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Privacy enhancing/protecting credentials

From: Manu Sporny <msporny@digitalbazaar.com>
Date: Thu, 04 Jun 2015 09:28:34 -0400
Message-ID: <55705282.5070702@digitalbazaar.com>
To: Credentials Community Group <public-credentials@w3.org>
One set of use cases that keep coming up are privacy enhancing
credentials. Specifically, can the ID that's associated with a
credential be used to track an individual between colluding sites (the
answer is clearly, yes). So, we've engaged the Cryptography Forum
Research Group[1] in an attempt to discover the most cutting edge ways
of establishing trustworthy credentials that are also privacy protecting:

http://www.ietf.org/mail-archive/web/cfrg/current/msg06864.html

We've also launched a research initiative at Digital Bazaar to look into
this space in more detail. We have a number of workable solutions that
we're looking at right now. They primarily revolve around creating a way
to automatically re-issue a short-lived bearer credential that is not
associated with an ID. Here's how the most promising solution we've come
up with could work:

Definitions
-----------

'bearer credential' - a short-lived one-time use credential (5 minutes)
that is not associated with an identity that "proves" that the holder of
the credential has been verified by the issuer as having a valid credential.

Credential Flow
---------------

1. An issuer issues a long-lived credential to a recipient. The
   credential has information in it on how to acquire a
   short-lived 'bearer credential'.
2. When a consumer asks the recipient for a credential, the recipient's
   software notices that the credential could be provided in an
   'anonymous' fashion using a 'bearer credential'. The recipient is
   asked if they'd like to protect their privacy by using the
   'bearer credential'.
3. The bearer credential is transmitted to the consumer, which verifies
   that the digital signature from the issuer is valid.

The issuer always has the option to reject bearer credentials if
pseudo-anonymity isn't desired on their end.

This mechanism could be built into a browser's "Incognito mode" such
that only bearer credentials can be used in "incognito mode".

This is just a heads-up that we're looking into it and have a few
solutions that we think may be workable.

-- manu

[1] https://irtf.org/cfrg

-- 
Manu Sporny (skype: msporny, twitter: manusporny, G+: +Manu Sporny)
Founder/CEO - Digital Bazaar, Inc.
blog: Web Payments: The Architect, the Sage, and the Moral Voice
https://manu.sporny.org/2015/payments-collaboration/
Received on Thursday, 4 June 2015 13:28:56 UTC

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