to avoid blocking on Windows. On Windows OpenSSLRAND_bytes (underlying implementation is RAND_poll incrypto/rand/rand_win.c) may be blocked at NetStatisticsGet. wiki.openssl.org/index.php/Random_Numbers#Windows_IssuesInstead of this, use Random.raw_seed directory (whose implementationCryptGenRandom is one of the source of entropy of RAND_poll on Windows). wiki.openssl.org/index.php/Random_NumbersNote: CryptGenRandom function is PRNG and doesn't check its entropy, soit won't block. [Bug #12139] msdn.microsoft.com/ja-jp/library/windows/desktop/aa379942.aspxtools.ietf.org/html/rfc4086#section-7.1.3eprint.iacr.org/2007/419.pdfwww.cs.huji.ac.il/dolev/pubs/thesis/msc-thesis-leo.pdf