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Pitfalls of provably secure systems in internet the case of chronos-NTP

: Jeitner, P.; Shulman, H.; Waidner, M.


Institute of Electrical and Electronics Engineers -IEEE-:
DSN-S 2020 supplemental volume. 50th Annual IEEE/IFIP International Conference on Dependable Systems and Networks : Proceedings : 29 June-2 July 2020, Valencia, Spain
Piscataway, NJ: IEEE, 2020
ISBN: 978-1-72817-260-6
ISBN: 978-1-72817-261-3
International Conference on Dependable Systems and Networks (DSN) <50, 2020, Online>
Fraunhofer SIT ()

The critical role that Network Time Protocol (NTP) plays in the Internet led to multiple efforts to secure it against time-shifting attacks. A recent proposal for enhancing the security of NTP with Chronos against on-path attackers seems the most promising one and is on a standardisation track of the IETF. In this work we demonstrate off-path attacks against Chronos enhanced NTP clients. The weak link is a central security feature of Chronos: The server pool generation mechanism using DNS. We show that the insecurity of DNS allows to subvert the security of Chronos making the time-shifting attacks against Chronos-NTP even easier than attacks against plain NTP.