Re: xoshiro** edge case (all zeros)

Hi On 8/4/22 10:09, Anton Smirnov wrote:

xoshiro** has a known edge case: all-zero seed

Indeed, good catch. I had that in mind, but forgot about it.

<?php $engine = new \Random\Engine\Xoshiro256StarStar(str_repeat("\0", 32)); while (true) {

     echo hex2bin($engine->generate()), PHP_EOL; // 0000000000000000

} It should be documented and/or handled It's only for a string seed, int seed is not affected

I've created a PR here: https://github.com/php/php-src/pull/9250 I've opted to throw a ValueError in that case, as that's the only safe option that does not introduce a bias. The 32xNUL seed basically should only happen for manually written testing input and not happen otherwise. An actual random seed will result in 32 NUL bytes with just a 2**-256 chance and when relying on the implicit CSPRNG seeding (null as seed parameter) my PR will just retry to catch even that edge case. Best regards Tim Düsterhus