Have you setup automatic disk unlocking with TPM2 and systemd-cryptenroll or clevis? Then chances are high that your disk can be decrypted by an attacker who just has brief physical access to your machine - with some preparation, 10 minutes will suffice. In this article we will explore how TPM2 based disk decryption works, and understand why many setups are vulnerable to a kind of filesystem confusion attack. We will follow along by exploiting two different real systems (Fedora + clevis, NixOS + systemd-cryptenroll).

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Physically Based Rendering describes both the mathematical theory behind a modern photorealistic rendering system and its practical implementation. A method known as literate programming combines human-readable documentation and source code into a single reference that is specifically designed to aid comprehension. The book’s leading-edge algorithms, software, and ideas—including new material on GPU ray tracing—equip the reader to design and employ a full-featured rendering system capable of creating stunning imagery.

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The “range” of a force is a measure of the distance across which it can easily be effective. Some forces, including electric and magnetic forces and gravity, are long-range, able to cause dramatic effects that can reach across rooms, planets, and even galaxies. Short-range forces tail off sharply, and are able to make a significant impact only at distances shorter than their “range”. The weak nuclear force, for instance, dies off at distances ten million times smaller than an atom! That makes its effects on atoms rather slow and rare, which is why it is called “weak”.

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That’s really weird! Why would top be using all of my CPU? It says 100% usr in the second line. Sometimes the usage showed up as 50% usr and 50% sys. Other times it would show up as 100% sys. And very rarely, it would show 100% idle. In that rare case, top would actually show up with 0% usage as I would expect. The 2.6.28 kernel did not have this problem, so it was something different about my newer kernel.

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One of the innovations that the V7 Bourne shell introduced was built in shell wildcard globbing, which is to say expanding things like *, ?, and so on. Of course Unix had shell wildcards well before V7, but in V6 and earlier, the shell didn’t implement globbing itself; instead this was delegated to an external program, /etc/glob (this affects things like looking into the history of Unix shell wildcards, because you have to know to look at the glob source, not the shell).

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The research unveils a new attack surface in Windows by exploiting Best-Fit, an internal charset conversion feature. Through our work, we successfully transformed this feature into several practical attacks, including Path Traversal, Argument Injection, and even RCE, affecting numerous well-known applications!

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To render any geometric figure to a GPU (with OpenGL / Direct3D / Vulkan / ...), they must first be triangulated, i.e. decomposed as a series of triangles. Some figures are trivial to transform into triangles: for instance, a segment with thickness is represented by a rectangle, which can be rendered with two triangles. But a segment strip with thickness (aka. polyline) is not trivial.

Ultimately, this exploration has been a rabbit hole, also partly due to some digressions along the path — let’s prototype with a bare implementation of GeoGebra in vanilla JavaScript — let’s do a WebGL + WASM demo to verify the algorithm works correctly ... 😅 At least, it gives some fancy interactive visuals for this blog post. 😁

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In my college Data Structures and Algorithms course, we covered B-Trees, but I didn’t grok why I’d choose to use one. As presented, B-Trees were essentially “better” Binary Search Trees, with some hand-waving done that they had improved performance when used in database applications. I remember needing to memorize a bunch of equations to determine the carrying capacity of a M-degree B-Tree, and a vague understanding of B-Tree lookup/insertion/deletion, but not much else. Which is a shame! They’re interesting structures.

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Rendering outlines is a technique that is often used in games either for aesthetic reasons or for supporting gameplay by using it for highlights and selections around an object. For example in the game Sable, outlines are used to create a comic-book-like style. In The Last of Us, outlines are used to highlight enemies when the player goes into stealth mode.

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This leads down the rabbit hole of how a second is defined. As long as a second is defined as 1/86400 th of a day, and a day is the time it takes for the earth to rotate once on its axis, there’s no cause for confusion. But when you measure the rotation of the earth precisely enough, you can detect that the rotation is slowing down.

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In this post, we will implement a static search tree (S+ tree) for high-throughput searching of sorted data, as introduced on Algorithmica. We’ll mostly take the code presented there as a starting point, and optimize it to its limits. For a large part, I’m simply taking the ‘future work’ ideas of that post and implementing them. And then there will be a bunch of looking at assembly code to shave off all the instructions we can. Lastly, there will be one big addition to optimize throughput: batching.

https://en.algorithmica.org/hpc/data-structures/s-tree/

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Verne’s famed novels Twenty Leagues Under the Sea, Journey to the Center of the Earth, and Around the World in Eighty Days constitute only a fraction of the 54-volume Voyages Extraordinaires, a collection of fiction conceived on the basis of a science we might not think of as a rich field for material.

Actual link: http://verne.garmtdevries.nl/en/maps/originals.html

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What if you had to fight against your company’s culture to bring a revolutionary tool to life? Meet Jeffrey Snover, the Microsoft architect behind PowerShell, a command tool that transformed Windows system administration. Initially met with skepticism, Snover’s idea faced resistance from a company that favored graphical interfaces.

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There are many things to take from this story — about beginner’s mind, the diversity of human experience, and the interoperability of language. But what stood out to me most was two opposing lessons about shared protocols and modularity. Tomás’ experiment failed. It failed because each amateur cartographer injected their own methodology and process, resulting in incompatible maps. But in another sense, Tomás succeeded. Sure, maybe this collection of artifacts would be useless for military strategy or commerce, but on the other hand... LOOK AT THESE MAPS, THESE MAPS RULE.

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Today, the team declared victory. They’ve finally verified the true value of a number called BB(5), which quantifies just how busy that fifth beaver is. They obtained the result — 47,176,870 — using a piece of software called the Coq proof assistant, which certifies that mathematical proofs are free of errors.

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A customer reported that a recent Windows update broke their ability to type a snowman by using Alt+9731. We explained that the update was not at fault; rather, Alt+9731 was never supposed to produce a snowman at all! But the customer insisted that it used to work.

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The Valve.Computer is an 8 bit computer, with the usual 12 bit address and data buses plus the rather unusual current demand of over 200 Amps. It can play a decent game of PONG using its valve and relay RAM, or run a 32 bit Fibonacci sequence using modern NVRAM. After switch on you have to wait a while for the last thermionic valve to warm up. If you look from the side you see a few start to show a red glow.

After visiting Bletchley Park, it occurred to me that several thermionic valve computers had been rebuilt, and now run in museums, but that no new design of a valve computer had been constructed in over 50 years. The thought of building one seemed ridiculous, but I wondered if a modern design could overcome the issues of size, power and the very real danger of high voltages.

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I, sadly, did not get a message from a teenage YouTuber earnestly offering to return my stolen phone. Instead I received a series of texts from someone cycling through a number of different strategies for engaging, convincing, tricking or scaring me into unlocking the phone for them.

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A new ant species, Paraparatrechina neela sp. nov., with a captivating metallic-blue color is described based on the worker caste from the East Siang district of Arunachal Pradesh, northeastern India. This discovery signifies the first new species of Paraparatrechina in 121 years, since the description of the sole previously known species, P. aseta (Forel, 1902), in the Indian subcontinent.

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