Message Authentication Codes for the Network Time Protocol

Document Type Replaced Internet-Draft (ntp WG)
Last updated 2017-04-29 (latest revision 2016-10-26)
Replaced by draft-ietf-ntp-mac
Stream IETF
Intended RFC status (None)
Expired & archived
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Stream WG state Adopted by a WG
Document shepherd No shepherd assigned
IESG IESG state Replaced by draft-ietf-ntp-mac
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This Internet-Draft is no longer active. A copy of the expired Internet-Draft can be found at


The Network Time Protocol (NTP) RFC 5905 [RFC5905] uses a message authentication code (MAC) to cryptographically authenticate its UDP packets. Currently, NTP packets are authenticated by appending a 128-bit key to the NTP data, and hashing the result with MD5 to obtain a 128-bit tag. However, as discussed in [BCK] and [RFC6151], this is not a secure MAC. As such, this draft considers different secure MAC algorithms for use with NTP, evaluates their performance, and recommends the use of CMAC-AES [RFC4493]. We also suggest deprecating the use of MD5 as defined in [RFC5905] for authenticating NTP packets.


Aanchal Malhotra (
Sharon Goldberg (

(Note: The e-mail addresses provided for the authors of this Internet-Draft may no longer be valid.)