Feature Suggestion: Decrypt/Encrypt in UI

The Keybase app (Mac OS X) is great and convenient for many functions, but seems to lack the ability to quickly encrypt/decrypt a block of text. For example, if a non-Keybase user Slack's me a PGP-encrypted block of text, I'd like to be able to copy/paste it into Keybase and have it decrypted.

The issue concerns the Mac OS X Keybase app and requests copy/paste encryption and decryption for blocks of text, but it names no files, tests, or entry points. Start by locating the app's existing encryption and decryption UI, then define the supported input and output behavior; done means users can encrypt and decrypt pasted text in the UI.

Written by the indexing model from the issue text.