🔐 Secure vs Non-Secure RNG — What's the Difference?

Random number generators come in two broad categories: non-secure (general-purpose) and secure (cryptographic). Understanding the difference helps you choose the right tool for the job — casual games vs. security-sensitive tasks like cryptography or lotteries.

Non-Secure RNGs (e.g., Math.random)

• Use case: UI effects, games, simple simulations, and casual utilities.
• Speed: Fast and lightweight.
• Predictability: Potentially predictable if attacker can observe internal state — not safe for security needs.

Secure (Cryptographic) RNGs (e.g., crypto.getRandomValues)

• Use case: Cryptography, secure token generation, lotteries, and anything that requires unpredictability.
• Strength: Designed to be unpredictable even if an attacker observes many outputs.
• Performance: Slightly slower but still fast for most real-world uses.

When to Use Each

• Use non-secure RNG for games, UI, and non-critical randomness where predictability is not a concern.
• Use secure RNG when you need strong unpredictability: session tokens, password resets, cryptographic keys, or legal draws.

Examples

• Non-secure: Math.random() in JavaScript for casual game rolls.
• Secure: window.crypto.getRandomValues() or server-side cryptographic RNGs for secure tokens.