The objective of this programming assignment is to design an

The objective of this programming assignment is to design and implement an encryption/decryption scheme. Consider the following encryption scheme: Initially, the plaintext is divided into two halves, left and right plaintext; each side is using Caesar\'s cipher with K1 and K2 respectively. The result of this encryption is interleaved character by character to generate an interleaved ciphertext. The ciphertext is then encrypted using Caesar\'s cipher with the key K3. Write a C/C++ program that takes as input a string and return the encrypted/decrypted message.

Solution

Code to copy:

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// This is another program by a different approach with sample ouput

import java.io.*;

import java.util.*;

class feistel

{

                public static void main(String args[]) throws Exception

                {

                                int a[]=new int[20];

                                int left[]=new int[10];

                                int right[]=new int[10];

                                int key[]=new int[10];

                                int temp[]=new int[10];

                                int m[]=new int[10];

                                int i,k;

                                Scanner sc=new Scanner(System.in);

                                BufferedReader br=new BufferedReader(new InputStreamReader(System.in));

                                System.out.println(\"Enter length of string:\");

                                int n=Integer.parseInt(br.readLine());

                                System.out.println(\"Enter plaintext:\");

                                for(i=0;i<n;i++)

                                                a[i]=sc.nextInt();

                                System.out.println(\"Enter key:\");

                                for(i=0;i<(n/2);i++)

                                                key[i]=sc.nextInt();

                                for(i=0;i<(n/2);i++)

                                                left[i]=a[i];

                                for(int j=0;i<n;i++,j++)

                                                right[j]=a[i];

                                System.out.println(\"Left string:\");

                                for(i=0;i<(n/2);i++)

                                                System.out.print(left[i]);

                                System.out.println();

                                System.out.println(\"Right string:\");

                                for(i=0;i<(n/2);i++)

                                                System.out.print(right[i]);

                                for(k=0;k<4;k++)

                                {

                                                for(i=0;i<(n/2);i++)

                                                {

                                                                if(key[i]==right[i])

                                                                                temp[i]=0;

                                                                else

                                                                                temp[i]=1;

                                                }

                                                for(i=0;i<(n/2);i++)

                                                {

                                                                if(left[i]==temp[i])

                                                                                m[i]=0;

                                                                else

                                                                                m[i]=1;

                                                }

                                                for(i=0;i<(n/2);i++)

                                                                left[i]=right[i];

                                                for(i=0;i<(n/2);i++)

                                                                right[i]=m[i];

                                                System.out.println();

                                                System.out.println(\"Round \" + (k+1));

                                                System.out.print(\"Left:\");

                                                for(i=0;i<(n/2);i++)

                                                                System.out.print(left[i]);

                                                System.out.println();

                                                System.out.print(\"Right:\");

                                                for(i=0;i<(n/2);i++)

                                                                System.out.print(right[i]);

                                }

                                System.out.println();

                                System.out.println(\"Encrypted string is:\");

                                for(i=0;i<(n/2);i++)

                                {

                                                System.out.print(left[i]);

                                }

                                System.out.print(\" \");

                                for(i=0;i<(n/2);i++)

                                System.out.print(right[i]);

                }

}

/*OUTPUT:

C:\\ins>java feistel

Enter length of string:

8

Enter plaintext:

0 1 0 1 0 1 0 1

Enter key:

1 0 1 0

Left string:

0101

Right string:

0101

Round 1

Left:0101

Right:1010

Round 2

Left:1010

Right:0101

Round 3

Left:0101

Right:0101

Round 4

Left:0101

Right:1010

Encrypted string is:

0101 1010

*/