Encryption In The 1790s

July 23, 2026 by Al Williams 12 Comments

For as long as humans have had writing, there’s been a need to send secret messages. It is easy to think that Enigma machines and their immediate predecessors are old tech, but they are much more recent than ancient systems used by the Greeks and Romans. Even Thomas Jefferson, one of the founding fathers of the United States, was interested in encryption and is often said to have invented the Jefferson Disk machine for encryption. The truth is, the device is probably older than Jefferson, but he certainly thought about using it for secret communications.

Simple but Effective

Thomas Jefferson was, apparently, a fan of secret messages

The idea is simple. We make a series of disks. Each disk has a number on it and, around the edge, all the letters of the alphabet. The placement of each wheel with the same number is the same, but, overall, the arrangement is random. That is, all disks marked #5 might start with XCBYG, but all disks marked with #10 could start with FAYQL. You take one set of disks, and I keep the other set.

When we want to send secret messages, we agree to arrange our disks on an axle in the same order. Jefferson used a 36-disk system, so we might agree to go left to right with the odd numbers first and then the even numbers, or any other setup that we could agree on.

Encryption

Once the wheels are in place, encryption is simple. There’s a bar across the device, and you line up your message using a wheel for each letter: ENEMYCOMESBYSEA, for example. Then you look at any different row, which will now read something crazy like: FSRSSXQCGAEEFOR (plus the random letters on the rest of the disks). That’s the message you send.

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Postal IRCs Are Almost A Thing Of The Past

July 21, 2026 by Al Williams 16 Comments

Have you ever found out that something you remember from your youth is now gone, and you didn’t even notice? If you are a certain age, you might feel that way when I deliver the news: You haven’t been able to buy International Reply Coupons (IRCs) at a US Post Office since early 2013. By the end of 2026, you won’t be able to buy them anywhere. The age of the IRC is over.

What’s an IRC?

If that didn’t mean anything to you, you might be too young to remember, or maybe you just weren’t into shortwave listening or ham radio. Although there were other reasons to get IRCs, a radio hobby is the most likely reason a Hackday reader would have bought an IRC.

For radio purposes, here’s the problem. You’ve worked on your station for months, and one winter night, you finally pull in that rare station from Luxembourg. They’ll send you a QSL card to verify that you heard them. You only have to send them a letter telling them what time you heard them, what frequency, and some details about the program you heard. But they probably don’t want to pay the postage required to send hundreds or thousands of cards overseas.

While this is a radio-specific problem, you might find the same issue with pen pals or when trying to buy things from an overseas company.

SASE

If everyone were in the same country, the solution would be easy. Take a stamp, put it on an envelope that has your address on it, and stuff it in with the letter. Or, you could just drop a stamp or two in the letter you sent.

The problem is, US postage won’t help Radio Luxembourg. On the other hand, the effort required for you to buy postage that works in Luxembourg would have been a nightmare.

Enter the UPU

The Universal Postal Union is a UN agency that is effectively an association of post offices in 192 countries. Their charter is to facilitate mailing things worldwide.

The IRCs date back to 1906. The idea is you buy an IRC at your post office. You send it to Radio Luxembourg, or wherever. There, the mail person at the radio station could go to their post office and trade the coupon for enough local postage to send a surface letter worldwide.

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Launching Rockets Is Hard, Bringing Them Back Is Harder

July 20, 2026 by Tom Nardi 19 Comments

Since the first V2 rocket sailed above the Kármán line back in 1944 and right up until the modern era, the trajectory of most space-bound rockets was more or less the same: after expending their propellants they would either crash into some desolate steppe or plunge into the ocean. In either event, the rocket was disposable. The important bit up top might go on to explore the stars or send a human crew off on their mission, but the booster rocket that lifted the spacecraft out of the atmosphere was always going to be sacrificed for the cause.

But in the 1970s NASA had a wild idea: what if we didn’t smash a brand-new rocket valued at millions of dollars into the ocean every time we wanted to put something in orbit? Instead, they would build a hybrid space vehicle that blended the vertical takeoff and raw power of a rocket with the capabilities of an airplane, allowing it and whatever it was carrying to make a gentle runway landing at the end of its mission. As such, the Space Shuttle was born.

With the benefit of hindsight, we now know the Shuttle wasn’t quite the spaceflight revolution that NASA had hoped for. The age of reusable rockets didn’t truly begin until 2015, when SpaceX landed the first stage of their Falcon 9. To date they’ve repeated the feat nearly 600 times, all the while increasing the reliability and speed of their operations. Today the Falcon 9 is the most prolific launch vehicle in history, and nearly every other rocket in active development is being designed to include some element of reusability.

Most recently, China demonstrated that they could recover their Long March 10B rocket by gently bringing it down into what amounts to a giant butterfly net. While it might seem a bit quaint compared to rockets that land on their tails like something out of a 1950s sci-fi movie, the idea offers considerable promise.

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The Death Of Physical Media And The Real Challenges To Software Archiving

July 13, 2026 by Maya Posch 30 Comments

Along with the many displays of outrage, gnashing of teeth and other displays of profound grief at the recent news that Sony will no longer manufacture physical game discs come 2028, we have also heard some voices pipe up with a variety of statements, such as that this decision makes game archiving basically impossible. Of course, the truth of the matter is that software archiving in general has become much harder already over the past decades, while game consoles are just late to the archiving-hostile party.

As an example, one merely has to contrast Sony’s PlayStation with e.g. the Valve Steam store and software by juggernauts like Adobe and Autodesk. Here the former moved after the Creative Suite (CS6) series of Photoshop and other tools fully over to the Creative Cloud (CC) subscription model, where DRM and constant rental software renewals are in order. Unlike that disc copy of CS6 Master Collection that will stay good practically forever, there’s nothing really to archive with Adobe’s CC software.

Similarly, with digital game downloads and their constant patches now put inside a heavily encrypted environment that relies on a special launcher, preserving video games has been turned into into a virtual nightmare for many years now.

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Ultra-Long Range Flights To Ease Australian Air Travel

July 6, 2026 by Zoe Skyforest 72 Comments

Pity the poor Australians. Isolated on a jagged hunk of land far from everywhere else, these industrious people have to take two-legged flights (or more) to reach a great many destinations in the northern hemisphere. It’s expensive, time consuming, and makes planning a trip a complete headache when wars break out around popular hub airports.

One airline is trying to solve this problem. The nation’s flag carrier, Qantas, has been hard at work on Project Sunrise. The goal is to run some of the longest non-stop commercial passenger flights ever, with great effort going into solving the technical and economic challenges involved.

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Know Your Food: Organic Production

July 2, 2026 by Jenny List 37 Comments

A few weeks ago we published the first in a new series of articles, Know Your Food. It was born out of the realisation that most people know surprisingly little about what they eat, and to apply a bit of Hackaday curiosity to received opinion on the subject. As we put it then: “To know both how common foodstuffs should be made, as well as how they are made industrially, should be an essential for everyone” We’ll continue in that vein, with a look at organic food.

If you buy your food in a supermarket it’s likely that in the vegetable aisle you’ll be presented with a choice. On one hand you will have the normal vegetable, and on the other and usually for a slightly higher price, the organic version of the same vegetable. What’s going on?

So What Is This Organic Stuff All About?

A watercolour picture of a bucolic scene with a farmhouse surrounded by trees, and some cows in the foreground. — It is unlikely that a typical organic farm in the 2020s will resemble this John Constable painting. John Constable, Public domain.

Organic production is a system of agriculture that emphasises natural fertilisers, pesticides, and farming methods over synthetic or intensive ones. It has its roots in the first half of the 20th century, and as the decades progressed it has become an important sector of agricultural industry. I grew up steeped in organic agriculture because my grandfather was an early adherent in the years following the war, so I’ve seen it from the sharpest end. There is a lot to commend organic production for and plenty of reasons to embrace it, but with that come some problematic aspects, and even dubious claims. Here I’ll try to unpick some of that.

It’s tempting to believe that all organic production is somehow a return to a 19th century rural idyl, complete with the obligatory chickens in the farmyard. Some organic producers do take a slice of this back-to-the-land approach to their craft, but the reality of organic farming is a very modern approach to managing the ecosystem. Organic farmers are not wary of progress, and neither are they reluctant to use pesticides or other chemicals. Instead they do so according to the principles of organic agriculture, so any techniques they use are designed to be beneficial to the ecosystem, and any chemicals have a natural origin. Continue reading “Know Your Food: Organic Production” →

UDP Broadcasting And Easily Finding Network Services

July 1, 2026 by Maya Posch 25 Comments

Local area networks (LANs) that use technologies like Ethernet and Wi-Fi are incredibly useful for letting devices talk with each other. Yet a core problem here is knowing which devices are where on the network, as anyone who has ever tried to add a network printer or network share to their system can probably attest to. Unless you happen to know the IP address of the LAN device, the port, and protocol, the target device may as well be located on the Moon without further help, such as automatic network discovery in lieu of waddling over to the device and reading the label listing its IP address.

Over the decades quite a few ways have been developed to enable such network discovery, with many of them using UDP broadcast as the first step. By broadcasting a global message on the entire LAN, any device that has an actively listening UDP socket on that particular port can parse said message and decide whether it’s feeling sociable enough to reply.

The topic of UDP broadcasting is however not as straightforward as it may sound if you’re just getting started, including the existence of many opinions on the ‘right way’. There is also a massive divide between a sprawling service discovery protocol like mDNS and a light-weight one like that one that I had to implement a few years ago for an open source project.

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