? Random vs SecureRandom in Java

? Quick Overview

In Java, Random and SecureRandom are used to generate random numbers. While both produce random values, they serve very different purposes in real-world applications.

? Interactive Simulation

Click "Generate" to see how they differ in security context.

java.util.Random

0000

Predictable Seed

java.security.SecureRandom

0000

Cryptographically Strong

? Key Concepts

Random → Fast, predictable, suitable for general-purpose tasks
SecureRandom → Cryptographically strong, unpredictable, secure
Security-sensitive applications must never use Random

? Syntax / Theory

java.util.Random uses a linear congruential algorithm
java.security.SecureRandom uses OS-level entropy sources
SecureRandom is slower but far more secure

? Code Example — Random

? View Code Example

// Generating random numbers using java.util.Random
import java.util.Random;

public class RandomDemo {
public static void main(String[] args) {
Random random = new Random();
int number = random.nextInt(100);
System.out.println(number);
}
}

? Code Example — SecureRandom

? View Code Example

// Generating secure random numbers using SecureRandom
import java.security.SecureRandom;

public class SecureRandomDemo {
public static void main(String[] args) {
SecureRandom secureRandom = new SecureRandom();
int number = secureRandom.nextInt(100);
System.out.println(number);
}
}

? Live Output / Explanation

Output

Each program prints a random number between 0 and 99. The difference is internal — SecureRandom ensures unpredictability suitable for security.

? Tips & Best Practices

Use Random for games, simulations, and testing
Use SecureRandom for passwords, tokens, and encryption keys
Never use Random in authentication systems

? Try It Yourself

Generate a random OTP using SecureRandom
Compare execution speed of Random vs SecureRandom
Create a password generator using SecureRandom