


How Can I Reliably Seed mt19937 in C for High-Quality Random Number Generation?
Nov 29, 2024 pm 01:36 PMAddressing PRNG Seeding Issues in C
Despite the widespread use of
Avoid Sole Reliance on std::random_device and time(NULL)
Using std::random_device or time(NULL) alone is insufficient for seeding mt19937 due to low entropy and non-uniform distribution.
Solution: Using a CSPRNG Wrapper
A minimal solution is to use a wrapper around a CSPRNG, such as sysrandom defined below. This wrapper provides access to cryptographic-grade random bytes:
size_t sysrandom(void* dst, size_t dstlen);
Platform-Specific Implementations
For Windows, we can utilize CryptGenRandom:
size_t sysrandom(void* dst, size_t dstlen) { HCRYPTPROV ctx; ... // Acquire and release cryptographic context CryptGenRandom(ctx, dstlen, dst); return dstlen; }
On Unix-like systems, we can employ /dev/urandom:
size_t sysrandom(void* dst, size_t dstlen) { std::ifstream stream("/dev/urandom", std::ios_base::binary | std::ios_base::in); stream.read(dst, dstlen); return dstlen; }
Seeding mt19937
Using the sysrandom wrapper, we can seed mt19937 with sufficient bits:
std::uint_least32_t seed; sysrandom(&seed, sizeof(seed)); std::mt19937 gen(seed);
Comparison with Boost
This approach parallels boost::random_device, which utilizes secure CSPRNGs on various platforms.
Additional Considerations
On Linux, getrandom provides a more secure alternative to /dev/urandom. OpenBSD lacks /dev/urandom; instead, use getentropy.
Conclusion
This article provides a comprehensive guide to effectively seeding the mt19937 PRNG, ensuring high-quality random number generation in C
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