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Autokey.java
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Autokey.java
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/*
Autokey encryption and decryption
*/
import java.util.*;
import java.lang.*;
import java.math.*;
public class Autokey{
private static String alpha = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";
public static void main(String[] args){
String text = "FOLLOWREGULATION";
String key = "P"; //15 - P
if(key.matches("[-+]?\\d*\\.?\\d+"))
key = ""+alpha.charAt(Integer.parseInt(key));
String enc = AutoEncryption(text,key);
System.out.println("Plaintext : "+text);
System.out.println("Encrypted : "+enc);
System.out.println("Decrypted : "+AutoDecryption(enc,key));
}
public static String AutoEncryption(String text,String key){
int len = text.length();
String subkey = key + text;
subkey = subkey.substring(0,subkey.length()-key.length());
String sb = "";
int y =0;
for(int x=0;x<len;x++){
char get = text.charAt(x);
char skey = subkey.charAt(y);
if(Character.isUpperCase(get)){
int get1 = alpha.indexOf(get);
int get2 = alpha.indexOf(skey);
int total = (get1 + get2)%26;
sb += alpha.charAt(total);
y++;
}
else if(Character.isLowerCase(get)){
int get1 = alpha.toLowerCase().indexOf(get);
int get2 = alpha.indexOf(skey);
int total = (get1 + get2)%26;
sb += alpha.toLowerCase().charAt(total);
y++;
}
else{
sb += get;
}
}
return sb;
}
public static String AutoDecryption(String text,String key){
int len = text.length();
String current = key;
String sb ="";
int y=0;
for(int x=0;x<len;x++){
char get = text.charAt(x);
char subkey = current.charAt(y);
if(Character.isUpperCase(get)){
int get1 = alpha.indexOf(get);
int get2 = alpha.indexOf(subkey);
int total = (get1 - get2)%26;
total = (total<0)? total + 26 : total;
sb += alpha.charAt(total);
current += alpha.charAt(total);
y++;
}
else if(Character.isLowerCase(get)){
int get1 = alpha.toLowerCase().indexOf(get);
int get2 = alpha.indexOf(subkey);
int total = (get1 - get2)%26;
total = (total<0)? total + 26 : total;
sb += alpha.charAt(total);
current += alpha.toLowerCase().charAt(total);
y++;
}
else{
sb += get;
}
}
return sb;
}
}