And you can compose them from "pre shared" secrets. For example, the password hint for a secret I send to my sister: - The name of our neighbors cat - The na

And you can compose them from "pre shared" secrets. For example, the password hint for a secret I send to my sister: - The name of our neighbors cat - The name of your first boyfriend who scratched dad's car - Mom's nickname for aunt Ilda Concatenate those three with a dot. And voila, a pretty secure password without need of a side channel. (just made this up, I don't have a sister...)