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KeyWord.java
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KeyWord.java
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/*Keyword cipher is a form of monoalphabetic substitution, where a keyword is used as the key. Now
a encryption is formed of alphabets from [a-z] such that the first part of encrption contains
unique letters of the keyword and the rest are the remaining alphabets from [a-z]. That is,
until the keyword is used up, whereupon the rest of the ciphertext letters are used in alphabetical
order, excluding those already used in the key.*/
import java.util.*;
public class KeyWord{
//This function builds the encoder based on the key given as input
static String encoder(char[] key){
String str = "";
int[] array = new int[26];
for(int k=0;k<26;k++){
array[k] = 0;
}
//Iterating the key and building the encoder
for(int i=0;i<key.length;i++){
if(key[i] != ' '){
if(array[key[i]-97] == 0){
str += key[i];
array[key[i]-97] = 1;
}
}
}
//Adding the remaining alphabetics
for(int i=0;i<26;i++){
if(array[i] == 0){
array[i] = 1;
str += (char)(i+97);
}
}
return str;
}
//We cipher the text in this function
static void cipher(String plaintext,String keyencoder){
String output="";
char space = ' ';
char[] message = plaintext.toCharArray();
/*for every letter in the plaintext we replace it with
the corresponding letter in the encoded string we use*/
for(int i=0;i<message.length;i++){
if(message[i] == space)
//adding the space if input has one
output += message[i];
else
output += keyencoder.charAt(message[i]-97);
}
//printing the cipher text
System.out.println("The cipher text is :"+output);
}
public static void main(String []args){
String plaintext,key;
Scanner scan = new Scanner(System.in);
//We take plaintext and key here
System.out.print("Enter the Plaintext :");
plaintext = scan.nextLine();
System.out.print("Enter the key :");
key = scan.nextLine();
scan.close();
//we call this function to cipher the plaintext
cipher(plaintext,encoder(key.toCharArray()));
}
}
/*
Simple I/O :
Enter the Plaintext :hello world
Enter the key :asdf
The cipher text is :gbkkn wnqkf
*/