⚠️ Warning: This is a draft ⚠️

This means it might contain formatting issues, incorrect code, conceptual problems, or other severe issues.

If you want to help to improve and eventually enable this page, please fork RosettaGit's repository and open a merge request on GitHub.

{{draft task|Encryption}} [[Category:String manipulation]]

Substitution Cipher Implementation - File Encryption/Decryption

;Task: Encrypt a input/source file by replacing every upper/lower case alphabets of the source file with another predetermined upper/lower case alphabets or symbols and save it into another output/encrypted file and then again convert that output/encrypted file into original/decrypted file.

This type of Encryption/Decryption scheme is often called a Substitution Cipher.

;Related tasks:

  • [[Caesar cipher]]
  • [[Rot-13]]
  • [[Vigenère Cipher/Cryptanalysis]]

;See also:

  • Wikipedia article: [https://en.wikipedia.org/wiki/Substitution_cipher Substitution cipher]

Ada


with Ada.Command_Line; use Ada.Command_Line;
with Ada.Sequential_IO;
with Ada.Strings.Maps; use Ada.Strings.Maps;
with Ada.Text_IO;

procedure Cipher is
   package Char_IO is new Ada.Sequential_IO (Character);
   use Char_IO;
   Alphabet: constant String := "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz";
   Key :     constant String := "VsciBjedgrzyHalvXZKtUPumGfIwJxqOCFRApnDhQWobLkESYMTN";
   My_Map : Character_Mapping;
   Input, Output : File_Type;
   Buffer        : Character;
begin
   declare
      use Ada.Text_IO;
   begin
      if Argument_Count /= 1 then
	 Put_Line("Usage: " & Command_Name & " <encode|decode>");
      else
	 if Argument(1) = "encode" then
	    My_Map := To_Mapping(From => Alphabet, To => Key);
	 elsif Argument(1) = "decode" then
	    My_Map := To_Mapping(From => Key, To => Alphabet);
	 else
	    Put_Line("Unrecognised Argument: " & Argument(1));
	    return;
	 end if;
      end if;
   end;
   Open       (File => Input,  Mode => In_File,  Name => "input.txt");
   Create     (File => Output, Mode => Out_File, Name => "output.txt");
   loop
      Read  (File => Input,  Item => Buffer);
      Buffer := Value(Map => My_Map, Element => Buffer);
      Write (File => Output, Item => Buffer);
   end loop;
exception
   when Char_IO.End_Error =>
      if Is_Open(Input) then
         Close (Input);
      end if;
      if Is_Open(Output) then
         Close (Output);
      end if;
end Cipher;

C

Takes input file name, plain and cipher keys and the action ( Encrypt or Decrypt) as inputs. Only the first character of the action string is checked, so if you are feeling really [https://www.nsa.gov/ NSA like], use whatever string you want as long as it has a d/D or e/E in front.


#include<stdlib.h>
#include<stdio.h>
#include<wchar.h>

#define ENCRYPT 0
#define DECRYPT 1
#define ALPHA 33
#define OMEGA 126

int wideStrLen(wchar_t* str){
	int i = 0;
	while(str[i++]!=00);

	return i;
}

void processFile(char* fileName,char plainKey, char cipherKey,int flag){

	FILE* inpFile = fopen(fileName,"r");
	FILE* outFile;

	int i,len, diff = (flag==ENCRYPT)?(int)cipherKey - (int)plainKey:(int)plainKey - (int)cipherKey;
	wchar_t str[1000], *outStr;
	char* outFileName = (char*)malloc((strlen(fileName)+5)*sizeof(char));

	sprintf(outFileName,"%s_%s",fileName,(flag==ENCRYPT)?"ENC":"DEC");

	outFile = fopen(outFileName,"w");

	while(fgetws(str,1000,inpFile)!=NULL){
		len = wideStrLen(str);

		outStr = (wchar_t*)malloc((len + 1)*sizeof(wchar_t));

		for(i=0;i<len;i++){
			if((int)str[i]>=ALPHA && (int)str[i]<=OMEGA && flag == ENCRYPT)
				outStr[i] = (wchar_t)((int)str[i]+diff);
			 else if((int)str[i]-diff>=ALPHA && (int)str[i]-diff<=OMEGA && flag == DECRYPT)
				outStr[i] = (wchar_t)((int)str[i]-diff);
			else
				outStr[i] = str[i];
		}
		outStr[i]=str[i];

		fputws(outStr,outFile);

		free(outStr);
	}

	fclose(inpFile);
	fclose(outFile);
}

int main(int argC,char* argV[]){
	if(argC!=5)
		printf("Usage : %s <file name, plain key, cipher key, action (E)ncrypt or (D)ecrypt>",argV[0]);
	else{
		processFile(argV[1],argV[2][0],argV[3][0],(argV[4][0]=='E'||argV[4][0]=='e')?ENCRYPT:DECRYPT);

		printf("File %s_%s has been written to the same location as input file.",argV[1],(argV[4][0]=='E'||argV[4][0]=='e')?"ENC":"DEC");
	}

	return 0;
}

A long, long time ago ( yes, [http://www.rosettacode.org/wiki/N-body_problem#C I have said it before] ), I read Digital Fortress by Dan Brown. One thing which struck me was Ensei Tankado using the same algorithm to encrypt itself ( or it's human readable Unicode version, if you are a purist). I remembered the name : Bigelman's Safe, but I got the spelling wrong so I had to [https://archive.org/stream/LostSymbol/Dan%20Brown/Digital%20Fortress#page/n29/mode/2up/search/bigel read the copy on archive.org], it's there on the last line of page 30/31, Biggleman's Safe.

So here it is, a program which encrypts itself, you saw the cleartext file above, now here's the invocation and ciphertext file.


C:\rosettaCode>biggleman.exe substitutionCipher.c a e E
File substitutionCipher.c_ENC has been written to the same location as input file.

And here's what substitutionCipher.c_ENC looks like :


3.Eflmwlio Klswl0 55xl Sgxsfiv 645;.3

'mrgpyhi@wxhpmf2lB
'mrgpyhi@wxhms2lB
'mrgpyhi@{glev2lB

'hijmri IRGV]TX 4
'hijmri HIGV]TX 5
'hijmri EPTLE 77
'hijmri SQIKE 56:

mrx {mhiWxvPir,{glevcx. wxv-
	mrx m A 4?
	{lmpi,wxv_m//a%A44-?

	vixyvr m?


zsmh tvsgiwwJmpi,glev. jmpiReqi0glev tpemrOi}0 glev gmtlivOi}0mrx jpek-

	JMPI. mrtJmpi A jstir,jmpiReqi0&v&-?
	JMPI. syxJmpi?

	mrx m0pir0 hmjj A ,jpekAAIRGV]TX-C,mrx-gmtlivOi} 1 ,mrx-tpemrOi}>,mrx-tpemrOi} 1 ,mrx-gmtlivOi}?
	{glevcx wxv_5444a0 .syxWxv?
	glev. syxJmpiReqi A ,glev.-qeppsg,,wxvpir,jmpiReqi-/9-.wm~isj,glev--?

	wtvmrxj,syxJmpiReqi0&)wc)w&0jmpiReqi0,jpekAAIRGV]TX-C&IRG&>&HIG&-?

	syxJmpi A jstir,syxJmpiReqi0&{&-?

	{lmpi,jkix{w,wxv054440mrtJmpi-%ARYPP-
		pir A {mhiWxvPir,wxv-?

		syxWxv A ,{glevcx.-qeppsg,,pir / 5-.wm~isj,{glevcx--?

		jsv,mA4?m@pir?m//-
			mj,,mrx-wxv_maBAEPTLE ** ,mrx-wxv_ma@ASQIKE ** jpek AA IRGV]TX-
				syxWxv_ma A ,{glevcx-,,mrx-wxv_ma/hmjj-?
			 ipwi mj,,mrx-wxv_ma1hmjjBAEPTLE ** ,mrx-wxv_ma1hmjj@ASQIKE ** jpek AA HIGV]TX-
				syxWxv_ma A ,{glevcx-,,mrx-wxv_ma1hmjj-?
			ipwi
				syxWxv_ma A wxv_ma?
		
		syxWxv_maAwxv_ma?

		jtyx{w,syxWxv0syxJmpi-?

		jvii,syxWxv-?
	

	jgpswi,mrtJmpi-?
	jgpswi,syxJmpi-?


mrx qemr,mrx evkG0glev. evkZ_a-
	mj,evkG%A9-
		tvmrxj,&Yweki > )w @jmpi reqi0 tpemr oi}0 gmtliv oi}0 egxmsr ,I-rgv}tx sv ,H-igv}txB&0evkZ_4a-?
	ipwi
		tvsgiwwJmpi,evkZ_5a0evkZ_6a_4a0evkZ_7a_4a0,evkZ_8a_4aAA+I+€€evkZ_8a_4aAA+i+-CIRGV]TX>HIGV]TX-?

		tvmrxj,&Jmpi )wc)w lew fiir {vmxxir xs xli weqi psgexmsr ew mrtyx jmpi2&0evkZ_5a0,evkZ_8a_4aAA+I+€€evkZ_8a_4aAA+i+-C&IRG&>&HIG&-?
	

	vixyvr 4?


And to decrypt :


C:\rosettaCode>biggleman.exe substitutionCipher.c_ENC e a D
File substitutionCipher.c_ENC_DEC has been written to the same location as input file.

And for the cleartext, just scroll up...btw, did you know that Digital Fortress was Brown's first novel and he wrote it back in 1998 ? Wonder why nobody ever saw Snowden happening ?

C++

The key file should look something like this: ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789SWoVR0kJLXQ8zbCd1OagTH5ie3nvYU2wfrM9yI4sKm6c7hNjtADqFPxpEZlBuG


#include <iostream>
#include <string>
#include <fstream>

class cipher {
public:
    bool work( std::string e, std::string f, std::string k ) {
        if( e.length() < 1 ) return false;
        fileBuffer = readFile( f );
        if( "" == fileBuffer ) return false;
        keyBuffer = readFile( k );
        if( "" == keyBuffer ) return false;

        outName = f;
        outName.insert( outName.find_first_of( "." ), "_out" );

        switch( e[0] ) {
            case 'e': return encode();
            case 'd': return decode();
        }
        return false;
    }
private:
    bool encode() {
        size_t idx, len = keyBuffer.length() >> 1;
        for( std::string::iterator i = fileBuffer.begin(); i != fileBuffer.end(); i++ ) {
            idx = keyBuffer.find_first_of( *i );
            if( idx < len ) outBuffer.append( 1, keyBuffer.at( idx + len ) );
            else outBuffer.append( 1, *i );
        }
        return saveOutput();
    }
    bool decode() {
        size_t idx, l = keyBuffer.length(), len = l >> 1;
        for( std::string::iterator i = fileBuffer.begin(); i != fileBuffer.end(); i++ ) {
            idx = keyBuffer.find_last_of( *i );
            if( idx >= len && idx < l ) outBuffer.append( 1, keyBuffer.at( idx - len ) );
            else outBuffer.append( 1, *i );
        }
        return saveOutput();
    }
    bool saveOutput() {
        std::ofstream o( outName.c_str() );
        o.write( outBuffer.c_str(), outBuffer.size() );
        o.close();
        return true;
    }
    std::string readFile( std::string fl ) {
        std::string buffer = "";
        std::ifstream f( fl.c_str(), std::ios_base::in );
        if( f.good() ) {
            buffer = std::string( ( std::istreambuf_iterator<char>( f ) ), std::istreambuf_iterator<char>() );
            f.close();
        }
        return buffer;
    }
    std::string fileBuffer, keyBuffer, outBuffer, outName;
};

int main( int argc, char* argv[] ) {
    if( argc < 4 ) {
        std::cout << "<d or e>\tDecrypt or Encrypt\n<filename>\tInput file, the output file will have"
        "'_out' added to it.\n<key>\t\tfile with the key to encode/decode\n\n";
    } else {
        cipher c;
        if( c.work( argv[1], argv[2], argv[3] ) ) std::cout << "\nFile successfully saved!\n\n";
        else std::cout << "Something went wrong!\n\n";
    }
    return 0;
}

C#

using System;
using System.IO;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace SubstitutionCipherProject
{
    class SubstitutionCipher
    {
        static void Main(string[] args)
        {
            doEncDec("e:\\source.txt", "enc.txt", true);
            doEncDec("enc.txt", "dec.txt", false);
            Console.WriteLine("Done");
            Console.ReadKey();
        }
        static void doEncDec(String source, String target, bool IsEncrypt)
        {
            ITransform trans;

            if (IsEncrypt)
                trans = new Encrypt();
            else
                trans = new Decrypt();

            FileInfo sfi = new FileInfo(source);
            FileStream sstream = sfi.OpenRead();
            StreamReader sr = new StreamReader(sstream);

            FileInfo tfi = new FileInfo(target);
            FileStream tstream = tfi.OpenWrite();
            TransformWriter tw = new TransformWriter(tstream, trans);
            StreamWriter sw = new StreamWriter(tw);

            String line;
            while ((line = sr.ReadLine()) != null)
                sw.WriteLine(line);
            sw.Close();
        }
    }
    public interface ITransform
    {
        byte transform(byte ch);
    }
    public class Encrypt : ITransform
    {
        const String str = "xyfagchbimpourvnqsdewtkjzl";
        byte ITransform.transform(byte ch)
        {
            if (char.IsLower((char)ch))
                ch = (byte)str[ch - (byte)'a'];
            return ch;
        }
    }
    class Decrypt : ITransform
    {
        const String str = "xyfagchbimpourvnqsdewtkjzl";
        byte ITransform.transform(byte ch)
        {
            if (char.IsLower((char)ch))
                ch = (byte)(str.IndexOf((char)ch) + 'a');
            return ch;
        }
    }
    class TransformWriter : Stream, IDisposable
    {
        private Stream outs;
        private ITransform trans;

        public TransformWriter(Stream s, ITransform t)
        {
            this.outs = s;
            this.trans = t;
        }

        public override bool CanRead
        {
            get { return false; }
        }

        public override bool CanSeek
        {
            get { return false; }
        }

        public override bool CanWrite
        {
            get { return true; }
        }
        public override void Flush()
        {
            outs.Flush();
        }

        public override long Length
        {
            get { return outs.Length; }
        }
        public override long Position
        {
            get
            {
                return outs.Position;
            }
            set
            {
                outs.Position = value;
            }
        }
        public override long Seek(long offset, SeekOrigin origin)
        {
            return outs.Seek(offset, origin);
        }

        public override void SetLength(long value)
        {
            outs.SetLength(value);
        }

        public override void Write(byte[] buf, int off, int len)
        {
            for (int i = off; i < off + len; i++)
                buf[i] = trans.transform(buf[i]);
            outs.Write(buf, off, len);
        }

        void IDisposable.Dispose()
        {
            outs.Dispose();
        }

        public override void Close()
        {
            outs.Close();
        }

        public override int Read(byte[] cbuf, int off, int count)
        {
            return outs.Read(cbuf, off, count);
        }
    }
}

D

import std.stdio;
import std.string;
import std.traits;

string text =
`Here we have to do is there will be a input/source
 file in which we are going to Encrypt the file by replacing every
 upper/lower case alphabets of the source file with another
 predetermined upper/lower case alphabets or symbols and save
 it into another output/encrypted file and then again convert
 that output/encrypted file into original/decrypted file. This
 type of Encryption/Decryption scheme is often called a
 Substitution Cipher.`;

void main() {
    auto enc = encode(text);
    writeln("Encoded: ", enc);
    writeln;
    writeln("Decoded: ", decode(enc));
}

enum FORWARD = "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\tbcdefghijkl\nmnopqrstuvwxyz";
auto encode(string input) {
    return tr(input, FORWARD, REVERSE);
}

enum REVERSE = "VsciBjedgrzy\nHalvXZKtUP um\tGf?I/w>J<x.q,OC:F;R{A]p}n[D+h=Q)W(o*b&L^k%E$S#Y@M!T~N";
auto decode(string input) {
    return tr(input, REVERSE, FORWARD);
}

{{out}}

Encoded: aQSQn!Qn([MQnY%n=%no#nY(QSQn!o&&n+Qn[nokE@Y,#%@ShQLn)o&Qnokn!(oh(n!Qn[SQnW%okWnY%ngkhS~EYnY(Qn)o&Qn+~nSQE&[hokWnQMQS~Ln@EEQS,&%!QSnh[#Qn[&E([+QY#n%)nY(Qn#%@ShQn)o&Qn!oY(n[k%Y(QSLnESQ=QYQS^okQ=n@EEQS,&%!QSnh[#Qn[&E([+QY#n%Sn#~^+%&#n[k=n#[MQLnoYnokY%n[k%Y(QSn%@YE@Y,QkhS~EYQ=n)o&Qn[k=nY(Qkn[W[oknh%kMQSYLnY([Yn%@YE@Y,QkhS~EYQ=n)o&QnokY%n%SoWok[&,=QhS~EYQ=n)o&QAnq(o#LnY~EQn%)ngkhS~EYo%k,eQhS~EYo%kn#h(Q^Qno#n%)YQknh[&&Q=n[Lnx@+#YoY@Yo%knBoE(QSA

Decoded: Here we have to do is there will be a input/source
 file in which we are going to Encrypt the file by replacing every
 upper/lower case alphabets of the source file with another
 predetermined upper/lower case alphabets or symbols and save
 it into another output/encrypted file and then again convert
 that output/encrypted file into original/decrypted file. This
 type of Encryption/Decryption scheme is often called a
 Substitution Cipher.

Fortran

{{works with|Fortran|90 and later}}

program substitution
  implicit none

  integer, parameter :: len_max = 256
  integer, parameter :: eof = -1
  integer :: in_unit = 9, out_unit = 10, ios
  character(len_max) :: line

  open(in_unit, file="plain.txt",  iostat=ios)
  if (ios /= 0) then
    write(*,*) "Error opening plain.txt file"
    stop
  end if

  open(out_unit, file="encrypted.txt", iostat=ios)
  if (ios /= 0) then
    write(*,*) "Error opening encrypted.txt file"
    stop
  end if

! Encryption
  do
    read(in_unit, "(a)", iostat=ios) line
    if (ios > 0) then
      write(*,*) "Error reading plain.txt file"
      stop
    else if (ios == eof) then
      exit
    end if

    call cipher(trim(line))
    write(out_unit, "(a)", iostat=ios) trim(line)
    if (ios /= 0) then
      write(*,*) "Error writing encrypted.txt file"
      stop
    end if
  end do

  close(in_unit)
  close(out_unit)

  open(in_unit, file="encrypted.txt",  iostat=ios)
  if (ios /= 0) then
    write(*,*) "Error opening encrypted.txt file"
    stop
  end if

  open(out_unit, file="decrypted.txt", iostat=ios)
  if (ios /= 0) then
    write(*,*) "Error opening decrypted.txt file"
    stop
  end if

! Decryption
  do
    read(in_unit, "(a)", iostat=ios) line
    if (ios > 0) then
      write(*,*) "Error reading encrypted.txt file"
      stop
    else if (ios == eof) then
      exit
    end if

    call cipher(trim(line))
    write(out_unit, "(a)", iostat=ios) trim(line)
    if (ios /= 0) then
      write(*,*) "Error writing decrypted.txt file"
      stop
    end if
  end do

  close(in_unit)
  close(out_unit)

contains

subroutine cipher(text)
  character(*), intent(in out) :: text
  integer :: i

! Substitutes A -> Z, B -> Y ... Y -> B, Z -> A and ditto for lower case
! works for both encryption and decryption

  do i = 1, len(text)
    select case(text(i:i))
      case ('A':'Z')
        text(i:i) = achar(155 - iachar(text(i:i)))
      case ('a':'z')
        text(i:i) = achar(219 - iachar(text(i:i)))
    end select
  end do
end subroutine

end program

{{out}}


Encrypted file:
Sviv dv szev gl wl rh gsviv droo yv z rmkfg/hlfixv urov rm dsrxs dv ziv
tlrmt gl Vmxibkg gsv urov yb ivkozxrmt vevib fkkvi/oldvi xzhv zokszyvgh
lu gsv hlfixv urov drgs zmlgsvi kivwvgvinrmvw fkkvi/oldvi xzhv zokszyvgh
li hbnyloh zmw hzev rg rmgl zmlgsvi lfgkfg/vmxibkgvw urov zmw gsvm ztzrm
xlmevig gszg lfgkfg/vmxibkgvw urov rmgl lirtrmzo/wvxibkgvw urov.
Gsrh gbkv lu Vmxibkgrlm/Wvxibkgrlm hxsvnv rh lugvm xzoovw z Hfyhgrgfgrlm Xrksvi.

Decrypted file:
Here we have to do is there will be a input/source file in which we are
going to Encrypt the file by replacing every upper/lower case alphabets
of the source file with another predetermined upper/lower case alphabets
or symbols and save it into another output/encrypted file and then again
convert that output/encrypted file into original/decrypted file.
This type of Encryption/Decryption scheme is often called a Substitution Cipher.

FreeBASIC

' FB 1.05.0 Win64

' uses same alphabet and key as Ada language example
Const string1 = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz"
Const string2 = "VsciBjedgrzyHalvXZKtUPumGfIwJxqOCFRApnDhQWobLkESYMTN"

Sub process(inputFile As String, outputFile As String, encrypt As Boolean)
   Open inputFile For Input As #1
   If err > 0 Then
     Print "Unable to open input file"
     Sleep
     End
   End If
   Dim As String alpha, key
   If encrypt Then
     alpha = string1 : key = string2
   Else
     alpha = string2 : key = string1
   End If
   Open outputFile For Output As #2
   Dim s As String
   Dim p As Integer
   While Not Eof(1)
     Line Input #1, s
     For i As Integer = 0 To Len(s) - 1
       If (s[i] >= 65 AndAlso s[i] <= 90) OrElse (s[i] >= 97 AndAlso s[i] <= 122) Then
         p =  Instr(alpha, Mid(s, i + 1, 1)) - 1
         s[i] = key[p]
       End If
     Next
     Print #2, s
   Wend
   Close #1 : Close #2
End Sub

process "plain.txt", "encrypted.txt", true
process "encrypted.txt", "decrypted.txt", false
Print
Print "Press any key to quit"
Sleep

{{out}} Encrypted.txt :


KEwLkRkEkRQh cRWFqb gDWnqDqhkIkRQh - jRnq BhJbTWkRQh/iqJbTWkRQh

tILp - dqbq Yq FISq kQ xQ RL kFqbq YRnn wq I RhWEk/LQEbJq ORnq Rh YFRJF Yq Ibq
 CQRhC kQ BhJbTWk kFq ORnq wT bqWnIJRhC qSqbT EWWqb/nQYqb JILq InWFIwqkL QO kFq
 LQEbJq ORnq YRkF IhQkFqb WbqxqkqbDRhqx EWWqb/nQYqb JILq InWFIwqkL Qb LTDwQnL
 Ihx LISq Rk RhkQ IhQkFqb QEkWEk/qhJbTWkqx ORnq Ihx kFqh ICIRh JQhSqbk kFIk
 QEkWEk/qhJbTWkqx ORnq RhkQ QbRCRhIn/xqJbTWkqx ORnq.

tFRL kTWq QO BhJbTWkRQh/iqJbTWkRQh LJFqDq RL QOkqh JInnqx I KEwLkRkEkRQh cRWFqb.

cnRJp Fqbq kQ phQY DQbq.

Decrypted.txt = Plain.txt :


Substitution Cipher Implementation - File Encryption/Decryption

Task - Here we have to do is there will be a input/source file in which we are
 going to Encrypt the file by replacing every upper/lower case alphabets of the
 source file with another predetermined upper/lower case alphabets or symbols
 and save it into another output/encrypted file and then again convert that
 output/encrypted file into original/decrypted file.

This type of Encryption/Decryption scheme is often called a Substitution Cipher.

Click here to know more.

Go

{{trans|Kotlin}}

package main

import (
    "fmt"
    "strings"
)

var key = "]kYV}(!7P$n5_0i R:?jOWtF/=-pe'AD&@r6%ZXs\"v*N[#wSl9zq2^+g;LoB`aGh{3.HIu4fbK)mU8|dMET><,Qc\\C1yxJ"

func encode(s string) string {
    bs := []byte(s)
    for i := 0; i < len(bs); i++ {
        bs[i] = key[int(bs[i]) - 32]
    }
    return string(bs)
}

func decode(s string) string {
    bs := []byte(s)
    for i := 0; i < len(bs); i++ {
        bs[i] = byte(strings.IndexByte(key, bs[i]) + 32)
    }
    return string(bs)
}

func main() {
    s := "The quick brown fox jumps over the lazy dog, who barks VERY loudly!"
    enc := encode(s)
    fmt.Println("Encoded: ", enc)
    fmt.Println("Decoded: ", decode(enc))
}

{{out}}


Encoded:  2bu]E,KHm].Tdc|]4d\]),8M>]dQuT]<bu]U31C]Idf_]cbd].3Tm>]+ZzL]Ud,IUCk
Decoded:  The quick brown fox jumps over the lazy dog, who barks VERY loudly!

=={{header|IS-BASIC}}== 100 PROGRAM "SuChiper.bas" 110 STRING ST$(1 TO 2)*52,K$*1 120 LET ST$(1)="ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz" 130 LET ST$(2)="VsciBjedgrzyHalvXZKtUPumGfIwJxqOCFRApnDhQWobLkESYMTN" 140 CLEAR SCREEN:PRINT "1 - encode, 2 - decode" 150 DO 160 LET K$=INKEY$ 170 LOOP UNTIL K$="1" OR K$="2" 180 IF K$="1" THEN 190 INPUT PROMPT "File name: ":NAME$ 200 IF OPENFILE(NAME$) THEN CALL CHIPER(1) 210 ELSE 220 IF OPENFILE("Encrypte.txt") THEN CALL CHIPER(2) 230 END IF 240 DEF OPENFILE(N$) 250 LET OPENFILE=0 260 WHEN EXCEPTION USE OPENERROR 270 OPEN #1:N$ 280 END WHEN 290 LET OPENFILE=-1 300 END DEF 310 DEF CHIPER(FUNC) 320 LET EOF=0 330 WHEN EXCEPTION USE OPENERROR 340 IF FUNC=1 THEN 350 OPEN #2:"Encrypte.txt" ACCESS OUTPUT 360 LET OUTP=2 370 ELSE 380 OPEN #2:"Decrypte.txt" ACCESS OUTPUT 390 LET OUTP=1 400 END IF 410 END WHEN 420 WHEN EXCEPTION USE IOERROR 430 DO 440 GET #1:K$ 450 IF UCASE$(K$)>="A" AND UCASE$(K$)<="Z" THEN 460 PRINT #2:ST$(OUTP)(POS(ST$(FUNC),K$)); 470 ELSE 480 PRINT #2:K$; 490 END IF 500 LOOP UNTIL EOF 510 END WHEN 520 HANDLER IOERROR 530 IF EXTYPE<>9228 THEN PRINT EXSTRING$(EXTYPE) 540 CLOSE #2 550 CLOSE #1 560 LET EOF=1 570 END HANDLER 580 END DEF 590 HANDLER OPENERROR 600 PRINT EXSTRING$(EXTYPE) 610 END 620 END HANDLER




## J


Example implementation:


```J
keysubst=: [`(a.i.])`(a."_)}
key=: 'Taehist' keysubst '!@#$%^&'
enc=: a. {~ key i. ]
dec=: key {~ a. i. ]

   enc 'This is a test.'
!$%^ %^ @ &#^&.
   dec '!$%^ %^ @ &#^&.'
This is a test.

Note that this particular implementation bakes the key itself into the implementations of enc and dec. Also note that this particular key is rather limited - letters not mentioned in the key encrypt as another identical character. That seems to be sufficient, given the current task description. But of course other approaches are also possible...

Java

public class SubstitutionCipher {

    final static String key = "]kYV}(!7P$n5_0i R:?jOWtF/=-pe'AD&@r6%ZXs\"v*N"
            + "[#wSl9zq2^+g;LoB`aGh{3.HIu4fbK)mU8|dMET><,Qc\\C1yxJ";

    static String text = "Here we have to do is there will be a input/source "
            + "file in which we are going to Encrypt the file by replacing every "
            + "upper/lower case alphabets of the source file with another "
            + "predetermined upper/lower case alphabets or symbols and save "
            + "it into another output/encrypted file and then again convert "
            + "that output/encrypted file into original/decrypted file. This "
            + "type of Encryption/Decryption scheme is often called a "
            + "Substitution Cipher.";

    public static void main(String[] args) {
        String enc = encode(text);
        System.out.println("Encoded: " + enc);
        System.out.println("\nDecoded: " + decode(enc));
    }

    static String encode(String s) {
        StringBuilder sb = new StringBuilder(s.length());

        for (char c : s.toCharArray())
            sb.append(key.charAt((int) c - 32));

        return sb.toString();
    }

    static String decode(String s) {
        StringBuilder sb = new StringBuilder(s.length());

        for (char c : s.toCharArray())
            sb.append((char) (key.indexOf((int) c) + 32));

        return sb.toString();
    }
}

Encoded: "uTu]cu]b3Qu]<d]Id]...><K<,<Kd|]6KMbuTi
Decoded: Here we have to do is... Substitution Cipher.

Julia

{{works with|Julia|0.6}} {{trans|Kotlin}}

'''Module''':

module SubstitutionCiphers

using Compat

const key = "]kYV}(!7P\$n5_0i R:?jOWtF/=-pe'AD&@r6%ZXs\"v*N[#wSl9zq2^+g;LoB`aGh{3.HIu4fbK)mU8|dMET><,Qc\\C1yxJ"

function encode(s::AbstractString)
    buf = IOBuffer()
    for c in s
        print(buf, key[Int(c) - 31])
    end
    return String(take!(buf))
end

function decode(s::AbstractString)
    buf = IOBuffer()
    for c in s
        print(buf, Char(findfirst(==(c), key) + 31))
    end
    return String(take!(buf))
end

end  # module SubstitutionCiphers

'''Main''':

let s = "The quick brown fox jumps over the lazy dog, who barks VERY loudly!"
    enc = SubstitutionCiphers.encode(s)
    dec = SubstitutionCiphers.decode(enc)
    println("Original: ", s, "\n -> Encoded: ", enc, "\n -> Decoded: ", dec)
end

{{out}}

Original: The quick brown fox jumps over the lazy dog, who barks VERY loudly!
 -> Encoded: 2bu]E,KHm].Tdc|]4d\]),8M>]dQuT]<bu]U31C]Idf_]cbd].3Tm>]+ZzL]Ud,IUCk
 -> Decoded: The quick brown fox jumps over the lazy dog, who barks VERY loudly!

Kotlin

{{trans|Java}}

// version 1.0.6

object SubstitutionCipher {
    val key = "]kYV}(!7P\$n5_0i R:?jOWtF/=-pe'AD&@r6%ZXs\"v*N[#wSl9zq2^+g;LoB`aGh{3.HIu4fbK)mU8|dMET><,Qc\\C1yxJ"

    fun encode(s: String): String {
        val sb = StringBuilder()
        for (c in s) sb.append(key[c.toInt() - 32])
        return sb.toString()
    }

    fun decode(s: String): String {
        val sb = StringBuilder()
        for (c in s) sb.append((key.indexOf(c) + 32).toChar())
        return sb.toString()
    }
}

fun main(args: Array<String>) {
    val s = "The quick brown fox jumps over the lazy dog, who barks VERY loudly!"
    val enc = SubstitutionCipher.encode(s)
    println("Encoded:  $enc")
    println("Decoded:  ${SubstitutionCipher.decode(enc)}")
}

{{out}}


Encoded:  2bu]E,KHm].Tdc|]4d\]),8M>]dQuT]<bu]U31C]Idf_]cbd].3Tm>]+ZzL]Ud,IUCk
Decoded:  The quick brown fox jumps over the lazy dog, who barks VERY loudly!

Lua

-- Generate a random substitution cipher for ASCII characters 65 to 122
function randomCipher ()
    local cipher, rnd = {plain = {}, encoded = {}}
    for ascii = 65, 122 do
        table.insert(cipher.plain, string.char(ascii))
        table.insert(cipher.encoded, string.char(ascii))
    end
    for i = 1, #cipher.encoded do
        rnd = math.random(#cipher.encoded)
        cipher.encoded[i], cipher.encoded[rnd] = cipher.encoded[rnd], cipher.encoded[i]
    end
    return cipher
end

-- Encipher text using cipher.  Decipher if decode is true.
function encode (text, cipher, decode)
    local output, letter, found, source, dest = ""
    if decode then
        source, dest = cipher.encoded, cipher.plain
    else
        source, dest = cipher.plain, cipher.encoded
    end
    for pos = 1, #text do
        letter = text:sub(pos, pos)
        found = false
        for k, v in pairs(source) do
            if letter == v then
                output = output .. dest[k]
                found = true
                break
            end
        end
        if not found then output = output .. letter end
    end
    return output
end

-- Main procedure
math.randomseed(os.time())
local subCipher = randomCipher()
print("Cipher generated:")
print("\tPlain:", table.concat(subCipher.plain))
print("\tCoded:", table.concat(subCipher.encoded))
local inFile = io.open("C:\\ulua\\taskDescription.txt", "r")
local input = inFile:read("*all")
inFile:close()
local encoded = encode(input, subCipher)
print("\nEncoded file contents:")
print("\t" .. encoded)
print("\nAbove text deciphers to: ")
print("\t" .. encode(encoded, subCipher, true))

{{out}}

Cipher generated:
        Plain:  ABCDEFGHIJKLMNOPQRSTUVWXYZ[\]^_`abcdefghijklmnopqrstuvwxyz
        Coded:  MwZ\zPaqSTNuLQpgbnG[V_xeJmlWYCI]rhFcv^UHXijR`yfKEktADsdoBO

Encoded file contents:
        qvkv dv Hrsv Af cf Xt AHvkv dXRR hv r XyKDA/tfDkFv ^XRv Xy dHXFH dv rkv
UfXyU Af zyFkBKA AHv ^XRv hB kvKRrFXyU vsvkB DKKvk/Rfdvk Frtv rRKHrhvAt f^ AHv t
fDkFv ^XRv dXAH ryfAHvk KkvcvAvk`Xyvc DKKvk/Rfdvk Frtv rRKHrhvAt fk tB`hfRt ryc
trsv XA XyAf ryfAHvk fDAKDA/vyFkBKAvc ^XRv ryc AHvy rUrXy FfysvkA AHrA fDAKDA/vy
FkBKAvc ^XRv XyAf fkXUXyrR/cvFkBKAvc ^XRv. [HXt ABKv f^ zyFkBKAXfy/\vFkBKAXfy tF
Hv`v Xt f^Avy FrRRvc r GDhtAXADAXfy ZXKHvk.

Above text deciphers to:
        Here we have to do is there will be a input/source file in which we are
going to Encrypt the file by replacing every upper/lower case alphabets of the s
ource file with another predetermined upper/lower case alphabets or symbols and
save it into another output/encrypted file and then again convert that output/en
crypted file into original/decrypted file. This type of Encryption/Decryption sc
heme is often called a Substitution Cipher.

Perl

{{trans|Java}}

sub encode {
    my $source = shift;
    my $key = shift;
    my $out = q();

    @ka = split //, $key;
    foreach $ch (split //, $source) {
        $idx = ord($ch) - 32;
        $out .= $ka[$idx];
    }

    return $out;
}

sub decode {
    my $source = shift;
    my $key = shift;
    my $out = q();

    foreach $ch (split //, $source) {
        $idx = index $key, $ch;
        $val = chr($idx + 32);
        $out .= $val;
    }

    return $out;
}

my $key = q(]kYV}(!7P$n5_0i R:?jOWtF/=-pe'AD&@r6%ZXs"v*N[#wSl9zq2^+g;LoB`aGh{3.HIu4fbK)mU8|dMET><,Qc\C1yxJ);
my $text = "Here we have to do is there will be a input/source "
         . "file in which we are going to Encrypt the file by replacing every "
         . "upper/lower case alphabets of the source file with another "
         . "predetermined upper/lower case alphabets or symbols and save "
         . "it into another output/encrypted file and then again convert "
         . "that output/encrypted file into original/decrypted file. This "
         . "type of Encryption/Decryption scheme is often called a "
         . "Substitution Cipher.";

my $ct = encode($text, $key);
print "Encoded: $ct\n";

my $pt = decode($ct, $key);
print "Decoded: $pt\n";

{{out}}

Encoded: "uTu]cu]b3Qu]<d]Id]K>]<buTu]cKUU].u]3]K|M,< >d,THu]4KUu]K|]cbKHb]cu]3Tu]fdK|f]<d]Z|HTCM<]<bu]4KUu].C]TuMU3HK|f]uQuTC],MMuT UdcuT]H3>u]3UMb3.u<>]d4]<bu]>d,THu]4KUu]cK<b]3|d<buT]MTuIu<uT8K|uI],MMuT UdcuT]H3>u]3UMb3.u<>]dT]>C8.dU>]3|I]>3Qu]K<]K|<d]3|d<buT]d,<M,< u|HTCM<uI]4KUu]3|I]<bu|]3f3K|]Hd|QuT<]<b3<]d,<M,< u|HTCM<uI]4KUu]K|<d]dTKfK|3U IuHTCM<uI]4KUui]2bK>]<CMu]d4]Z|HTCM<Kd| %uHTCM<Kd|]>Hbu8u]K>]d4<u|]H3UUuI]3]q,.><K<,<Kd|]6KMbuTi
Decoded: Here we have to do is there will be a input/source file in which we are going to Encrypt the file by replacing every upper/lower case alphabets of the source file with another predetermined upper/lower case alphabets or symbols and save it into another output/encrypted file and then again convert that output/encrypted file into original/decrypted file. This type of Encryption/Decryption scheme is often called a Substitution Cipher.

Perl 6

{{works with|Rakudo|2015-11-20}} Feed it an action (encode, decode) and a file name at the command line and it will spit out the (en|de)coded file to STDOUT. Redirect into a file to save it. If no parameters are passed in, does the demo encode/decode.

my $chr = (' ' .. '}').join('');
my $key = $chr.comb.pick(*).join('');

# Be very boring and use the same key every time to fit task reqs.
$key = q☃3#}^",dLs*>tPMcZR!fmC rEKhlw1v4AOgj7Q]YI+|pDB82a&XFV9yzuH<WT%N;iS.0e:`G\n['6@_{bk)=-5qx(/?$JoU☃;

sub MAIN ($action = 'encode', $file = '') {

    die 'Only options are encode or decode.' unless $action ~~ any 'encode'|'decode';

    my $text = qq:to/END/;
        Here we have to do is there will be a input/source file in which
        we are going to Encrypt the file by replacing every upper/lower
        case alphabets of the source file with another predetermined
        upper/lower case alphabets or symbols and save it into another
        output/encrypted file and then again convert that output/encrypted
        file into original/decrypted file. This type of Encryption/Decryption
        scheme is often called a Substitution Cipher.
        END

    $text = $file.IO.slurp if $file;

    say "Key = $key\n";

    if $file {
        say &::($action)($text);
    } else {
        my $encoded;
        say "Encoded text: \n {$encoded = encode $text}";
        say "Decoded text: \n {decode $encoded}";
    }
}

sub encode ($text) { $text.trans($chr => $key) }

sub decode ($text) { $text.trans($key => $chr) }

{{out}} with no passed parameters:

Key = 3#}^",dLs*>tPMcZR!fmC rEKhlw1v4AOgj7Q]YI+|pDB82a&XFV9yzuH<WT%N;iS.0e:`G\n['6@_{bk)=-5qx(/?$JoU

Encoded text:
 +`=`3(`3n.x`35b3:b3[-35n`=`3([@@30`3.3[{kq5Z-bq=e`3G[@`3[{3(n[en3
(`3.=`3\b[{\35b3]{e=?k535n`3G[@`30?3=`[email protected][{\3`x`=?3qkk`=Z@b(`=3
e.-`[email protected]`5-3bG35n`3-bq=e`3G[@`3([5n3.{b5n`=3k=`:`5`=_[{`:3
qkk`=Z@b(`=3e.-`[email protected]`5-3b=3-?_0b@-3.{:3-.x`3[53[{5b3.{b5n`=3
bq5kq5Z`{e=?k5`:3G[@`3.{:35n`{3.\.[{3eb{x`=535n.53bq5kq5Z`{e=?k5`:3
G[@`3[{5b3b=[\[{.@Z:`e=?k5`:3G[@`c39n[-35?k`3bG3]{e=?k5[b{ZQ`e=?k5[b{
-en`_`3[-3bG5`{3e.@@`:3.3Vq0-5[5q5[b{37[kn`=c

Decoded text:
 Here we have to do is there will be a input/source file in which
we are going to Encrypt the file by replacing every upper/lower
case alphabets of the source file with another predetermined
upper/lower case alphabets or symbols and save it into another
output/encrypted file and then again convert that output/encrypted
file into original/decrypted file. This type of Encryption/Decryption
scheme is often called a Substitution Cipher.

Phix

constant plain = tagset('Z','A')&tagset('z','a'),
         key = shuffle(plain)

function encode(string s, integer decrypt=false)
    sequence {p,k} = iff(decrypt?{plain,key}:{key,plain})
    for i=1 to length(s) do
        integer ki = find(s[i],p)
        if ki then s[i] = k[ki] end if
    end for
    return s
end function

string original = "A simple example.",
       encoded = encode(original),
       decoded = encode(encoded, true)

printf(1,"original: %s\nencoded: %s\ndecoded: %s\n",{original,encoded,decoded})

{{Out}}


original: A simple example.
encoded: j wqGuMv vsQGuMv.
decoded: A simple example.

PicoLisp

(setq *A (chop "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz"))
(setq *K (chop "VsciBjedgrzyHalvXZKtUPumGfIwJxqOCFRApnDhQWobLkESYMTN"))

(de cipher (Str D)
   (let (K *K  A *A)
      (and D (xchg 'A 'K))
      (pack
         (mapcar
            '((N)
               (or
                  (pick
                     '((A K) (and (= A N) K))
                     A
                     K )
                  N ) )
            (chop Str) ) ) ) )
(and
   (println 'encode (cipher "The quick brown fox jumped over the lazy dog's back"))
   (println 'decode (cipher @ T)) )

{{out}}

encode "tFq oERJp wbQYh OQM AEDWqx QSqb kFq nINT xQC'L wIJp"
decode "The quick brown fox jumped over the lazy dog's back"

Python


from string import printable
import random

EXAMPLE_KEY = ''.join(sorted(printable, key=lambda _:random.random()))

def encode(plaintext, key):
    return ''.join(key[printable.index(char)] for char in plaintext)

def decode(plaintext, key):
    return ''.join(printable[key.index(char)] for char in plaintext)

original = "A simple example."
encoded = encode(original, EXAMPLE_KEY)
decoded = decode(encoded, EXAMPLE_KEY)
print("""The original is: {}
Encoding it with the key: {}
Gives: {}
Decoding it by the same key gives: {}""".format(
    original, EXAMPLE_KEY, encoded, decoded))

A straightforward implementation. The output is:

The original is: A simple example. Encoding it with the key: dV1>r7:TLlJa�uY o]MjH\hI^X cPN#!fmv[ <e=04|O'~{y$bAq@}U.WtF*)x/K? Q%S(�RB;25&s6Z9C3+D-_8kn,`Egiwzp"G Gives: iPMhX\YiYmJhX\Y5 Decoding it by the same key gives: A simple example.




## Racket


Uses [[#REXX]] input file (in data/substitution.in.txt).

The check-equal? tests assure us that we return the plain text after a cypher/decypher pair;
so I don't display the plaintext in the output.


```racket
#lang racket/base
(require racket/list racket/function racket/file)

(define abc "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz")

;; Used to generate my-key for examples
(define (random-key (alphabet abc))
  (list->string (shuffle (string->list alphabet))))

(define (cypher/decypher key (alphabet abc))
  ;; alist is fine, hashes are better over 40 chars... so alist for
  ;; abc, hash for ASCII.
  (define ab-chars (string->list alphabet))
  (define ky-chars (string->list key))
  (define cypher-alist (map cons ab-chars ky-chars))
  (define decypher-alist (map cons ky-chars ab-chars))
  (define ((subst-map alist) str)
    (list->string (map (lambda (c) (cond [(assoc c alist) => cdr] [else c]))
                       (string->list str))))
  (values (subst-map cypher-alist)
          (subst-map decypher-alist)))

(define (cypher/decypher-files key (alphabet abc))
  (define-values (cypher decypher) (cypher/decypher key alphabet))
  (define ((convert-file f) in out #:exists (exists-flag 'error))
     (curry with-output-to-file out #:exists exists-flag
            (lambda () (display (f (file->string in))))))
  (values (convert-file cypher)
          (convert-file decypher)))

(module+ test
  (require rackunit)
  (define my-key "LXRWzUrIYPJiVQyMwKudbAaDjSEefvhlqmOkGcBZCFsNpxHTgton")

  (define-values (cypher decypher) (cypher/decypher my-key abc))

  (define in-text #<<T
The quick brown fox...
.. jumped over
the lazy dog!
T
    )
  (define cypher-text (cypher in-text))

  (define plain-text (decypher cypher-text))
  (displayln cypher-text)
  (check-equal? plain-text in-text)

  (define-values (file-cypher file-decypher) (cypher/decypher-files my-key abc))
  (file-cypher "data/substitution.in.txt" "data/substitution.crypt.txt" #:exists 'replace)
  (file-decypher "data/substitution.crypt.txt" "data/substitution.plain.txt" #:exists 'replace)
  (displayln "---")
  (displayln (file->string "data/substitution.crypt.txt"))
  (check-equal? (file->string "data/substitution.in.txt")
                (file->string "data/substitution.plain.txt")))

{{out}}

dmh sHOfG eNCgZ lCt...
.. kHBFhv CThN
xmh cEno vCq!
---
             "zThNo  xCCc  mEp  E  pFhfOlOf  'xmNhpmCcv',
               EZv gmhZ xmh HphN htfhhvp xmh xmNhpmCcv,
           xmh xCCc ehfCBhp E mOZvNEZfh NExmhN xmEZ E mhcF.
          LZo pClxgENh Hphv ehoCZv Oxp xmNhpmCcv gOcc fEHph
              vhfNhEphp OZ FNCvHfxOTOxo, ZCx OZfNhEphp.
       LZv gmhZ OZvOTOvHEc FNCvHfxp ENh FHx xCqhxmhN FOhfhBhEc,
       xmh NhpHcx Op E popxhB xmEx mEp qCZh FEpx Oxp xmNhpmCcv
       ─── E fCHZxhNFNCvHfxOTh fCcchfxOCZ Cl BOplOx HZOxp xmEx
        gCNG EqEOZpx hEfm CxmhN NExmhN xmEZ gOxm hEfm CxmhN."
                               ─── VhNch MENGp

REXX

Programming notes: the cipher key (as used by this REXX program) is stored in a file as two records: ::* the 1st record is the plain-text characters to be encrypted. ::* the 2nd record is the crypt-text characters used for encryption. ::* the two records should be equal in the number of characters. ::* the Nth character of record '''1''' will be encrypted to the Nth character of record '''2'''.

/*REXX program implements & demonstrates a substitution cipher for the records in a file*/
parse arg fid.1 fid.2 fid.3 fid.4 .              /*obtain optional arguments from the CL*/
if fid.1==''  then fid.1= "CIPHER.IN"            /*Not specified?  Then use the default.*/
if fid.2==''  then fid.2= "CIPHER.OUT"           /* "      "         "   "   "     "    */
if fid.3==''  then fid.3= "CIPHER.KEY"           /* "      "         "   "   "     "    */
if fid.4==''  then fid.4= "CIPHER.ORI"           /* "      "         "   "   "     "    */
say '    input file: '   fid.1                   /*display the fileID used for  input.  */
say '   output file: '   fid.2                   /*   "     "     "     "   "  output.  */
say '   cipher file: '   fid.3                   /*   "     "     "     "   " cipher-key*/
say 'decrypted file: '   fid.4                   /*   "     "     "     "   "  decrypted*/
call closer                                      /*close all files in case they're open.*/
say
       do c=1  while lines(fid.3)\==0            /*read (hopefully 2 records) from key. */
       @.c=space(linein(fid.3),0)                /*assign input record to an  @.  array.*/
       end   /*c*/
c=c-1                                            /*adjust the number of recores (for DO)*/
if c==0                       then call ser fid.3,  'not found or is empty.'
if c>2                        then call ser fid.3,  'has too many records  (>2).'
if c<2                        then call ser fid.3,  'has too few records   (<2).'
if length(@.1)\==length(@.2)  then call ser fid.3,  'has unequal length records.'
call encrypt  fid.1, fid.2                       /*encrypt the input file  ───►  output.*/
[email protected];    @[email protected];   @.2=_                       /*switch the cipher keys for decryption*/
call encrypt  fid.2, fid.4                       /*decrypt the output file ───► decrypt.*/
call show     'cipher file ('fid.3")" , fid.3    /*display the cipher─key file.         */
call show      'input file ('fid.1")" , fid.1    /*   "     "     input     "           */
call show     'output file ('fid.2")" , fid.2    /*   "     "    output     "           */
call show ' decrypted file ('fid.4")" , fid.4    /*   "     "   decrypted   "           */
exit                                             /*stick a fork in it,  we're all done. */
/*──────────────────────────────────────────────────────────────────────────────────────*/
closer:  do f=1  for 4;   call lineout fid.f;    end  /*f*/;                     return
ser:     say  '***error!***  file '     arg(1)" "    arg(2);                     exit
show:    say;   say center(arg(1),79,'═');       "TYPE"  arg(2);                 return
/*──────────────────────────────────────────────────────────────────────────────────────*/
encrypt: parse arg @in,@out;  'ERASE'  @out      /*delete the output file using  ERASE. */
                                  do j=1  while lines(@in)\==0
                                  call lineout @out, translate(linein(@in), @.2, @.1)
                                  end   /*j*/
         j=j-1                                   /*adjust the number of recores (for DO)*/
         if j==0  then call ser @in, 'is empty.' /*was the file not found or was empty? */
         say @in  ' records processed: '   j     /*show the number of records processed.*/
         call closer                             /*close all the files to be neat & safe*/
         return

'''output''' when using the default input files:


    input file:  CIPHER.IN
   output file:  CIPHER.OUT
   cipher file:  CIPHER.KEY
decrypted file:  CIPHER.ORI

CIPHER.IN  records processed:  10
CIPHER.OUT  records processed:  10

═══════════════════════════cipher file (CIPHER.KEY)════════════════════════════
abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ
WXYZabcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUV

════════════════════════════input file (CIPHER.IN)═════════════════════════════
             "Every  tool  has  a  specific  'threshold',
               and when the user exceeds the threshold,
           the tool becomes a hindrance rather than a help.
          Any software used beyond its threshold will cause
              decreases in productivity, not increases.
       And when individual products are put together piecemeal,
       the result is a system that has gone past its threshold
       ─── a counterproductive collection of misfit units that
        work against each other rather than with each other."
                               ─── Merle Parks

═══════════════════════════output file (CIPHER.OUT)════════════════════════════
             "Aranu  pkkh  dWo  W  olaYebeY  'pdnaodkhZ',
               WjZ sdaj pda qoan atYaaZo pda pdnaodkhZ,
           pda pkkh XaYkiao W dejZnWjYa nWpdan pdWj W dahl.
          wju okbpsWna qoaZ XaukjZ epo pdnaodkhZ sehh YWqoa
              ZaYnaWoao ej lnkZqYperepu, jkp ejYnaWoao.
       wjZ sdaj ejZereZqWh lnkZqYpo Wna lqp pkcapdan leaYaiaWh,
       pda naoqhp eo W ouopai pdWp dWo ckja lWop epo pdnaodkhZ
       ─── W YkqjpanlnkZqYpera YkhhaYpekj kb ieobep qjepo pdWp
        skng WcWejop aWYd kpdan nWpdan pdWj sepd aWYd kpdan."
                               ─── Ianha LWngo

═════════════════════════ decrypted file (CIPHER.ORI)══════════════════════════
             "Every  tool  has  a  specific  'threshold',
               and when the user exceeds the threshold,
           the tool becomes a hindrance rather than a help.
          Any software used beyond its threshold will cause
              decreases in productivity, not increases.
       And when individual products are put together piecemeal,
       the result is a system that has gone past its threshold
       ─── a counterproductive collection of misfit units that
        work against each other rather than with each other."
                               ─── Merle Parks

Ring


# Project : Substitution Cipher

plaintext = "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
ciphertext = "ZEBRASCDFGHIJKLMNOPQTUVWXY"
test = "flee at once. we are discovered!"
encrypt = "SIAA ZQ LKBA. VA ZOA RFPBLUAOAR!"

see "Plaintext : " + plaintext + nl
see "Ciphertext : " + ciphertext + nl
see "Test : " + test + nl
see "Encoded : "
encodetext = encode(test)
see encodetext + nl
see "Decoded : "
decodetext = decode(encodetext)
see decodetext + nl

func encode(test)
        str = ""
        for n = 1 to len(test)
              pos = substr(plaintext, upper(test[n]))
              if test[n] = " "
                 str = str + " "
              elseif test[n] = "!"
                 str = str + "!"
              elseif test[n] = "."
                 str = str + "."
              else
                 str = str + substr(ciphertext, pos, 1)
              ok
        next
        return str

func decode(test)
        str = ""
        for n = 1 to len(encodetext)
              pos = substr(ciphertext, upper(encodetext[n]))
              if test[n] = " "
                 str = str + " "
              elseif test[n] = "!"
                 str = str + "!"
              elseif test[n] = "."
                 str = str + "."
              else
                 str = str + lower(substr(plaintext, pos, 1))
              ok
        next
        return str

Output:


Plaintext : ABCDEFGHIJKLMNOPQRSTUVWXYZ
Ciphertext : ZEBRASCDFGHIJKLMNOPQTUVWXY
Test : flee at once. we are discovered!
Encoded : SIAA ZQ LKBA. VA ZOA RFPBLUAOAR!
Decoded : flee at once. we are discovered!

Scala

object SubstitutionCipher extends App {
  private val key = "]kYV}(!7P$n5_0i R:?jOWtF/=-pe'AD&@r6%ZXs\"v*N" + "[#wSl9zq2^+g;LoB`aGh{3.HIu4fbK)mU8|dMET><,Qc\\C1yxJ"
  private val text =
    """"It was still dark, in the early morning hours of the twenty-second of December
      | 1946, on the second floor of the house at Schilderskade 66 in our town,
      | when the hero of this story, Frits van Egters, awoke."""".stripMargin

  val enc = encode(text)
  println("Encoded: " + enc)
  println("Decoded: " + decode(enc))

  private def encode(s: String) = {
    val sb = new StringBuilder(s.length)
    s.map {
      case c if (' ' to '~').contains(c) => sb.append(key(c.toInt - 32))
      case _ =>
    }
    sb.toString
  }

  private def decode(s: String) = {
    val sb = new StringBuilder(s.length)
    s.map {
      case c if (' ' to '~').contains(c) =>
        sb.append((key.indexOf(c.toInt) + 32).toChar)
      case _ =>
    }
    sb.toString
  }
}

{{Out}}See it running in your browser by [https://scalafiddle.io/sf/f9yNWk7/0 ScalaFiddle (JavaScript, non JVM)] or by [https://scastie.scala-lang.org/8CyCsxnnRZyn0JH0yegndA Scastie (JVM)].

Sidef

{{trans|Julia}}

module SubstitutionCipher {

    const key = %c"]kYV}(!7P$n5_0i R:?jOWtF/=-pe'AD&@r6%ZXs\"v*N[#wSl9zq2^+g;LoB`aGh{3.HIu4fbK)mU8|dMET><,Qc\\C1yxJ"

    func encode(String s) {
        var r = ""
        s.each {|c|
            r += key[c.ord - 32]
        }
        return r
    }

    func decode(String s) {
        var r = ""
        s.each {|c|
            r += (key.first_index { _ == c } + 32 -> chr)
        }
        return r
    }
}


with ("The quick brown fox jumps over the lazy dog, who barks VERY loudly!") { |s|
    var enc = SubstitutionCipher::encode(s)
    var dec = SubstitutionCipher::decode(enc)
    say("Original: ", s, "\n -> Encoded: ", enc, "\n -> Decoded: ", dec)
}

{{out}}

Original: The quick brown fox jumps over the lazy dog, who barks VERY loudly!
 -> Encoded: 2bu]E,KHm].Tdc|]4d\]),8M>]dQuT]<bu]U31C]Idf_]cbd].3Tm>]+ZzL]Ud,IUCk
 -> Decoded: The quick brown fox jumps over the lazy dog, who barks VERY loudly!

Tcl

Here we implement a SubCipher class with three public methods:

  • key ?newkey? -- set or return the current substitution key. This validates the key for correspondence with the alphabet, returning an error if something is not right.
  • enc plaintext -- encrypt text with the current key
  • dec ciphertext -- decrypt text with the current key

The default alphabet is a-zA-Z, but can be overridden by providing an argument to the constructor. A random initial key will be generated at construction time, unless that is also provided as an argument.

oo::class create SubCipher {
    variable Alphabet
    variable Key
    variable EncMap
    variable DecMap
    constructor {{alphabet abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ} {cipherbet ""}} {
        set Alphabet $alphabet
        if {$cipherbet eq ""} {
            my key [my RandomKey]
        } else {
            my key $cipherbet
        }
    }
    method key args {
        if {$args eq ""} {
            return $Key
        } elseif {[llength $args] > 1} {
            throw {TCL WRONGARGS} "Expected \"[self class] key\" or \"[self class]\" key keystring"
        }
        lassign $args s

        set size [string length $Alphabet]
        if {[string length $s] != $size} {
            return -code error "Key must be $size chars long!"
        }
        set encmap {}
        set decmap {}
        foreach c [split $Alphabet {}] e [split $s {}] {
            dict set encmap $c $e
            dict set decmap $e $c
        }
        if {[dict size $encmap] != $size} {
            return -code error "Alphabet has repeating characters!"
        }
        if {[dict size $decmap] != $size} {
            return -code error "Key has repeating characters!"
        }
        set Key $s
        set EncMap $encmap
        set DecMap $decmap
    }
    method RandomKey {} {
        set chars $Alphabet
        set key {}
        for {set n [string length $chars]} {$n > 0} {incr n -1} {
            set i [expr {int(rand()*$n)}]
            append key [string index $chars $i]
            set chars [string range $chars 0 $i-1][string range $chars $i+1 end]
        }
        return $key
    }

    method enc {s} {
        string map $EncMap $s
    }
    method dec {s} {
        string map $DecMap $s
    }
}

Testing looks like this:

SubCipher create sc
set text [read [open /etc/motd]]
puts "Original:\n$text\n----\n"
puts "Ciphered:\n[set cipher [sc enc $text]]\n----\n"
puts "Decrypted:\n[sc dec $cipher]\n----\n"
puts "Key:\n[sc key]\n----\n"

{{out}}

Original:

The programs included with the Debian GNU/Linux system are free software;
the exact distribution terms for each program are described in the
individual files in /usr/share/doc/*/copyright.

Debian GNU/Linux comes with ABSOLUTELY NO WARRANTY, to the extent
permitted by applicable law.

----

Ciphered:

eVv yzhQzGwm KnLjDFvF lKZV ZVv CvuKGn MgA/rKnDc mJmZvw Gzv Xzvv mhXZlGzv;
ZVv vcGLZ FKmZzKuDZKhn Zvzwm Xhz vGLV yzhQzGw Gzv FvmLzKuvF Kn ZVv
KnFKOKFDGj XKjvm Kn /Dmz/mVGzv/FhL/*/LhyJzKQVZ.

CvuKGn MgA/rKnDc Lhwvm lKZV TbHIrAeWrY gI ETUUTgeY, Zh ZVv vcZvnZ
yvzwKZZvF uJ GyyjKLGujv jGl.

----

Decrypted:

The programs included with the Debian GNU/Linux system are free software;
the exact distribution terms for each program are described in the
individual files in /usr/share/doc/*/copyright.

Debian GNU/Linux comes with ABSOLUTELY NO WARRANTY, to the extent
permitted by applicable law.

----

Key:
GuLFvXQVKRNjwnhyozmZDOlcJBTbfCWdMkxqprtgIasUHeAiESYP
----

zkl

class SubstitutionCipher{
   // 92 characters: " !"#$%&" ... "xyz{|}", doesn't include "~"
   const KEY="]kYV}(!7P$n5_0i R:?jOWtF/=-pe'AD&@r6%ZXs\"v*N"
             "[#wSl9zq2^+g;LoB`aGh{3.HIu4fbK)mU8|dMET><,Qc\\C1yxJ";
   fcn encode(s){ s.apply(fcn(c){ try{ KEY[c.toAsc()-32] }catch{ c } }) }
   fcn decode(s){ s.apply(fcn(c){ try{ (KEY.index(c)+32).toChar() }catch{ c } }) }
}

text:="Here we have to do is there will be a input/source "
      "file in which we are going to Encrypt the file by replacing every "
      "upper/lower case alphabets of the source file with another "
      "predetermined upper/lower case alphabets or symbols and save "
      "it into another output/encrypted file and then again convert "
      "that output/encrypted file into original/decrypted file. This "
      "type of Encryption/Decryption scheme is often called a "
      "Substitution Cipher.";
encoded:=SubstitutionCipher.encode(text);
println(  "Encoded: ",encoded);
println("\nDecoded: ",SubstitutionCipher.decode(encoded));

{{out}}


Encoded: "uTu]cu]b3Qu]<d]Id]K>]<buTu]cKUU].u]3]K|M,< >d,THu]4KUu]K|]cbKHb]cu]3Tu]fdK|f]<d]Z|HTCM<]<bu]4KUu].C]TuMU3HK|f]uQuTC],MMuT UdcuT]H3>u]3UMb3.u<>]d4]<bu]>d,THu]4KUu]cK<b]3|d<buT]MTuIu<uT8K|uI],MMuT UdcuT]H3>u]3UMb3.u<>]dT]>C8.dU>]3|I]>3Qu]K<]K|<d]3|d<buT]d,<M,< u|HTCM<uI]4KUu]3|I]<bu|]3f3K|]Hd|QuT<]<b3<]d,<M,< u|HTCM<uI]4KUu]K|<d]dTKfK|3U IuHTCM<uI]4KUui]2bK>]<CMu]d4]Z|HTCM<Kd| %uHTCM<Kd|]>Hbu8u]K>]d4<u|]H3UUuI]3]q,.><K<,<Kd|]6KMbuTi

Decoded: Here we have to do is there will be a input/source file in which we are going to Encrypt the file by replacing every upper/lower case alphabets of the source file with another predetermined upper/lower case alphabets or symbols and save it into another output/encrypted file and then again convert that output/encrypted file into original/decrypted file. This type of Encryption/Decryption scheme is often called a Substitution Cipher.