Additional password protection

[RChutchev]

I propose to add an additional layer of security - password protection.
When I create a message, I want to be able to add an additional password to decrypt the message.
The people who opened that message then have to provide a password (maybe a pin) to decrypt that message.
The message should only be shown to those who provide the password.

[axtonprice]

I've transferred this discussion to an issue. Thanks