RFC 9523

A Secure Selection and Filtering Mechanism for the Network Time Protocol with Khronos, February 2024

File formats:

icon for HTML icon for text file icon for v3pdf icon for XML
Also available: XML file for editing
N. Rozen-Schiff
D. Dolev
T. Mizrahi
M. Schapira
ntp (int)

Cite this RFC: TXT  |  XML  |   BibTeX

DOI:  https://doi.org/10.17487/RFC9523

Discuss this RFC: Send questions or comments to the mailing list ntp@ietf.org

Other actions: Submit Errata  |  Find IPR Disclosures from the IETF  |  View History of RFC 9523


The Network Time Protocol version 4 (NTPv4), as defined in RFC 5905, is the mechanism used by NTP clients to synchronize with NTP servers across the Internet. This document describes a companion application to the NTPv4 client, named "Khronos", that is used as a "watchdog" alongside NTPv4 and that provides improved security against time-shifting attacks. Khronos involves changes to the NTP client's system process only. Since it does not affect the wire protocol, the Khronos mechanism is applicable to current and future time protocols.

For the definition of Status, see RFC 2026.

For the definition of Stream, see RFC 8729.

Advanced Search