Random Number Generator

About This Generator

This tool provides two types of random number generators for testing purposes:

Good RNG (Cryptographically Secure)

Uses the browser's crypto.getRandomValues() which provides cryptographically secure random numbers. This implementation:

• High entropy: Uses the operating system's secure random source
• Unpredictable: Cannot be reproduced or predicted
• Suitable for security: Safe for cryptographic applications
• Should pass all tests: Designed to pass rigorous statistical tests

Poor RNG (Linear Congruential Generator)

Implements a simple Linear Congruential Generator (LCG) using parameters similar to old C library implementations (a = 1103515245, c = 12345, m = 2^31). This is the same type of RNG used in PHP's old rand() function and has well-documented statistical flaws.

Known Weaknesses:

• Sequential correlation: Consecutive values show strong linear relationships
• Low-bit quality: Lower bits have shorter periods and more correlation
• Predictable patterns: Fails many statistical tests including spectral test
• Not cryptographically secure: State can be recovered from output

Why Use Both?

Compare results between good and poor RNG to understand how statistical tests detect quality issues. The poor RNG represents a realistic "almost good" implementation - the kind you might encounter from a buggy implementation or simplified version.