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 1.8, 2, and 3 of this specification are normative and can contain the terms MAY, SHOULD, MUST, MUST NOT, and SHOULD NOT as defined in RFC 2119. Sections 1.5 and 1.9 are also normative but cannot contain those terms. All other sections and examples in this specification are informative.