Re: [W3C Web Crypto WG] PROPOSAL to close ISSUE-22 (Should CryptoOperations be clonable)

Unless I am missing something, if multi-part operations are permitted, then
in the complete step the variable copy contains only the data since the
last process. I don't see where you reset the state of the operation to the
same point.

Anyway, this seems like a premature optimization. It complicates the API
and procedures for a minor use-case which could be achieved (marginally
less optimally) by keeping multiple CryptoOperation objects, one for each
prefix of the input data for which a digest is required.

...Mark

Sent from my iPhone

On Apr 4, 2013, at 5:18 AM, Aymeric Vitte <vitteaymeric@gmail.com> wrote:

 If ISSUE-22 is closed, then it becomes impossible to do correctly
progressive hash/encryption with the WebCrypto API.

This might be destroyed right away but please see below a proposal, it is
not really a clone but a continuation of the operation resuming from the
previous state (which as a non crypto expert maybe I am simplifying too
much), see the example at the end, at least that's an attempt...

This is based on the assumption than independently of which progress could
be fired following some process invocations at the same time you call
finish, you are only interested by the final result.


interface CryptoOperation : EventTarget {
  void process <http://www.w3.org/TR/WebCryptoAPI/#dfn-CryptoOperation-method-process>(ArrayBufferView
buffer);
  void finish <http://www.w3.org/TR/WebCryptoAPI/#dfn-CryptoOperation-method-finish>(boolean?
resume);
  void abort <http://www.w3.org/TR/WebCryptoAPI/#dfn-CryptoOperation-method-abort>();

  readonly attribute Key <http://www.w3.org/TR/WebCryptoAPI/#dfn-Key>?
key <http://www.w3.org/TR/WebCryptoAPI/#dfn-CryptoOperation-key>;
  readonly attribute Algorithm
<http://www.w3.org/TR/WebCryptoAPI/#dfn-Algorithm> algorithm
<http://www.w3.org/TR/WebCryptoAPI/#dfn-CryptoOperation-algorithm>;
  readonly attribute any result
<http://www.w3.org/TR/WebCryptoAPI/#dfn-CryptoOperation-result>;
readonly attribute any? resume
<http://www.w3.org/TR/WebCryptoAPI/#dfn-CryptoOperation-result>;
readonly attribute any? final;


12.4.2. The finish(boolean? resume) method

When finish(boolean?
resume)<http://www.w3.org/TR/WebCryptoAPI/#dfn-CryptoOperation-method-finish>
 method is called, the user agent must run the steps below.

   1.

   If the internal state is in the "error" state, throw an InvalidStateError
    exception and abort these steps.
    2.

   Set the internal state to "complete". If resume is true let copy be a
   copy of the list of pending data and set the resume attribute to result
    3.

   If the underlying cryptographic implementation for the specified
   algorithm<http://www.w3.org/TR/WebCryptoAPI/#dfn-CryptoOperation-algorithm>
    does not support multi-part cryptographic operations,
asynchronously process
   data<http://www.w3.org/TR/WebCryptoAPI/#dfn-CryptoOperation-process-data>,
   allowing the task that invoked this algorithm to continue.
    4.

   Once all items in the list of pending
data<http://www.w3.org/TR/WebCryptoAPI/#dfn-CryptoOperation-list-of-pending-data>
    have been processed<http://www.w3.org/TR/WebCryptoAPI/#dfn-CryptoOperation-process-data>
   , if resume is true, restore the list of pending data with copy and set
   final to result, queue a
task<http://www.w3.org/TR/WebCryptoAPI/#queue-a-task>
    to fire a simple
event<http://www.w3.org/TR/WebCryptoAPI/#fire-a-simple-event>
    called oncomplete<http://www.w3.org/TR/WebCryptoAPI/#dfn-CryptoOperation-oncomplete>
    at the CryptoOperation<http://www.w3.org/TR/WebCryptoAPI/#dfn-CryptoOperation>
   .


12.4.1. process(ArrayBufferView data)

When the process(ArrayBufferView data) method is called, the user agent
must run the following steps:

   1.

   If the internal state is in the "error" state, throw an InvalidStateError
    exception and abort these steps.
    2.

   Let data be the data to be processed.
    3.

   Add data to the list of pending
data<http://www.w3.org/TR/WebCryptoAPI/#dfn-CryptoOperation-list-of-pending-data>
   .
    4. If the resume attribute is not undefined, update result with resume
    5.

   If the underlying cryptographic implementation for the specified
   algorithm<http://www.w3.org/TR/WebCryptoAPI/#dfn-CryptoOperation-algorithm>
    supports multi-part cryptographic operations, asynchrously process
data<http://www.w3.org/TR/WebCryptoAPI/#dfn-CryptoOperation-process-data>,
   allowing the task that invoked this algorithm to continue.

Example :

The algorithm processes 3 bytes :

process(ABCD) {result=abc, pending=D}
finish(true) {result=abcd,final=abcd,resume=abc,pending=D}
process(EFGH)
    step 4 {result=abc,final=abcd,resume=abc,pending=D}
    step 5 {result=abcdefg,final=abcd,resume=abc,pending=H}
finish(true) {result=abcdefgh,final=abcdefgh,resume=abcdefg,pending=H}

The reason to use final attribute is that process does modify result and
then progress could fire before complete and then the result in complete
would not be the good one.


Le 04/04/2013 11:46, GALINDO Virginie a écrit :

  Dear all,

I suggest that we close the ISSUE-22
http://www.w3.org/2012/webcrypto/track/issues/22 , with the rationale that
the WG did not make any progress /contribution on cloning. As such I
interpret it as no interest or need to have that feature covered by our Web
Crypto API.

This proposal will be submitted to the vote during our next call on
the 15thof April.

Regards,

Virginie




-- 
jCore
Email :  avitte@jcore.fr
iAnonym : http://www.ianonym.com
node-Tor : https://www.github.com/Ayms/node-Tor
GitHub : https://www.github.com/Ayms
Web :    www.jcore.fr
Webble : www.webble.it
Extract Widget Mobile : www.extractwidget.com
BlimpMe! : www.blimpme.com