ntp should be ported to use NSS library for cryptography.
See the tracking bug for details and links on how it could be done.
What cryptographic operations does NTP use?
From openssl are used functions dealing with certificates, encrypting, decrypting, signing and verification.
An overview of NTP cryptography is here:
I think it's time to close this bug, it looks like the crypto consolidation effort has stopped long time ago and porting ntpd to NSS won't be easy.