The tool One Time Secret
is a great solution to securely and relatively simply share a private, encrypted message with someone, just with a link. The link expires after being clicked or 7 days, whichever happens first.
Here’s some more about the service from the creator:
Originally, the idea was to share passwords but since launching the service in 2012 we’ve heard from people all over the world who use it in ways we never imagined. We help people share over 50,000 secrets a month. All of the code is open-source and available on Github
A fair question to ask is: okay, but how can I trust this service to not intercept and read the info? They address this as well:
Why should I trust you?
General we can’t do anything with your information even if we wanted to (which we don’t). If it’s a password for example, we don’t know the username or even the application that the credentials are for.
If you include a passphrase (available under “Privacy Options”), we use it to encrypt the secret. We don’t store the passphrase (only a bcrypted hash) so we can never know what the secret is because we can’t decrypt it.
Beside all that, the code is opensource so you can review the code and/or run your own instance.
My guess is you won’t need a tool like this too often, but if you do, One Time Secret strikes a great balance between ease of use and security.