# How A Hacker Remembers A PIN

If you have more than a few bank cards, door-entry keycodes, or other small numeric passwords to remember, it eventually gets to be a hassle. The worst, for me, is a bank card for a business account that I use once in a blue moon. I probably used it eight times in five years, and then they gave me a new card with a new PIN. Sigh.

How would a normal person cope with a proliferation of PINs? They’d write down the numbers on a piece of paper and keep it in their wallet. We all know how that ends, right? A lost wallet and multiple empty bank accounts. How would a hacker handle it? Write each number down on the card itself, but encrypted, naturally, with the only unbreakable encryption scheme there is out there: the one-time pad (OTP).

The OTP is an odd duck among encryption methods. They’re meant to be decrypted in your head, but as long as the secret key remains safe, they’re rock solid. If you’ve ever tried to code up the s-boxes and all that adding, shifting, and mixing that goes on with a normal encryption method, OTPs are refreshingly simple. The tradeoff is a “long” key, but an OTP is absolutely perfect for encrypting your PINs.

The first part of this article appears to be the friendly “life-hack” pablum that you’ll get elsewhere, but don’t despair, it’s also a back-door introduction to the OTP. The second half dives into the one-time pad with some deep crypto intuition, some friendly math, and hopefully a convincing argument that writing down your encrypted PINs is the right thing to do. Along the way, I list the three things you can do wrong when implementing an OTP. (And none of them will shock you!) But in the end, my PIN encryption solution will break one of the three, and remain nonetheless sound. Curious yet? Read on.

# The Hackaday Store Lives Again!

Once upon a time there was a store where you could find the most amazing Hackaday shirts and other swag. If you managed to get one of the rare Jolly Wrencher adorned shirts back then, it’s probably about worn out by now. Prepare to rejoice, Hackaday has a completely new store packed with T-shirts, tools, and stuff to help you fill up those waking hours with hardware hacking goodness.

We’ve had a little fun over the last couple of days with posts that hint (maybe a bit too subtly?) that this was coming. We always try to have a little bit of fun for those of you who are really paying attention. Now we’re wondering who will be the first to implement the one-time pad as a dedicated piece of hardware… project ideas need to come from somewhere, right?

Take a look around the general store and you’ll see this time we have more than just stuff you wear. Hackers need tools and we’ve selected a small but inspiring group of must-have’s. The kits and toys we’ve selected are surely a rabbit hole of personal challenges and evolving hacks for you. And the best part is that these choices are one more way for us to promote the virtue of Open Design (it is the way). The only question now is what other open hardware do you want to see added to those ranks?

# Running Custom Code On Cheap One-time Password Tokens

One-time passwords (OTP) are often used in America but not so much in Europe. For our unfamiliar readers, OTP tokens like the one shown above generate passwords that are only valid for one login session or transaction, making them invulnerable to replay attacks. [Dmitry] disassembled one eToken (Aladin PASS) he had lying around and managed to reprogram it for his own needs.

Obviously, these kind of devices don’t come with their schematics and layout files so [Dmitry] had to do some reverse engineering. He discovered six holes in a 3×2 arrangement on the PCB so he figured that they must be used to reprogram the device. However, [Dmitry] also had to find which microcontroller was present on the board as its only marking were “HA4450” with a Microchip logo. By cross-referencing the number of pins, package and peripherals on Microchip parametric search tool he deduced it was a PIC16F913. From there, it was just a matter of time until he could display what he wanted on the LCD.

We love seeing tiny consumer hardware hacked like this. Most recently we’ve been enthralled by the Trandscend Wi-Fi SD card hacking which was also one of [Dmitry’s] hacks.