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

Subject: Re: [Boost-users] Seeding boost::mt19937 with bytes from CryptoGenRandom
From: Steven Watanabe (watanabesj_at_[hidden])
Date: 2010-02-10 23:58:05

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