[Cryptography] Heartbleed and fundamental crypto programming practices

[Jerry Leichter]

On Apr 11, 2014, at 1:55 AM, Kevin W. Wall <kevin.w.wall at gmail.com> wrote:
> I'd bet one way that you could clear the password would be to overwrite
> it with random characters or just '*'.... But you likely are leaking is a password length.
The password reader I wrote for the same system I mentioned earlier solved this problem in a way that's so obvious that it's always amazed me no one else has come up with it:  As you type your password, each character echoed as '*'.  When you hit RETURN, the system echoed enough extra '*' characters to make the total echoed a multiple of, say, 10.

You as typist got the feedback needed to know your characters were being recognized as you typed them.  Someone seeing the completed entry would know the length of your password mod 10 - which is of little practical value.  Unless you're a slow hunt-and-peck typist, someone watching the screen had little chance of detecting the difference between the character echoes and the fill echoes.  (Of course the system doesn't have to print all the fill echoes in one shot - in fact, it can echo them with a timing that matches what it's just observed in your own typing.  I didn't get that sophisticated.)
                                                        -- Jerry