One-Touch Keypad Masher





Introduction: One-Touch Keypad Masher

About: I’m a researcher and PhD candidate at Brunel University in London, specialising in design for behaviour change for social and environmental benefit, and I also do consultancy as Requisite Variety, much of wh...

Wasting valuable seconds typing in a code every time you need to open the door?

This little 'device' streamlines the process by pressing the right keys for you, and can be hidden in your palm so you simply mash your hand against the keypad and - apparently miraculously to anyone watching - unlock the door in one go.

Time to make: Less than 10 minutes
Time saved: About 30 seconds per day in my case; your mileage may vary.
Payback time: 20 days, in this case

Background: The research group I work in was moved to a new office. In the old place, I'd got used to an RFID card in my pocket allowing me to open the door just by leaning against the sensor, but the new office had a keypad on the door. It was going to use an extra 5-6 seconds every time I needed to get in the office!

There had to be a better way...

Step 1: Combinations Rather Than Permutations

Let's say the code given to us for the keypad was "C13259" (it wasn't, by the way, in case you're in west London and feel like trying).

First off, we realised that it was unnecessary to type the "C" (clear) at the start unless the previous person to try had entered the code wrongly. That cut maybe half a second off the time taken to enter the code.

But then we noticed something: the code had a sequence of digits ("132") that weren't in numerical order - yet when they were typed in numerical order ("123"), the door still opened. That is, this model of keypad is a combination lock rather than a permutation lock. It didn't matter what order you typed in the code, as long as you typed in all the digits that made it up. You could type "1-3-2-5-9" or "3-2-1-9-5" or "9-2-3-5-1" or any other arrangement.

The other crucial point was that these keys didn't have to be pressed separately - i.e. not only was there no requirement for the digits to be in the 'right' sequence, there was no requirement for there to be a sequence at all. Thinking about how a simple mechanical lock like this works, that ought to be obvious.

So, if we could press multiple keys at once, we could save a lot of time. If you angled your hand just right, it was just about possible to press all the keys required at once, but it was pretty awkward.

We really needed to make some kind of device which did that. But we couldn't just press all the keys, or press any wrong ones: whatever device we made needed to press only the right keys.

The simplest thing to do seemed to be to make something which, when held onto the keypad, pressed the right buttons.

Step 2: Working Out the Layout

I started by drawing a grid over the keypad, and filling in the cells that I wanted to be pressed at the same time (first image).

Then, looking at how these were actually arranged, it seemed easiest to fill in gaps between adjacent keys that need to be pressed (second image).

And, to ensure that the device lined up correctly with the keypad, i.e. no incorrect keys were pressed, it seemed sensible to put a frame of sorts along two edges (third image).

Step 3: Making the 'keypad Masher'

Now, since the example code I've used in this article isn't the real code, the layout of the device I made is slightly different to the one shown here. But it ought to be good enough to demonstrate one way of doing it.

I took a scrap piece of "Cay Foam", a plastic foam board which used to be available from C & A Building Plastics (though it doesn't seem to be any more) and cut it with a scalpel into a backing sheet, and individual strips and bits which could then be put together to make the right layout.

You could use thick cardboard, MDF, acrylic, anything - even a sheet of something with pins or nails stuck into it at the right points. If you have access to a bandsaw, router or milling machine you could produce something quite beautiful. The Cay Foam is ugly, but it was very quick to cut by hand, at my desk!

Mirroring the layout from the previous step, copy it onto the backing sheet, and then stick the strips/bits on in the right places. I used double-sided foam tape; you could use superglue or anything really; you may want the pieces to be repositionable at some point (e.g. if you make a mistake, or if the code is changed).

Step 4: Try It Out!

That's it, pretty much - try the keypad masher out: check that it works, that it only presses the right keys and doesn't press any others. With the 'frame' pieces along the two edges, I found it easy to line it up OK on the keypad.

The first few times you might find it easiest to hold it between finger and thumb (first two images) to make sure you can line it up correctly, and to get a feel for how much force you need to use. But fairly soon you'll be able to palm the masher and hide it (third image). If you become skilled enough at doing it in a fluid motion, it really can look (to anyone else walking past) as if you're just slamming your palm against the keypad and somehow unlocking the door...

If you're so minded, it would be easy to improve the fit of the masher into your hand, giving it more comfortable edges or making it from something transparent or flesh-coloured so it's even easier to hide. Or make a set of keypad masher knuckledusters, where it looks like you're literally punching the keypad with your fist to get access. Or an elbow-pad!

Alternatively, you could stick the key-pressing bits on the back of a card which looks like some kind of official access card anyway, so that you appear to have a kind of contactless swipe card that simply needs to be pressed against the keypad.

Some risks: Don't label your masher with the code, or the room number. You're basically creating a device which changes the security of the keypad from a"what you know" method (a code) to a "what you have" method (a key). If you lose it, and it has the room number on it, then it's equivalent to losing a key with the room number written on it.

Be careful, but have fun!



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    21 Discussions

    It's not really analogue to digital, the lock is a very simple mechanical one, no electronics at all

    dude why not make a mold of the key & cast a copy out of something sturdy & then it would be great. P.S. GREAT instructable.

    Unfortunately, working for the gov't our keypad lock have buttons with LED displays on them and the number arrangement changes randomly every time you enter the code. Clever idea nonetheless.

    1 reply

    smashing things with hammers always works... I bet it'll open the door to new opportunities... by that i mean you'll get fired and you'll have a new opportunity of picking out a job..

    >replaces all locks with biometric locks and puts certain lock company out of business

    Even the best biometric fingerprint lock to date can be hacked open with a little bit of preparation :)

    Nice! Only suggestion to make it even easier that I can think of is try using shapelock, which is oddly appropriately named for this application. You could either shape it by hand or just mold it over the lock, then fill in the divots corresponding to the keys to be pressed with more shapelock(you might need to heat gun it a bit to get it to stick). Disclaimer: I'm not affiliated with shapelock, I just buy the stuff and love it. It's basically moldable plastic, reuseable, and almost as handy as duct-tape. I thought of it immediately when I saw where you were going with this instructable. Regrettably, the locks I have to deal with are "cyberkeys", which have sequences you have to push in order. So I'm gonna go see about some solenoids...

    1 reply

    Good idea! I have some Polymorph which I think is the same stuff as Shapelock - could certainly allow a quick mould of the keypad to be made!

    There must be some clever roller-action device (player piano-esque) that could deal with pressing keys in sequence... or like you say, solenoids!

    Lol I've seen those locks alot, now I know how open them! Cilk some of the keys once I did that if its wrong press C first! Thanks now I can "picklock"!

    4 replies

    To be fair none of the above actually lets you pick the lock!
    There are still 1,287 combinations you'd need to try, i.e. from 13 choose 5:

    Combinations = n! / (r! (n-r)! ) = 13! / (5! 8!) = (6.227E9) / (120 x 40,320) = 1,287

    - assuming the correct code has 5 digits and you can't repeat any digits. With these locks the code can be set to between 4 and 7 digits I think, though I might be wrong.

    So I guess it would depend how long you're willing to stand there trying all the combinations before someone notices! Much more secure keypad locks are available - e.g. if the order of the digits was important (i.e. a permutation lock) there would be 154,440 permutations to try...

    Are the 3 other letters (X, Y, Z) valid options for the lock? Or is it 0-9? Even a binary number (each key is either on-or-off) with 10 digits is only 1024 options... If there is a restriction that the key must be a certain length, like 5 digits, that actually REDUCES the complexity of the code in this case, 5 must be off, 5 must be on. If that was the case, then there are only 252 different options, and I would bet that most people would do like the posters example, and choose either the left or right item going down the row, making those 32 values much more likely. 32 combos could be pushed in a couple of minutes.... Wow, this lock is INSECURE. Also.. just a helpful hint: Typing "13 choose 5" in Google returns 1287. Those guys are amazing!! :)

    and if you chose 6

    13! / 6! (13-6)

    13 x12x11x10x9x8x7x6! 13x12x11x10x9x8 1235520
    = = =

    6! x 7x6x5x4x3x2 6x5x4x3x2 720

    1716 combinations. (7 would also be 1716)

    my division signs got cut out. but the point is that there are 1716 combinations if you choose 6 or 7 good work Dan Lockton

    Dude, That is so awesome! If I ever work someplace with a lock like that, this is the first thing I'm going to try. Thanks for the awesome 'ible!