It is so a free source code from Github and very secure.
Have you ever wanted to send confidential information within your work environment, to family or friends, but were afraid to do so over the internet, because some malicious hacker could be spying on you?
Privnote is a free web based service that allows you to send top secret notes over the internet. It's fast, easy, and requires no password or user registration at all.
NOTE: You can also password protect your notes and share the password with your intended receipt as well as set a notification destruction to help you know when the note has been read.
https://privnote.com