signify was (is) developed on OpenBSD-current and depends on a few features only found there. The first signed OpenBSD release, 5.5, will also be the first release to include signify. What to do if you’re running OpenBSD 5.3 or 5.4 and want to verify the 5.5 release you just downloaded is legit? You need the signify backport.
It’s all the necessary files packed into one directory. It should work on a few previous OpenBSD releases, and possibly other BSD systems, but beyond that it’s a lost cause. I don’t have much interest in making a true portable version.
This tgz also includes the set of public keys for 5.5 and 5.6. Building is simple. Run make and make install.