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
>
>
>