1 Introduction

The Network Time Protocol (NTP) Authentication Extensions consist of two authentication extensions that extend the Network Time Protocol (NTP) version 3, as specified in [RFC1305], and the Simple Network Time Protocol (SNTP) version 4, as specified in [RFC2030].

[RFC1305] Appendix C describes a mechanism similar to the authentication extensions documented here. The extensions documented here provide a strong checksum algorithm and use keying material that is readily available to systems joined to a domain.

SNTP, as specified in [RFC2030], provides a simplified version of NTP. [RFC2030] section 4 refers to the Authenticator field of [RFC1305] Appendix A; the first extension documented here replaces that referral and specifies the way in which an SNTP message exchange can be secured; the second extension defines an ExtendedAuthenticator field that extends the NTP version 3 message format.

Sections 1.5, 1.8, 1.9, 2, and 3 of this specification are normative. All other sections and examples in this specification are informative.