Simple Encryption You Can Do On Paper

It’s a concern for Europeans as it is for people elsewhere in the world: there have been suggestions among governments to either outlaw, curtail, or backdoor strong end-to-end encryption. There are many arguments against ruining encryption, but the strongest among them is that encryption can be simple enough to implement that a high-school student can understand its operation, and almost any coder can write something that does it in some form, so to ban it will have no effect on restricting its use among anyone who wants it badly enough to put in the effort to roll their own.

With that in mind, we’re going to have a look at the most basic ciphers, the kind you could put together yourself on paper if you need to.

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Voja Antonic: Designing The Cube

Voja Antonic designed this fantastic retrocomputing badge for Hackaday Belgrade in 2018, and it was so much fun that we wanted to bring it stateside to the Supercon essentially unaltered. And that meant that Voja had some free time to devote to a new hardware giveaway: the Cube. So while his talk at Supercon in November was ostensibly about the badge, he just couldn’t help but tell us about his newer love, and some of the extremely clever features hidden within.

It’s funny how the hardware we design can sometimes reflect so much on the creator. Voja designed then-Yugoslavia’s first widely used home computer (and published the DIY plans in a magazine!). Thousands were built from their kits. The Galaksija was a Z80-based design with a custom BASIC that was just barely squeezed into the available 4K of ROM. So you shouldn’t be shocked that the retro-badge has a working keyboard and a nice BASIC on board.

But let’s jump ahead to the Cube, because that’s even more of a passion project. On the outside, they’re very simple devices, with only a USB port and a sweet diffused LED ring visible. Aesthetic? Minimalistic? Beautiful, honestly.
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Encryption For The Most Meager Of Devices

It seems that new stories of insecure-by-design IoT devices surface weekly, as the uneasy boundary is explored between the appliance and the Internet-connected computer. Manufacturers like shifting physical items rather than software patches, and firmware developers may not always be from the frontline of Internet security.

An interesting aside on the security of IoT traffic comes from [boz], who has taken a look at encryption of very low data rate streams from underpowered devices. Imagine perhaps that you have an Internet-connected sensor which supplies only a few readings a day that you would like to keep private. Given that your sensor has to run on tiny power resources so a super-powerful processor is out of the question, how do you secure your data? Simple encryption schemes are too easily broken.

He makes the argument for encryption from a rather unexpected source: a one-time pad. We imagine a one-time pad as a book with pages of numbers, perhaps as used by spies in Cold-War-era East Berlin or something. Surely storing one of those would be a major undertaking! In fact a one-time pad is simply a sequence of random keys that are stepped through, one per message, and if your message is only relatively few bytes a day then you have no need to generate more than a few K of pad data to securely encrypt it for years. Given that even pretty meager modern microcontrollers have significant amounts of flash at their disposal, pad storage for sensor data of this type is no longer a hurdle.

Where some controversy might creep in is the suggestion that a pad could be recycled when its last entry has been used. You don’t have to be a cryptologist to know that reusing a one-time pad weakens the integrity of the cypher, but he has a valid answer there too, If the repeat cycle is five years, your opponent must have serious dedication to capture all packets, and at that point it’s worth asking yourself just how sensitive the sensor data in question really is.

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.

Quick, What’s My PIN?

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.

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THP Semifinalist: NSA Away

Back when we started The Hackaday Prize, security, big brother, and the NSA were making headlines every day. Since that time, there has been enough bread and circuses in the news to wipe the consequences of these leaks out of the public consciousness, but work is still being done by hackers and tinkerers the world over to give you the tools to protect your data.

NSA Away is one of these tools. The first part of the project is a standalone key generator that writes the same random bits to a pair of SD cards simultaneously. With their random number generator, this is perfect encryption. The only way to crack the one time pad the team is using for encryption is to 1) use parts of the pad more than once, 2) have a terrible RNG, or 3) do something really stupid like sell the one time pad in a store.

The other part of the build is an Android-based encryption device with a camera, keyboard, SD card reader, and a USB port. This device reads the ‘OTP SD cards’ and reads data with the camera using OCR and decrypts it on the screen. Provided the OTP doesn’t fall into the wrong hands, this is a perfectly secure way to transmit data to anyone.

As far as progress goes, the members of the team have a fully functional pad generator, writing random data to SD cards. This device can also output random bits to a computer as a USB HID device, should you want to transmit your pad over unsecured mediums.

It’s an impressive bit of work, especially in the RNG department. The team is using eight avalanche noise generators in the circuit description. This part of the build isn’t quite working yet, but that’s really not needed for a proof of concept.

SpaceWrencherThe project featured in this post is a quarterfinalist in The Hackaday Prize.

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?