Substitution Cipher - Java

Downloadable file : Substitution Cipher


import java.util.HashMap;
import java.util.Iterator;
import java.util.Map;

public class subs_cipper { 
      public static void main(String[] args) { 
  
      System.out.println("This is to demonstrate the Substitution Cipher");
      System.out.println("Each alphanumeric char is mapped to a String (arbitrarily, of two chars length)");
      System.out.println("For example, 'A' is mapped to \"OA\", 'B' is mapped to \"9B\", and so on...");
      System.out.print("\nTest String = ");
      String plaintext = "WHYAMIDOINGTHISWHYAREWEHEREWHATAREWEDOING";
      //string to be ciphered
      //String plaintext = "ABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890"; 
      //use this to check. With this, 
      //...plaintext = Keys, and Ciphertext = Values
      System.out.print(plaintext);
      
      //Encryption
      System.out.println("\n\nCiphertext = ");
      Cipher ObjCipher = new Cipher();
      String ciphertext = ObjCipher.Encrypt(plaintext);  
      //output ciphered string
      System.out.println(ciphertext);
      
      //Decryption
      System.out.print("\nPlaintext = \n");
      String outplaintext = ObjCipher.Decrypt(ciphertext);  
      //output deciphered string
      System.out.print(outplaintext);
   }
}


//the class that that implements the actual encryption
class Cipher {
String keys, values;  
     //Keys & Values for HashMap
String plaintext, ciphertext;
HashMap<String, String> map = new HashMap<String, String>(); 
     //HashMap to do the mapping


//constructor, instantiates the HashMap
public Cipher(){
//one-to-one mapping (Keys - Values) of different length. In this example, 
//A:OA, B:9B, C:8C &  so on...
 keys = "ABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890";
values = "0A9B8C7F6E5R4F3T2J1K4LX2VN18K9LC42B7" +
         "ABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890";


//use for loop to fill up & map the Keys to the respective Values
for (int i=0; i<keys.length(); i++){
char charkey = keys.charAt(i);  
       //get each char from the Keys & convert to String
String tempkey = Character.toString(charkey);

char charval1 = values.charAt(i*2);  
       //get every two chars from the Values & convert to String
String tempval1 = Character.toString(charval1);  
       //...and concatenate both chars to form a single String
char charval2 = values.charAt(i*2+1);
String tempval2 = Character.toString(charval2);
String tempval = tempval1 + tempval2;

map.put(tempkey, tempval);  
       //fill the HashMap
}

}


//Encrypt method, do the Encryption, takes Plaintext as argument
public String Encrypt(String plaintext){
String output = "";
char ch;

for (int i=0; i<plaintext.length(); i++){  
   //go through the plaintext 
ch = plaintext.charAt(i);    
       //take each chars as 'Key'
String str = Character.toString(ch);  
       //..and map to its corresponding 'Value'
output = output + map.get(str);
}
 
   return output;  
   //returns the the encrypted String
}


//Decrypt method, do the Decryption, takes Ciphertext as argument
public String Decrypt(String ciphertext){
String output = "";
char ch;
String str = "";

for (int i=0; i<ciphertext.length(); i = i+2){  
  //get next two adjacent chars from the Ciphertext
ch = ciphertext.charAt(i);    
       //concatenates them into a single String
str = Character.toString(ch);
ch = ciphertext.charAt(i+1); 
str = str + Character.toString(ch);

Iterator j = map.entrySet().iterator();  
       //look up through HashMap by the Value 

while (j.hasNext()) {  
       //...to find the corresponding Key
Map.Entry entry = (Map.Entry) j.next();
if (str.equals((String)entry.getValue())){  
                //concatenates the output with each Key found
output = output + (String)entry.getKey();
}
}
}

return output;  
  //return the Decrypted String
}

}

UI design (again!)

Since we have passed the first demonstration, it's time now to design for the final prototype. I have considered a few ideas of how our App will look like, and what kind of functionality that we will be offering. Unline UniKey, we don't have our system connected to the net, which makes our system simpler than theirs (apart from more secured, that's it). These are the interfaces that I came out with, as of now.

  

What do you think?