[whatwg] Cryptographically strong random numbers

Allen Wirfs-Brock allen at wirfs-brock.com
Mon Feb 14 15:03:54 PST 2011

If the intent is to get ECMAScript implementations to quickly provide this function then I would suggest that it be specified only in terms of things that are already in ES5.  That would preclude use of anything from the Harmony binary data strawman.

I don't particularly see why a "binary array" is needed in this situations.  A regular ES5 array is perfectly capable of holding the numeric results.  And why overwrite the elements of an existing array?  Why not just creating a new Array and use the argument to specify the desired length?

I don't understand the use cases that would justify the various integer length options for the random elements..  One reasonable size seems fine.  I would probably go with 16 bit units in recognitions that many JavaScript implementations have optimized small integer sizes < 32 bits.  If you want 8 bit or 32 bit values, assemble them yourself out of the 16 bits values.

Alternative, if you are are attached to pure binary data. The function could return a string value, as ECMAScript strings are really immutable vectors of 16-bit unsigned values.

In either case, I would attach the method to Array (or string) if we went down that path:

Array.randomValues = function randomValues (len) {
   //Return an Array of ToUInt32(len) elements where each element is a number in the range 0 to 65535
  // The values of the elements must be generated using a strong crypto PRNG
  //  If ToUInt32(len) random values are not available, throw a RangeError Exception

String.randomValues = function randomValues (len) {
   //Return an string value consisting of ToInteger(len) characters.
  // The character code  of the element of the string must be generated using a strong crypto PRNG
  //  If ToInteger(len) is not a positive integer or if that many random values are not available, throw a RangeError Exception


On Feb 14, 2011, at 2:25 PM, Mark S. Miller wrote:

> While we're waiting for Adam to subscribe to es-discuss and repost his messages on this thread, this one seems worth pre-posting.
> Changes needed for this to become an EcmaScript strawman:
> Replace references to ArrayBufferView with appropriate abstractions from <http://wiki.ecmascript.org/doku.php?id=strawman:binary_data>.
> Replace WebIDL as a specification language with a JavaScript based API spec.
> Get rid of the dependence on "window". Probably avoid introducing a new global "crypto" as well, though we can argue about that.
> Are there any other lurking browser dependencies in Adam's spec that we need to scrub away?
> On Mon, Feb 14, 2011 at 2:08 PM, Adam Barth <w3c at adambarth.com> wrote:
> On Mon, Feb 14, 2011 at 12:49 PM, Brendan Eich <brendan at mozilla.org> wrote:
> > On Feb 14, 2011, at 12:26 PM, Adam Barth wrote:
> > > Ok.  I'll write up a spec later today.
> >
> > Thanks.
> Done: http://wiki.whatwg.org/wiki/Crypto
> Feedback appreciated.
> Adam
> -- 
>     Cheers,
>     --MarkM
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