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The Joy of Cryptography

joyofcryptography.com

21–30 of 105 posts

Re: The Joy of Cryptography

#21
post #4

This is exactly the kind of book on cryptography I need. The book uses math & pseudocode to describe algorithms instead of using popular languages like Python or C/C++. This makes it language agnostic. Code can be very opinionated in my opinion.

I got that same impression from “Applied Cryptography” (Schneier). But Bruce isn’t exactly giving it away! :)

[deleted]

Re: The Joy of Cryptography

#22
post #19
post #13

Earlier quoted context omitted.

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

How did you graduate with a CS degree?

Depends on which country you are in. Not sure eg in Germany you have to do that much calculus for a CS degree.

(Though, what do you mean by calculus? I assume you mean integration and differentiation and real numbers and stuff? Or something else?)

Re: The Joy of Cryptography

#23
post #4

This is exactly the kind of book on cryptography I need. The book uses math & pseudocode to describe algorithms instead of using popular languages like Python or C/C++. This makes it language agnostic. Code can be very opinionated in my opinion.

I don't know mathematic notation well at all, but can easily reason about most code.

They are different notations for different purposes. With some overlap.

In some sense, programming languages are a mathematical notation, too.

Re: The Joy of Cryptography

#24
post #19
post #13

Earlier quoted context omitted.

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

How did you graduate with a CS degree?

In my school, to get the CS degree you only need as much calculus as needed to get to the second Physics course, which covers electromagnetism. You don't need a deep understanding of calculus. A lot of applications of calculus in the course can be handled by rote memorization.

I took extra calculus classes from the math department. Those are way harder than what you need for introductory physics.

Re: The Joy of Cryptography

#25
I've often thought the use of prime numbers to be the weakness in cryptography. Whilst theory is different in practice due to machine limitations, there are only so many prime numbers a machine can present in a limited timespan restricting the range of primes available to use. With this in mind, and then knowing what a webserver will typically use by simply browsing the website with different encryption algo's disabled in the browser if its not possible to work out the underlying webserver software and version from a variety of methods like a simple 404 message, decoding the URL or using DPI, further limits the encryption algorithms to spend time reversing when using the replay attack method making it somewhat more targeted. Its still a sort of brute force but a more targeted brute force.

So should I see primes as a weakness in cryptography?

Re: The Joy of Cryptography

#26

I've often thought the use of prime numbers to be the weakness in cryptography. Whilst theory is different in practice due to machine limitations, there are only so many prime numbers a machine can present in a limited timespan restricting the range of primes available to use. With this in mind, and then knowing what a webserver will typically use by simply browsing the website with different encryption algo's disabl…

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 security, but that's a whole different thing.)

Second, the supply of prime numbers is countable but also infinite, and the relation between a number space and the number of primes within it is well established within the workable sizes. We have upper and lower bounds on the number of primes within certain ranges. This is partly why we end up with certain key sizes as being secure and other key sizes as being insufficient. Secure key sizes (in asymmetric algorithms) partly are secure because there are so many primes that can be fodder for key generation.

Re: The Joy of Cryptography

#27
post #13
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.

If the whole of math were represented by the surface of the planet, "discrete math" would be more than half of it. Calculus (i.e. differentiation/integration on the reals) on the other hand, would be a city. Perhaps a very populated city, but just one.

It's a shame that match curriculum for non-math-majors is an all-roads-lead-to-calculus affair. I think we scare a lot of potentially talented people away from math with that approach.

Re: The Joy of Cryptography

#28

I've often thought the use of prime numbers to be the weakness in cryptography. Whilst theory is different in practice due to machine limitations, there are only so many prime numbers a machine can present in a limited timespan restricting the range of primes available to use. With this in mind, and then knowing what a webserver will typically use by simply browsing the website with different encryption algo's disabl…

Not an expert, but I don't think it's necessarily a weakness in the current applications of cryptography. In something like RSA a typical key is >=1024 bits, which is 1.7e308 possible number so even though primes are more "limited" the actual reduction in security (if non-primes could have been used by magic) the primes that are left are still plentiful. One reason RSA is not really used anymore is because other algorithms such as elliptic curve cryptography provides much better efficiency (partially due to it not requiring primes keys). So it's less efficient than more modern technologies, but not necessarily weaker.

Re: The Joy of Cryptography

#29
post #19
post #13

Earlier quoted context omitted.

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

How did you graduate with a CS degree?

My college just removed Calculus as a requirement...Although that could be partially because they have such a crazy high dropout rate for the compsci program. Graduation rate at the school as a whole is < 50%. I think they average like 10-30 comp sci majors a semester with an average student population of 4,000. Most students get scared off by the psychotic "teach as though this is an ivy league school" new teachers who get fired in two to four semesters because not a single student gives them a positive review.

Re: The Joy of Cryptography

#30
post #13

Earlier quoted context omitted.

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

If the whole of math were represented by the surface of the planet, "discrete math" would be more than half of it. Calculus (i.e. differentiation/integration on the reals) on the other hand, would be a city. Perhaps a very populated city, but just one. It's a shame that match curriculum for non-math-majors is an all-roads-lead-to-calculus affair. I think we scare a lot of potentially talented people away from math wi…

"Calculus" is just the most accessible corner of the broader field of Analysis. And a lot of "discrete" mathematics ends up drawing upon analysis (especially complex analysis) as you delve deeper.
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