less_less

36 ms·

1.
by less_less 20d ago
> My belly says the naive formula is summing the triangle pyramid volumes to the origin with sign in orientation. Yeah, that would also work but it's a slightly slower formula, sum(det(v1,v2,v3))/6. This one is summing sort of
2.
by less_less 24d ago
It's still relevant (and probably also rather difficult) to prove that seL4 itself conforms to those best practices.
3.
by less_less 24d ago
Power draw is a side channel, yeah. It's not as easy to exploit in software as timing (including memory timing), but there are software exploits in some cases if it affects the CPU's frequency (HertzBleed) or if it can be read th
4.
by less_less 2mo ago
I agree to some extent with your thesis. But also you don't have to encode all the properties of the program in dependent types everywhere. You can have the implementation contain either no proofs or fairly few (e.g., termination and
5.
by less_less 2mo ago
It isn't balanced quinary, but rather redundant balanced quaternary (base 4). In balanced quinary (base 5), each digit has 5x the significance of the previous one, but in Booth's encoding algorithm it's 4x. If digit i has si
6.
by less_less 2mo ago
It's still a modified base 4, because the significance of the i'th digit is 4^i, not 5^i. Edited to add: I'm also not sure whether real-life implementations have -0 as an option. Of course -0 could be normalized to +0, but i
7.
by less_less 2mo ago
The model usually measures in terms of fixed-size operations, e.g. 2-input binary gates. There's some variation in how to count memory lookups, but even in models where accessing a large memory counts as only one step, any tables pres
8.
by less_less 2mo ago
Yeah, that shift-and-add algorithm is sometimes used on microcontrollers, either in software if there's no hardware multiplier, or in hardware if you want the bare minimum in acceleration at a tiny cost in area. Adds are not really con
9.
by less_less 2mo ago
Residue number systems are really neat! They're sometimes used in crypto implementations, but there you're doing modular multiplication and in most cases the modular reduction then becomes costly, so it's not a free lunch.
10.
by less_less 2mo ago
Hardware multipliers often use a sort of base-4-ish lookup table trick as well, using the Booth-Wallace algorithm. Booth's idea is to rewrite one of the inputs in base (usually) "4", except that the digits go from -2 to +2 i
11.
by less_less 4mo ago
Ah, thanks for the correction. Do I have the soundness bit right? I guess it might apply even if the proof system is only computationally sound, since the simulator has to be efficient, right?
12.
by less_less 4mo ago
Cryptographer here, but this is not my area and I've only skimmed the paper. As far as I can tell, it's a purely theoretical result but a really cool one. Wall of text that might be wrong, as a rough summary of the result as I u
13.
by less_less 5mo ago
I've hung out with a lot of pharma folks, and the business is really complicated. Most of the companies aim to both help people and to make a lot of money, and will choose projects based on some balance of those -- sometimes in dubiou
14.
by less_less 5mo ago
I'm pretty the spec sheet claimed 1000 cycles when I bought my iPhone 17. They do claim it at least for iPhone 15 "under ideal conditions": https://support.apple.com/en-us/101575
15.
by less_less 5mo ago
If I understand correctly, Baillie-PSW has been shown to be correct for all integers < 2^64, so for 64-bit ints you might use (some variant of) that instead of M-R. Edited to add: Sieving has got to be much faster than M-R if you want a
16.
by less_less 7mo ago
I picked Hunter's Point because I used to live near it. The problems from decommissioning radioactive ships are bad, but they're far from the only pollution that was there. Lots of VOCs, solvents, oils, radiation from other stuf
17.
by less_less 7mo ago
Yeah. It's especially relevant for the author's focus on shipbuilding. The old shipyard at Hunter's Point in San Francisco is horribly polluted, and they've been working to decontaminate it for more than three decades
18.
by less_less 7mo ago
The laptop keyborad is good enough, but I'd enjoyed using the Kineses before. I moved long distance and the Kinesis was bulky and didn't make the cut for things to haul. Once I was settled I started looking to set up a proper of
19.
by less_less 7mo ago
In addition to what others have pointed out, many of these aren't actually missing from traditional dictionaries: they're just inflected differently. So your example lists phrases like "operating systems", "immune
20.
by less_less 7mo ago
Glove80 is super nice, though rather expensive. I got one with low-force switches. It's very comfortable to type on, but between the low-force switches and slightly different layout from a regular keyboard (column-staggered, concave,
21.
by less_less 8mo ago
This thread is pretty weird. My phrase "how economists expect you to set it" is probably wrong here, since I'm not an economist, I've just read the most basic theory about how to use this tool, and also used it myself (o
22.
by less_less 8mo ago
I'm not defending "you shouldn't ever need to snipe, just bid your max price" as a hard principle, just trying to explain where the idea comes from. Sniping can be strategic for lots of reasons: you don't have to c
23.
by less_less 8mo ago
It's not supposed to be some red line absolute max price, but rather "how much is this item worth to you?" You set that as your max bid price. If you get it at auction for less than that, you got a good deal, but if you buy
24.
by less_less 8mo ago
See also the paper Ribbon filter: practically smaller than Bloom and Xor : https://arxiv.org/abs/2103.02515 , which is a similar idea though not by the same authors. IIRC, binary fuse filters are faster to construct th
25.
by less_less 9mo ago
Another answer to this: https://en.wikipedia.org/wiki/Cayley–Bacharach_theorem A second special case of this theorem is Pascal's theorem, which says (roughly) that a variant of the elliptic curve group law also wo
26.
by less_less 11mo ago
Annoyingly, while that d = e^-1 usually isn't used in practice (except in cases where you care about side-channel / fault resistance more than the 4x speedup), the Carmichael totient itself still is used in practice. At least if
27.
by less_less 11mo ago
Do the standards require strong primes for RSA? I think FIPS doesn't ... it gives you that option, either for the legacy reasons or to get a proof with Pocklington's theorem that (p,q) really are prime, but just choosing a random
28.
by less_less 1y ago
The intro textbook descriptions of cryptographic systems omit a lot of very important details. When using RSA to sign a message m, in practice you don't send m^d mod N. That would generally be insecure, depending on what kinds of mess
29.
by less_less 1y ago
Internally, most signature algorithms use hash functions. RSA-PSS, EdDSA and ML-DSA use them to provide something like randomness, and the security analysis of those signature schemes includes arguments assuming (in some very particular, t
30.
by less_less 1y ago
As I understand the paper, the point is that Fiat-Shamir does *not* give a correct proof of the program's output. They gave a (maliciously constructed) program whose outputs are pairs (a,b) where certainly a != b (instead the program i

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