Dear students today CNS lab program on RSA
*RSA ALGORITHM*
*AIM:* Write a Java program to implement RSA Algoithm.
*Description:*
RSA Algorithm is used to encrypt and decrypt data in modern computer systems and other electronic devices. RSA algorithm is an asymmetric cryptographic algorithm as it creates 2 different keys for the purpose of encryption and decryption. ... RSA makes use of prime numbers (arbitrary large numbers) to function.
*Source Code:*
import java.util.*;
public class RSA {
public static void main(String args[]) {
Scanner sc=new Scanner(System.in);
int d=0,e,i;
double c,msg;
System.out.println("Enter the numbered message: ");
int m=sc.nextInt();
System.out.println("Enter two prime numbers: ");
int p=sc.nextInt();
int q=sc.nextInt();
int n=p*q;
int phi=(p-1)*(q-1);
System.out.println("the value of totent function = "+phi);
for(e=2;e<phi;e++) {
if(gcd(e,phi)==1)
break;
}
System.out.println("The value of e = "+e);
for(i=1;i<phi;i++) {
if((e*i)%phi == 1) {
d=i;
break;
}
}
System.out.println("The value of d = "+d);
c=(Math.pow(m,e))%n;
System.out.println("Encrypted message is: ");
System.out.println(c);
msg=(Math.pow(c,d))%n;
System.out.println("Derypted message is: ");
System.out.println(msg);
}
static int gcd(int a,int b) {
if(a%b == 0)
return b;
else
return gcd(b,a%b);
}
}
*Output:*
Enter the numbered message: 2
Enter two prime numbers: 7 11
the value of totent function = 60
The value of e = 7
The value of d = 43
Encrypted message is: 51.0
Derypted message is: 12.0
Today second program
*DIFFIE-HELLMAN*
*AIM:* Implement the Diffie-Hellman Key Exchange mechanism using HTML and JavaScript. Consider the end user as one of the parties (Alice) and the JavaScript application as other party (bob).
*Description:*
The Diffie-Hellmann key exchange is a secure method for exchanging cryptographic keys. This method allows two parties which have no prior knowledge of each other to establish a shared, secret key, even over an insecure channel.
*Source Code:*
import java.io.*;
import java.util.*;
class DiffieHellman {
public static void main(String args[]) {
Scanner s=new Scanner(System.in);
System.out.println("Enter modulo(p)");
int p=s.nextInt();
System.out.println("Enter primitive root of "+p);
int g=s.nextInt();
System.out.println("Choose 1st secret no(Alice)");
int a=s.nextInt();
System.out.println("Choose 2nd secret no(BOB)");
int b=s.nextInt();
int A = (int)Math.pow(g,a)%p;
int B = (int)Math.pow(g,b)%p;
int S_A = (int)Math.pow(B,a)%p;
int S_B =(int)Math.pow(A,b)%p;
if(S_A==S_B) {
System.out.println("ALice and Bob can communicate with each other!!!");
System.out.println("They share a secret no = "+S_A);
}
else
System.out.println("ALice and Bob cannot communicate with each other!!!");
}
}
*Output:*
Enter modulo(p) : 17
Enter primitive root of : 17 3
Choose 1st secret no(Alice) : 12
Choose 2nd secret no(BOB) : 14
ALice and Bob can communicate with each other!!!
They share a secret no = 16
4. JAVA PROGRAM FOR DES ALGORITHM LOGIC
AIM: Write a Java program to implement the DES algorithm logic
Source Code:
import java.util.*;
class Main {
private static class DES {
// CONSTANTS
// Initial Permutation Table
int[] IP = { 58, 50, 42, 34, 26, 18,
10, 2, 60, 52, 44, 36, 28, 20,
12, 4, 62, 54, 46, 38,
30, 22, 14, 6, 64, 56,
48, 40, 32, 24, 16, 8,
57, 49, 41, 33, 25, 17,
9, 1, 59, 51, 43, 35, 27,
19, 11, 3, 61, 53, 45,
37, 29, 21, 13, 5, 63, 55,
47, 39, 31, 23, 15, 7 };
// Inverse Initial Permutation Table
int[] IP1 = { 40, 8, 48, 16, 56, 24, 64,
32, 39, 7, 47, 15, 55,
23, 63, 31, 38, 6, 46,
14, 54, 22, 62, 30, 37,
5, 45, 13, 53, 21, 61,
29, 36, 4, 44, 12, 52,
20, 60, 28, 35, 3, 43,
11, 51, 19, 59, 27, 34,
2, 42, 10, 50, 18, 58,
26, 33, 1, 41, 9, 49,
17, 57, 25 };
// first key-hePermutation Table
int[] PC1 = { 57, 49, 41, 33, 25,
17, 9, 1, 58, 50, 42, 34, 26,
18, 10, 2, 59, 51, 43, 35, 27,
19, 11, 3, 60, 52, 44, 36, 63,
55, 47, 39, 31, 23, 15, 7, 62,
54, 46, 38, 30, 22, 14, 6, 61,
53, 45, 37, 29, 21, 13, 5, 28,
20, 12, 4 };
// second key-Permutation Table
int[] PC2 = { 14, 17, 11, 24, 1, 5, 3,
28, 15, 6, 21, 10, 23, 19, 12,
4, 26, 8, 16, 7, 27, 20, 13, 2,
41, 52, 31, 37, 47, 55, 30, 40,
51, 45, 33, 48, 44, 49, 39, 56,
34, 53, 46, 42, 50, 36, 29, 32 };
// Expansion D-box Table
int[] EP = { 32, 1, 2, 3, 4, 5, 4,
5, 6, 7, 8, 9, 8, 9, 10,
11, 12, 13, 12, 13, 14, 15,
16, 17, 16, 17, 18, 19, 20,
21, 20, 21, 22, 23, 24, 25,
24, 25, 26, 27, 28, 29, 28,
29, 30, 31, 32, 1 };
// Straight Permutation Table
int[] P = { 16, 7, 20, 21, 29, 12, 28,
17, 1, 15, 23, 26, 5, 18,
31, 10, 2, 8, 24, 14, 32,
27, 3, 9, 19, 13, 30, 6,
22, 11, 4, 25 };
// S-box Table
int[][][] sbox = {
{ { 14, 4, 13, 1, 2, 15, 11, 8, 3, 10, 6, 12, 5, 9, 0, 7 },
{ 0, 15, 7, 4, 14, 2, 13, 1, 10, 6, 12, 11, 9, 5, 3, 8 },
{ 4, 1, 14, 8, 13, 6, 2, 11, 15, 12, 9, 7, 3, 10, 5, 0 },
{ 15, 12, 8, 2, 4, 9, 1, 7, 5, 11, 3, 14, 10, 0, 6, 13 } },
{ { 15, 1, 8, 14, 6, 11, 3, 4, 9, 7, 2, 13, 12, 0, 5, 10 },
{ 3, 13, 4, 7, 15, 2, 8, 14, 12, 0, 1, 10, 6, 9, 11, 5 },
{ 0, 14, 7, 11, 10, 4, 13, 1, 5, 8, 12, 6, 9, 3, 2, 15 },
{ 13, 8, 10, 1, 3, 15, 4, 2, 11, 6, 7, 12, 0, 5, 14, 9 } },
{ { 10, 0, 9, 14, 6, 3, 15, 5, 1, 13, 12, 7, 11, 4, 2, 8 },
{ 13, 7, 0, 9, 3, 4, 6, 10, 2, 8, 5, 14, 12, 11, 15, 1 },
{ 13, 6, 4, 9, 8, 15, 3, 0, 11, 1, 2, 12, 5, 10, 14, 7 },
{ 1, 10, 13, 0, 6, 9, 8, 7, 4, 15, 14, 3, 11, 5, 2, 12 } },
{ { 7, 13, 14, 3, 0, 6, 9, 10, 1, 2, 8, 5, 11, 12, 4, 15 },
{ 13, 8, 11, 5, 6, 15, 0, 3, 4, 7, 2, 12, 1, 10, 14, 9 },
{ 10, 6, 9, 0, 12, 11, 7, 13, 15, 1, 3, 14, 5, 2, 8, 4 },
{ 3, 15, 0, 6, 10, 1, 13, 8, 9, 4, 5, 11, 12, 7, 2, 14 } },
{ { 2, 12, 4, 1, 7, 10, 11, 6, 8, 5, 3, 15, 13, 0, 14, 9 },
{ 14, 11, 2, 12, 4, 7, 13, 1, 5, 0, 15, 10, 3, 9, 8, 6 },
{ 4, 2, 1, 11, 10, 13, 7, 8, 15, 9, 12, 5, 6, 3, 0, 14 },
{ 11, 8, 12, 7, 1, 14, 2, 13, 6, 15, 0, 9, 10, 4, 5, 3 } },
{ { 12, 1, 10, 15, 9, 2, 6, 8, 0, 13, 3, 4, 14, 7, 5, 11 },
{ 10, 15, 4, 2, 7, 12, 9, 5, 6, 1, 13, 14, 0, 11, 3, 8 },
{ 9, 14, 15, 5, 2, 8, 12, 3, 7, 0, 4, 10, 1, 13, 11, 6 },
{ 4, 3, 2, 12, 9, 5, 15, 10, 11, 14, 1, 7, 6, 0, 8, 13 } },
{ { 4, 11, 2, 14, 15, 0, 8, 13, 3, 12, 9, 7, 5, 10, 6, 1 },
{ 13, 0, 11, 7, 4, 9, 1, 10, 14, 3, 5, 12, 2, 15, 8, 6 },
{ 1, 4, 11, 13, 12, 3, 7, 14, 10, 15, 6, 8, 0, 5, 9, 2 },
{ 6, 11, 13, 8, 1, 4, 10, 7, 9, 5, 0, 15, 14, 2, 3, 12 } },
{ { 13, 2, 8, 4, 6, 15, 11, 1, 10, 9, 3, 14, 5, 0, 12, 7 },
{ 1, 15, 13, 8, 10, 3, 7, 4, 12, 5, 6, 11, 0, 14, 9, 2 },
{ 7, 11, 4, 1, 9, 12, 14, 2, 0, 6, 10, 13, 15, 3, 5, 8 },
{ 2, 1, 14, 7, 4, 10, 8, 13, 15, 12, 9, 0, 3, 5, 6, 11 } }
};
int[] shiftBits = { 1, 1, 2, 2, 2, 2, 2, 2,
1, 2, 2, 2, 2, 2, 2, 1 };
// hexadecimal to binary conversion
String hextoBin(String input)
{
int n = input.length() * 4;
input = Long.toBinaryString(
Long.parseUnsignedLong(input, 16));
while (input.length() < n)
input = "0" + input;
return input;
}
// binary to hexadecimal conversion
String binToHex(String input)
{
int n = (int)input.length() / 4;
input = Long.toHexString(
Long.parseUnsignedLong(input, 2));
while (input.length() < n)
input = "0" + input;
return input;
}
// per-mutate input hexadecimal
// according to specified sequence
String permutation(int[] sequence, String input)
{
String output = "";
input = hextoBin(input);
for (int i = 0; i < sequence.length; i++)
output += input.charAt(sequence[i] - 1);
output = binToHex(output);
return output;
}
// xor 2 hexadecimal strings
String xor(String a, String b)
{
// hexadecimal to decimal(base 10)
long t_a = Long.parseUnsignedLong(a, 16);
// hexadecimal to decimal(base 10)
long t_b = Long.parseUnsignedLong(b, 16);
// xor
t_a = t_a ^ t_b;
// decimal to hexadecimal
a = Long.toHexString(t_a);
// prepend 0's to maintain length
while (a.length() < b.length())
a = "0" + a;
return a;
}
// left Circular Shifting bits
String leftCircularShift(String input, int numBits)
{
int n = input.length() * 4;
int perm[] = new int[n];
for (int i = 0; i < n - 1; i++)
perm[i] = (i + 2);
perm[n - 1] = 1;
while (numBits-- > 0)
input = permutation(perm, input);
return input;
}
// preparing 16 keys for 16 rounds
String[] getKeys(String key)
{
String keys[] = new String[16];
// first key permutation
key = permutation(PC1, key);
for (int i = 0; i < 16; i++) {
key = leftCircularShift(
key.substring(0, 7), shiftBits[i])
+ leftCircularShift(key.substring(7, 14),
shiftBits[i]);
// second key permutation
keys[i] = permutation(PC2, key);
}
return keys;
}
// s-box lookup
String sBox(String input)
{
String output = "";
input = hextoBin(input);
for (int i = 0; i < 48; i += 6) {
String temp = input.substring(i, i + 6);
int num = i / 6;
int row = Integer.parseInt(
temp.charAt(0) + "" + temp.charAt(5), 2);
int col = Integer.parseInt(
temp.substring(1, 5), 2);
output += Integer.toHexString(
sbox[num][row][col]);
}
return output;
}
String round(String input, String key, int num)
{
// fk
String left = input.substring(0, 8);
String temp = input.substring(8, 16);
String right = temp;
// Expansion permutation
temp = permutation(EP, temp);
// xor temp and round key
temp = xor(temp, key);
// lookup in s-box table
temp = sBox(temp);
// Straight D-box
temp = permutation(P, temp);
// xor
left = xor(left, temp);
System.out.println("Round "
+ (num + 1) + " "
+ right.toUpperCase()
+ " " + left.toUpperCase() + " "
+ key.toUpperCase());
// swapper
return right + left;
}
String encrypt(String plainText, String key)
{
int i;
// get round keys
String keys[] = getKeys(key);
// initial permutation
plainText = permutation(IP, plainText);
System.out.println(
"After initial permutation: "
+ plainText.toUpperCase());
System.out.println(
"After splitting: L0="
+ plainText.substring(0, 8).toUpperCase()
+ " R0="
+ plainText.substring(8, 16).toUpperCase() + "\n");
// 16 rounds
for (i = 0; i < 16; i++) {
plainText = round(plainText, keys[i], i);
}
// 32-bit swap
plainText = plainText.substring(8, 16)
+ plainText.substring(0, 8);
// final permutation
plainText = permutation(IP1, plainText);
return plainText;
}
String decrypt(String plainText, String key)
{
int i;
// get round keys
String keys[] = getKeys(key);
// initial permutation
plainText = permutation(IP, plainText);
System.out.println(
"After initial permutation: "
+ plainText.toUpperCase());
System.out.println(
"After splitting: L0="
+ plainText.substring(0, 8).toUpperCase()
+ " R0=" + plainText.substring(8, 16).toUpperCase()
+ "\n");
// 16-rounds
for (i = 15; i > -1; i--) {
plainText = round(plainText, keys[i], 15 - i);
}
// 32-bit swap
plainText = plainText.substring(8, 16)
+ plainText.substring(0, 8);
plainText = permutation(IP1, plainText);
return plainText;
}
}
public static void main(String args[])
{
String text = "123456ABCD132536";
String key = "AABB09182736CCDD";
DES cipher = new DES();
System.out.println("Encryption:\n");
text = cipher.encrypt(text, key);
System.out.println(
"\nCipher Text: " + text.toUpperCase() + "\n");
System.out.println("Decryption\n");
text = cipher.decrypt(text, key);
System.out.println(
"\nPlain Text: "
+ text.toUpperCase());
}
}
Output: Encryption
After initial permutation: 14A7D67818CA18AD
After splitting: L0=14A7D678 R0=18CA18AD
Round 1 18CA18AD 5A78E394 194CD072DE8C
Round 2 5A78E394 4A1210F6 4568581ABCCE
Round 3 4A1210F6 B8089591 06EDA4ACF5B5
Round 4 B8089591 236779C2 DA2D032B6EE3
Round 5 236779C2 A15A4B87 69A629FEC913
Round 6 A15A4B87 2E8F9C65 C1948E87475E
Round 7 2E8F9C65 A9FC20A3 708AD2DDB3C0
Round 8 A9FC20A3 308BEE97 34F822F0C66D
Round 9 308BEE97 10AF9D37 84BB4473DCCC
Round 10 10AF9D37 6CA6CB20 02765708B5BF
Round 11 6CA6CB20 FF3C485F 6D5560AF7CA5
Round 12 FF3C485F 22A5963B C2C1E96A4BF3
Round 13 22A5963B 387CCDAA 99C31397C91F
Round 14 387CCDAA BD2DD2AB 251B8BC717D0
Round 15 BD2DD2AB CF26B472 3330C5D9A36D
Round 16 19BA9212 CF26B472 181C5D75C66D
Cipher Text: C0B7A8D05F3A829C
Output: Decryption
After initial permutation: 19BA9212CF26B472
After splitting: L0=19BA9212 R0=CF26B472
Round 1 CF26B472 BD2DD2AB 181C5D75C66D
Round 2 BD2DD2AB 387CCDAA 3330C5D9A36D
Round 3 387CCDAA 22A5963B 251B8BC717D0
Round 4 22A5963B FF3C485F 99C31397C91F
Round 5 FF3C485F 6CA6CB20 C2C1E96A4BF3
Round 6 6CA6CB20 10AF9D37 6D5560AF7CA5
Round 7 10AF9D37 308BEE97 02765708B5BF
Round 8 308BEE97 A9FC20A3 84BB4473DCCC
Round 9 A9FC20A3 2E8F9C65 34F822F0C66D
Round 10 2E8F9C65 A15A4B87 708AD2DDB3C0
Round 11 A15A4B87 236779C2 C1948E87475E
Round 12 236779C2 B8089591 69A629FEC913
Round 13 B8089591 4A1210F6 DA2D032B6EE3
Round 14 4A1210F6 5A78E394 06EDA4ACF5B5
Round 15 5A78E394 18CA18AD 4568581ABCCE
Round 16 14A7D678 18CA18AD 194CD072DE8C
Plain Text: 123456ABCD132536
