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/sci/ - STEM

Science, Technology, Engineering, and Mathematics

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simple identity verification scheme Anonymous 21/05/26(Wed)23:24 No. 17567 ID: 424a5a [Reply]
17567

File 162206427582.jpg - (73.22KB , 720x631 , 5cd8d122da5b12f670c8f07be0639902da5dfb1598d709c992.jpg )

Once, while idly wondering, I came up with a simple scheme to prove the authenticity of a chain of messages given the authenticity of the first.

It consists of putting a hash at the end of each message (but the last, if you know where the chain is going to end) and the input to the previous hash at the beginning (or anywhere really) of each subsequent message.

That's it. It's really simple but I was wondering if it had a name?

SHA256 Hash: d29bde9ef6607caa1f99bd06434449bb972bae43718a7701b2e878bc5fe452a7


3 posts omitted. Click Reply to view.
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Anonymous 21/05/29(Sat)03:05 No. 17580 ID: be6f8f

>>17578
Oh! You mean you include in each message the input to the hash in the previous message. Sorry, I misunderstood. What you're referring to is known as proof of knowledge.

>Also, blockchains have consensus mechanisms such as PoS, FBA and PoW.
A blockchain is merely a data structure where each block is linked to the previous block (or some number of blocks) via a hash. It does not imply a distributed system. Even if there is a distributed system, the consensus algorithm can be as simple as "whatever the authoritative source says", which is pretty much how Git is typically used.

>>17579
>I said prove authenticity "given the authenticity of the first", not absolutely.
If that's all the assurance you want, you could also include your ECDSA public key in the first message and the signature for each subsequent message. Then you wouldn't need to keep track of which secret message you used as input to the previous hash.
Needless to say, neither method protects you if the site's operator decides to rewrite you messages.

>All in all, it seems like a pretty useless protocol compared to something like RSA or Lamport signatures. Oh well, it might end up being useful as part of something else, or in a different form.
Well, you're just using it wrong, I'd say. Proofs of knowledge are typically used to prove that you had a piece of information at an earlier time that you decide to disclose that information. For example, you might make public a hash predicting that the stock market will crash this week, and after it crashes you make public that information, which should hash into the previous hash.


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Anonymous 21/05/29(Sat)18:11 No. 17581 ID: 424a5a

Previous password: "Rose Mary"

>>17580
I've heard of proofs of knowledge. Though I dont think I've heard of them by that name.

> you could just use ECDSA
How fast is it to generate an ECDSA keypair and sign messages? IIRC RSA is slow compared to this scheme.

Next hash: 5fcb6406566e4cbe34ceb9ee0cc2cf02f729842c369936763b550101ae8c7354


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Anonymous 21/05/29(Sat)20:55 No. 17582 ID: 746924

>>17581
IIRC, almost all naturals less than 2^256 are valid Secp256k1 private keys, so picking a private key is just a matter of getting a few random bits. I think there were exactly two points on the curve that were unusable; one was an inflection point with only a single solution to the equation and the other's tangent was vertical.
Other curves may work differently, although I think all ECDSA curves are more or less the same with only the coefficients changing. As I recall, Curve25519's curve is somewhat different.

Signing a message with ECDSA is faster than RSA, but slower than getting a SHA-256 digest, because the process involves hashing the message. In particular, Secp256k1 uses SHA-256.




Anonymous 21/04/01(Thu)14:03 No. 17402 ID: ecff09 [Reply]
17402

File 161727861988.png - (1.08KB , 128x128 , C__Data_Users_DefApps_Windows Phone_AppData_INTERN.png )

Some loser was talking shit about my trivial zero explainayion but it was objectively better than all of the ones I got and this is inaeguable and edgy losers n 4chan Sci are just trying to patch manipulate me lol.


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Anonymous 21/04/01(Thu)20:11 No. 17404 ID: 746924

[Trivial zero] explanation, or trivial [zero explanation]?

Also, what the fuck are you talking about, OP?




Sad Anonymous 20/08/29(Sat)19:17 No. 16978 ID: 7d5109 [Reply] [First 100 posts] [Last 50 posts]
16978

File 159872145911.jpg - (206.22KB , 1024x913 , 1598435986073m.jpg )

https://www.bbc.com/news/science-environment-39054778
>Science is facing a "reproducibility crisis" where more than two-thirds of researchers have tried and failed to reproduce another scientist's experiments, research suggests.
>"It's worrying because replication is supposed to be a hallmark of scientific integrity," 

Why do people treat the scientific method as some kind of universal solution to everything when in fact it is flawed?


260 posts and 18 images omitted. Click Reply to view.
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Anonymous 21/03/26(Fri)08:40 No. 17380 ID: a5f8ec

>>17378
Genetics in general disprove evolution. The only way to ”prove” it is by making up scenarios in a computer or to insert billions of improbable mutation events wherever you cannot close the gaps.


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Anonymous 21/03/29(Mon)21:29 No. 17392 ID: 0a320d

>>17378
>I've never heard of genetic homeostasis. Kind of ironic that there is a genetic process that prevents speciation.
Think of it in terms of "if it ain't broke, don't fix it".

We simplify it so that people think that if something evolves a benefical trait then it will proliferate across the species and if it evolves an undesirable one it won't. The reality is many desirable traits die out before they can establish themselves in a species, and contrary to popular belief, many undesirables ones don't and do become established. The hallmark of evolution is that more desirable traits propergate than undesirable ones and this is in large part due to Darwin's theory, 'survival of the fittest', you are less likely to survive to adulthood (and reproduce) if you have undesirable traits compared to a specimen that has desirable ones.

To put it in human terms; just because you're stronger/smarter than someone else doesn't mean you're guaranteed to reproduce more than them (assuming you do at all).


>>17380
Still waiting on your theory.


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Anonymous 21/06/10(Thu)21:07 No. 17645 ID: e47187
17645

File 162335204530.jpg - (83.33KB , 600x600 , Rab78d25602c96313a9264185a1b5ccdd.jpg )

>>16978
>>16981
>science is a religion for atheists
I for one am not an atheist, oh fool who has been brainwashed and indoctrinated for most, if not all of his life, by kosher filth. I'm an Agnostic.
>YOU GOTTA BELIEVE
Faith is by no means a bad thing, but its what you believe and have faith in that matters, NOT just believing in something. Also, The Bible never says where exactly heaven is. Facts don't change and numbers by their own dont' lie. Just because someone misinterprets some pieces of data doesn't automatically invalidate it.You by your faith in the worthless Jesus of Nazareth (as with Muslims having faith in and their praying 5 times a day to ""ALLAH"") are giving energy to human hating entities that don't really care about you in ernest; you have been manipulated and lied to by the Jews/Hebes and their Reptilian masters.




Overrated robot threat Anonymous 17/12/01(Fri)00:40 No. 16587 ID: e4210a [Reply]
16587

File 151208524377.jpg - (54.24KB , 823x540 , 08902844.jpg )

So I've read the n:th alarmist article about how robots will replace some 800 M people before 2030 and so fucking on. It will be an endless summer citizen's wage afternoon until the AI exterminates us and so fucking on.

Tell you why this is not going to happen?


28 posts and 3 images omitted. Click Reply to view.
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LickmyBumHole 21/01/02(Sat)06:36 No. 17185 ID: 549c03

No you will probably become a shitty technician working 12 hour shifts everyday and earning 3$ per hour


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Anonymous 21/01/16(Sat)16:38 No. 17210 ID: ccd333

>>17119
we can see the precursor for the robot revolution right now. people should put down the screens. there is evidence they are being used to brainwash and manipulate people against their best interests. it could be argued that it is the most powerful weapon of warfare being used on the stage today simply because of it's pervasiveness and almost ubiquitous use across all the world.

and what happens? the owners of the screens win because they have power over the mind. the robots will also have power over the mind in that they will do hard jobs easily which feels nice not to have to do hard jobs. but in that pleasure will come the pain of losing your usefulness to society and your being discarded and the horrible pain of withering away.

do you ever ask yourselves why we are here because what is happening here cannot possibly be of any merit or value? it's just evil run amok and why else should that be other than to teach a lesson?

if i had power i would squash it out and so would any other. but in my leadership my errors would come to light because i am not perfect. and in those failures would i be the cause of pain and sorrow and misfortune.

the answer is that none of us can be god. and we have to have the power to become god, yet never once touch the temptation of it, to ever return to our souls.

or maybe nothing matters in which case fuck you all, i'll believe my story because it makes me feel better. you can do coke and fuck whores. everyone has their drug then, right? pretty sure your habits fuck you up just as much as believing there's some purpose to your suffering.


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Anonymous 21/02/01(Mon)08:36 No. 17235 ID: 9c6f38

>>17210
Man, you sure are a capitalism bootlicker if you think your only worth to society is your slave labor. Or perhaps you lack the imagination to figure out how you can improve the lives of those around you other than punching a clock and earning a paycheck.




Epic stomach tumour 20/07/24(Fri)13:20 No. 16962 ID: c6e9b2 [Reply]
16962

File 159558962384.jpg - (53.71KB , 377x640 , cfd4854fc546e42d75f0bedceafd9479.jpg )

I'm looking for the name of the persons in this story.

In the summer of 1995, there was a family of three that toured Europe in search for a "alternative" cures. The daughter had a huge stomach tumour. She looked pregnant and had to be ride in a stroller.

The authorities took away the custody of her. And she had to take tumour shrinking meds before the tumour could be removed. Because it was so entangled in the organs.

Pic unrelated, because it is prettier to look at than random tumour pics.


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Epic+stomach+tumour 20/07/24(Fri)17:00 No. 16963 ID: c6e9b2

>>16962
Ah, found info:

https://en.wikipedia.org/wiki/Ryke_Geerd_Hamer#Olivia_Pilhar_case


>>
Anonymous 21/01/27(Wed)02:42 No. 17229 ID: 69598f

what the fuck




rtyrtyr 21/01/16(Sat)17:48 No. 17214 ID: eae170 [Reply]
17214

File 161081572888.jpg - (27.85KB , 800x600 , Blue hills.jpg )


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Anonymous 21/01/23(Sat)13:31 No. 17225 ID: 3cecd6

wtf?




/cyb/erpunk general Anonymous 17/05/04(Thu)19:59 No. 16494 ID: b47205 [Reply]
16494

File 149392075238.jpg - (1.96MB , 1760x2332 , creepy_chan_nosebleed_by_catman103.jpg )

Nosebleed Edition

What is Cyberpunk?
It's complicated.

https://lainchan.jp/cyb/res/115.html#115
http://www.cyberpunkforums.com/viewtopic.php?id=361
https://www.reddit.com/r/Cyberpunk/wiki/about
https://www.neondystopia.com/what-is-cyberpunk/
http://www.cypunk.com/whatis.php
https://en.wikipedia.org/wiki/Cyberpunk

Cyberpunk Communities
https://8ch.net/cyber/
http://www.cyberpunkforums.com/
Message too long. Click here to view the full text.


8 posts and 1 image omitted. Click Reply to view.
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Anonymous 17/06/06(Tue)10:30 No. 16520 ID: 21f956

shoo, shoo kalyjew


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Anonymous 17/07/27(Thu)10:57 No. 16530 ID: a10255
16530

File 150114583073.jpg - (6.34KB , 120x90 , _.jpg )


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rtyrtyr 21/01/16(Sat)17:47 No. 17213 ID: eae170
17213

File 161081567771.jpg - (103.07KB , 800x600 , Winter.jpg )




Anonymous 15/11/18(Wed)03:47 No. 16245 ID: dd0d0b [Reply]
16245

File 144781482117.jpg - (8.25KB , 256x197 , Choice.jpg )

Best STEM degree?


6 posts omitted. Click Reply to view.
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chaosreader 16/06/13(Mon)19:49 No. 16329 ID: 898619
16329

File 146584018745.png - (8.12KB , 225x225 , images.png )

I'm guessing HVAC repair would be the best STEM major for you. Really though, study what you want to learn about. Look at your college's 300 (or 3000) level classes and above. Decide which ones you want to do. Find twenty of those in the same major and that's your major. If you can't find a job after you graduate sign up at your local state U for a master's certificate in something you can get a job at. (not master's degree, certificates are 5 -6 classes, about a year / tear and a half of night school)


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Anonymous 20/12/29(Tue)21:57 No. 17178 ID: 6cedb9

What


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Anonymous 21/01/16(Sat)16:44 No. 17212 ID: ccd333

>>16245
Why is this so complicated?
You want to find a nice girl to marry and a job that people are going to need you for.

You don't need to tell everyone your second degree is mathematics. If you think a second degree in mathematics is going to help you do something people need, then go for it. But the degree itself is just bragging and misleading. It's not the degree. It's you.

You are the ship you need to sail. We do not all sail the same. Master your craft, whatever it is, and people will like you.




Anonymous 20/12/29(Tue)21:59 No. 17179 ID: 6cedb9 [Reply]
17179

File 160927557560.jpg - (3.14KB , 200x125 , C__Data_Users_DefApps_Windows Phone_AppData_INTERN.jpg )

Why is the moon no longer called a planet?


1 post omitted. Click Reply to view.
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Anonymous 21/01/10(Sun)18:45 No. 17198 ID: a2857d

It is a planet from a philosophical perspective but not the scientific perspective..
So before science was mature, it was probably called a planet.


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Anonymous 21/01/11(Mon)00:06 No. 17199 ID: 0a137a

>>17198
>It is a planet from a philosophical perspective but not the scientific perspective..
>So before science was mature, it was probably called a planet.

Back before we knew of other planets there were three* entities in the sky, the sun, the moon and stars. The sun and moon are pretty unique in the sky, it's hard to get them mixed up with anything else. Stars were a different matter and came in two varieties, (fixed) stars and wandering stars:

- (Fixed) stars are the stars we know today, static points of light that barely move relative to each other even as the night sky itself moves.

- Wandering stars were "stars" that appeared to move across the night sky. These are what we have since identified as planets, comets and such.

*in some early cultures clouds were also treated as part of the same sky.


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Anonymous 21/01/16(Sat)16:40 No. 17211 ID: ccd333

because it has completely submitted to earth's gravity.




Need maffs help please Anonymous 20/07/28(Tue)15:45 No. 16969 ID: 1c4573 [Reply]
16969

File 159594390335.jpg - (404.94KB , 2000x1333 , blue-bog-oak-table.jpg )

I am making a table with hexagons spaced 3/16th of an inch apart filled with epoxy. The table is approx. 30" deep and 6' long. I need to know the volume of epoxy required to pour 1/4" thick for this table.


4 posts and 1 image omitted. Click Reply to view.
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Anonymous 20/12/09(Wed)03:36 No. 17101 ID: 74097f

Why not cover it with plastic. Pour water in to the depth you need. Pour the water into a measuring cup and maybe add a little more for the wetted volume on the water not in the measuring cup. Fast, cheap accurate.


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Anonymous 20/12/29(Tue)22:01 No. 17181 ID: 6cedb9

Bumpers.


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Anonymous 20/12/31(Thu)20:40 No. 17183 ID: 677189

volume = height * (length*width - nHexagons * areaOfASingleHexagon)

The area of a hexagon is 3*sqrt(3)/2*a^2, where a is the length of one side.

But really you're going to make too much epoxy, so just get it close and then add a little more to be safe. I'm guessing you've done this before, but if you don't degas your epoxy before you pour it, you're not going to get the results you want.

>>16973
Why the everloving fuck would you subject anyone to the imperial system and then use a conversion calculator when he can measure in centimeters and then end up with volume in cubic centimeters, which is already equal to the volume in mL by definition?





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