CDR design document

Here is a proposal for consideration for inclusion in the OpenPGP
standard:

	http://www.dcs.ex.ac.uk/~aba/cdr/

(Also attached text version below [1])

It describes a mechanism for commercial data recovery which attempts
to minimise the security risks inherent in allowing disaster recovery
of stored encrypted documents.  The CDR design also avoids the
security risks in building systems which send recovery information
over open communications networks, as the CMR proposal currently does.

The CDR design offers the option of more ergonomic recovery from
forgotten passphrase.  CDR allows for more secure use to be made of
the existing pgp5.0 key expiry functionality when applied to
communications-only keys because they can be deleted with out loss of
data-availability, providing a form of PFS which is backwards
compatible with pgp5.0 and pgp5.5 clients.

Comments?

The only change addition to the standard required is to create a
distinction between a storage only key and a communications only key.
This distinction could be made via the use of an extra flag, ideally
so that keyrings can remain standardised and interchangeable between
different implementations.

The document can also be viewed as a recommendation to implementors of