Substitution Cipher

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

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.

See also


Ada[edit]

 
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[edit]

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 NSA like, use whatever string you want as long as it has a d/D or e/E in front.

 
/*Abhishek Ghosh, 11th October 2017*/
 
#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, 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 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

'[email protected]
'[email protected]
'[email protected]{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,[email protected]?m//-?
			mj,,mrx-wxv_maBAEPTLE ** ,[email protected] ** jpek AA IRGV]TX-
				syxWxv_ma A ,{glevcx-,,mrx-wxv_ma/hmjj-?
			 ipwi mj,,mrx-wxv_ma1hmjjBAEPTLE ** ,[email protected] ** 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++[edit]

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#[edit]

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);
}
}
}

Fortran[edit]

Works with: Fortran version 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
Output:
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[edit]

' 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
Output:

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.

J[edit]

Example implementation:

keysubst=: [`(a.i.])`(a."_)}
key=: 'Taehist' keysubst '[email protected]#$%^&'
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[edit]

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.

Kotlin[edit]

Translation of: 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)}")
}
Output:
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[edit]

-- 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))
Output:
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 6[edit]

Works with: Rakudo version 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.
$key = q☃3#}^",dLs*>tPMcZR!fmC rEKhlw1v4AOgj7Q]YI+|pDB82a&XFV9yzuH<WT%N;iS.0e:`G\n['[email protected]_{bk)=-5qx(/?$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 => $chr) }
Output:
with no passed parameters:
Key = 3#}^",dLs*>tPMcZR!fmC rEKhlw1v4AOgj7Q]YI+|pDB82a&XFV9yzuH<WT%N;iS.0e:`G\n['[email protected]_{bk)=-5qx(/?$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`[email protected](`=3
e.-`[email protected]`5-3bG35n`3-bq=e`3G[@`3([5n3.{b5n`=3k=`:`5`=_[{`:3
qkk`[email protected](`=3e.-`[email protected]`[email protected]{:3-.x`3[53[{5b3.{b5n`=3
bq5kq5Z`{e=?k5`:3G[@`3.{:35n`{3.\.[{3eb{x`=535n.53bq5kq5Z`{e=?k5`:3
G[@`3[{5b3b=[\[{[email protected]:`e=?k5`:3G[@`c39n[-35?k`3bG3]{e=?k5[b{ZQ`e=?k5[b{
-en`_`3[-3bG5`{[email protected]@`: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[edit]

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})
Output:
original: A simple example.
encoded: j wqGuMv vsQGuMv.
decoded: A simple example.

PicoLisp[edit]

(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)) )
Output:
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[edit]

 
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'~{[email protected]}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[edit]

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.

#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")))
Output:
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[edit]

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].1; @.[email protected].2; @.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

Tcl[edit]

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"
Output:
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[edit]

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));
Output:
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.