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The Joy of Cryptography

joyofcryptography.com

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Re: The Joy of Cryptography

#81

Post by ZoomZoomZoom »

pkage wrote: post #80
ZoomZoomZoom wrote: post #72

Earlier quoted context omitted.

The only negative adjectives I used were "irritating" and "impolite". The first one is strictly my feelings, and if you don't share them, I can only congratulate you on your self-restrain. The second one is just my opinion, I could explain why I think so, but I don't think it's that big of a deal to waste time on further discussions. Just please, keep file naming in mind if you can. No one will come to any harm if yo…

Using negative adjectives is not the only way to be negative.

I don't know what standards you hold me to. I don't know how can you point at what you perceive as an issue and not be negative besides not speaking at all.

Re: The Joy of Cryptography

#82

Post by upofadown »

garmaine wrote: post #78
upofadown wrote: post #62

Earlier quoted context omitted.

To be clear, there is no rational reason not to reach for RSA unless you need the smaller keys of elliptic curves or you are afraid of quantum cryptography and have to avoid elliptic curves as well.

There is a massive performance difference—not just size, but computation as well. Especially if you want a constant-time implementation. There is also an order of magnitude more ways to screw up and not do input validation correctly, thereby introducing vulnerabilities. For all these reasons there aren’t really good libraries for RSA outside of TLS implementations, and that’s a lot of baggage to inherit if you are no…

RSA is faster for signature generation. RSA is faster by more than an order of magnitude for signature verification[1] and encryption[2].

All these libraries listed here are bad in some way for RSA?

* https://en.wikipedia.org/wiki/Comparison_of_cryptography_lib...

[1] https://www.ijser.org/researchpaper/Performance-Based-Compar...

[2] https://hal.archives-ouvertes.fr/hal-02926106/document

Re: The Joy of Cryptography

#83

Post by [deleted] »

tptacek wrote: post #38
slig wrote: post #12

Related question: when using Block Cipher Mode, how does Alice and Bob exchange the IV?

The IV (or the nonce, in an AEAD) is usually public, but authenticated; often just appended to the message; with CBC mode, you'd normally prefix the message with the IV, and include the IV in your HMAC.

[deleted]

Re: The Joy of Cryptography

#84

Post by jimmygrapes »

ZoomZoomZoom wrote: post #59

Again I complain on the irritating habit of non-descriptive naming of files. book.pdf Really? I'm saving the file for a later review and this name will guarantee I either completely lose the file or will spend more time than necessary to locate it. The other option is to rename the file on saving, which is some work which needs to be performed by each user, instead of being done just once on the source. I think this…

I know there are a ton of pitfalls with spaces in filenames, but surely this is not one of the cases where it would apply? Unless your file save dialog replaces spaces for some reason, in which case even %20 is about as readable as _ to me.

Re: The Joy of Cryptography

#85

Post by __MatrixMan__ »

smus wrote: post #79
__MatrixMan__ wrote: post #75

Earlier quoted context omitted.

Yes, I have a degree in it. I'd have to ask around but I know a few algebraic topologists and I'd bet that if pressed to describe their work as more-continuous or more-discrete they'd first tell you that this is a silly way to classify subfields in math and then they'd says it's probably more on the discrete side since it's all about categorizing topological spaces based on whether they have certain discrete properti…

I mean the notion of compactness is inspired pretty clearly from the continuum. I also have a degree in pure math and disagree strongly with your characterization of topology, which is literally defined up to homeomorphism which is itself defined by it's continuity. Arguably the whole point of topology is characterized by that which is preserved by continuous deformation, which clearly is inspired by more continuous…

Yeah, I think you're right.

There's something about real analysis that makes me uncomfortable. I've been struggling for years to put my finger on it. Whatever it is, topology doesn't have it.

I had mistakenly decided that it was an overappreciation of continuity, but I think it must be something else.

Re: The Joy of Cryptography

#86

Post by garmaine »

upofadown wrote: post #82
garmaine wrote: post #78

Earlier quoted context omitted.

There is a massive performance difference—not just size, but computation as well. Especially if you want a constant-time implementation. There is also an order of magnitude more ways to screw up and not do input validation correctly, thereby introducing vulnerabilities. For all these reasons there aren’t really good libraries for RSA outside of TLS implementations, and that’s a lot of baggage to inherit if you are no…

RSA is faster for signature generation. RSA is faster by more than an order of magnitude for signature verification[1] and encryption[2]. All these libraries listed here are bad in some way for RSA? * https://en.wikipedia.org/wiki/Comparison_of_cryptography_lib... [1] https://www.ijser.org/researchpaper/Performance-Based-Compar... [2] https://hal.archives-ouvertes.fr/hal-02926106/document

Your own link [2] shows RSA being 10-50x slower than the EC algo they used, which itself is many factors slower than state of the art. Are you reading the table right?

Re: The Joy of Cryptography

#87

Post by bdamm »

Terry_Roll wrote: post #76
bdamm wrote: post #26

Earlier quoted context omitted.

No. First of all, primes are only used to arrive at a session key, and once you have a session key you're in the land of symmetric algorithms, which provide security by permutations rather than vectoring into prime spaces. The content of a web page does not matter at all in terms of the security being provided. A 404 is just as secure as a valid home page, in terms of cryptography. (Not in terms of application securi…

So in a replay attack all the communication is recorded including the session keys, and whilst primes are infinite dont dispute this, where the theory (human) and the practical (cpu's) differs is the limitations in the machine hardware, in much the same way Spectre and Meltdown exploited the hardware to obtain secrets. The point about the webserver was using methods to work out what the underlying webserver and versi…

Cryptanalysis is a pretty robust area of research. There are in fact a lot of cryptanalysts that know CPUs quite deeply. Certain organizations spend a great deal of money to make it so. If vulnerabilities are found we learn from them and advance the understanding of cryptography design. It has been that way for 76 years now, at least.

Re: The Joy of Cryptography

#88

Post by smus »

__MatrixMan__ wrote: post #85
smus wrote: post #79

Earlier quoted context omitted.

I mean the notion of compactness is inspired pretty clearly from the continuum. I also have a degree in pure math and disagree strongly with your characterization of topology, which is literally defined up to homeomorphism which is itself defined by it's continuity. Arguably the whole point of topology is characterized by that which is preserved by continuous deformation, which clearly is inspired by more continuous…

Yeah, I think you're right. There's something about real analysis that makes me uncomfortable. I've been struggling for years to put my finger on it. Whatever it is, topology doesn't have it. I had mistakenly decided that it was an overappreciation of continuity, but I think it must be something else.

Maybe it's the differential structure itself? Or an (over?)emphasis on the study of functions from space to space instead of the study of the space itself? Or the specificity of calculus (the study of one specific space) instead of the generality of topology (thinking about a lot of spaces and comparing them to each other)

Re: The Joy of Cryptography

#89

Post by nabeelms »

k__ wrote: post #13
le-mark wrote: post #5

> All the sensible textbook titles were already taken. Actual joy not guaranteed. Like a lot of people (I imagine) I made it through a CS bachelors program not really ‘getting’ the discrete math combinatorics part. Crypto is an area where those concepts really really matter. It’s great to see this resource available!

Somehow discrete math was the only math I understood in CS. Calculus, on the other hand, completely eluded me.

My book recommendation for learning calculus would be Calculus Basic Concepts For High School by Tarasov.

Re: The Joy of Cryptography

#90

Post by mavelikara »

ZoomZoomZoom wrote: post #59

Again I complain on the irritating habit of non-descriptive naming of files. book.pdf Really? I'm saving the file for a later review and this name will guarantee I either completely lose the file or will spend more time than necessary to locate it. The other option is to rename the file on saving, which is some work which needs to be performed by each user, instead of being done just once on the source. I think this…

Also, avoid resume.pdf for similar reasons.
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