Schneier on Security

Jesse Thompson • April 6, 2016 3:42 PM

I’unno, I have yet to use any of these systems yet myself, but I’d imagine a UI like this one to be simple enough.

1: at beginning of the call, app rates call as “not yet secure”. You also have a “is this line clean?” button that simply invalidates the call into a “not yet secure” state again. Interface is colored red; soft, low pitched but psychologically disappointing hum in the background (maybe sobbing, maybe sad song, I’unno) with a sad beep or slightly stronger note or something every now and again to remind you of the insufficient security of the call without materially getting in the way of the call or being anywhere near as annoying as a repeated alarm.. just a sad enough background theme that folks will be prompted not to leave it suffering and get their jobs done.

2: Visual interface clarifies how to secure the line. It’s the standard “read a code to each other” shtick, but instead of numbers or letters we exploit the higher entropy per syllable idea of 1700-3000 easily digestible dictionary words. I’ve always favored my personally groomed list of 2845 for this:
http://lightsecond.com/password_building_block_dict.txt

Each word spoken is far easier to say and far harder to fabricate and FAR far easier to verify on the line than the equivalent 3 and a third numeric digits it would require to match the same level of entropy. Each word could even be paired with a small icon to help the verifier’s brain much more easily digest what is being heard and compare it to what is read from the screen.

I don’t presently know if it’s important or helpful for only one end of the call to read the code to the other, or to use two codes and both ends read one code to the other, but once both callers are satisfied the line is clear the press a “Satisfied now” button to change the interface back to something more happy and fulfilled.

Altogether this approach should be effective to get the people who are most concerned about security to verify the integrity of their connections to begin with (people who don’t care will either press the “satisfied” button right away or else change settings to “I don’t care if my line is clear, leave me alone!”), you’re protected from tricky “dropped call” scenarios because the sad sounds etc pick back up reminding you to reverify, the process feels less like doing taxes or inputting codes into a lock (both can be psychologically intimidating and breed procrastination) and more like some goofy kids game to humor a hyperactive 3 year old and bribe them to leave you alone for a bit.

And it’s very helpful to prevent an interface from feeling intimidating, even to the people who really care, because perceived intimidation leads to the human element failing over time and an increase in mistakes and missed steps.

The fact that people who DON’T care can easily disarm the interface is still helpful to the entire ecosystem because, well they pay the price directly with no meaningful splash damage if they do get MITM’d.. plus there exists no reliable automated way for a third party to know if the players are trying to secure the line or not, and the “satisfied now” button has only client-side effect on the UI, no data is shared with a central server or anything.

To an attacker the effect is: everyone looks e2e secure, and if you attempt an MITM then either you get people who don’t care (which also means they probably are not targets. Or, at least they are on par with people who own door locks but never use them.) or you get people who care enough to follow the procedure, and are not likely to leak sensitive data prior to running the codes.. and noticing that they don’t match, so getting a TON more suspicious and then retrying the call. 😛