Subject: CAT pk recovery internet draft summary

From: [email-masked] (Jonathan Trostle)
Date: Mon, 9 Mar 1998 01:30:44 -0500

I recently submitted the internet draft draft-ietf-cat-kerberos
-pk-recovery-00.txt to the cat group internet drafts. Here is
a summary:
 
The motivation comes in an environment where smart cards are not
ubiquitous and the pk-init extensions are being used. Thus
users are likely to have their private keys encrypted on the
KDC. Users thus share a long term secret with the KDC. If the
KDC is compromised, a big problem results. The goal of the draft
is to enable the secret keys to be updated with a minimum
amount of administration work, and for the process to be
transparent to users. The recovery protocols are designed to
work in either an environment where the KDC public keys are
signed as keys in a PKI, or where the KDC public keys are 
self-signed.

For a recovery operation, the KDC is cleaned up and reloaded 
from backup media. In the case of self-signed certificates,
the KDC sends new self-signed certificates to clients using
a KRB_ERROR message with error code KDC_ERR_RECOVERY_HOST_NEEDED.
Secret keys can also be updated with this exchange. The
exchange uses Diffie Hellman with signed public parameters.
Users also engage in a subsequent Diffie Hellman based 
exchange if they store secrets on the KDC. New user secrets
are created by OWF(salt + password); the salt is changed
for each new recovery operation.

The recovery protocol improves the security of Kerberos V5
by using public key cryptography to enable easy cleanup of
compromised KDC's.

-Jonathan