[tptacek]

Using OpenPGP is a bad idea here. All the mainstream rubies have access to high-quality X.509 in their mainline distros without a third-party gem.

Both OpenPGP and X.509 are going to require a little of fiddley semantic details that will take time to hash out. The bottleneck here isn't the technology.

I like, and routinely recommend, OpenPGP for solving app crypto problems. X.509 makes a lot more sense here.