NTP - securing with MD5 authentication and a Windows NTP server

Network Time Protocol (NTP) on Cisco IOS devices supports MD5 authentication to secure NTP communications. However, the Windows NTP server  which uses Windows Time Service (W32Time), does not natively support MD5 authentication for NTP as Cisco devices do. If you want to use MD5 you will have to look for another NTP server solution such as using a Linux server with the NTP daemon "ntpd."