CryptoRandom

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 5/6/7/8/9/10

---

CryptoRandom API:

All APIs of System.Random (link)
CryptoRandom.Shared static shared instance for convenience (thread-safe of course)
Seeded constructors:
CryptoRandom(ReadOnlySpan 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(ref T @struct) where T : unmanaged
T Next() where T : unmanaged

---

Utils API (`SecurityDriven.Core.Utils`):

static Span AsSpan(ref T @struct) where T : unmanaged
Casts unmanaged struct T as equivalent Span
static ref T AsStruct(Span span) where T : unmanaged
Casts Span as equivalent unmanaged struct T
int StructSizer.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 |

--- Tranlated By Open Ai Tx | Last indexed: 2026-02-09 ---

SecurityDriven.Core