MasterMann / SecurityDriven.Core

Modern, fast, safe, cryptographically strong .NET replacement for Random and RandomNumberGenerator.

SecurityDriven.Core

What's wrong with Random and RandomNumberGenerator?

• Random is slow and not thread-safe (fails miserably and silently on concurrent access)
• Random is incorrectly implemented:

Random r = new Random(); // new CryptoRandom();
const int mod = 2;
int[] hist = new int[mod];
for (int i = 0; i < 10000000; i++)
{
	int num = r.Next(0x55555555);
	int num2 = num % 2;
	++hist[num2];
}
for (int i = 0; i < mod; i++)
	Console.WriteLine($"{i}: {hist[i]}");
// Run this on .NET 5 or below. Surprised? Now change to CryptoRandom

• Random/.NET 6 unseeded is fast (new algorithm), with a safe .Shared property, but instances are not thread-safe
• Random/.NET 6 seeded falls back to legacy slow non-thread-safe .NET algorithm
• Neither Random implementation aims for cryptographically-strong results
• RandomNumberGenerator can be much faster with intelligent wrapping and more useful Random API

CryptoRandom : Random

• .NET Random done right
• [Fast], [Thread-safe], [Cryptographically strong]: choose 3
• Subclasses and replaces System.Random
• Also replaces System.Security.Cryptography.RandomNumberGenerator (link)
• CryptoRandom is (unlike System.Random):
  • Fast (much faster than Random or RandomNumberGenerator)
  • Thread-safe (all APIs)
  • Cryptographically strong (seeded or unseeded)
• Implements Fast-Key-Erasure RNG for seeded CryptoRandom
• Wraps RandomNumberGenerator for unseeded (with additional smarts)
• Achieves ~1.3cpb (cycles-per-byte) performance, similar to AES-NI
• Scales per-CPU/Core
• Example: CryptoRandom.NextGuid() vs. Guid.NewGuid() [BenchmarkDotNet]:
  • 2~4x faster on Windows-x64
  • 5~30x faster on Linux-x64
  • 3~4x faster on Linux-ARM64 (AWS Graviton-2)
• Built for .NET 5.0+ and 6.0+
• Extensive test coverage & correctness validation

---

CryptoRandom API:

• All APIs of System.Random (link)
• CryptoRandom.Shared static shared instance for convenience (thread-safe of course)
• Seeded constructors:
  • CryptoRandom(ReadOnlySpan<byte> seedKey)
  • CryptoRandom(int Seed) (just like seeded Random ctor)
• byte[] NextBytes(int count)
• Guid NextGuid()
• Guid SqlServerGuid()
  • Returns new Guid well-suited to be used as a SQL-Server clustered key
  • Guid structure is [8 random bytes][8 bytes of SQL-Server-ordered DateTime.UtcNow]
  • Each Guid should be sequential within 100-nanoseconds UtcNow precision limits
  • 64-bit entropy for reasonable unguessability and protection against online brute-force attacks
• long NextInt64()
• long NextInt64(long maxValue)
• long NextInt64(long minValue, long maxValue)
• Random struct 's (make sure you know what you're doing):
  • void Next<T>(ref T @struct) where T : unmanaged
  • T Next<T>() where T : unmanaged

---

Utils API (SecurityDriven.Core.Utils):

• static Span<byte> AsSpan<T>(ref T @struct) where T : unmanaged
  • Casts unmanaged struct T as equivalent Span<byte>
• static ref T AsStruct<T>(Span<byte> span) where T : unmanaged
  • Casts Span<byte> as equivalent unmanaged struct T
• int StructSizer<T>.Size
  • Returns byte-size of struct T

---

Quick benchmark:

// using System.Threading.Tasks;
// using SecurityDriven.Core;

var sw = new Stopwatch();
const long ITER = 100_000_000, REPS = 5;

for (int i = 0; i < REPS; ++i)
{
	sw.Restart();
	Parallel.For(0, ITER, static i => CryptoRandom.Shared.NextGuid());
	Console.WriteLine($"{sw.Elapsed} cryptoRandom.NextGuid()");
}
Console.WriteLine(new string('=', 40));
for (int i = 0; i < REPS; ++i)
{
	sw.Restart();
	Parallel.For(0, ITER, i => Guid.NewGuid());
	Console.WriteLine($"{sw.Elapsed} Guid.NewGuid()");
}