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Re: Request for feedback: DOMCrypt API proposal

From: Rich Tibbett <richt@opera.com>
Date: Fri, 03 Jun 2011 13:25:15 +0200
Message-ID: <4DE8C49B.4060804@opera.com>
To: David Dahl <ddahl@mozilla.com>
CC: public-webapps@w3.org
I wonder whether the problem is actually just one of generating 
sufficiently cryptographically secure PRNGs or whether there are real 
benefits to creating a full-blown UA-based Crypto API and the can of 
worms that might open.

There was a proposal on the WHATWG back in February for producing a 
cryptographic pseudo-random number generation API (ala the NS4 
window.crypto.random API IIRC) within browsers [1].

A 2009 Stanford white paper entitled 'Symmetric Cryptography in 
Javascript' [2] detailed a number of optimizations to make symmetric 
cryptography performant in pure-Javascript (i.e. maximizing 
precomputation, loop unrolling, bitslicing). There is an implementation 
available at [3]. The paper concluded by saying that one of their 
biggest problems was finding a way to generate enough cryptographic 
randomness in the browser for key generation - other than that their 
solution is quite performant.

So would window.crypto.random allow performant symmetric and asymmetric 
cryptography to be written in pure JS? It would be good to see some 
benchmarks between JS and Native around SHA256 and SHA512 key generation 
(for example) to really understand the performance benefits that this 
API could bring.

Other than that, it's still a very rough proposal but it could be 
interesting pending some performance benchmark data (or details of 
additional benefits that this proposal brings) :)

- Rich

[1] 
http://lists.whatwg.org/htdig.cgi/whatwg-whatwg.org/2011-February/030241.html

[2] http://crypto.stanford.edu/sjcl/acsac.pdf

[3] http://crypto.stanford.edu/sjcl/

David Dahl wrote:
> Hello public-webapps members,
>
> (I wanted to post this proposed draft spec for the DOMCrypt API ( https://wiki.mozilla.org/Privacy/Features/DOMCryptAPISpec/Latest ) to this list - if there is a more fitting mailing list, please let me know)
>
> I recently posted this draft spec for a crypto API for browsers to the whatwg (see: http://lists.whatwg.org/htdig.cgi/whatwg-whatwg.org/2011-May/031741.html) and wanted to get feedback from W3C as well.
>
> Privacy and user control on the web is of utter importance. Tracking, unauthorized user data aggregation and personal information breaches are becoming so commonplace you see a new headline almost daily. (It seems).
>
> We need crypto APIs in browsers to allow developers to create more secure communications tools and web applications that don’t have to implicitly trust the server, among other use cases.
>
> The DOMCrypt API is a good start, and more feedback and discussion will really help round out how all of this should work – as well as how it can work in any browser that will support such an API.
>
> This API will provide each web browser window with a ‘cipher’ property[1] that facilitates:
>
>      asymmetric encryption key pair generation
>      public key encryption
>      public key decryption
>      symmetric encryption
>      signature generation
>      signature verification
>      hashing
>      easy public key discovery via meta tags or an ‘addressbookentry’ tag
>
> [1] There is a bit of discussion around adding this API to window.navigator or consolidation within window.crypto
>
> I have created a Firefox extension that implements most of the above, and am working on an experimental patch that integrates this API into Firefox.
>
> The project originated in an extension I wrote, the home page is here: http://domcrypt.org
>
> The source code for the extension is here: https://github.com/daviddahl/domcrypt
>
> The Mozilla bugs are here:
>
> https://bugzilla.mozilla.org/show_bug.cgi?id=649154
> https://bugzilla.mozilla.org/show_bug.cgi?id=657432
>
> Firefox "feature wiki page": https://wiki.mozilla.org/Privacy/Features/DOMCryptAPI
>
> You can test the API by installing the extension hosted at domcrypt.org, and going to http://domcrypt.org
>
> A recent blog post updating all of this is posted here: http://monocleglobe..wordpress.com/2011/06/01/domcrypt-update-2011-06-01/
>
> The API:
>
> window.cipher = {
>   // Public Key API
>   pk: {
>     set algorithm(algorithm){ },
>     get algorithm(){ },
>
>    // Generate a keypair and then execute the callback function
>    generateKeypair: function ( function callback( aPublicKey ) { } ) {  },
>
>    // encrypt a plainText
>    encrypt: function ( plainText, function callback (cipherMessageObject) ) {  } ) {  },
>
>    // decrypt a cipherMessage
>    decrypt: function ( cipherMessageObject, function callback ( plainText ) { } ) {  },
>
>    // sign a message
>    sign: function ( plainText, function callback ( signature ) { } ) {  },
>
>    // verify a signature
>    verify: function ( signature, plainText, function callback ( boolean ) { } ) {  },
>
>    // get the JSON cipherAddressbook
>    get addressbook() {},
>
>    // make changes to the addressbook
>    saveAddressbook: function (JSONObject, function callback ( addresssbook ) { }) {  }
>    },
>
>    // Symmetric Crypto API
>    sym: {
>    get algorithm(),
>    set algorithm(algorithm),
>
>    // create a new symmetric key
>    generateKey: function (function callback ( key ){ }) {  },
>
>    // encrypt some data
>    encrypt: function (plainText, key, function callback( cipherText ){ }) {  },
>
>    // decrypt some data
>    decrypt: function (cipherText, key, function callback( plainText ) { }) {  },
>    },
>
>    // hashing
>    hash: {
>      SHA256: function (function callback (hash){}) {  }
>    }
> }
>
> Your feedback and criticism will be invaluable.
>
> Best regards,
>
> David Dahl
>
> Firefox Engineer, Mozilla Corp.
>
Received on Friday, 3 June 2011 11:25:48 GMT

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