OpenNTPD - now with OpenSSL support
For a few weeks, I've been working on implementing OpenSSL support and vastly improved configurability to OpenBSD-based NTP daemon OpenNTPD. Both of which I have done now. OpenNTPD is written in C. See the implementation on GitHub - openntpd-openssl.
I run a Linux server infrastructure with time-critical daemons such as Kerberos and Bind9 DNS server. Therefore, I see it's essential to have a local, secure NTP server software.