Cryptographically secure pseudo-random numbers (Windows only)

winrand.py

#!/usr/bin/env python
# -*- coding: utf-8 -*-

import ctypes
from ctypes import wintypes
import struct

PROV_RSA_FULL = 1


class Random(object):
    """
    Generate cryptographically secure pseudo-random numbers (Windows only).
    """
    # Could/Should be a singleton.
    
    advapi = ctypes.windll.LoadLibrary("advapi32")

    genRandom = advapi.CryptGenRandom
    genRandom.restype = ctypes.c_bool
    genRandom.argtypes = [ctypes.c_void_p, wintypes.DWORD, ctypes.c_char_p]

    acquireContext = advapi.CryptAcquireContextW
    acquireContext.restype = ctypes.c_bool
    acquireContext.argtypes = [ctypes.POINTER(ctypes.c_void_p), wintypes.LPCWSTR, wintypes.LPCWSTR, wintypes.DWORD, wintypes.DWORD]

    releaseContext = advapi.CryptReleaseContext
    releaseContext.restype = ctypes.c_bool
    releaseContext.argtypes = [ctypes.c_void_p, wintypes.DWORD]

    def __init__(self):
        self.ctx = ctypes.c_void_p()
        if not self.acquireContext(ctypes.byref(self.ctx), None, None, PROV_RSA_FULL, 0):
            raise RuntimeError("Could not acquire context")
        self.buf = ctypes.create_string_buffer(8)

    def __del__(self):
        if self.ctx.value is not None:
            if not self.releaseContext(self.ctx, 0):
                raise RuntimeError("Could not release context")

    def rand(self, upperBound = None):
        """Returns a 64bit pseudo-random number.
        If parameter `upperBound` is given, limit result to `upperBound` (inclusive).
        """
        self.genRandom(self.ctx, 8, self.buf)
        result = int(struct.unpack('Q', self.buf.raw)[0])
        return result % (upperBound + 1) if upperBound else result

##
## Demo code.
##
random = Random()

for i in range(128):
    print("{0:08X}".format(random.rand())),