Pool
You're invited to a private GPU pool

Two steps on an Android phone.

1
Install Pool
Android asks once to allow the install. Already have Pool? Skip this.
2
Open my invite
Pool opens with your invite. Type your name, tap Ask to join, and show the code to the person who invited you.
Copy the invite instead

Your invite never left this phone: it is the part of this link after “#”, which browsers don't send to any server. Prompts you send later are sealed on your phone.