CryptGenRandom

CryptGenRandom is a cryptographically secure pseudorandom number generator function included in the Microsoft CryptoAPI, which Microsoft long recommended for any random number generation in Win32 programs. It is now deprecated together with the CryptoAPI and replaced by BCryptGenRandom in the Cryptography API: Next Generation; RtlGenRandom is the equivalent lower level function. Before Windows Vista its output followed FIPS 186-2 with SHA-1 and was seeded from many system sources such as process and thread identifiers, the tick count, performance counters and CPU counters. From Windows Vista on it uses AES-CTR-DRBG as specified in FIPS SP800-90, with a hierarchy in which a root generator seeds one generator per logical processor and each process in turn. A 2007 analysis by Leo Dorrendorf and colleagues found weaknesses in the Windows 2000 implementation, which was based on the RC4 stream cipher and ran in user mode, and Microsoft fixed the problem for Windows XP in Service Pack 3. Several programming language facilities, such as the Python os.urandom function on Windows, call it.