> Le 9 sept. 2017 à 03:07, Xiaodi Wu via swift-evolution > <swift-evolution@swift.org> a écrit : > > On Fri, Sep 8, 2017 at 7:50 PM, Stephen Canon <sca...@apple.com > <mailto:sca...@apple.com>> wrote: >> On Sep 8, 2017, at 8:09 PM, Xiaodi Wu via swift-evolution >> <swift-evolution@swift.org <mailto:swift-evolution@swift.org>> wrote: >> >> This topic has been broached on Swift Evolution previously. It's interesting >> to me that Steve Canon is so certain that CSPRNGs are the way to go. I >> wasn't aware that hardware CSPRNGs have come such a long way and are so >> ubiquitous as to be feasible as a basis for Swift random numbers. If so, >> great. >> >> Otherwise, if there is any way that a software, non-cryptographically secure >> PRNG is going to outperform a CSPRNG, then I think it's worthwhile to have a >> (carefully documented) choice between the two. I would imagine that for many >> uses, such as an animation in which you need a plausible source of noise to >> render a flame, whether that is cryptographically secure or not is >> absolutely irrelevant but performance may be key. > > Let me be precise: it is absolutely possible to outperform CSPRNGs. They have > simply become fast enough that the performance gap doesn’t matter for most > uses (let’s say amortized ten cycles per byte or less—whatever you are going > to do with the random bitstream will be much more expensive than getting the > bits was). > > That said, yes, there should definitely be other options. It should be > possible for users to get reproducible results from a stdlib random interface > run-to-run, and also across platforms. That alone requires that at least one > other option for a generator be present. There may also be a place for a very > high-throughput generator like xorshiro128+. > > All I’m really saying is that the *default* generator should be an > os-provided unseeded CSPRNG, and we should be very careful about documenting > any generator options. > > > Agree on all points. Much like Swift's strings are Unicode-correct instead of > the fastest possible way of slicing and dicing sequences of ASCII characters, > Swift's default PRNG should be cryptographically secure.
I agree too. Anyone that need a random generator but don’t know how it works and what’s a CSPRNG is need a CSPRNG. For other users, we still need a couple of other implementations.
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