Re: getLength

On Mon, Oct 20, 2014 at 11:35 AM, Mike Jones <Michael.Jones@microsoft.com>
wrote:

>  Does getLength need to be in the key_ops list in JWA or should it not
> be?  I think the answer is that it should not be, but I wanted to ask.
>

No. It's not a method supported by the crypto.subtle interface.


>
>
> As far as I can tell, there’s only one use of the string “getLength” in
> the current editor’s draft, which is confusing, because it’s not defined.
>
>
>
>                                                             -- Mike
>
>
>
> *From:* Mark Watson [mailto:watsonm@netflix.com]
> *Sent:* Monday, October 20, 2014 11:32 AM
> *To:* Mike Jones
> *Cc:* public-webcrypto@w3.org
> *Subject:* Re: getLength
>
>
>
> Hi Mike,
>
>
>
> "operations" supported by the various WebCrypto algorithms are *not* the
> same as the "methods" supported by the crypto.subtle interface.
>
>
>
> Each method has an associated procedure which, amongst other things, calls
> out to one or more of the operations supported by the algorithms.
>
>
>
> For example, the encrypt method does various pieces of work before calling
> the encrypt operation.
>
>
>
> The deriveKey method calls out to three operations, first the getLength
> operation of the derived key algorithm then the deriveBits operation of the
> key derivation algorithm and finally the import operation of the derived
> key algorithm
>
>
>
> getLength is needed because the number of bits to generate depends on
> interpretation of the Algorithm object for the *derived* key (the target).
> This interpretation can only be done by the algorithm, not entirely within
> the method, so we need an operation to do that.
>
>
>
> I have argued several times that we should have a clearer distinction
> between operation and method names, to avoid this confusion, which keeps
> coming up again and again. But so far *no one* has supported or even
> commented on my suggestions.
>
>
>
> ...Mark
>
>
>
> On Mon, Oct 20, 2014 at 11:24 AM, Mike Jones <Michael.Jones@microsoft.com>
> wrote:
>
> What is the getLength operation in
> https://dvcs.w3.org/hg/webcrypto-api/raw-file/tip/spec/Overview.html#algorithm-concepts-operations?
> And why is this list different than the list at
> https://dvcs.w3.org/hg/webcrypto-api/raw-file/tip/spec/Overview.html#subtlecrypto-interface-methods,
> which doesn’t include it?
>
>
>
>                                                             -- Mike
>
>
>
>
>