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Re: Additional use cases

From: Seetharama Rao Durbha <S.Durbha@cablelabs.com>
Date: Tue, 7 May 2013 16:10:23 +0000
To: Mountie Lee <mountie@paygate.net>
CC: Lu HongQian Karen <karen.lu@gemalto.com>, Arun Ranganathan <arun@mozilla.com>, "public-webcrypto@w3.org Working Group" <public-webcrypto@w3.org>
Message-ID: <CDAE8087.C8C3%s.durbha@cablelabs.com>
I am not sure I follow what is meant by user owns the cert Vs. origin owns the cert. For all practical purposes, the origin uses a secure protocol to associate a cert to a user. Cert could have been obtained by the user from a 3rd party or issued by the origin. But for non-repudiation purposes, it does not matter.

The problem for non-repudiation is whether someone else could have generated the signature. With no secure SOP, a malicious script can easily generate the signature and submit to the origin.

In case of TLS, there are no signatures involved, and the keys are not exposed to scripts. The user can demonstrate the ownership of a certificate to anyone who cares – whether malicious content or genuine content. So, TLS usage is totally different.


On 5/7/13 9:44 AM, "Mountie Lee" <mountie@paygate.net<mailto:mountie@paygate.net>> wrote:

existing TLS client X509 certificate can be used on any sites for establishing TLS connection.

if keys are totally owned by origin, the origin has full control for the keys of UA with silent operation.
if keys are owned by user, the origin has limited control for the keys with user consent (like TLS client x509 certificate).

before going to certificate discussion,
we have to conclude how to handle key ownership issue and solve the conflict between existing TLS client x509 certificate and webcrypto's certificate.

the definition of certificate in wikipedia(http://en.wikipedia.org/wiki/Public_key_certificate) describe as following
"In cryptography<http://en.wikipedia.org/wiki/Cryptography>, a public key certificate (also known as a digital certificate or identity certificate) is an electronic document that uses a digital signature<http://en.wikipedia.org/wiki/Digital_signature> to bind a public key<http://en.wikipedia.org/wiki/Public_key> with an identity — information such as the name of a person or an organization, their address, and so forth. The certificate can be used to verify that a public key belongs to an individual."

the certificate is issued to identify the entities (individuals or organizations)
means

certificate is tightly binded into key ownership.

if the keys are controlled by origins (provisioners, servers or the cloud), it can not be used for non-repudiation of individual.
technically the cross-origin issued can be addressed with suggested solutions (CORS, postMessage...).
but it can not be the answer for non-repudiation requirement.

user owns the certificate key pair and has control --> generated digital signature --> non-repudiable

regards
mountie.


On Wed, May 8, 2013 at 12:14 AM, Seetharama Rao Durbha <S.Durbha@cablelabs.com<mailto:S.Durbha@cablelabs.com>> wrote:
With the ownership of the key based on SOP that is not cognizant of tampering (as of now), I am afraid that any discussion of signatures will be futile, they cannot be used for non-repudiation, at the end of the day.

http://lists.w3.org/Archives/Public/public-webcrypto/2013Apr/0247.html


On 5/6/13 10:38 AM, "Lu HongQian Karen" <karen.lu@gemalto.com<mailto:karen.lu@gemalto.com>> wrote:

Hi Arun,

Here are the two use cases that I have talked about at the recent F2F meeting.

Cross-origin use cases:


1.  Asymmetric key use case: A healthcare association (origin 1) issued Dr. Smith an X.509 certificate and the corresponding private key. Dr. Smith accesses an e-prescription service (origin 2) and uses her private key to sign e-prescriptions.

2.  Secret key use case: Danny signed up at a cloud storage (origin 1) that created him a secret access key and persisted it through Danny’s UA. Danny stores his 3D model data in the cloud storage. He then uses an online 3D printing service (origin 2) to print his model. To access Danny’s model in Origin 1, Origin 2 needs to use Danny’s secret key. Danny tells Origin 2 certain attribute(s) of his key. The Origin 2 finds the key object through the UA and uses the key to sign API requests for getting the model from cloud storage.

Although these two use cases are out of the current WG scope. It’ll be good to collect them for future work.

Regards,
Karen




--
Mountie Lee

PayGate
CTO, CISSP
Tel : +82 2 2140 2700
E-Mail : mountie@paygate.net<mailto:mountie@paygate.net>


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Received on Tuesday, 7 May 2013 16:11:11 UTC

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