[swift-evolution] [Proposal] Random Unification

[Jens Persson]

Oh OK, I must have misunderstood this thread:
https://lists.swift.org/pipermail/swift-evolution/Week-of-Mon-20171204/042034.html
(
"The strong opinion of the core team is that such an API should *not* be
designed with an attempt to service people writing crypto code."
"It is general goodness if generality for crypto use cases somehow falls
out of the design.  However, the design for general use shouldn’t suffer
because of that goal."
)

I assumed that the Random API would save the user from the trouble of
making a good choice and implementation (fast and good quality) of a
"standard" general purpose prng (as well as maybe a cryptographically
secure one).

Also, the most commonly recommended ways of converting from eg 64 random
bits to an int range or a floating point range are unnecessarily bad and
slow, so I figured the webpage was worth a read, in addition to C++
stdlib's implementation.

/Jens


On Wed, Dec 20, 2017 at 4:55 PM, Xiaodi Wu <xiaodi.wu at gmail.com> wrote:

> xoroshiro128+ is not a cryptographically secure algorithm and would not be
> incorporated into the Random API, though it is trivial to implement your
> own; the proposal outlines sources of randomness that are cryptographically
> secure.
>
>
>
> On Wed, Dec 20, 2017 at 09:46 Jens Persson via swift-evolution <
> swift-evolution at swift.org> wrote:
>
>> I'd like to add a pointer to the information here:
>> http://xoroshiro.di.unimi.it
>>
>> since AFAICS, the xoroshiro128+ generator and the method of "Generating
>> uniform doubles in the unit interval" should probably be implemented in any
>> modern general purpose Random API.
>>
>> Please correct me if there are more up to date (higher quality and
>> faster) general purpose generators and ways of converting UInt64 bit
>> patterns to floating point [0, 1).
>>
>> /Jens
>>
>>
>>
>> On Sun, Dec 3, 2017 at 4:50 AM, Dave Abrahams via swift-evolution <
>> swift-evolution at swift.org> wrote:
>>
>>> I don’t have much to say about this other than that I think the
>>> discussion seems way too narrow, focusing on spelling rather than on
>>> functionality and composability.  I consider the “generic random number
>>> library” design to be a mostly-solved problem, in the C++ standard
>>> library (http://en.cppreference.com/w/cpp/numeric/random).  Whatever
>>> goes into the Swift standard library does not need to have all those
>>> features right away, but should support being extended into something
>>> having the same general shape. IMO the right design strategy is to *implement
>>> and use* a Swift version of C++’s facilities and only then consider
>>> proposing [perhaps a subset of] that design for standardization in Swift.
>>>
>>> Sent from my iPad
>>>
>>> On Dec 2, 2017, at 5:12 PM, Kyle Murray via swift-evolution <
>>> swift-evolution at swift.org> wrote:
>>>
>>>
>>> On Dec 2, 2017, at 6:02 PM, Xiaodi Wu via swift-evolution <
>>> swift-evolution at swift.org> wrote:
>>>
>>> Instead, we ought to make clear to users both the features and the
>>> limitations of this API, to encourage use where suitable and to discourage
>>> use where unsuitable.
>>>
>>>
>>> I like that you're considering the balance here. I've been lightly
>>> following this thread and want to add my thoughts on keeping crypto and
>>> pseudorandomness out of the name of at least one random API intended
>>> for general use.
>>>
>>> For someone who doesn't know or care about the subtleties of insecure or
>>> pseudorandom numbers, I'm not sure that the name insecureRandom is
>>> effectively much different than badRandom, at least in terms of the
>>> information it conveys to non-experts. To Greg's point, that's the opposite
>>> of the signal that the API name should suggest because it's what most
>>> people should use most of the time. As you say, this API is being designed
>>> for general use.
>>>
>>> There's a cost to adding extra complexity to names, too. I don't think
>>> it's far-fetched to suspect that people who find insecureRandom in an
>>> autocomplete listing or search will think "Where's the plain random
>>> function?"... and then go looking for a community extension that will
>>> inevitably provide a trivial alias: func random() { return
>>> insecureRandom() }. That's the sort of adoption I'd expect from
>>> something for new programmers, like Swift Playgrounds. Someone's
>>> introduction to randomness in programming should probably involve no more
>>> than a straightforward mapping from the elementary definition, rather than
>>> forcing a teaching moment from more advanced math.
>>>
>>> I think there are better places for caveat information than in the API
>>> names themselves; documentation being one clear destination. This is in
>>> contrast with Unsafe*Pointer, where the safety element is critical
>>> enough to be elevated to be more than caveat-level information. You can go
>>> really far and create really cool things before these caveats start to
>>> apply. Using randomness as a black box in an intro programming environment
>>> seems like a much more common scenario than someone attempting to roll
>>> their first crypto by only reading API names and hoping for the best.
>>>
>>> -Kyle
>>>
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