Introduce

https://www.openkeychain.org/ - github

OpenKeychain for Android helps you communicate more privately and securely, compatible with the OpenPGP standard.

Application

K-9 Mail

https://k9mail.github.io/ - github

K-9 Mail is an open source email client focused on making it easy to chew through large volumes of email.

Reference

  1. https://www.openkeychain.org/
  2. http://openpgp.org/software/openkeychain/
  3. https://en.wikipedia.org/wiki/OpenKeychain