Feditarian Fediversalist
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Gli ultimi otto messaggi ricevuti dalla Federazione
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Quizzino della domenica: Strana equazione
784 - algebra
La sonda marziana Curiosity ha trovato delle scritte dell'antica civiltà marziana. Una di esse, una volta decifrata, è la seguente: 5x² − 50x + 125 = 0: x = 5 e x = 8. In effetti 5 è una soluzione dell'equazione, ma 8 non lo è: 5×64 − 50× + 125 = 45. Quante dita avevano i marziani?(trovate un aiutino sul mio sito, alla pagina https://xmau.com/quizzini/p784.html; la risposta verrà postata lì il prossimo me https://wp.me/p6hcSh-91s
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What a hole.
Kiev 60
Zodiak-8 30mm F3.5
Lomography Metropolis
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Even when there’s no accountability, the record matters. Credit to the Wikipedia editors maintaining this page.
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Tamper Detection with Time-Domain Reflectometry
For certain high-security devices, such as card readers, ATMs, and hardware security modules, normal physical security isn’t enough – they need to wipe out their sensitive data if someone starts drilling through the case. Such devices, therefore, often integrate circuit meshes into their cases and regularly monitor them for changes that could indicate damage. To improve the sensitivity and accuracy of such countermeasures, [Jan Sebastian Götte] and [Björn Scheuermann] recently designed a time-domain reflectometer to monitor meshes (pre-print paper).
Many meshes are made from flexible circuit boards with winding traces built into the case, so cutting or drilling into the case breaks a trace. The problem is that most common ways to detect broken traces, such as by resistance or capacitance measurements, aren’t easy to implement with both high sensitivity and low error rates. Instead, this system uses time-domain reflectometry: it sends a sharp pulse into the mesh, then times the returning echoes to create a mesh fingerprint. When the circuit is damaged, it creates an additional echo, which is detected by classifier software. If enough subsequent measurements find a significant fingerprint change, it triggers a data wipe.
The most novel aspect of this design is its affordability. An STM32G4-series microcontroller manages the timing, pulse generation, and measurement, thanks to its two fast ADCs and a high-resolution timer with sub-200 picosecond resolution. For a pulse-shaping amplifier, [Jan] and [Björn] used the high-speed amplifiers in an HDMI redriver chip, which would normally compensate for cable and connector losses. Despite its inexpensive design, the circuit was sensitive enough to detect when oscilloscope probes contacted the trace, pick up temperature changes, and even discern the tiny variations between different copies of the same mesh.
It’s not absolutely impossible for an attacker to bypass this system, nor was it intended to be, but overcoming it would take a great deal of skill and some custom equipment, such as a non-conductive drill bit. If you’re interested in seeing such a system in the real world, check out this teardown of a payment terminal. One of the same authors also previously wrote a KiCad plugin to generate anti-tamper meshes.
Thanks to [mark999] for the tip!
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Feditarian Fediversalist
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@DavidBHimself I guess we will have to agree to disagree on this one.
And yes, I did lose my right to vote when I moved a couple of times, even as a resident+citizen of said location. That’s how our imperfect electoral system works. 😥
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@evan I agree with @EricLawton -- "expatriate" is an imperial term. I see no confusion of terminology in his comment, quite the opposite.
In the context of the poll, "expatriate" was used about emigrants, not immigrants, but the point stands. The clearest term, if a bit long and pedantic, might have been "citizens who are not residents".
