OSes All Apple OSes have moved to Fortuna since at least December 2019, possibly earlier. It is based on SHA-256. Multiple entropy sources such as the secure enclave RNG, boot phase timing jitter, hardware interrupt (timing assumed) are used. RDSEED/RDRAND is used on Intel-based Macs that support it. Seed (entropy) data is also stored for subsequent reboots. Prior to the change, macOS and iOS used 160-bit Yarrow based on SHA-1. There is no difference between and ; both behave identically. Other operating systems and are also available on Solaris, NetBSD, Tru64 UNIX 5.1B, AIX 5.2 and HP-UX 11i v2. As with FreeBSD, AIX implements its own Yarrow-based design, however AIX uses considerably fewer entropy sources than the standard implementation and stops refilling the pool when it thinks it contains enough entropy. In Windows NT, similar functionality is delivered by , but reading the special file does not work as in UNIX. The documented methods to generate cryptographically random bytes are CryptGenRandom and RtlGenRandom. Windows PowerShell provides access to a cryptographically secure pseudorandom number generator via the cmdlet. Cygwin on Windows provides implementations of both and , which can be used in scripts and programs. See also CryptGenRandom – The Microsoft Windows API's CSPRNG Entropy-supplying system calls Fortuna algorithm Hardware random number generator Standard streams References External links Unix file system technology Device file Random number generation