyjoh xjabset kvnq rvjdlmz The five boxing wizards jump quickly Caesar cipher, key: 2 The five boxing wizards jump quickly Vjg hkxg dqzkpi ykbctfu lwor swkemna The five boxing wizards jump quickly Caesar cipher, key: 20 The five boxing wizards jump quickly Nby zcpy vircha qctulxm dogj kocwefs The five boxing wizards jump quickly Caesar cipher, key: 25 The five boxing wizards jump quickly Sgd ehud anwhmf vhyzqcr itlo pthbjkx The five boxing wizards jump quickly Caesar cipher, key: 13 The five boxing wizards jump quickly Gur svir obkvat jvmneqf whzc dhvpxyl The five boxing wizards jump quickly Rot-13: The five boxing wizards jump quickly Gur svir obkvat jvmneqf whzc dhvpxyl The five boxing wizards jump quickly Caesar cipher, key: 1 Attack at dawn! Buubdl bu ebxo! Attack at dawn! Caesar cipher, key: 2 Attack at dawn! Cvvcem cv fcyp! Attack at dawn! Caesar cipher, key: 20 Attack at dawn! Unnuwe un xuqh! Attack at dawn! Caesar cipher, key: 25 Attack at dawn! Zsszbj zs czvm! Attack at dawn! Caesar cipher, key: 13 Attack at dawn! Nggnpx ng qnja! Attack at dawn! Rot-13: Attack at dawn! Nggnpx ng qnja! Attack at dawn! Caesar cipher, key: 1 HI IJ HI Caesar cipher, key: 2 HI JK HI Caesar cipher, key: 20 HI BC HI Caesar cipher, key: 25 HI GH HI Caesar cipher, key: 13 HI UV HI Rot-13: HI UV HI
OCaml
<lang ocaml>let islower c =
c >= 'a' && c <= 'z'
let isupper c =
c >= 'A' && c <= 'Z'
let rot x str =
let upchars = "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
and lowchars = "abcdefghijklmnopqrstuvwxyz" in
let rec decal x =
if x < 0 then decal (x + 26) else x
in
let x = (decal x) mod 26 in
let decal_up = x - (int_of_char 'A')
and decal_low = x - (int_of_char 'a') in
let len = String.length str in
let res = String.create len in
for i = 0 to pred len do
let c = str.[i] in
if islower c then
let j = ((int_of_char c) + decal_low) mod 26 in
res.[i] <- lowchars.[j]
else if isupper c then
let j = ((int_of_char c) + decal_up) mod 26 in
res.[i] <- upchars.[j]
else
res.[i] <- c
done;
(res)
(* or in OCaml 4.00+: let rot x =
let upchars = "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
and lowchars = "abcdefghijklmnopqrstuvwxyz" in
let rec decal x =
if x < 0 then decal (x + 26) else x
in
let x = (decal x) mod 26 in
let decal_up = x - (int_of_char 'A')
and decal_low = x - (int_of_char 'a') in
String.map (fun c ->
if islower c then
let j = ((int_of_char c) + decal_low) mod 26 in
lowchars.[j]
else if isupper c then
let j = ((int_of_char c) + decal_up) mod 26 in
upchars.[j]
else
c
)
- )</lang>
<lang ocaml>let () =
let key = 3 in let orig = "The five boxing wizards jump quickly" in let enciphered = rot key orig in print_endline enciphered; let deciphered = rot (- key) enciphered in print_endline deciphered; Printf.printf "equal: %b\n" (orig = deciphered)
- </lang>
Output:
$ ocaml caesar.ml Wkh ilyh eralqj zlcdugv mxps txlfnob The five boxing wizards jump quickly equal: true
PARI/GP
<lang parigp>enc(s,n)={
Strchr(Vecsmall(apply(k->if(k>96&&k<123,(k+n-97)%26+97, if(k>64&&k<91, (k+n-65)%26+65, k)), Vec(Vecsmall(s)))))
}; dec(s,n)=enc(s,-n);</lang>
Pascal
<lang pascal>Program CaesarCipher(output);
procedure encrypt(var message: string; key: integer);
var
i: integer;
begin
for i := 1 to length(message) do
case message[i] of
'A'..'Z': message[i] := chr(ord('A') + (ord(message[i]) - ord('A') + key) mod 26);
'a'..'z': message[i] := chr(ord('a') + (ord(message[i]) - ord('a') + key) mod 26);
end;
end;
procedure decrypt(var message: string; key: integer);
var
i: integer;
begin
for i := 1 to length(message) do
case message[i] of
'A'..'Z': message[i] := chr(ord('A') + (ord(message[i]) - ord('A') - key + 26) mod 26);
'a'..'z': message[i] := chr(ord('a') + (ord(message[i]) - ord('a') - key + 26) mod 26);
end;
end;
var
key: integer; message: string;
begin
key := 3;
message := 'The five boxing wizards jump quickly';
writeln ('Original message: ', message);
encrypt(message, key);
writeln ('Encrypted message: ', message);
decrypt(message, key);
writeln ('Decrypted message: ', message);
end.</lang> Output:
>: ./CaesarCipher Original message: The five boxing wizards jump quickly Encrypted message: Wkh ilyh eralqj zlcdugv mxps txlfnob Decrypted message: The five boxing wizards jump quickly >:
Perl
It's supposed to be a cipher, so all non-letters are dropped. <lang Perl>sub encipher {
my ($_, $k, $decode) = @_;
$k = 26 - $k if $decode;
join(, map(chr(((ord(uc $_) - 65 + $k) % 26) + 65), /([a-z])/gi));
}
my $msg = 'THE FIVE BOXING WIZARDS JUMP QUICKLY'; my $enc = encipher($msg, 10); my $dec = encipher($enc, 10, 'decode');
print "msg: $msg\nenc: $enc\ndec: $dec\n";</lang>output
msg: THE FIVE BOXING WIZARDS JUMP QUICKLY enc: DROPSFOLYHSXQGSJKBNCTEWZAESMUVI dec: THEFIVEBOXINGWIZARDSJUMPQUICKLY
Perl 6
<lang perl6>my @alpha = 'A' .. 'Z'; sub encrypt ( $key where 1..25, $plaintext ) {
$plaintext.trans( @alpha Z=> @alpha.rotate($key) );
} sub decrypt ( $key where 1..25, $cyphertext ) {
$cyphertext.trans( @alpha.rotate($key) Z=> @alpha );
}
my $original = 'THE FIVE BOXING WIZARDS JUMP QUICKLY'; my $en = encrypt( 13, $original ); my $de = decrypt( 13, $en );
.say for $original, $en, $de;
say 'OK' if $original eq all( map { .&decrypt(.&encrypt($original)) }, 1..25 );</lang>
Output:
THE FIVE BOXING WIZARDS JUMP QUICKLY GUR SVIR OBKVAT JVMNEQF WHZC DHVPXYL THE FIVE BOXING WIZARDS JUMP QUICKLY OK
PHP
<lang php><?php function caesarEncode( $message, $key ){
$plaintext = strtolower( $message );
$ciphertext = "";
$ascii_a = ord( 'a' );
$ascii_z = ord( 'z' );
while( strlen( $plaintext ) ){
$char = ord( $plaintext );
if( $char >= $ascii_a && $char <= $ascii_z ){
$char = ( ( $key + $char - $ascii_a ) % 26 ) + $ascii_a;
}
$plaintext = substr( $plaintext, 1 );
$ciphertext .= chr( $char );
}
return $ciphertext;
}
echo caesarEncode( "The quick brown fox Jumped over the lazy Dog", 12 ), "\n"; ?></lang>
Output:
ftq cguow ndaiz raj vgybqp ahqd ftq xmlk pas
PicoLisp
<lang PicoLisp>(setq *Letters (apply circ (mapcar char (range 65 90))))
(de caesar (Str Key)
(pack
(mapcar '((C) (cadr (nth (member C *Letters) Key)))
(chop (uppc Str)) ) ) )</lang>
Test:
: (caesar "IBM" 25) -> "HAL" : (caesar @ 1) -> "IBM" : (caesar "The quick brown fox jumped over the lazy dog's back" 7) -> "AOLXBPJRIYVDUMVEQBTWLKVCLYAOLSHGFKVNZIHJR" : (caesar @ (- 26 7)) -> "THEQUICKBROWNFOXJUMPEDOVERTHELAZYDOGSBACK"
PL/I
<lang PL/I>caesar: procedure options (main);
declare cypher_string character (52) static initial
((2)'ABCDEFGHIJKLMNOPQRSTUVWXYZ');
declare (text, encyphered_text) character (100) varying,
offset fixed binary;
get edit (text) (L); /* Read in one line of text */
get list (offset);
if offset < 1 | offset > 25 then signal error;
put skip list ('Plain text=', text);
encyphered_text = translate(text, substr(cypher_string, offset+1, 26),
'ABCDEFGHIJKLMNOPQRSTUVWXYZ' );
put skip list ('Encyphered text=', encyphered_text);
text = translate(encyphered_text, substr(cypher_string, 27-offset, 26),
'ABCDEFGHIJKLMNOPQRSTUVWXYZ' );
put skip list ('Decyphered text=', text);
end caesar;</lang> Output with offset of 5:
Plain text= THEQUICKBROWNFOXJUMPSOVERTHELAZYDOG Encyphered text= YMJVZNHPGWTBSKTCOZRUXTAJWYMJQFEDITL Decyphered text= THEQUICKBROWNFOXJUMPSOVERTHELAZYDOG
Prolog
<lang Prolog>:- use_module(library(clpfd)).
caesar :- L1 = "The five boxing wizards jump quickly", writef("Original : %s\n", [L1]),
% encryption of the sentence encoding(3, L1, L2) , writef("Encoding : %s\n", [L2]),
% deciphering on the encoded sentence encoding(3, L3, L2), writef("Decoding : %s\n", [L3]).
% encoding/decoding of a sentence encoding(Key, L1, L2) :- maplist(caesar_cipher(Key), L1, L2).
caesar_cipher(_, 32, 32) :- !.
caesar_cipher(Key, V1, V2) :- V #= Key + V1,
% we verify that we are in the limits of A-Z and a-z. ((V1 #=< 0'Z #/\ V #> 0'Z) #\/ (V1 #=< 0'z #/\ V #> 0'z) #\/ (V1 #< 0'A #/\ V2 #>= 0'A)#\/ (V1 #< 0'a #/\ V2 #>= 0'a)) #==> A,
% if we are not in these limits A is 1, otherwise 0. V2 #= V - A * 26,
% compute values of V1 and V2 label([A, V1, V2]).</lang> Output :
?- caesar. Original : The five boxing wizards jump quickly Encoding : Wkh ilyh eralqj zlcdugv mxps txlfnob Decoding : The five boxing wizards jump quickly true .
PureBasic
The case is maintained for alphabetic characters (uppercase/lowercase input = uppercase/lowercase output) while non-alphabetic characters, if present are included and left unchanged in the result. <lang PureBasic>Procedure.s CC_encrypt(plainText.s, key, reverse = 0)
;if reverse <> 0 then reverse the encryption (decrypt)
If reverse: reverse = 26: key = 26 - key: EndIf
Static alphabet$ = "ABCEFGHIJKLMNOPQRSTUVWXYZABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwxyz"
Protected result.s, i, length = Len(plainText), letter.s, legal
If key < 1 Or key > 25: ProcedureReturn: EndIf ;keep key in range
For i = 1 To length
letter = Mid(plainText, i, 1)
legal = FindString(alphabet$, letter, 1 + reverse)
If legal
result + Mid(alphabet$, legal + key, 1)
Else
result + letter
EndIf
Next
ProcedureReturn result
EndProcedure
Procedure.s CC_decrypt(cypherText.s, key)
ProcedureReturn CC_encrypt(cypherText, key, 1)
EndProcedure
If OpenConsole()
Define key, plainText.s, encryptedText.s, decryptedText.s
key = Random(24) + 1 ;get a random key in the range 1 -> 25
plainText = "The quick brown fox jumped over the lazy dogs.": PrintN(RSet("Plain text = ", 17) + #DQUOTE$ + plainText + #DQUOTE$)
encryptedText = CC_encrypt(plainText, key): PrintN(RSet("Encrypted text = ", 17) + #DQUOTE$ + encryptedText + #DQUOTE$)
decryptedText = CC_decrypt(encryptedText, key): PrintN(RSet("Decrypted text = ", 17) + #DQUOTE$ + decryptedText + #DQUOTE$)
Print(#CRLF$ + #CRLF$ + "Press ENTER to exit"): Input()
CloseConsole()
EndIf</lang> Sample output:
Plain text = "The quick brown fox jumped over the lazy dogs." Encrypted text = "Znk waoiq hxuct lud pasvkj ubkx znk rgfe jumy." Decrypted text = "the quick brown fox jumped over the lazy dogs."
Alternate solution
Here is an alternate and more advanced form of the encrypt procedure. It improves on the simple version in terms of speed, in case Caesar is using the cipher on some very long documents. It is meant to replace the encrypt procedure in the previous code and produces identical results. <lang PureBasic>Procedure.s CC_encrypt(text.s, key, reverse = 0)
;if reverse <> 0 then reverse the encryption (decrypt)
Protected i, *letter.Character, *resultLetter.Character, result.s = Space(Len(text))
If reverse: key = 26 - key: EndIf
If key < 1 Or key > 25: ProcedureReturn: EndIf ;exit if key out of range
*letter = @text: *resultLetter = @result
While *letter\c
Select *letter\c
Case 'A' To 'Z'
*resultLetter\c = ((*letter\c - 65 + key) % 26) + 65
Case 'a' To 'z'
*resultLetter\c = ((*letter\c - 97 + key) % 26) + 97
Default
*resultLetter\c = *letter\c
EndSelect
*letter + SizeOf(Character): *resultLetter + SizeOf(Character)
Wend
ProcedureReturn result
EndProcedure</lang>
Python
<lang Python>def caesar(s, k, decode = False): if decode: k = 26 - k return "".join([chr((ord(i) - 65 + k) % 26 + 65) for i in s.upper() if ord(i) >= 65 and ord(i) <= 90 ])
msg = "The quick brown fox jumped over the lazy dogs" print msg enc = caesar(msg, 11) print enc
print caesar(enc, 11, decode = True)</lang>Output:
The quick brown fox jumped over the lazy dogs ESPBFTNVMCZHYQZIUFXAPOZGPCESPWLKJOZRD THEQUICKBROWNFOXJUMPEDOVERTHELAZYDOGS
Alternate solution
(for 3.x change string.maketrans to str.maketrans)
<lang python>import string def caesar(s, k, decode = False):
if decode: k = 26 - k
return s.translate(
string.maketrans(
string.ascii_uppercase + string.ascii_lowercase,
string.ascii_uppercase[k:] + string.ascii_uppercase[:k] +
string.ascii_lowercase[k:] + string.ascii_lowercase[:k]
)
)
msg = "The quick brown fox jumped over the lazy dogs" print msg enc = caesar(msg, 11) print enc print caesar(enc, 11, decode = True)</lang> Output:
The quick brown fox jumped over the lazy dogs Esp bftnv mczhy qzi ufxapo zgpc esp wlkj ozrd The quick brown fox jumped over the lazy dogs
A compact alternative solution <lang python> from string import ascii_uppercase as abc
def caesar(s, k, decode = False):
trans = dict(zip(abc, abc[(k,26-k)[decode]:] + abc[:(k,26-k)[decode]])) return .join(trans[L] for L in s.upper() if L in abc)
msg = "The quick brown fox jumped over the lazy dogs" print(caesar(msg, 11)) print(caesar(caesar(msg, 11), 11, True)) </lang> Output:
ESPBFTNVMCZHYQZIUFXAPOZGPCESPWLKJOZRD THEQUICKBROWNFOXJUMPEDOVERTHELAZYDOGS
Racket
<lang scheme>#lang racket
(define A (char->integer #\A)) (define Z (char->integer #\Z)) (define a (char->integer #\a)) (define z (char->integer #\z))
(define (rotate c n)
(define cnum (char->integer c))
(define (shift base) (integer->char (+ base (modulo (+ n (- cnum base)) 26))))
(cond [(<= A cnum Z) (shift A)]
[(<= a cnum z) (shift a)]
[else c]))
(define (caesar s n)
(list->string (for/list ([c (in-string s)]) (rotate c n))))
(define (encrypt s) (caesar s 1)) (define (decrypt s) (caesar s -1))</lang> Example: <lang scheme>> (define s (encrypt "The five boxing wizards jump quickly.")) > s "Uif gjwf cpyjoh xjabset kvnq rvjdlmz." > (decrypt s) "The five boxing wizards jump quickly."</lang>
Retro
Retro provides a number of classical cyphers in the crypto' library. This implementation is from the library. <lang Retro>{{
variable offset : rotate ( cb-c ) tuck - @offset + 26 mod + ; : rotate? ( c-c ) dup 'a 'z within [ 'a rotate ] ifTrue dup 'A 'Z within [ 'A rotate ] ifTrue ;
---reveal---
: ceaser ( $n-$ ) !offset dup [ [ @ rotate? ] sip ! ] ^types'STRING each@ ;
}}
( Example ) "THEYBROKEOURCIPHEREVERYONECANREADTHIS" 3 ceaser ( returns encrypted string ) 23 ceaser ( returns decrypted string )</lang>
REXX
only Latin letters
This version conforms to the task's restrictions. <lang rexx>/*REXX pgm: Caesar cypher: Latin alphabet only, no punctuation or blanks*/ /* allowed, all lowercase Latin letters are treated as uppercase. */ arg key p /*get key and text to be cyphered*/ p=space(p,0) /*remove all blanks from text. */
say 'Caesar cypher key:' key
say ' plain text:' p
y=caesar(p, key) ; say ' cyphered:' y z=caesar(y,-key) ; say ' uncyphered:' z if z\==p then say "plain text doesn't match uncyphered cyphered text." exit /*stick a fork in it, we're done.*/ /*──────────────────────────────────CAESAR subroutine───────────────────*/ caesar: procedure; arg s,k; @='ABCDEFGHIJKLMNOPQRSTUVWXYZ'; L=length(@) ak=abs(k) if ak > length(@)-1 | k==0 | k== then call err k 'key is invalid' _=verify(s,@) /*any illegal char specified ? */ if _\==0 then call err 'unsupported character:' substr(s,_,1)
/*now that error checks are done:*/
if k>0 then ky=k+1 /*either cypher it, or ... */
else ky=27-ak /* decypher it. */
return translate(s,substr(@||@,ky,L),@)
/*──────────────────────────────────ERR subroutine──────────────────────*/
err: say; say '***error!***'; say; say arg(1); say; exit 13</lang>
output when using the input of:
22 The definition of a trival program is one that has no bugs
Caesar cypher key: 22
plain text: THEDEFINITIONOFATRIVALPROGRAMISONETHATHASNOBUGS
cyphered: PDAZABEJEPEKJKBWPNERWHLNKCNWIEOKJAPDWPDWOJKXQCO
uncyphered: THEDEFINITIONOFATRIVALPROGRAMISONETHATHASNOBUGS
almost all characters
This version allows upper and lowercase Latin alphabet as well as all the characters on the standard (computer) keyboard including blanks. <lang rexx>/*REXX pgm: Caesar cypher for almost all keyboard chars including blanks*/ parse arg key p /*get key and text to be cyphered*/
say 'Caesar cypher key:' key
say ' plain text:' p
y=caesar(p, key) ; say ' cyphered:' y z=caesar(y,-key) ; say ' uncyphered:' z if z\==p then say "plain text doesn't match uncyphered cyphered text." exit /*stick a fork in it, we're done.*/ /*──────────────────────────────────CAESAR subroutine───────────────────*/ caesar: procedure; parse arg s,k; @='abcdefghijklmnopqrstuvwxyz' @=translate(@)@'0123456789(){}[]<>' /*add uppercase, digs, group symb*/ @=@'~!@#$%^&*_+:";?,./`-= /*add other characters here. */
/*last char is doubled, REXX quoted syntax rules.*/
L=length(@) ak=abs(k) if ak>length(@)-1 | k==0 then call err k 'key is invalid' _=verify(s,@) /*any illegal char specified ? */ if _\==0 then call err 'unsupported character:' substr(s,_,1) if k>0 then ky=k+1
else ky=L+1-ak
return translate(s,substr(@||@,ky,L),@)
/*──────────────────────────────────ERR subroutine──────────────────────*/
err: say; say '***error!***'; say; say arg(1); say; exit 13</lang>
output when using the input of:
31 Batman's hood is called a "cowl" (old meaning).
Caesar cypher key: 31
plain text: Batman's hood is called a "cowl" (old meaning).
cyphered: g5^>5~e%d{!!8d}%d75<<98d5dU7!_<UdA!<8d>95~}~)BY
uncyphered: Batman's hood is called a "cowl" (old meaning).
Ruby
(use of rotate)
<lang ruby>@atoz = Hash.new do |hash, key|
str = ('A'..'Z').to_a.rotate(key).join("")
hash[key] = (str << str.downcase)
end
def encrypt(key, plaintext)
(1..25) === key or raise ArgumentError, "key not in 1..25" plaintext.tr(@atoz[0], @atoz[key])
end
def decrypt(key, ciphertext)
(1..25) === key or raise ArgumentError, "key not in 1..25" ciphertext.tr(@atoz[key], @atoz[0])
end
original = "THEYBROKEOURCIPHEREVERYONECANREADTHIS" en = encrypt(3, original) de = decrypt(3, en)
[original, en, de].each {|e| puts e}
puts 'OK' if
(1..25).all? {|k| original == decrypt(k, encrypt(k, original))}</lang>
The Ruby translation saves the rotations in an @atoz hash. (The Perl 6 code called rotate() during each encrypt or decrypt.) The code block on Hash.new makes the rotation and puts it in the hash.
@atoz[0]becomes"ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz",@atoz[3]becomes"DEFGHIJKLMNOPQRSTUVWXYZABCdefghijklmnopqrstuvwxyzabc",- and so on.
When the key is 3, encryption uses String#tr(@atoz[0], @atoz[3]) to substitute characters. Decryption uses String#tr(@atoz[3], @atoz[0]).
To make a rotation, Ruby is worse than Perl 6. Ruby needs two extra conversions: the code ('A'..'Z').to_a.rotate(key).join("") uses to_a to convert a Range to an Array, to access the Array#rotate method. Then join("") converts the rotated Array to a String, because String#tr needs a String, not an Array.
Run BASIC
<lang runbasic>input "Gimme a ofset:";ofst ' set any offset you like
a$ = "Pack my box with five dozen liquor jugs" print " Original: ";a$ a$ = cipher$(a$,ofst) print "Encrypted: ";a$ print "Decrypted: ";cipher$(a$,ofst+6)
FUNCTION cipher$(a$,ofst) for i = 1 to len(a$)
aa$ = mid$(a$,i,1) code$ = " " if aa$ <> " " then ua$ = upper$(aa$) a = asc(ua$) - 64 code$ = chr$((((a mod 26) + ofst) mod 26) + 65) if ua$ <> aa$ then code$ = lower$(code$) end if cipher$ = cipher$;code$
next i END FUNCTION</lang>Output:
Gimme a ofset:?9 Original: Pack my box with five dozen liquor jugs Encrypted: Zkmu wi lyh gsdr psfo nyjox vsaeyb teqc Decrypted: Pack my box with five dozen liquor jugs
Scala
<lang scala>object Caesar {
private val alphaU='A' to 'Z' private val alphaL='a' to 'z'
def encode(text:String, key:Int)=text.map{
case c if alphaU.contains(c) => rot(alphaU, c, key)
case c if alphaL.contains(c) => rot(alphaL, c, key)
case c => c
}
def decode(text:String, key:Int)=encode(text,-key)
private def rot(a:IndexedSeq[Char], c:Char, key:Int)=a((c-a.head+key+a.size)%a.size)
}</lang> <lang scala>val text="The five boxing wizards jump quickly" println("Plaintext => " + text) val encoded=Caesar.encode(text, 3) println("Ciphertext => " + encoded) println("Decrypted => " + Caesar.decode(encoded, 3))</lang> Output:
Plaintext => The five boxing wizards jump quickly Ciphertext => Wkh ilyh eralqj zlcdugv mxps txlfnob Decrypted => The five boxing wizards jump quickly
scheme
<lang scheme>#!/usr/bin/env gosh
(use srfi-13) ;; xsubstring
(define message "To craunch the marmoset.") (define key 1)
(define (caesar-encrypt enc key message)
(let* ((msg-lst (string->list (string-upcase message)))
(clr-lst (string->list "ABCDEFGHIJKLMNOPQRSTUVWXYZ"))
(enc-lst (string->list (xsubstring (list->string clr-lst) key)))
(xlt-tab (if enc (map list clr-lst enc-lst) (map list enc-lst clr-lst))))
(let loop ((msg msg-lst)(out (list)))
(if (not (pair? msg))
(list->string out)
(let* ((mchr (car msg))
(xchr (assq mchr xlt-tab))
(echr (if xchr (cdr xchr) (list mchr))))
(loop (cdr msg) (append out echr)))))))
(format #t " Key: ~a~%" key)
(format #t "Message: ~a~%" message)
(let* ((em (caesar-encrypt #t key message))
(dm (caesar-encrypt #f key em))) (format #t "Encrypt: ~a~%" em) (format #t "Decrypt: ~a~%" dm))
</lang>
Example output:
Key: 1 Message: To craunch the marmoset. Encrypt: UP DSBVODI UIF NBSNPTFU. Decrypt: TO CRAUNCH THE MARMOSET.
sed
This code is roughly equivalent to the rot-13 cypher sed implementation, except that the conversion table is parameterized by a number and that the conversion done manually, instead of using `y///' command. <lang sed>#!/bin/sed -rf
- Input: <number 0..25>\ntext to encode
/^[0-9]+$/ { # validate a number and translate it to analog form s/$/;9876543210dddddddddd/ s/([0-9]);.*\1.{10}(.?)/\2/ s/2/11/ s/1/dddddddddd/g /[3-9]|d{25}d+/ { s/.*/Error: Key must be <= 25/ q } # append from-table s/$/\nabcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ/ # .. and to-table s/$/abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ/ # rotate to-table, lower and uppercase independently, removing one `d' at a time : rotate s/^d(.*\n[^Z]+Z)(.)(.{25})(.)(.{25})/\1\3\2\5\4/ t rotate s/\n// h d }
- use \n to mark character to convert
s/^/\n/
- append conversion table to pattern space
G
- loop
# look up converted character and place it instead of old one s/\n(.)(.*\n.*\1.{51}(.))/\n\3\2/ # advance \n even if prev. command fails, thus skip non-alphabetical characters /\n\n/! s/\n([^\n])/\1\n/ t loop s/\n\n.*//</lang> Output:
$ ./caesar.sed 3 The five boxing wizards jump quickly Wkh ilyh eralqj zlcdugv mxps txlfnob 23 Wkh ilyh eralqj zlcdugv mxps txlfnob The five boxing wizards jump quickly 26 Error: Key must be <= 25
Seed7
<lang seed7>$ include "seed7_05.s7i";
const func string: rot (in string: stri, in integer: encodingKey) is func
result
var string: encodedStri is "";
local
var char: ch is ' ';
var integer: index is 0;
begin
encodedStri := stri;
for ch key index range stri do
if ch >= 'a' and ch <= 'z' then
ch := chr((ord(ch) - ord('a') + encodingKey) rem 26 + ord('a'));
elsif ch >= 'A' and ch <= 'Z' then
ch := chr((ord(ch) - ord('A') + encodingKey) rem 26 + ord('A'));
end if;
encodedStri @:= [index] ch;
end for;
end func;
const proc: main is func
local
const integer: exampleKey is 3;
const string: testText is "The five boxing wizards jump quickly";
begin
writeln("Original: " <& testText);
writeln("Encrypted: " <& rot(testText, exampleKey));
writeln("Decrypted: " <& rot(rot(testText, exampleKey), 26 - exampleKey));
end func;</lang>
Output:
Original: The five boxing wizards jump quickly Encrypted: Wkh ilyh eralqj zlcdugv mxps txlfnob Decrypted: The five boxing wizards jump quickly
Smalltalk
well, I'm lucky: the standard library already contains a rot:n method! <lang Smalltalk>'THE QUICK BROWN FOX' rot:3 -> 'WKH TXLFN EURZQ IRA' </lang> but if it wasn't, here is an implementation:
<lang smalltalk> !CharacterArray methodsFor:'encoding'! rot:n
^ self class
streamContents:[:aStream |
self do:[:char |
aStream nextPut:(char rot:n) ]]
!Character methodsFor:'encoding'! rot:n
(self isLetter) ifTrue:[
self isLowercase ifTrue:[
^ 'abcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwxyz' at:(self-$a+1+n)
] ifFalse:[
^ 'ABCDEFGHIJKLMNOPQRSTUVWXYZABCDEFGHIJKLMNOPQRSTUVWXYZ' at:(self-$A+1+n)
]
].
^ self
</lang>
Tcl
<lang tcl>package require Tcl 8.6; # Or TclOO package for 8.5
oo::class create Caesar {
variable encryptMap decryptMap
constructor shift {
for {set i 0} {$i < 26} {incr i} { # Play fast and loose with string/list duality for shorter code append encryptMap [format "%c %c %c %c " \ [expr {$i+65}] [expr {($i+$shift)%26+65}] \ [expr {$i+97}] [expr {($i+$shift)%26+97}]] append decryptMap [format "%c %c %c %c " \ [expr {$i+65}] [expr {($i-$shift)%26+65}] \ [expr {$i+97}] [expr {($i-$shift)%26+97}]] }
}
method encrypt text {
string map $encryptMap $text
}
method decrypt text {
string map $decryptMap $text
}
}</lang> Demonstrating: <lang tcl>set caesar [Caesar new 3] set txt "The five boxing wizards jump quickly." set enc [$caesar encrypt $txt] set dec [$caesar decrypt $enc] puts "Original message = $txt" puts "Encrypted message = $enc" puts "Decrypted message = $dec"</lang> Output:
Original message = The five boxing wizards jump quickly. Encrypted message = Wkh ilyh eralqj zlcdugv mxps txlfnob. Decrypted message = The five boxing wizards jump quickly.
TUSCRIPT
<lang tuscript>$$ MODE TUSCRIPT text="THE QUICK BROWN FOX JUMPS OVER THE LAZY DOG" PRINT "text orginal ",text
abc="ABCDEFGHIJKLMNOPQRSTUVWXYZ",key=3,caesarskey=key+1 secretbeg=EXTRACT (abc,#caesarskey,0) secretend=EXTRACT (abc,0,#caesarskey) secretabc=CONCAT (secretbeg,secretend)
abc=STRINGS (abc,":</:"),secretabc=STRINGS (secretabc,":</:") abc=SPLIT (abc), secretabc=SPLIT (secretabc) abc2secret=JOIN(abc," ",secretabc),secret2abc=JOIN(secretabc," ",abc)
BUILD X_TABLE abc2secret=* DATA {abc2secret}
BUILD X_TABLE secret2abc=* DATA {secret2abc}
ENCODED = EXCHANGE (text,abc2secret) PRINT "text encoded ",encoded
DECODED = EXCHANGE (encoded,secret2abc) PRINT "encoded decoded ",decoded</lang> Output:
text orginal THE QUICK BROWN FOX JUMPS OVER THE LAZY DOG text encoded WKH TXLFN EURZQ IRA MXPSV RYHU WKH ODCB GRJ encoded decoded THE QUICK BROWN FOX JUMPS OVER THE LAZY DOG
TXR
The strategy here, one of many possible ones, is to build, at run time,the arguments to be passed to deffilter to construct a pair of filters enc and dec for encoding and decoding. Filters are specified as tuples of strings.
<lang txr>@(next :args)
@(cases)
@{key /[0-9]+/}
@text
@(or)
@ (throw error "specify <key-num> <text>")
@(end)
@(do
(defvar k (int-str key 10)))
@(bind enc-dec
@(collect-each ((i (range 0 25)))
(let* ((p (tostringp (+ #\a i)))
(e (tostringp (+ #\a (mod (+ i k) 26))))
(P (upcase-str p))
(E (upcase-str e)))
'(((,p ,e) (,P ,E))
((,e ,p) (,E ,P))))))
@(deffilter enc . @(mappend (fun first) enc-dec)) @(deffilter dec . @(mappend (fun second) enc-dec)) @(output) encoded: @{text :filter enc} decoded: @{text :filter dec} @(end)</lang> Run:
$ ./txr caesar.txr 12 'Hello, world!' encoded: Tqxxa, iadxp! decoded: Vszzc, kcfzr! $ ./txr caesar.txr 12 'Vszzc, kcfzr!' encoded: Hello, world! decoded: Jgnnq, yqtnf!
Ursala
The reification operator (-:) generates efficient code for applications like this given a table of inputs and outputs, which is obtained in this case by zipping the alphabet with itself rolled the right number of times, done separately for the upper and lower case letters and then combined.
<lang Ursala>#import std
- import nat
enc "n" = * -:~&@T ^p(rep"n" ~&zyC,~&)~~K30K31X letters # encryption function dec "n" = * -:~&@T ^p(~&,rep"n" ~&zyC)~~K30K31X letters # decryption function
plaintext = 'the five boxing wizards jump quickly THE FIVE BOXING WIZARDS JUMP QUICKLY'
- show+ # exhaustive test
test = ("n". <.enc"n",dec"n"+ enc"n"> plaintext)*= nrange/1 25</lang> output:
uif gjwf cpyjoh xjabset kvnq rvjdlmz UIF GJWF CPYJOH XJABSET KVNQ RVJDLMZ the five boxing wizards jump quickly THE FIVE BOXING WIZARDS JUMP QUICKLY vjg hkxg dqzkpi ykbctfu lwor swkemna VJG HKXG DQZKPI YKBCTFU LWOR SWKEMNA the five boxing wizards jump quickly THE FIVE BOXING WIZARDS JUMP QUICKLY wkh ilyh eralqj zlcdugv mxps txlfnob WKH ILYH ERALQJ ZLCDUGV MXPS TXLFNOB the five boxing wizards jump quickly THE FIVE BOXING WIZARDS JUMP QUICKLY xli jmzi fsbmrk amdevhw nyqt uymgopc XLI JMZI FSBMRK AMDEVHW NYQT UYMGOPC the five boxing wizards jump quickly THE FIVE BOXING WIZARDS JUMP QUICKLY ymj knaj gtcnsl bnefwix ozru vznhpqd YMJ KNAJ GTCNSL BNEFWIX OZRU VZNHPQD the five boxing wizards jump quickly THE FIVE BOXING WIZARDS JUMP QUICKLY znk lobk hudotm cofgxjy pasv waoiqre ZNK LOBK HUDOTM COFGXJY PASV WAOIQRE the five boxing wizards jump quickly THE FIVE BOXING WIZARDS JUMP QUICKLY aol mpcl ivepun dpghykz qbtw xbpjrsf AOL MPCL IVEPUN DPGHYKZ QBTW XBPJRSF the five boxing wizards jump quickly THE FIVE BOXING WIZARDS JUMP QUICKLY bpm nqdm jwfqvo eqhizla rcux ycqkstg BPM NQDM JWFQVO EQHIZLA RCUX YCQKSTG the five boxing wizards jump quickly THE FIVE BOXING WIZARDS JUMP QUICKLY cqn oren kxgrwp frijamb sdvy zdrltuh CQN OREN KXGRWP FRIJAMB SDVY ZDRLTUH the five boxing wizards jump quickly THE FIVE BOXING WIZARDS JUMP QUICKLY dro psfo lyhsxq gsjkbnc tewz aesmuvi DRO PSFO LYHSXQ GSJKBNC TEWZ AESMUVI the five boxing wizards jump quickly THE FIVE BOXING WIZARDS JUMP QUICKLY esp qtgp mzityr htklcod ufxa bftnvwj ESP QTGP MZITYR HTKLCOD UFXA BFTNVWJ the five boxing wizards jump quickly THE FIVE BOXING WIZARDS JUMP QUICKLY ftq ruhq najuzs iulmdpe vgyb cguowxk FTQ RUHQ NAJUZS IULMDPE VGYB CGUOWXK the five boxing wizards jump quickly THE FIVE BOXING WIZARDS JUMP QUICKLY gur svir obkvat jvmneqf whzc dhvpxyl GUR SVIR OBKVAT JVMNEQF WHZC DHVPXYL the five boxing wizards jump quickly THE FIVE BOXING WIZARDS JUMP QUICKLY hvs twjs pclwbu kwnofrg xiad eiwqyzm HVS TWJS PCLWBU KWNOFRG XIAD EIWQYZM the five boxing wizards jump quickly THE FIVE BOXING WIZARDS JUMP QUICKLY iwt uxkt qdmxcv lxopgsh yjbe fjxrzan IWT UXKT QDMXCV LXOPGSH YJBE FJXRZAN the five boxing wizards jump quickly THE FIVE BOXING WIZARDS JUMP QUICKLY jxu vylu renydw mypqhti zkcf gkysabo JXU VYLU RENYDW MYPQHTI ZKCF GKYSABO the five boxing wizards jump quickly THE FIVE BOXING WIZARDS JUMP QUICKLY kyv wzmv sfozex nzqriuj aldg hlztbcp KYV WZMV SFOZEX NZQRIUJ ALDG HLZTBCP the five boxing wizards jump quickly THE FIVE BOXING WIZARDS JUMP QUICKLY lzw xanw tgpafy oarsjvk bmeh imaucdq LZW XANW TGPAFY OARSJVK BMEH IMAUCDQ the five boxing wizards jump quickly THE FIVE BOXING WIZARDS JUMP QUICKLY max ybox uhqbgz pbstkwl cnfi jnbvder MAX YBOX UHQBGZ PBSTKWL CNFI JNBVDER the five boxing wizards jump quickly THE FIVE BOXING WIZARDS JUMP QUICKLY nby zcpy vircha qctulxm dogj kocwefs NBY ZCPY VIRCHA QCTULXM DOGJ KOCWEFS the five boxing wizards jump quickly THE FIVE BOXING WIZARDS JUMP QUICKLY ocz adqz wjsdib rduvmyn ephk lpdxfgt OCZ ADQZ WJSDIB RDUVMYN EPHK LPDXFGT the five boxing wizards jump quickly THE FIVE BOXING WIZARDS JUMP QUICKLY pda bera xktejc sevwnzo fqil mqeyghu PDA BERA XKTEJC SEVWNZO FQIL MQEYGHU the five boxing wizards jump quickly THE FIVE BOXING WIZARDS JUMP QUICKLY qeb cfsb ylufkd tfwxoap grjm nrfzhiv QEB CFSB YLUFKD TFWXOAP GRJM NRFZHIV the five boxing wizards jump quickly THE FIVE BOXING WIZARDS JUMP QUICKLY rfc dgtc zmvgle ugxypbq hskn osgaijw RFC DGTC ZMVGLE UGXYPBQ HSKN OSGAIJW the five boxing wizards jump quickly THE FIVE BOXING WIZARDS JUMP QUICKLY sgd ehud anwhmf vhyzqcr itlo pthbjkx SGD EHUD ANWHMF VHYZQCR ITLO PTHBJKX the five boxing wizards jump quickly THE FIVE BOXING WIZARDS JUMP QUICKLY
Vedit macro language
This implementation ciphers/deciphers a highlighted block of text in-place in current edit buffer. <lang vedit>#10 = Get_Num("Enter the key: positive to cipher, negative to de-cipher: ", STATLINE)
Goto_Pos(Block_Begin) while(Cur_Pos < Block_End) {
#11 = Cur_Char & 0x60 + 1
if (Cur_Char >= 'A') {
Ins_Char((Cur_Char - #11 + 26 + #10) % 26 + #11, OVERWRITE)
} else {
Char(1)
}
}</lang>
Sample output with key 13:
Original text: Quick brown Fox jumps over the lazy Dog. Encrypted text: Dhvpx oebja Sbk whzcf bire gur ynml Qbt. Decrypted text: Quick brown Fox jumps over the lazy Dog.
XPL0
To decrypt a message use the negative value of the encrypting key. Usage: caesar key <infile.txt >outfile.xxx
<lang XPL0>code ChIn=7, ChOut=8, IntIn=10; int Key, C; [Key:= IntIn(8); repeat C:= ChIn(1);
if C>=^a & C<=^z then C:= C-$20;
if C>=^A & C<=^Z then
[C:= C+Key;
if C>^Z then C:= C-26
else if C<^A then C:= C+26;
];
ChOut(0, C);
until C=$1A; \EOF ]</lang>
Example outfile.xxx:
SDFN PB ERA ZLWK ILYH GRCHQ OLTXRU MXJV.
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