W3C home > Mailing lists > Public > public-webcrypto@w3.org > May 2012

RE: ECC vs RSA, and Similar Conflicts

From: Alex Radutskiy <Alex.Radutskiy@microsoft.com>
Date: Thu, 10 May 2012 18:58:12 +0000
To: Ryan Sleevi <sleevi@google.com>, Cullen Jennings <fluffy@cisco.com>
CC: David Dahl <ddahl@mozilla.com>, "Richard L. Barnes" <rbarnes@bbn.com>, Nadim <nadim@nadim.cc>, "public-webcrypto@w3.org" <public-webcrypto@w3.org>
Message-ID: <C750AACDA78B6F43BB6F2E874038527508686D34@SN2PRD0310MB370.namprd03.prod.outlook.com>
I think this classification is reasonable. I sense that by separating certain use case in the 3rd group you are trying to protect against a feature creep to satisfy endless financial and government regulations and their use of different protocols/hardware/etc. I would agree with that scoping as well.

As a side note... Judging by the fact that at least some banks today use long-lived cookies as an additional authenticator in order to allow me to do online banking, I could see them being very happy with the functionality provided in your second group below. This doesn't apply to all countries of course. Some countries have more stringent requirements that would require something like what you've outlined in the third group.



From: Ryan Sleevi [mailto:sleevi@google.com]
Sent: Thursday, May 10, 2012 11:37 AM
To: Cullen Jennings
Cc: Alex Radutskiy; David Dahl; Richard L. Barnes; Nadim; public-webcrypto@w3.org
Subject: Re: ECC vs RSA, and Similar Conflicts

In my mind, this gets closer to the "High Value Transaction" case.

At the risk of creating more ontologies, and truly just throwing out a strawman here, I see three types of keys:

  *   Origin-bound: These are keys generated via .generateKey() [or whatever it becomes], that are bound to a single origin. They may be short-lived (session cookie style?), they may be long-lived (persistent cookie style). They may be cleared when the user chooses to clear data. They may be not persisted when using "private" browsing

     *   Use case: DHE/ECDHE/PAKE key agreement for opportunistic encryption of chat over Websockets, where the intermediary is not trusted.
     *   Use case: Perhaps some binding of a user login/cookie data to some encrypted context. The key is only as useful as long as the cookie lives, and vice-versa.

  *   Persistent: These are keys that are effectively super-cookie, in that they don't follow the same "personal data cleanup" rules that might apply to cookies/cache/other data.

     *   Use case: You may wish to create and register an "identity key" with a service. Possession of this key is now a strong connector to some concept of 'identity' (putting the cryptopolitics of this concept aside). This identity might be used for mail signing, HTML5 file storage, online chat, etc
     *   This key may be bound to a single origin, it may be allowed to be shared with multiple origins, or it might be allowed to be shared with all origins.
     *   Because of the sensitivity of this, this would likely require user confirmation/assent, much like other APIs such as Geolocation or increased storage do in browsers today.
     *   Keys may be stored in software (managed by the UA), in the OS or some global key store (making them available to other applications beyond the UA), in "the cloud" as part of some sync service, or even stored on another device such as TPM or smart card.
     *   Use Case: For embedders (such as Netflix), keys may be pre-provisioned and pre-bound to certain origins.
     *   Use Case: Users may wish to purchase USB TPMs (as you mentioned) as a portable way to transfer these keys between machines they authenticate with.

  *   High Value: These are the keys that have a strong correlation to certain high value transactions - particularly where force of law is involved. Unlike the above 'persistent' keys, HVKs are strongly correlated to identity, and may reflect government or financial services issuance.

     *   These keys will typically be stored on smart card or TPM, where the provisioner has previously guaranteed that the key storage and generation matches their criteria. Specifically, I'm not trying to get into the side debate about provisioning, end to end protocols, PoP, and that whole mess, as has been discussed and rightfully discouraged/discarded in the past here.
     *   Use Case: Signing a legal document - tax forms, contract, etc
     *   Use Case: Performing 'sensitive' transactions (bank transaction confirmation, etc)
     *   While I don't know if it can be stated as MANDATORY, I think the assumption is that there MUST be user interaction throughout the process, and likely custom chrome to facilitate these sorts of HVTs.
     *   The API for interacting with them is likely very different than the above two key types, due to the nature of what's being done with them.
AIUI, David's strawman is focused exclusively on the first type (Origin-bound) at present. Netflix's use case best fits within the second type (persistent).

For my take, I believe we're best served focusing on the first two types. I would prefer that the API, as much as possible, make the distinction between the two invisible. I only imagine the edges between the two will show up when discussing the API for key generation and the detection of existing keys. For everything else, referring to a "key id" has an added benefit of hiding the distinction between the two.

On Thu, May 10, 2012 at 10:41 AM, Cullen Jennings <fluffy@cisco.com<mailto:fluffy@cisco.com>> wrote:

So if I plug in a USB TPM to my computer with some private keys on it, can any website ask for somehting to be encrypted with theses keys? That seems like it would be a problem (as well as super cookie).


On May 10, 2012, at 10:55 AM, Alex Radutskiy wrote:

> I believe it is a very important use case to be able to create a key that is secured by hardware such as TPM or smart card. Even software keys isolation (i.e. keeping key material in a separate process from the application that is using it) will be useful. For example, if an application is compromised it will not be possible to extract a key and send it somewhere for later use.
>
> In all of those examples, you need a model that can simply reference keys by some IDs when performing crypto operations without directly interacting with key material.
>
> Thank you,
>
> Alex Radutskiy
> Senior Program Manager, Windows PKI
>
> alex.radutskiy@microsoft.com<mailto:alex.radutskiy@microsoft.com>
>
>
>
> -----Original Message-----
> From: David Dahl [mailto:ddahl@mozilla.com<mailto:ddahl@mozilla.com>]
> Sent: Thursday, May 10, 2012 9:35 AM
> To: Cullen Jennings
> Cc: Richard L. Barnes; Nadim; public-webcrypto@w3.org<mailto:public-webcrypto@w3.org>
> Subject: Re: ECC vs RSA, and Similar Conflicts
>
> If you are referring to the Netflix use-case, the browser in question is an embedded webkit browser inside a blu-ray player. The Netflix use case is about identification of said blu-ray player to know what kind of streams it can accept and if it is authorized to view streams in the first place. The keys are pre-positioned by the blu-ray manufacturer.
>
> I doubt this API will be used to decode encrypted video produced in Hollywood, I could be wrong.
>
> David
>
>
> ----- Original Message -----
> From: "Cullen Jennings" <fluffy@cisco.com<mailto:fluffy@cisco.com>>
> To: "David Dahl" <ddahl@mozilla.com<mailto:ddahl@mozilla.com>>
> Cc: "Richard L. Barnes" <rbarnes@bbn.com<mailto:rbarnes@bbn.com>>, "Nadim" <nadim@nadim.cc<mailto:nadim@nadim.cc>>, public-webcrypto@w3.org<mailto:public-webcrypto@w3.org>
> Sent: Thursday, May 10, 2012 11:15:51 AM
> Subject: Re: ECC vs RSA, and Similar Conflicts
>
>
> I get what you are saying but I would like to push on making sure we have a complete solution. How do the private keys get into the browser? And if the private keys are for DRM protected video running in an open source browser, what does the whole system look like to make this work.
>
> I'm not arguing against something like this, I just want to understand the big picture so I understand the requirements for this work.
>
>
>
> On May 10, 2012, at 8:30 AM, David Dahl wrote:
>
>> One of the reasons for establishing this WG is to try and provide a more secure way of using crypto on the web. Keeping the private keys private is at the top of this list. We can establish a spec that only ever references private key IDs, making this much more secure than existing JS crypto libraries that have access to private key material.
>>
>> David
>>
>> ----- Original Message -----
>> From: "Richard L. Barnes" <rbarnes@bbn.com<mailto:rbarnes@bbn.com>>
>> To: "Cullen Jennings" <fluffy@cisco.com<mailto:fluffy@cisco.com>>
>> Cc: "Nadim" <nadim@nadim.cc<mailto:nadim@nadim.cc>>, public-webcrypto@w3.org<mailto:public-webcrypto@w3.org>
>> Sent: Thursday, May 10, 2012 9:18:44 AM
>> Subject: Re: ECC vs RSA, and Similar Conflicts
>>
>> Note, however, that that approach would require that private keys be exposed to the JS layer.  It seems like we have at least some use cases (e.g., the Netflix cases) where maintaining the secrecy of the private key is important.
>>
>> --Richard
>>
>>
>>
>> On May 10, 2012, at 9:42 AM, Cullen Jennings wrote:
>>
>>>
>>> One way to deal with the ECC / RSA issues is instead provide the underlining big math libraries that are needed to implement these and leave the actually IPR encumbered implementation to an JS library. If done right, this would could have approximately the same performance as a native implementation.
>>>
>>>
>>> On May 9, 2012, at 11:33 AM, Nadim wrote:
>>>
>>>> Hi everyone,
>>>> I think we need to have a discussion regarding whether the API will exclusively implement (and rely on) newer, faster standards (such as ECDH, ECDSA) or whether there will be a larger dependence on RSA, either for fallback or stronger compatibility reasons.
>>>>
>>>> If it is eventually decided that not only the best available per-task algorithm is implemented, but rather, all possible algorithms, where do we draw the line? Do we implement SHA1 in addition to SHA2? Does that also warrant an MD5 implementation?
>>>>
>>>> Personally, I believe that focusing only on the newer, more efficient standards (such as ECC) is a better idea, but I stand very humbly by my opinion and a much more interested in listening to the group's opinions.
>>>>
>>>> Thank you,
>>>> NK
>>>
>>>
>>
>>
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>
>
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Received on Thursday, 10 May 2012 18:59:16 UTC

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