These release files have been cryptographically signed using the "signify"
program. It is contained within OpenBSD, LibertyBSD and Bitrig, and you can
download a GNU/Linux version here:
https://github.com/aperezdc/signify

To perform the verification, simply download the files SHA256, SHA256.sig and
libertybsd.pub. Then, use the command:
 signify -S -s /home/user/signify-keys/libertybsd.sec -m SHA256 -x SHA256.sig