Rail Fence Cipher Java implementation





Source Code:


/* railfence cipher*/
package railfence;
import java.util.*;

public class RailFence {


public static void main(String arg[]){


System.out.println("Enter the number of rails:");
Scanner in=new Scanner (System.in);
int rails=in.nextInt();



System.out.println("Enter the plaintext for encryption");
Scanner inn=new Scanner (System.in);
String plaintext=inn.next();

encryption(plaintext,rails);


System.out.println("------------------Decryption process start----------");

System.out.println("Enter the number of rails:");
rails=in.nextInt();
System.out.println("Enter the ciphertext for decryption:");
String ciphertext=in.next();
decryption(ciphertext,rails);

}
public static void encryption(String str,int rails){

boolean checkdown=false;  //check whether it is moving downward or upward
int j=0;
int row=rails;                  // no of row is the no of rails entered by user
int col=str.length();             //column length is the size of string
char[][] a=new char[row][col];
//we create a matrix of a of row *col size

for(int i=0;i<col;i++){  //matrix visitin in rails order and putting the character of plaintext


if(j==0||j==row-1)
checkdown=!checkdown;
a[j][i]=str.charAt(i);
if(checkdown){


j++;
}
else
j--;
}

//visiting the matrix in usual order to get ciphertext
for(int i=0;i<row;i++){
for(int k=0;k<col;k++){
System.out.print(a[i][k]+"  ");
}
System.out.println();
}
String en="";

System.out.println("----------------------");
for(int i=0;i<row;i++){
for(int k=0;k<col;k++){
if(a[i][k]!=0)
en=en+a[i][k];

}

}
System.out.println(en);//printing the ciphertext


}



public static void decryption(String str,int rails){


boolean checkdown=false;
int j=0;
int row=rails;
int col=str.length();
char[][] a=new char[row][col];

//first of all mark the rails position by * in the matrix
for(int i=0;i<col;i++){
if(j==0||j==row-1)
checkdown=!checkdown;



a[j][i]='*';
if(checkdown)j++;
else j--;

}


//now enter the character of cipheetext in the matrix positon that have * symbol
int index=0;

for(int i=0;i<row;i++){
for(int k=0;k<col;k++){


if(a[i][k]=='*'&&index<str.length()){
a[i][k]=str.charAt(index++);




}

}



}

// visit each character in rails order as character are put in the encryption function
for(int i=0;i<row;i++){
for (int k=0;k<col;k++){
System.out.print(a[i][k]+ "\t");
}
System.out.println();
}


checkdown=false;
String s="";
j=0;

for(int i=0;i<col;i++){
if( j==0||j==row-1)
checkdown=!checkdown;


s+=a[j][i];


if(checkdown)j++;
else j--;

}



System.out.print(s);//print the plaintext that was decrypted by rail fence cipher







}
}