fontconfig should be ported to use NSS library for cryptography.
See the tracking bug for details and links on how it could be done.
Upstreamed, but not closing.
Fontconfig only has an internal implementation of MD5. Does that count?
Upstream is happy with it and closed WONTFIX.
Reopen if you know what it should be using NSS for.
What is the internal MD5 hash used for?
Hashing: to create a directory name to use for caching contents of a font directory.