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Modify SDES to encrypt and decrypt the text message
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@iamrohitsuthar
iamrohitsuthar committed Feb 23, 2021
1 parent abb5e2e commit 9f83e54
Showing 1 changed file with 160 additions and 88 deletions.
248 changes: 160 additions & 88 deletions ICS/Assignment1/SDES.java
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Original file line number Diff line number Diff line change
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import java.util.Arrays;
import java.util.Scanner;
import java.util.*;
import java.util.regex.*;

public class SDES {

Expand Down Expand Up @@ -144,119 +146,189 @@ private int[] fk(int[] rBlock, int key[], int[] lBlock) {
return P4PermRes;
}

public String encrypt(String input) {
//create 8bit msg block
int[] msgBlock = new int[8];
for(int i = 0 ; i < 8 ; i++) {
msgBlock[i] = Integer.parseInt(String.valueOf(input.charAt(i)));
}

//initial permutation
msgBlock = permute(msgBlock, IP);
System.out.println("Initial Permutation Res: "+Arrays.toString(msgBlock));

//divide 8bit msgblock into left and right halfs
int leftHalf[] = new int[4];
int rightHalf[] = new int[4];
System.arraycopy(msgBlock, 0, leftHalf, 0, 4);
System.arraycopy(msgBlock, 4, rightHalf, 0, 4);
System.out.println("left block: "+Arrays.toString(leftHalf));
System.out.println("right block: "+Arrays.toString(rightHalf));

System.out.println("\n***** First Round - fk1 *****");
//first round - fk function with key1
int fk1Res[] = fk(rightHalf, key1, leftHalf);
System.out.println("fk1 Result: "+Arrays.toString(fk1Res));

//swap function
leftHalf = rightHalf;
rightHalf = fk1Res;
private String convertStringToBinary(String input) {
StringBuilder result = new StringBuilder();
char[] chars = input.toCharArray();
for (char aChar : chars) {
result.append(
String.format("%8s", Integer.toBinaryString(aChar))
.replaceAll(" ", "0")
);
}
return result.toString();
}

private String convertBinaryToString(String input) {
StringBuilder sb = new StringBuilder();
Pattern p = Pattern.compile("[\\w ]{0,8}");
Matcher m = p.matcher(input);
while (m.find()) {
if(!m.group().isEmpty())
sb.append(new Character((char)Integer.parseInt(m.group(), 2)).toString());
}
return sb.toString();
}

System.out.println("\n***** Second Round - fk2 *****");
//second round - fk function with key2
int fk2Res[] = fk(fk1Res,key2,leftHalf);
System.out.println("fk2 Result: "+Arrays.toString(fk2Res));
private List<String> convertBinaryIntoBlocks(String binary, int blockSize, String separator) {

int res[] = new int[8];
System.arraycopy(fk2Res, 0, res, 0, 4);
System.arraycopy(rightHalf, 0, res, 4, 4);
System.out.println("\nResult before IP inverse: "+Arrays.toString(res));
List<String> result = new ArrayList<>();
int index = 0;
while (index < binary.length()) {
result.add(binary.substring(index, Math.min(index + blockSize, binary.length())));
index += blockSize;
}

//inverse initial permutation
int encrypedRes[] = permute(res, IP_INV);
return result;
}

//return the encrypted message
public String encrypt(String input, String type) {
//type - BINARY FORM | TEXT MESSAGE FORM
List<String> blocks;
StringBuilder builder = new StringBuilder();
for(int ele: encrypedRes) {
builder.append(ele);
}
return builder.toString();
}

public String decrypt(String encryptedInput) {
//create 8bit msg block
int[] msgBlock = new int[8];
for(int i = 0 ; i < 8 ; i++) {
msgBlock[i] = Integer.parseInt(String.valueOf(encryptedInput.charAt(i)));
if(type.equals("TEXT_MESSAGE_FORM")) {
blocks = convertBinaryIntoBlocks(convertStringToBinary(input), 8, " ");
}
else {
blocks = new ArrayList<>();
blocks.add(input);
}

//initial permutation
msgBlock = permute(msgBlock, IP);
System.out.println("Initial Permutation Res: "+Arrays.toString(msgBlock));

//divide 8bit msgblock into left and right halfs
int leftHalf[] = new int[4];
int rightHalf[] = new int[4];
System.arraycopy(msgBlock, 0, leftHalf, 0, 4);
System.arraycopy(msgBlock, 4, rightHalf, 0, 4);
System.out.println("left block: "+Arrays.toString(leftHalf));
System.out.println("right block: "+Arrays.toString(rightHalf));

System.out.println("\n***** First Round - fk1 *****");
//first round - fk function with key1
int fk1Res[] = fk(rightHalf, key2, leftHalf);
System.out.println("fk1 Result: "+Arrays.toString(fk1Res));

//swap function
leftHalf = rightHalf;
rightHalf = fk1Res;

System.out.println("\n***** Second Round - fk2 *****");
//second round - fk function with key2
int fk2Res[] = fk(fk1Res,key1,leftHalf);
System.out.println("fk2 Result: "+Arrays.toString(fk2Res));

int res[] = new int[8];
System.arraycopy(fk2Res, 0, res, 0, 4);
System.arraycopy(rightHalf, 0, res, 4, 4);
System.out.println("\nResult before IP inverse: "+Arrays.toString(res));
for(int i = 0 ; i < blocks.size() ; i++) {
String block = blocks.get(i);
//create 8bit msg block
int[] msgBlock = new int[8];
for(int j = 0 ; j < 8 ; j++) {
msgBlock[j] = Integer.parseInt(String.valueOf(block.charAt(j)));
}

//initial permutation
msgBlock = permute(msgBlock, IP);
System.out.println("Initial Permutation Res: "+Arrays.toString(msgBlock));

//divide 8bit msgblock into left and right halfs
int leftHalf[] = new int[4];
int rightHalf[] = new int[4];
System.arraycopy(msgBlock, 0, leftHalf, 0, 4);
System.arraycopy(msgBlock, 4, rightHalf, 0, 4);
System.out.println("left block: "+Arrays.toString(leftHalf));
System.out.println("right block: "+Arrays.toString(rightHalf));

System.out.println("\n***** First Round - fk1 *****");
//first round - fk function with key1
int fk1Res[] = fk(rightHalf, key1, leftHalf);
System.out.println("fk1 Result: "+Arrays.toString(fk1Res));

//swap function
leftHalf = rightHalf;
rightHalf = fk1Res;

System.out.println("\n***** Second Round - fk2 *****");
//second round - fk function with key2
int fk2Res[] = fk(fk1Res,key2,leftHalf);
System.out.println("fk2 Result: "+Arrays.toString(fk2Res));

int res[] = new int[8];
System.arraycopy(fk2Res, 0, res, 0, 4);
System.arraycopy(rightHalf, 0, res, 4, 4);
System.out.println("\nResult before IP inverse: "+Arrays.toString(res));

//inverse initial permutation
int encrypedRes[] = permute(res, IP_INV);

for(int ele: encrypedRes) {
builder.append(ele);
}
}

//inverse initial permutation
int decryptedRes[] = permute(res, IP_INV);
//return the encrypted message
return builder.toString();
}

//return the decrypted message
public String decrypt(String encryptedInput, String type) {
StringBuilder builder = new StringBuilder();
for(int ele: decryptedRes) {
builder.append(ele);
List<String> blocks = convertBinaryIntoBlocks(encryptedInput, 8, " ");
//System.out.println("blocks:"+blocks.toString());

for(int i = 0 ; i < blocks.size() ; i++) {
String block = blocks.get(i);
//create 8bit msg block
int[] msgBlock = new int[8];
for(int j = 0 ; j < 8 ; j++) {
msgBlock[j] = Integer.parseInt(String.valueOf(block.charAt(j)));
}
//System.out.println("Msg block: "+Arrays.toString(msgBlock));

//initial permutation
msgBlock = permute(msgBlock, IP);
System.out.println("Initial Permutation Res: "+Arrays.toString(msgBlock));

//divide 8bit msgblock into left and right halfs
int leftHalf[] = new int[4];
int rightHalf[] = new int[4];
System.arraycopy(msgBlock, 0, leftHalf, 0, 4);
System.arraycopy(msgBlock, 4, rightHalf, 0, 4);
System.out.println("left block: "+Arrays.toString(leftHalf));
System.out.println("right block: "+Arrays.toString(rightHalf));

System.out.println("\n***** First Round - fk1 *****");
//first round - fk function with key1
int fk1Res[] = fk(rightHalf, key2, leftHalf);
System.out.println("fk1 Result: "+Arrays.toString(fk1Res));

//swap function
leftHalf = rightHalf;
rightHalf = fk1Res;

System.out.println("\n***** Second Round - fk2 *****");
//second round - fk function with key2
int fk2Res[] = fk(fk1Res,key1,leftHalf);
System.out.println("fk2 Result: "+Arrays.toString(fk2Res));

int res[] = new int[8];
System.arraycopy(fk2Res, 0, res, 0, 4);
System.arraycopy(rightHalf, 0, res, 4, 4);
System.out.println("\nResult before IP inverse: "+Arrays.toString(res));

//inverse initial permutation
int decryptedRes[] = permute(res, IP_INV);

for(int ele: decryptedRes) {
builder.append(ele);
}
}
return builder.toString();
//return the decrypted message
if(type.equals("TEXT_MESSAGE_FORM"))
return convertBinaryToString(builder.toString());
else
return builder.toString();
}

public static void main(String[] args) {
String key = null, msg = null;
String key = null, msg = null, type = null;
int typeInput = -1;
Scanner sc = new Scanner(System.in);
System.out.print("Enter 10-bit key: ");
key = sc.next();
SDES sdes = new SDES(key);

System.out.print("Enter plain text for encryption: ");
msg = sc.nextLine() + sc.nextLine();

System.out.println("Text message is in which form? ");
System.out.println("1 - For binary form");
System.out.println("2 - For Text message form");
typeInput = sc.nextInt();
if(typeInput == 1) type = "BINARY_FORM";
else if(typeInput == 2)type = "TEXT_MESSAGE_FORM";

SDES sdes = new SDES(key);

System.out.println("\n***** ENCRYPTION *****");
String encryptedMsg = sdes.encrypt(msg);
String encryptedMsg = sdes.encrypt(msg, type);
System.out.println("Encrypted Message: "+encryptedMsg);

System.out.println("\n***** DECRYPTION *****");
String decryptedMsg = sdes.decrypt(encryptedMsg);
String decryptedMsg = sdes.decrypt(encryptedMsg, type);
System.out.println("Decrypted Message: "+decryptedMsg);
}
}

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