A quartet of researchers from Carnegie Mellon University's Computer Science Department have explained a method they feel makes it possible to memorise several complex passwords.

As their ArXiv paper, Spaced Repetition and Mnemonics Enable Recall of Multiple Strong Passwords explains, passwords are important but most people choose weak ones because they're easier to remember. That's obviously not optimal, so the boffins decided to experiment with a technique called “spaced repetition”, which they describe as “a memorization technique that incorporates increasing intervals of time between subsequent review of previously learned material.”

Spaced repetition will be familiar to anyone who has leaned a language using flash cards: after first encountering knowledge you review it, then review it again after a longer period of time, then again after an even longer interval.

The boffins found test subjects who were asked to memorise four “Person-Action-Object (PAO) stories where they chose a famous person from a drop-down list and were given machine-generated random action-object pairs.” Participants were then shown a photo of a scene and asked to imagine the PAO story taking place in the scene. This produced passphrases like “Bill Gates swallowing bike on a beach” and “Darth Vader bribing the roach on the lily pad”.

12 hours later, participants were later shown an image they'd previously seen when creating their PAO story and asked if they could recall the the passphrases they created. Further tests were conducted “in 1.5 × increasing intervals” out to an interval of 102 days.

As hoped, participants' recall of the passphrases they cooked up improved over time, to the extent that the researchers feel spaced repetition and PAO stories could enable people to recall up to 14 complex passphrases.

The authors suggest their study makes policies mandating fresh passwords every 30 days a bad idea, as “By forcing users to reset their password frequently an organization forces its users to remain within the most difficult rehearsal region.” They also feel that the PAO method is likely to result in the creation of more complex passwords, which is helpful under any circumstances.

It probably didn't hurt that some combinations offered by the boffins can produce pretty funny results. A quick play with the list of people, actions and objects used in the study yields the phrase “Pope Francis popping pill”. ®

Bootnote

The lists of people, actions and objects used in the study.

People: Bill Gates, Bill Clinton, George W Bush, Lebron James, Kobe Bryant, Brad Pitt, Darth Vader, Luke Skywalker, Frodo, Gandalf, Michael Jordan, Tiger Woods, Michael Phelps, Angelina Jolie, Albert Einstein, Oprah Winfrey, Nelson Mandela, Bart Simpson, Homer Simpson, Adolf Hitler, Steve Jobs, Mark Zuckerberg, Justin Timberlake, Jay Z, Beyonce, Kim Jong Un, Joe Biden, Barack Obama, Pope Francis, Rand Paul, Ron Paul, Ben Afleck, Hillary Clinton, Jimmy Fallon.

Actions: gnawing, mowing, rowing, oiling, egging, waving, bowing, seizing, stewing, signing, searing, bribing, swallowing, sucking, saving, sipping, tazing, tattooing, drying, dueling, dodging, tugging, taping, nosing, hunting, numbing, inhaling, knifing, nipping, muddying, miming, marrying, mauling, mashing, mugging, moving, mopping, racing, riding, reeling, reaching, raking, lassoing, welding, aligning, leashing, elbowing, juicing, shining, sheering, judging, choking, chipping, coating, concealing, destroying, kissing, aiming, kicking, punching, canning, combing, gluing, cooking, giving, copying, vising, voting, fanning, fuming, firing, fishing, high fiving, batting, burying, plowing, puking, popping, tasting, pulling, climbing, weeping, swimming, stretching, following, paddling, howling, smelling, rolling, waking, jumping.

Objects: saw, teacup, hen, ammo, arrow, owl, shoe, cow, hoof, boa, sauce, suit, snow, piranha, chainsaw, shark, tiger, snake, razor-blade, sumo, seal, sock, safe, soap, daisy, toad, dime, tire, dish, duck, dove, ant, onion, wiener, nail, navy, menu, mummy, hammer, mail, microphone, horse, rat, iron, ram, pin, roach, rib, lion, lime, leach, lock, leaf, cheese, jet, chain, chime, gyro, chili, jeep, goose, cat, wagon, igloo, couch, cake, coffee, cab, vase, foot, phone, waffle, fish, bus, patty, bunny, bomb, pill, bush, bike, beehive, puppy, kite, canoe, boar, apple, moon, moose, tepee, ditch, key, shoe, home, toe, nose, cheetah.