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CryptoRandom GitHub Actions NuGet

by Stan Drapkin

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
  • Produces the same sequence of seeded CryptoRandom values on all .NET versions (unlike Random)
  • Wraps RandomNumberGenerator for unseeded (with additional smarts)
  • Provides backtracking resistance: internal state cannot be used to recover the output
  • Achieves ~1.3cpb (cycles-per-byte) performance, similar to AES-NI
  • Scales per-CPU/Core
  • Example: CryptoRandom.NextGuid() vs. Guid.NewGuid() [BenchmarkDotNet]:
    • 4~5x faster on Windows-x64
    • 5~30x faster on Linux-x64
    • 4~5x faster on Linux-ARM64 (AWS Graviton-2)
  • Built for .NET 5.0+ and 6.0+
  • Extensive test coverage & correctness validation (110+ tests)
    • CI runs on Linux-latest & Windows-latest for .NET 5/6/7/8/9

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()
    • 5x (500%) faster than Guid.NewGuid() on Windows
    • 15x (1500%) faster than Guid.NewGuid() on Linux
    • 128 random bits, instead of 122
  • 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
    • ~15% faster than Guid.NewGuid()
  • 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 SecurityDriven.Core;
using System;
using System.Diagnostics;
using System.Runtime.InteropServices;
using System.Threading.Tasks;

Console.WriteLine($"[{RuntimeInformation.FrameworkDescription}]");
Stopwatch sw1 = new(), sw2 = new();
const long ITER = 100_000_000, REPS = 5;

for (int i = 0; i++ < REPS;)
{
    sw1.Restart();
    Parallel.For(0, ITER, static i => CryptoRandom.Shared.NextGuid());
    sw1.Stop();
    Console.WriteLine($"{sw1.Elapsed} cryptoRandom.NextGuid()");

    sw2.Restart();
    Parallel.For(0, ITER, static i => Guid.NewGuid());
    sw2.Stop();

    var ratio = sw2.Elapsed / sw1.Elapsed;
    Console.WriteLine($"{sw2.Elapsed} Guid.NewGuid() [{ratio:N2}x slower]");
}
Output:
[.NET 6.0.0-rc.1.21451.13]
00:00:00.5486513 cryptoRandom.NextGuid()
00:00:02.0587652 Guid.NewGuid() [3.75x slower]
00:00:00.4117180 cryptoRandom.NextGuid()
00:00:02.0485556 Guid.NewGuid() [4.98x slower]
00:00:00.4103378 cryptoRandom.NextGuid()
00:00:02.0534771 Guid.NewGuid() [5.00x slower]
00:00:00.4100701 cryptoRandom.NextGuid()
00:00:02.0823213 Guid.NewGuid() [5.08x slower]
00:00:00.4017192 cryptoRandom.NextGuid()
00:00:02.0488105 Guid.NewGuid() [5.10x slower]

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
// Fails on .NET 6 if you use seeded "new Random(seed)"
  • 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

Throughput (single-threaded) .NET 6:

BenchmarkDotNet=v0.13.1, OS=Windows 10.0.19042.1165 (20H2/October2020Update)
Intel Core i7-10510U CPU 1.80GHz, 1 CPU, 8 logical and 4 physical cores
.NET SDK=6.0.100-preview.7.21379.14
  [Host] : .NET 6.0.0 (6.0.21.37719), X64 RyuJIT
Method BYTES Mean Error StdDev Ratio RatioSD Throughput
SystemRandom 32 7.483 μs 0.2714 μs 0.0149 μs 0.21 0.00 4,176 MB/s
SystemSharedRandom 32 13.197 μs 3.3861 μs 0.1856 μs 0.38 0.00 2,368 MB/s
SeededSystemRandom 32 261.568 μs 12.8670 μs 0.7053 μs 7.46 0.04 119 MB/s
CryptoRandom 32 35.083 μs 1.6305 μs 0.0894 μs 1.00 0.00 891 MB/s
SeededCryptoRandom 32 27.551 μs 0.9383 μs 0.0514 μs 0.79 0.00 1,134 MB/s
RNG_Fill 32 106.507 μs 14.8172 μs 0.8122 μs 3.04 0.02 293 MB/s
SystemRandom 1024 132.600 μs 4.5819 μs 0.2511 μs 0.35 0.00 7,541 MB/s
SystemSharedRandom 1024 139.345 μs 28.1093 μs 1.5408 μs 0.37 0.00 7,176 MB/s
SeededSystemRandom 1024 8,260.379 μs 265.3543 μs 14.5450 μs 21.79 0.01 121 MB/s
CryptoRandom 1024 379.137 μs 8.8802 μs 0.4868 μs 1.00 0.00 2,638 MB/s
SeededCryptoRandom 1024 320.513 μs 21.3931 μs 1.1726 μs 0.85 0.00 3,120 MB/s
RNG_Fill 1024 447.914 μs 15.4506 μs 0.8469 μs 1.18 0.00 2,233 MB/s

Throughput (single-threaded) .NET 5:

BenchmarkDotNet=v0.13.1, OS=Windows 10.0.19042.1165 (20H2/October2020Update)
Intel Core i7-10510U CPU 1.80GHz, 1 CPU, 8 logical and 4 physical cores
.NET SDK=6.0.100-preview.7.21379.14
  [Host] : .NET 5.0.9 (5.0.921.35908), X64 RyuJIT
Method BYTES Mean Error StdDev Ratio RatioSD Throughput
SystemRandom 32 252.89 μs 53.609 μs 2.938 μs 7.30 0.09 124 MB/s
SeededSystemRandom 32 259.82 μs 3.966 μs 0.217 μs 7.50 0.03 120 MB/s
CryptoRandom 32 34.66 μs 2.193 μs 0.120 μs 1.00 0.00 902 MB/s
SeededCryptoRandom 32 26.71 μs 3.703 μs 0.203 μs 0.77 0.01 1,170 MB/s
RNG_Fill 32 105.98 μs 9.724 μs 0.533 μs 3.06 0.02 295 MB/s
SystemRandom 1024 8,403.73 μs 510.750 μs 27.996 μs 22.35 0.06 119 MB/s
SeededSystemRandom 1024 8,262.47 μs 721.788 μs 39.564 μs 21.98 0.13 121 MB/s
CryptoRandom 1024 375.98 μs 8.603 μs 0.472 μs 1.00 0.00 2,660 MB/s
SeededCryptoRandom 1024 318.11 μs 219.420 μs 12.027 μs 0.85 0.03 3,144 MB/s
RNG_Fill 1024 450.76 μs 32.919 μs 1.804 μs 1.20 0.00 2,218 MB/s