// File Name: OneTimePad.java
import java.util.*;
class msg{
int a=97;
char all[]=new char[27];
msg()
{
for(int i=0;i < 26;i++)
{
all[i]=(char)a;
a++;
}
}
int Ipos(char c)
{
int i=0;
for(;i < 26;i++)
{
if(all[i]==c)
{
break;
}
}
return i;
}
char Cpos(int c)
{
int i=0;
for(;i < c;i++)
{
}
return all[i];
}
}
class OneTimePadCipherImplementation{
String Encryption(String plaintext,String key)
{
plaintext=plaintext.toLowerCase();
msg m1=new msg();
int pt[]=new int[plaintext.length()];
int k[]=new int[key.length()];
int ct[]=new int[plaintext.length()];
for(int i=0;i < plaintext.length();i++)
{
pt[i]=m1.Ipos(plaintext.charAt(i));
}
for(int i=0;i < key.length();i++)
{
k[i]=m1.Ipos(key.charAt(i));
}
int j=0;
for(int i=0;i < plaintext.length();i++)
{
ct[i]=pt[i]+k[j];
j++;
if(j==key.length())
j=0;
if(ct[i]>26)
ct[i]=ct[i]%26;
}
String cipher="";
for(int i=0;i < plaintext.length();i++)
{
cipher+=m1.Cpos(ct[i]);
}
return cipher;
}
String Decryption(String ciphertext,String key)
{
String plaintext="";
msg m1=new msg();
int pt[]=new int[ciphertext.length()];
int k[]=new int[key.length()];
int ct[]=new int[ciphertext.length()];
for(int i=0;i < ciphertext.length();i++)
{
ct[i]=m1.Ipos(ciphertext.charAt(i));
}
for(int i=0;i < key.length();i++)
{
k[i]=m1.Ipos(key.charAt(i));
}
int j=0;
for(int i=0;i < ciphertext.length();i++)
{
pt[i]=ct[i]-k[j];
j++;
if(j==key.length())
j=0;
if(pt[i] < 0)
pt[i]+=26;
}
String cipher="";
for(int i=0;i < ciphertext.length();i++)
{
plaintext+=m1.Cpos(pt[i]);
}
return plaintext;
}
}
class OneTimePad{
public static void main(String args[])throws Exception
{
String plaintext,key;
Scanner scn=new Scanner(System.in);
System.out.println("Enter plaintext:");
plaintext=scn.nextLine();
System.out.println("Enter key:");
key=scn.nextLine();
OneTimePadCipherImplementation OneTimePad=new OneTimePadCipherImplementation();
String ciphertext=OneTimePad.Encryption(plaintext,key);
System.out.println("Encrpted text is:"+ciphertext);
System.out.println("Decrypted text is:"+OneTimePad.Decryption(ciphertext,key));
}
}
OUTPUT
Enter plaintext:
onetimepadalogrihtmsneedlongkey
Enter key:
longkeyisrequiredforonetimepad
Encrpted text is:zbrzsqcxsuebioimky jbriwt rvkhj
Decrypted text is:onetimepadalogrihtmsneedlongkey
