Function Random_SanityCheck

src/random.cpp:638–682

}

bool Random_SanityCheck()
{
    uint64_t start = GetPerformanceCounter();

    /* This does not measure the quality of randomness, but it does test that
     * GetOSRand() overwrites all 32 bytes of the output given a maximum
     * number of tries.
     */
    static const ssize_t MAX_TRIES = 1024;
    uint8_t data[NUM_OS_RANDOM_BYTES];
    bool overwritten[NUM_OS_RANDOM_BYTES] = {}; /* Tracks which bytes have been overwritten at least once */
    int num_overwritten;
    int tries = 0;
    /* Loop until all bytes have been overwritten at least once, or max number tries reached */
    do {
        memset(data, 0, NUM_OS_RANDOM_BYTES);
        GetOSRand(data);
        for (int x=0; x < NUM_OS_RANDOM_BYTES; ++x) {
            overwritten[x] |= (data[x] != 0);
        }

        num_overwritten = 0;
        for (int x=0; x < NUM_OS_RANDOM_BYTES; ++x) {
            if (overwritten[x]) {
                num_overwritten += 1;
            }
        }

        tries += 1;
    } while (num_overwritten < NUM_OS_RANDOM_BYTES && tries < MAX_TRIES);
    if (num_overwritten != NUM_OS_RANDOM_BYTES) return false; /* If this failed, bailed out after too many tries */

    // Check that GetPerformanceCounter increases at least during a GetOSRand() call + 1ms sleep.
    std::this_thread::sleep_for(std::chrono::milliseconds(1));
    uint64_t stop = GetPerformanceCounter();
    if (stop == start) return false;

    // We called GetPerformanceCounter. Use it as entropy.
    CSHA512 to_add;
    to_add.Write((const unsigned char*)&start, sizeof(start));
    to_add.Write((const unsigned char*)&stop, sizeof(stop));
    GetRNGState().MixExtract(nullptr, 0, std::move(to_add), false);

    return true;
}

FastRandomContext::FastRandomContext(bool fDeterministic) noexcept : requires_seed(!fDeterministic), bytebuf_size(0), bitbuf_size(0)
{