By Mary Branscombe
21st May 2006
PGP is often thought of as an encryption system, but your private key
is a digital signature that can prove who your message comes from, as
well as showing that it hasn't been tampered with.
The reason a Public Key Infrastructure doesn't look like a widespread
identity system is that it needs a web of trust; if somebody you know
has signed my PGP key, then you take their word that I am who I say I
am. That works well for close groups of friends - or for the
corporations and government departments around the world who rely on
PKIs based on the commercial PGP offerings or the OpenPGP SDK 
that's now available.
That's where PGP has really made its mark, says Jon Callas (now the
CTO of PGP Corporation ; and part of the team that shepherded the
commercial side of PGP out of the wilderness where Network Associates
left it). "We thought it would be a grass roots system.
But now it's really corporations setting up PKIs for their own
business reasons. The entities are organisations like BMW or Siemens
rather than individuals." Some of the companies who failed to sell
PKIs in the past had bad business models that were too expensive: "it
was like buying a camera and having to buy 1,000 rolls of film at the
The OpenPGP  standard is one of the things that's helped PGP become
more widespread; the other is the rise of systems that need to
identify people on many different platforms. But PGP doesn't solve all
of the problems for that. The Friend of a Friend project (FOAF) uses
digital signatures to attach PGP key IDs that verify the email of the
address of the author to documents; you still have to decide for
yourself if you trust the author which the PGP key identifies. There's
a PKI at the heart of Skype, for example, to make sure you're talking
to the person you want to call. But that tells you nothing about
anything else to do with their identity.
PGP software is mature and the technology is both tested and flexible;
you can use an LDAP server as a PGP keyserver or use the PGPticket
protocol to issue secure authorisations instead of vulnerable
passwords for access to a network service.
What many people want to do with identity now means making those
identities work more widely. That comes down to the architecture of
the systems that will accept identities, and the ways those identities
are secured will include PGP (read more about PGP Identity Management
Identity management is changing into claims management and different
claims will come from different systems, bringing together claims like
your Skype ID, your age and your eBay ranking only when someone needs
to know you're old enough to buy what they're selling before they call
you. Some of those claims will be secured and verified by PGP.
Instead of building up as much information about your users as
possible - something marketing departments are happier about than the
users themselves - you can think about the smallest pieces of
information you need for a specific authorisation or transaction.
Whether it's issues of liability or commercial advantage, businesses
don't want to share more of their customer database than they have to,
Callas points out. Ironically, their commercial interests are turning
out to enable our desire for privacy. =AE
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