[shuffle1990]

Hi, i am new in java. i was thinking of doing a substitution cipher program. i have searched quite a lot of forum. and usually they all are using the key shifting method by assigning the 1st character in the loop. for example normal alphabet sequence "a,b,c,d,e,...z" to shifted alphabet "c,a,b,d,e,...z.". i was thinking about finding a method that can specific the alphabet sequence that i want the encrypt and decrypt because with that the encryption will be vary to others people. for example, "a,b,c,d,e,...,z" to "f,e,a,t,h,...,b". well, is there anyway to do it?

[g00se]

Quote

well, is there anyway to do it?

Yes, just use Map<Character, Character> and you can map one character to any other

This post has been edited by g00se: 15 November 2012 - 04:30 AM
Reason for edit:: typo

[JHol]

if you are intrested learning cryptation a good place to start is with the Caesar cipher algorithm

My link

[g00se]

Quote

a good place to start is with the Caesar cipher algorithm

Not in this case. shuffle1990 has already rejected the functionality used in Caesar

[pbl]

You can use two arrays to fill g00se's Map

    class Ceasar {
       private Map<Character,Character> map;

       public Ceasar() {
          String from = "abcdefghijklmnopqrstuvwxyz";
          String to   = "qwertyuiopasdfghjklzxcvbnm";

          map = new HashMap<Character,Character>();
          for(int i = 0; i < from.length(); ++i)
             map.put(from.charAt(i), to.charAt(i));
      }
}

JHol, on 15 November 2012 - 07:47 AM, said:

if you are intrested learning cryptation a good place to start is with the Caesar cipher algorithm

My link

Nice article by the way.
And the code is here in DIC
http://www.dreaminco...-ceasar-cipher/
as at least 8 other secret codes programs.

[shuffle1990]

so while encryption is using this

 
map = new HashMap<Character,Character>();
          for(int i = 0; i < from.length(); ++i)
             map.put(from.charAt(i), to.charAt(i));

and decryption will be using this?

 map = new HashMap<Character,Character>();
          for(int i = 0; i < from.length(); ++i)
             map.put(to.charAt(i), from.charAt(i));

[shuffle1990]

import java.util.HashMap;

public class Caesar {
    private HashMap<Character,Character> encr;
    private HashMap<Character,Character> decr;
    
    public Caesar() {
       String from = "abcdefghijklmnopqrstuvwxyz";
       String to   = "qwertyuiopasdfghjklzxcvbnm";

       encr = new HashMap<Character,Character>();
       for(int i = 0; i < from.length(); ++i)
          encr.put(from.charAt(i), to.charAt(i));
       
       decr = new HashMap<Character,Character>();
       for(int i = 0; i < from.length(); ++i)
          decr.put(to.charAt(i), from.charAt(i));
   }
}

something like this?

[pbl]

Make it in a single loop

import java.util.HashMap;

public class Caesar {
    private HashMap<Character,Character> encr;
    private HashMap<Character,Character> decr;
    
    public Caesar() {
       String from = "abcdefghijklmnopqrstuvwxyz";
       String to   = "qwertyuiopasdfghjklzxcvbnm";

       encr = new HashMap<Character,Character>();
       decr = new HashMap<Character,Character>();
       for(int i = 0; i < from.length(); ++i) {
          encr.put(from.charAt(i), to.charAt(i));
          decr.put(to.charAt(i), from.charAt(i));
       }
   }

[shuffle1990]

hmm, single loop is much better practice for programming?

[pbl]

don't see why you would have to this twice:

for(int i = 0; i < from.length(); ++i) {

which is:

adding 26 times 1 to i
calling 26 times the method length(| of String from
checking 26 times that i < from.length()

[g00se]

A Map in this case isn't really necessary as you can just do

char cipherC = to[from.indexOf(plainC)];

[shuffle1990]

g00se, on 20 November 2012 - 07:20 PM, said:

A Map in this case isn't really necessary as you can just do

char cipherC = to[from.indexOf(plainC)];

oh? so with that for encrypt would be

char cipherE = to[from.indexOf(plainC)];

while decrypt would be as below?

char cipherD = from[to.indexOf(plainC)];

g00se, on 20 November 2012 - 07:20 PM, said:

A Map in this case isn't really necessary as you can just do

char cipherC = to[from.indexOf(plainC)];

oh? so with that for encrypt would be

char cipherE = to[from.indexOf(plainC)];

while decrypt would be as below?

char cipherD = from[to.indexOf(plainC)];

g00se, on 20 November 2012 - 07:20 PM, said:

A Map in this case isn't really necessary as you can just do

char cipherC = to[from.indexOf(plainC)];

and what is the (plainC) refer to? is it plainText?

[g00se]

Quote

while decrypt would be as below?

Not quite. You need to invert everything:

char cipherC = to[from.indexOf(plainC)];

char plainC = from[to.indexOf(cipherC)];

Quote

and what is the (plainC) refer to? is it plainText?

Yes, a single char thereof

[pbl]

Not really as they are String you have to use the charAt() method so it is

char cipherC = to.charAt(from.indexOf(plainC));

char plainC = from.charAt(to.indexOf(cipherC));

[shuffle1990]

@@ well, i come up with a way to make it without using the hashmap @@ but i encounter some problem @@
which are the input file are consist of both uppercase and lower case alphabet. but the output only able to display uppercase only. and is it possible for me to change ' ' to '#' as well? and i also having some problem in doing the decrypting as well @@ below is the coding that so far i am having now. hope you guys can help me out. @@ and thanks in advance.

import java.util.Scanner;
import java.io.FileReader;
import java.io.IOException;
import java.io.PrintWriter;

public class SubstitutionCipher{
    public static final String plainText = "abcdefghijklmnopqrstuvwxyz";
    public static String encrypt(String inputWord, String cipherText){    
    		String encryptedString = inputWord.toLowerCase();
        
            for (int i = 0; i < 26; i++){    
                char cipherTextChar = cipherText.charAt(i);    
                char plainTextChar = plainText.charAt(i);    
                encryptedString = encryptedString.replace(plainTextChar,cipherTextChar);    
            }    
            return encryptedString;    
	}    
	public static void main(String[] args){
		String cipherText = "FEATHRZYXWVUSQPONMLKJIGDCB";
			System.out.println("Caesar Cipher Encryption\n");
			Scanner console = new Scanner(System.in);
			System.out.print("Input file: ");
			String inputFileName = console.next();
			System.out.print("Output file: ");
			String outputFileName = console.next();
    	       
			try{ 
				FileReader reader = new FileReader("C:/"+inputFileName+".txt");
				Scanner in = new Scanner(reader);
				PrintWriter out = new PrintWriter("C:/"+outputFileName+".txt");
		    	            
					while (in.hasNextLine()){
						String line = in.nextLine();
						String encipheredText = encrypt(line, cipherText);
						System.out.println("Plaintext: " + line);
						System.out.println("Ciphertext: " + encipheredText);
						out.println(encipheredText);         
					}
					out.close();
			}
			catch (IOException exception){ 
				System.out.println("Error processing file:" + exception);
			}
	}
}

and for the

String cipherText = "FEATHRZYXWVUSQPONMLKJIGDCB";

this line, it seem that lowercase cant be use @@ any idea to make it lower change to lower, while upper change to upper?