I've just uploaded to GitHub the latest version of the OpenBSD signify tool, extracted from OpenBSD 6.1. Signify is a lean tool for digital signatures that is much easier to learn and use than gpg or similar. All functionality is described in the easily digestible man page. The latest code include support for signing and verify gzip archives, which was not present in the 6.0 version.
This port strives to minimize the delta between the OpenBSD source and the portable version. The complete list of changes from the version shipped with OpenBSD is included in a ~200-line patch