![]() No facility for a user-provided seed, preventing programs from getting reproducible results.The BSD implementations (which are the only widely used ones) have several additional issues.In fact, in FreeBSD prior to the 7.1 release (late 2008), OS X prior to OS X Lion, and iOS prior to iOS 5, the implementation of arc4random did not take steps to avoid very short periods-more than 1 time in 75,000, the period of the generator could be tiny, producing only 16320 integers before repeating.Unlike some generators with a very large period, does not provide k-dimensional equidistribution.In fact, even though the test is not included in TestU01's suite, tests exist that can distinguish the output of arc4random from a true random sequence.Has been mathematically shown to be nonuniform.Although the standard variant does pass TestU01's BigCrush battery, that isn't much of an achievement given 2064 bits of internal state-a simple LCG passes with 88 bits of internal state! If we reduce the number of S-boxes from 256 to 64, requiring 396 bits of internal state, it still passes, but if we reduce the number to 32, which is 170 bits of state, it fails badly. ![]()
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