Re: [Boost-users] Seeding boost::mt19937 with bytes from CryptoGenRandom

11 Feb 2010

      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 (&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