In the context of cryptography, authentication means "ensuring that the message you got comes from who you think it did".
Authentication is how we prevent the man-in-the-middle attack.
Authentication is one of the hardest parts of cryptography, because the only truly secure way to do it is by driving to the other party yourself to establish a pre-shared key so you can do message authentication code. Or to share your public key with them if you are satisfied with the safety of post-quantum cryptography.
What if Process 1 tries to access
0x00003000, which is not present?The hardware notifies the software via a Page Fault Exception.
When an exception happens, the CPU jumps to an address that the OS had previously registered as the fault handler. This is usually done at boot time by the OS.
This could happen for example due to a programming error:but there are cases where it is not a bug, for example in Linux when:
int *is = malloc(1);
is[2] = 1;- the program wants to increase its stack.It just tries to accesses a certain byte in a given possible range, and if the OS is happy it adds that page to the process address space, otherwise, it sends a signal to the process.
- the page was swapped to disk.The OS will need to do some work behind the processes back to get the page back into RAM.The OS can discover that this is the case based on the contents of the rest of the page table entry, since if the present flag is clear, the other entries of the page table entry are completely left for the OS to to what it wants.On Linux for example, when present = 0:
- if all the fields of the page table entry are 0, invalid address.
- else, the page has been swapped to disk, and the actual values of those fields encode the position of the page on the disk.
In any case, the OS needs to know which address generated the Page Fault to be able to deal with the problem. This is why the nice IA32 developers set the value of
cr2 to that address whenever a Page Fault occurs. The exception handler can then just look into cr2 to get the address.
Neon isotope line split photograph by J. J. Thomson
. Source. J. J. Thomson took this picture in 1912:
There can, therefore, I think, be little doubt that what has been called neon is not a simple gas but a mixture of two gases, one of which has an atomic weight about 20 and the other about 22. The parabola due to the heavier gas is always much fainter than that due to the lighter, so that probably the heavier gas forms only a small percentage of the mixture.
How to decide if an ORM is decent? Just try to replicate every SQL query from nodejs/sequelize/raw/many_to_many.js on PostgreSQL and SQLite.
There is only a very finite number of possible reasonable queries on a two table many to many relationship with a join table. A decent ORM has to be able to do them all.
If it can do all those queries, then the ORM can actually do a good subset of SQL and is decent. If not, it can't, and this will make you suffer. E.g. Sequelize v5 is such an ORM that makes you suffer.
The next thing to check are transactions.
Basically, all of those come up if you try to implement a blog hello world world such as gothinkster/realworld correctly, i.e. without unnecessary inefficiencies due to your ORM on top of underlying SQL, and dealing with concurrency.
By Andy Haas, an experimental particle physics professor: as.nyu.edu/content/nyu-as/as/faculty/andy-haas.html What an awesome dude!
It is true that one image is worth a thousand words, but unfortunately it is also true that one image takes up at least as much bytes as a thousand words!
Having one single page to rule them all is of course the ideal setup for a website, as you can Ctrl + F one ToC and quickly find what you want.
And, with Linux Kernel Module Cheat Ciro noticed that it is very hard to write so much intelligent prose that becomes larger than reasonable to load on a single webpage.
He then started using this technique for everything he writes, including this page and Chinese government.
However, if there are too many images on the page, the loading of the last images would take forever in case users want to view the last sections.
There are two solutions to that:
- be traditional and create separate web pages
- be bold and load images as they appear on the viewport: stackoverflow.com/questions/2321907/how-do-you-make-images-load-only-when-they-are-in-the-viewport/57389607#57389607Edit: OK, it was standardized with
loading=lazy, without need JavaScript!Now the last awesome thing would be a method that loads first images in viewport, then those below, and then those above, that would be the ultimate solution.This question comes close: stackoverflow.com/questions/7906348/change-loading-order-of-images-already-on-page
Ciro is still deciding between those two. The traditional approach works for sure but loses the one page to rule them all benefits.
The innovative approach will work for interactive viewing, but archive.org will fail to load the images for example, and there may be other unforseen consequences.
Wikimedia Commons is awesome and automatically converts and serves smaller versions of images, so always choose the smallest images size needed by the output document. Readers can then find the higher resolution versions by following the page source.
This also comes to mind: motherfuckingwebsite.com
zettelkasten.de/posts/overview/ from zettelkasten:
How many Zettelkästen should I have? The answer is, most likely, only one for the duration of your life. But there are exceptions to this rule.
FFmpeg is the assembler of audio and video.
As a result, Ciro Santilli who likes "lower level stuff", has had many many hours if image manipulation fun with this software, see e.g.:
- the "Media" section of the best articles by Ciro Santillis.
- Figure "Ciro knows how to convert videos to GIFs"
As older Ciro grows, the more he notices that FFmpeg can do basically any lower level audio video task. It is just an amazing piece of software, the immediate go-to for any low level operation.
FFmpeg was created by Fabrice Bellard, which Ciro deeply respects.
Resize a video: superuser.com/questions/624563/how-to-resize-a-video-to-make-it-smaller-with-ffmpeg:Unlike every other convention under the sun, the height in
ffmpeg -i input.avi -filter:v scale=720:-1 -c:a copy output.mkvscale is the first number.Projects:
899 USD as of 2022, takes a year to ship as they gather up a lot of orders before producing.
Sounds so cool, especially the multi functionality. Shame so expensive.
Are particles bounced by the first wall in the double slit experiment? Updated 2025-03-28 +Created 1970-01-01
It would be amazing to answer this with single particle double slit experiment measurements!
- bb41a757f405890fb0f5856228e23b715702d714d59bf2b1feb70d8b2b4e3e08 999,657 bytes. Joins a bunch of tiny inputs into a single output
- 623463a2a8a949e0590ffe6b2fd3e4e1028b2b99c747e82e899da4485eb0b6be and 5143cf232576ae53e8991ca389334563f14ea7a7c507a3e081fbef2538c84f6e both have 3,075 outputs of 1 satoshi each and a single input. We were not able to identify any meaningful data in it,
filejust saysdata, and there aren't long ASCII strings. However, the outputs were unspent as of 2021, which suggests that they might actually be data.
Analysis of some of them follows.
- dd9f6bbf80ab36b722ca95d93268667a3ea6938288e0d4cf0e7d2e28a7a91ab3 has 13107 with payload 256KB in size, but some of them at least have been spent: www.blockchain.com/btc/tx/dd9f6bbf80ab36b722ca95d93268667a3ea6938288e0d4cf0e7d2e28a7a91ab3 therefore it's not data.
filesays their payload is a DOS executable, but it must be a coincidence
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