How to Implement Scrypt Using Bouncy Castle in Java?

Question

What is the process to implement Scrypt using Bouncy Castle in a Java application?

// Example Java code for Scrypt using Bouncy Castle
import org.bouncycastle.crypto.generators.SCrypt;
import org.bouncycastle.util.encoders.Hex;

public class ScryptExample {
    public static void main(String[] args) {
        String password = "password";
        byte[] salt = Hex.decode("3d3e4e2f521776a3");
        int N = 16384; // CPU/memory cost parameter
        int r = 8;     // block size parameter
        int p = 1;     // parallelization parameter
        int dkLen = 32; // desired key length

        byte[] derivedKey = SCrypt.generate(password.getBytes(), salt, N, r, p, dkLen);

        System.out.println(Hex.toHexString(derivedKey));
    }
}

Answer

The Scrypt algorithm is a password-based key derivation function designed for securely hashing passwords and is widely used in cryptographic applications. In Java, the Bouncy Castle library provides a robust implementation of the Scrypt algorithm, making it easy to integrate secure hashing into your applications.

// Complete example of Scrypt implementation with explanation
import org.bouncycastle.crypto.generators.SCrypt;
import org.bouncycastle.util.encoders.Hex;

public class ScryptExample {
    public static void main(String[] args) {
        String password = "password"; // User's password
        byte[] salt = Hex.decode("3d3e4e2f521776a3"); // Fixed salt for example, use random in production
        int N = 16384; // Cost factor
        int r = 8;     // Block size
        int p = 1;     // Parallelization factor
        int dkLen = 32; // Desired key length

        // Generate derived key
        byte[] derivedKey = SCrypt.generate(password.getBytes(), salt, N, r, p, dkLen);

        // Outputting the derived key in hex format
        System.out.println(Hex.toHexString(derivedKey));
    }
}

Causes

Using inadequate parameters for N, r, and p can compromise security.
Improperly handling salts can lead to vulnerabilities.
Not using secure random generation for salts.

Solutions

Ensure to use recommended values for N (at least 16384), r (8), and p (1) for adequate security.
Generate salts using a secure random number generator before hashing.
Keep the Bouncy Castle library updated to leverage the latest enhancements.

Common Mistakes

Mistake: Using a fixed salt value for all password hashes.

Solution: Always generate a new, random salt for each password hash.

Mistake: Choosing very low parameters for N, r, p, reducing security.

Solution: Follow best practices for parameter choices to ensure adequate security.

Helpers

Bouncy Castle Scrypt implementation
Java Scrypt example
Bouncy Castle password hashing
Secure password storage Java
Key derivation function Java