CNS Lab Exercise-7

EXERCISE – 7

Using Java Cryptography, encrypt the text “Hello world” using Blowfish. Create your own key using Java keytool.

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Step 1: Generate Blowfish Secret Key

Open Command Prompt and move to your working directory (Example: Desktop):

cd Desktop

Now execute the following command:

keytool -genseckey -alias blowfishKey -keyalg Blowfish -keysize 128 -storetype JCEKS -keystore blowfish.jceks -storepass 123456 -keypass 123456

Explanation:

• -genseckey
  → Generates a secret key
• -alias blowfishKey
  → Name of the key
• -keyalg Blowfish
  → Algorithm name
• -keysize 128
  → 128-bit key
• -storetype JCEKS
  → Required to store secret keys
• -keystore blowfish.jceks
  → File name of keystore
• -storepass 123456
  → Keystore password
• -keypass 123456
  → Key password

After running this command, a file named blowfish.jceks will be created in your folder. This file stores the secret key securely.

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Step 2: Create Java Program

Create a new Java file named:

BlowfishEncrypt.java

Paste the following code inside the file:

import javax.crypto.Cipher;
import javax.crypto.SecretKey;
import java.io.FileInputStream;
import java.security.KeyStore;
import java.util.Base64;

public class BlowfishEncrypt {

    public static void main(String[] args) {

        try {

            String text = "Hello world";

            // Load the keystore
            KeyStore ks = KeyStore.getInstance("JCEKS");
            FileInputStream fis = new FileInputStream("blowfish.jceks");
            ks.load(fis, "123456".toCharArray());

            // Retrieve the secret key
            SecretKey key = (SecretKey) ks.getKey("blowfishKey", "123456".toCharArray());

            // Create cipher object
            Cipher cipher = Cipher.getInstance("Blowfish");

            // Initialize cipher for encryption
            cipher.init(Cipher.ENCRYPT_MODE, key);

            // Encrypt the text
            byte[] encrypted = cipher.doFinal(text.getBytes("UTF-8"));

            // Convert encrypted bytes to Base64 string
            String encryptedText = Base64.getEncoder().encodeToString(encrypted);

            System.out.println("Original Text  : " + text);
            System.out.println("Encrypted Text : " + encryptedText);

        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

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Step 3: Compile the Program

javac BlowfishEncrypt.java

If no errors appear, the program compiled successfully.

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Step 4: Run the Program

java BlowfishEncrypt

Sample Output:

Original Text  : Hello world
Encrypted Text : qK8Jz5hM3V4kLw==

Note: The encrypted text will be different on each system depending on the generated key.

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Result

• Blowfish secret key generated successfully
• Text encrypted using Blowfish algorithm
• Encrypted output displayed in Base64 format