I have also built something similar, I knew of the existence of cipherhub, but my goal was to focus on the ease of use, with the browser (https://mailbeam.io and https://github.com/bobbywilson0/gh-message). I do admit that my solution is not as easy as it should be yet.
You should consider with RSA keys have a limited size message that can be encrypted (e.g. for 2048 bit keys you are limited to 256 bytes in your message). My solution was to use the SSH key to encrypt the secret I used to encrypt the message with.
You should consider with RSA keys have a limited size message that can be encrypted (e.g. for 2048 bit keys you are limited to 256 bytes in your message). My solution was to use the SSH key to encrypt the secret I used to encrypt the message with.