Function SeedHardwareSlow

src/random.cpp:199–221

Add 256 bits of entropy gathered from hardware to hasher. Do nothing if not supported. */

/** Add 256 bits of entropy gathered from hardware to hasher. Do nothing if not supported. */
static void SeedHardwareSlow(CSHA512& hasher) noexcept {
#if defined(__x86_64__) || defined(__amd64__) || defined(__i386__)
    // When we want 256 bits of entropy, prefer RdSeed over RdRand, as it's
    // guaranteed to produce independent randomness on every call.
    if (g_rdseed_supported) {
        for (int i = 0; i < 4; ++i) {
            uint64_t out = GetRdSeed();
            hasher.Write((const unsigned char*)&out, sizeof(out));
        }
        return;
    }
    // When falling back to RdRand, XOR the result of 1024 results.
    // This guarantees a reseeding occurs between each.
    if (g_rdrand_supported) {
        for (int i = 0; i < 4; ++i) {
            uint64_t out = 0;
            for (int j = 0; j < 1024; ++j) out ^= GetRdRand();
            hasher.Write((const unsigned char*)&out, sizeof(out));
        }
        return;
    }
#endif
}

/** Use repeated SHA512 to strengthen the randomness in seed32, and feed into hasher. */
static void Strengthen(const unsigned char (&seed)[32], int microseconds, CSHA512& hasher) noexcept