Yes it does, and I do this with my gems, but it's not widely used and I'm sure virtually none of the users of the gems I author probably take advantage of it.
> However, this method of securing gems is not widely used. It requires a number of manual steps on the part of the developer, and there is no well-established chain of trust for gem signing keys. Discussion of new signing models such as X509 and OpenPGP is going on in the rubygems-trust wiki, the RubyGems-Developers list and in IRC. The goal is to improve (or replace) the signing system so that it is easy for authors and transparent for users.
https://guides.rubygems.org/security/
> However, this method of securing gems is not widely used. It requires a number of manual steps on the part of the developer, and there is no well-established chain of trust for gem signing keys. Discussion of new signing models such as X509 and OpenPGP is going on in the rubygems-trust wiki, the RubyGems-Developers list and in IRC. The goal is to improve (or replace) the signing system so that it is easy for authors and transparent for users.