What3Words as a password generator

One of my coworkers shared an interesting site last week. What3Words assigns a three-word “address” to every 3m-by-3m square on Earth. The idea behind the site is that many areas of the world don’t have street numbers and names, and a three-word combination is much easier to remember than latitude/longitude pairs. Similar combinations are deliberately placed far apart so as to make them unambiguous.

It’s an interesting idea, but I immediately began thinking of a different use for it. What if people used it to come up with long, memorable, and hard-to-guess passwords? After all, the longer a password is (generally speaking), the better it is. And while correcthorsebatterystaple might be amusing, it’s much easier to remember a place. So you pick a memorable spot on the map and now you have a long password that you can look up if you forget it.

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XKCD "Password Strength" by Randall Munroe. Used under the Creative Commons Attribution-NonCommercial 2.5 license.

This method isn’t perfect. The main problem is that with a 3x3m grid, it’s very sensitive to differences in location. But especially for the technically unsavvy, it can be a good way to enable better password habits.

Sidebar: why Randall Munroe is wrong (-ish)
There’s another reason What3Words isn’t perfect, and the XKCD cartoon above is subject to the same weakness. If a password cracker knows people are mostly using concatenated words, they’ll start guessing combinations of words instead of combinations of characters. These sorts of passwords are stronger when they’re rare. Of course, there are trivial ways to mitigate the risks (insertion of special characters, selective capitalization, etc.).

Still, given the choice between a 20-character random string and a 20-character set of words, I’ll take the random string as my password (unless the site/app disables paste, in which case I’ll cry). I use a password manager precisely so I don’t have to worry about trying to balance security and memorability. The What3Words method could be helpful as a password for my password safe, though.