OpenBSD
Since OpenBSD 5.1 (May 1, 2012) /dev/random and /dev/arandom use an algorithm based on RC4 but renamed, for licensing purposes, ARC4. While random number generation here uses system entropy gathered in several ways, the ARC4 algorithm provides a fail-safe, ensuring that a rapid and high quality pseudo-random number stream is provided even on a low entropy pool. The system automatically uses hardware random number generators (such as those provided on some Intel PCI hubs) if they are available, through the OpenBSD Cryptographic Framework.
Read more about this topic: /dev/random