EX N0-01 IMPLEMENT SYMMETRIC KEY ALGORITHM USING CAESAR CIPHER.
PROGRAM:
class caesarCipher
{
public static String encode(String enc, int offset)
{
offset = offset % 26 + 26;
StringBuilder encoded = new StringBuilder();
for (char i : enc.toCharArray())
{
if (Character.isLetter(i))
{
if (Character.isUpperCase(i))
{
encoded.append((char) ('A' + (i - 'A' + offset) % 26));
}
else
{
encoded.append((char) ('a' + (i - 'a' + offset) % 26));
}
}
else
{
encoded.append(i);
}
}
return encoded.toString();
}
public static String decode(String enc, int offset)
{
return encode(enc, 26 - offset);
}
public static void main(String[] args) throws java.lang.Exception
{
String msg = "Anna University";
System.out.println("Simulating Caesar Cipher\n------------------------");
System.out.println("Input : " + msg);
System.out.printf("Encrypted Message : ");
System.out.println(caesarCipher.encode(msg, 3));
System.out.printf("Decrypted Message : ");
System.out.println(caesarCipher.decode(caesarCipher.encode(msg, 3), 3));
}
}
OUTPUT:
Simulating Caesar Cipher
------------------------
Input : Anna University
Encrypted Message : Dqqd Xqlyhuvlwb
Decrypted Message : Anna University
EX NO-02 IMPLEMENT AYMMETRIC KEY ALGORITHMS AND KEY EXCHANGE ALGORITHMS.
PROGRAM:
import java.math.*;
import java.util.*;
class RSA
{
public static void main(String args[])
{
int p, q, n, z, d = 0, e, i;
int msg = 12;
double c;
BigInteger msgback;
p = 3;
q = 11;
n = p * q;
z = (p - 1) * (q - 1);
System.out.println("The value of z = " + z);
for (e = 2; e < z; e++)
{
if (gcd(e, z) == 1)
{
break;
}
}
System.out.println("The value of e = " + e);
for (i = 0; i <= 9; i++)
{
int x = 1 + (i * z);
if (x % e == 0)
{
d = x / e;
break;
}
}
System.out.println("The value of d = " + d);
c = (Math.pow(msg, e)) % n;
System.out.println("Encrypted message is : " + c);
BigInteger N = BigInteger.valueOf(n);
BigInteger C = BigDecimal.valueOf(c).toBigInteger();
msgback = (C.pow(d)).mod(N);
System.out.println("Decrypted message is : "+ msgback);
}
static int gcd(int e, int z)
{
if (e == 0)
return z;
else
return gcd(z % e, e);
}
}
OUTPUT:
The value of z = 20
The value of e = 3
The value of d = 7
Encrypted message is : 12.0
Decrypted message is : 12
EX NO-03 IMPLEMENT DIGITAL SIGNATURE SCHEMES
PROGRAM:
import java.security.KeyPair;
import java.security.KeyPairGenerator;
import java.security.PrivateKey;
import java.security.Signature;
import java.util.Scanner;
public class CreatingDigitalSignature
public static void main(String args[])throws Exception
Scanner sc=new Scanner(System.in);
System.out.println("Enter some text:");
String msg=sc.nextLine();
KeyPairGenerator KeyPairGen=KeyPairGenerator.getInstance("DSA");
KeyPairGen.initialize(2048);
KeyPair pair=KeyPairGen.generateKeyPair();
PrivateKey privKey=pair.getPrivate();
Signature sign=Signature.getInstance("SHA256withDSA");
sign.initSign(privKey);
byte[] bytes="msg".getBytes();
sign.update(bytes);
byte[] signature=sign.sign();
System.out.println("Digital Signature for given text:"+new String(signature,"UTF8"));
OUTPUT:
Enter some text:
Hii
Digital Signature for given text: 0<0$:h]�)ҵ�!�S�����@!
(<�N*&�l�fu�#�ٍk6�P���9jܺ"
