[Resource Topic] 2006/009: Breaking and Fixing Public-Key Kerberos

Welcome to the resource topic for 2006/009

Breaking and Fixing Public-Key Kerberos

Authors: Iliano Cervesato, Aaron D. Jaggard, Andre Scedrov, Joe-Kay Tsay, Christopher Walstad


We report on a man-in-the-middle attack on PKINIT, the public key extension of the widely deployed Kerberos 5 authentication protocol. This flaw allows an attacker to impersonate Kerberos administrative principals (KDC) and end-servers to a client, hence breaching the authentication guarantees of Kerberos. It also gives the attacker the keys that the KDC would normally generate to encrypt the service requests of this client, hence defeating confidentiality as well. The discovery of this attack caused the IETF to change the specification of PKINIT and Microsoft to release a security update for some Windows operating systems. We discovered this attack as part of an ongoing formal analysis of the Kerberos protocol suite, and we have formally verified several fixes to PKINIT that prevent our attack.

ePrint: https://eprint.iacr.org/2006/009

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