Message Authentication Codes for the Network Time Protocol
Boston University
Boston University
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.