compare-RtlGenRando-BCryptGenRandom

test.c

// performance comparison between RtlGenRandom and BCryptGenRandom
// with BCRYPT_USE_SYSTEM_PREFERRED_RNG.
//
// gcc -O3 -std=c99 -Wall test.c -lbcrypt && a
#include <windows.h>
#include <stdio.h>
#include <bcrypt.h>

BOOLEAN(APIENTRY *RtlGenRandom)
	(void *, ULONG);
HANDLE BCryptoProvider = NULL;

DOUBLE GetTime()
{
	LARGE_INTEGER t, f;
	QueryPerformanceCounter(&t);
	QueryPerformanceFrequency(&f);
	return (DOUBLE) t.QuadPart / (DOUBLE) f.QuadPart;
}

int PrepareRtlGenRandom()
{
	LoadLibrary("advapi32.dll");
	HMODULE advapi = GetModuleHandle("advapi32.dll");

	if (!advapi) {
		puts("advapi32 load error");
		return 1;
	}

	RtlGenRandom = (BOOLEAN(APIENTRY*)(void *, ULONG)) GetProcAddress(advapi, "SystemFunction036");
	if (!RtlGenRandom) {
		puts("RtlGenRandom proc error");
		return 1;
	}

	return 0;
}

int RunSingleTest(PBYTE Buffer, DWORD BufferSize, DWORD TestIterations)
{
	DOUBLE StartTime;
	printf("\nBufferSize: %lu\n", BufferSize);

	// test BCryptGenRandom
	StartTime = GetTime();
	for (int i = 0; i < TestIterations; i++) {
		if (BCryptGenRandom(
			BCryptoProvider,
			Buffer,
			BufferSize,
			0)) { // BCRYPT_USE_SYSTEM_PREFERRED_RNG
			puts("BCryptGenRandom failed");
			return 1;
		}
	}

	printf("BCryptGenRandom: %fs\n", GetTime() - StartTime);

	// -------------------------------------------------------------------------

	// test RtlGenRandom
	StartTime = GetTime();
	for (int i = 0; i < TestIterations; i++) {
		if (!RtlGenRandom(Buffer, BufferSize)) {
			puts("RtlGenRandom failed");
			return 1;
		}
	}

	printf("RtlGenRandom: %fs\n", GetTime() - StartTime);
	return 0;
}

int main(void)
{
	const DWORD TestIterations = 100000;
	BYTE Buffer[16384];
	DWORD MaxBufferSize = sizeof(Buffer);
	memset(Buffer, 0, MaxBufferSize);

	// -------------------------------------------------------------------------

	// verify the timer
	DOUBLE StartTime = GetTime();
	Sleep(1000);
	printf("Veryfing timer precision; result should be close to 1.0, got %f\n", GetTime() - StartTime);

	// -------------------------------------------------------------------------

	// prepare RtlGenRandom
	if (PrepareRtlGenRandom()) {
		return 1;
	}
	
	// -------------------------------------------------------------------------
	
	// prepare BCryptGenRandom
	
	if (BCryptOpenAlgorithmProvider(
		&BCryptoProvider,
		BCRYPT_RNG_ALGORITHM,
    	NULL,
		0)) {
		puts("BCryptOpenAlgorithmProvider failed");
		return 1;
	}

	// -------------------------------------------------------------------------
	// test various buffer sizes

	printf("TestIterations: %lu\n", TestIterations);
	for (DWORD BufferSize = 1; BufferSize <= MaxBufferSize; BufferSize *= 2) {
		if (RunSingleTest(Buffer, BufferSize, TestIterations)) {
			return 1;
		}
	}
}

zresults-win7-64bit-intel-i3.txt

Veryfing timer precision; result should be close to 1.0, got 0.999352
TestIterations: 100000

BufferSize: 1
BCryptGenRandom: 0.097258s
RtlGenRandom: 0.100814s

BufferSize: 2
BCryptGenRandom: 0.095720s
RtlGenRandom: 0.100624s

BufferSize: 4
BCryptGenRandom: 0.095737s
RtlGenRandom: 0.100634s

BufferSize: 8
BCryptGenRandom: 0.095641s
RtlGenRandom: 0.100441s

BufferSize: 16
BCryptGenRandom: 0.095755s
RtlGenRandom: 0.100434s

BufferSize: 32
BCryptGenRandom: 0.108264s
RtlGenRandom: 0.113315s

BufferSize: 64
BCryptGenRandom: 0.133766s
RtlGenRandom: 0.139911s

BufferSize: 128
BCryptGenRandom: 0.183334s
RtlGenRandom: 0.190524s

BufferSize: 256
BCryptGenRandom: 0.284192s
RtlGenRandom: 0.292344s

BufferSize: 512
BCryptGenRandom: 0.482821s
RtlGenRandom: 0.495196s

BufferSize: 1024
BCryptGenRandom: 0.879791s
RtlGenRandom: 0.902300s

BufferSize: 2048
BCryptGenRandom: 1.673630s
RtlGenRandom: 1.714524s

BufferSize: 4096
BCryptGenRandom: 3.260548s
RtlGenRandom: 3.340992s

BufferSize: 8192
BCryptGenRandom: 6.437690s
RtlGenRandom: 6.626667s

BufferSize: 16384
BCryptGenRandom: 12.841288s
RtlGenRandom: 13.214990s