Thank you Steven. While I do not have boost installed on this computer, the code below compiles and runs as I would expect. Upon each execution, the value of seed changes. I expect boost::mt19937 rng(seed); will work. And now I have a very good random seed thanks to your advice.

Your friend,

Ed

#include <iostream>
#include <windows.h>
#include <wincrypt.h>

int main()
{

    HCRYPTPROV hProvider = 0;
    BYTE randomBytes[8];
    CryptAcquireContext(&hProvider, 0, 0, PROV_RSA_FULL, CRYPT_VERIFYCONTEXT);
    CryptGenRandom(hProvider, sizeof(randomBytes), randomBytes);
    CryptReleaseContext(hProvider, 0);

    uint64_t seed;
    memcpy(&seed, &randomBytes[0], sizeof(seed));

    std::cout << seed << std::endl;

    return 0;

}


On Wed, Feb 10, 2010 at 11:58 PM, Steven Watanabe <watanabesj@gmail.com> wrote:
AMDG


e m wrote:
I have a C++ program that uses /dev/urandom on Unix systems to seed boost::mt19937. I'm porting the program to Windows. I can get good, random seed data on Windows similar to random seed data produced from /dev/urandom on Unix systems like so:

HCRYPTPROV hProvider = 0;
BYTE randomBytes[8];
CryptAcquireContext(&hProvider, 0, 0, PROV_RSA_FULL, CRYPT_VERIFYCONTEXT);
CryptGenRandom(hProvider, sizeof(randomBytes), randomBytes);   CryptReleaseContext(hProvider, 0);

However, I'm running into trouble attempting to pass these randomBytes to boost::mt19937. On Unix I do something similar to this:

uint64_t GetSeed()
{
uint64_t seed;
std::ifstream urandom;
urandom.open("/dev/urandom");
urandom.read(reinterpret_cast<char*> (&seed), sizeof(seed));
urandom.close();
return seed;
}

boost::mt19937 rng(GetSeed());

That works OK on Unix I think. Could anyone suggest how to get the random data from the Windows CryptoAPI passed to boost::mt19937 as seed data? I don't normally program Windows systems, so this has been a bit of a challenge for me.

Try

uint64_t seed;
memcpy(&seed, &randomBytes[0], sizeof(seed));

In Christ,
Steven Watanabe

_______________________________________________
Boost-users mailing list
Boost-users@lists.boost.org
http://lists.boost.org/mailman/listinfo.cgi/boost-users