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Crypto 101 – Introductory course on cryptography

crypto101.io

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Re: Crypto 101 – Introductory course on cryptography

#51

Post by sorokod »

stcredzero wrote: post #12

When I was taking Aikido, there was a day when the sensei was going through all of our techniques and showed how the uke (initiator of the attack, receiver of the technique) could turn things around on the tori . (receiver of the attack, initiator of the technique) It seemed like there were a half dozen ways each that a technique could go seriously wrong, and that many of them didn't require much skill, only determin…

The act of reversing a technique is called "kaeshiwaza". Kaeshiwaza is possible only if there there is an opening (weakness) in the waza.

That is all there is to it.

Some examples here https://www.youtube.com/watch?v=C_SB0TqvUb8

Re: Crypto 101 – Introductory course on cryptography

#52

Post by htrp »

eponeponepon wrote: post #19
dom0 wrote: post #14

Earlier quoted context omitted.

> I really have no way of verifying if I'm learning the correct DHE, and I know that it's easy to get wrong. Perhaps I can do some testing in code, but I may test it incorrectly too, and those small errors can be exploited. Well this is step 0 in cryptography engineering: You don't implement primitives. Use reviewed components providing primitives and implement your protocol on top of that. Step -1 is to not design y…

There's a difficult rabbithole here - eventually you have to draw a line and decide to trust someone . Otherwise it's just layer after layer of paranoia until you implode in a puff of Philip Dick :)

The only problem with that is that at some point you get into outright (justified or not) paranoia. Is your computer the victim of a supply chain attack? Did someone intercept your switch/router in delivery?

Re: Crypto 101 – Introductory course on cryptography

#54

Post by tptacek »

Raed667 wrote: post #30

I'm really disappointed that (9.4) Elliptic curve cryptography is still under TODO. If anyone is interested in ECC, ars has a pretty good introduction [0]. [0] : http://arstechnica.com/security/2013/10/a-relatively-easy-to...

You can also mail Sean Devlin to get Set 8 of the Crypto Challenges, which cover ECC. Finding the right place to mail I'll leave as an exercise for the reader.

Re: Crypto 101 – Introductory course on cryptography

#56

Post by __jal »

daenney wrote: post #41
dom0 wrote: post #20

Earlier quoted context omitted.

Of course; my point is (and I assume that's also the point of other people who assert similar stances on the topic) that the average programmer or software engineer should leave these things to recognized cryptographers. This also highlights a peculiarity with cryptography, in that it is very hard to understand for laymen (assuming laymen are ppl with some CS or math education), so most arguments in discussions of la…

> Of course; my point is (and I assume that's also the point of other people who assert similar stances on the topic) that the average programmer or software engineer should leave these things to recognized cryptographers. If "crypto is for cryptographers" is your stance I think you're doing yourself a disservice. Understanding crypto, as in learning the foundations of it, is important for everyone. Having a good gra…

I agree that everyone should learn more about crypto. It helps people understand what is actually going on, and what they can count on and not count on.

Engineers working around crypto that will be responsible for anything important, even doing seemingly simple things like feeding the entry point a password, need to either have their code audited by someone with experience here, or be a person who could audit it. This is because there are so very many ways that seemingly inconsequential things (function timing, hardware behavior in the face of voltage manipulation, nonzero-ed memory in deallocated buffers... and these are the more obvious things) that can lead to a break.

And that's really only a starting point... this stuff is hard. I won't try to write it other than for my own amusement.

Re: Crypto 101 – Introductory course on cryptography

#58

Post by lvh »

dom0 wrote: post #43
dom0 wrote: post #20

Earlier quoted context omitted.

Of course; my point is (and I assume that's also the point of other people who assert similar stances on the topic) that the average programmer or software engineer should leave these things to recognized cryptographers. This also highlights a peculiarity with cryptography, in that it is very hard to understand for laymen (assuming laymen are ppl with some CS or math education), so most arguments in discussions of la…

To clarify: I didn't mean that people shouldn't learn or read about the topic, or try designing their own block or stream ciphers, hashes, KDFs and of course protocols (which are great fun!), not at all. Both my original comment and this one are directed at production use of cryptography.

Hi! I'm the author of Crypto 101.

I couldn't agree more. I think the fact that we have so much crypto foot guns available is a UX issue that we should address. Ideally, Crypto 101 would only be to satisfy one's own curiosity; not mandatory reading for anyone who wants to do something cryptographic. Alas, that's also not the world we live in right now. Realistically, plenty of crypto libraries will offer up e.g. unauthenticated AES-CBC. Then you probably want to know about some of the attacks on that, why you want a MAC, and where that MAC should live; if only to convince your coworkers that the concerns you have are real.

Re: Crypto 101 – Introductory course on cryptography

#59

Post by baby »

TrinaryWorksToo wrote: post #9

With everything in Crypto I have to wonder: Is the information correct? I really have no way of verifying if I'm learning the correct DHE, and I know that it's easy to get wrong. Perhaps I can do some testing in code, but I may test it incorrectly too, and those small errors can be exploited.

You learn about DHE reading this. You implement DHE following specs and standards.

Re: Crypto 101 – Introductory course on cryptography

#60

Post by lvh »

TrinaryWorksToo wrote: post #9

With everything in Crypto I have to wonder: Is the information correct? I really have no way of verifying if I'm learning the correct DHE, and I know that it's easy to get wrong. Perhaps I can do some testing in code, but I may test it incorrectly too, and those small errors can be exploited.

Hi! I'm the author of Crypto 101.

Firstly, I'm a real, honest-to-God cryptographer. I don't know if there are any particular people you had in mind whose recommendations you'd like to see, but there are a few HN bigwigs who'd probably be willing to generally endorse it :-) Also, it's been posted on HN a few times before, so it's had some scrutiny. That doesn't mean I don't make mistakes, but generally speaking, an active reader should be OK.

The other thing is in the way the book is structured. I teach you to break crypto; so when I say something is broken, I prove it by showing you how to break it.

Finally, the goal of this book is absolutely not to help you implement DHE. In an ideal world, the primitives we offer people are hard to misuse. Crypto 101 then only exists to satisfy programmer curiosity. It is not a replacement for a traditional academic education that will help you design new primitives; it also doesn't show you how to write secure implementations. However, Crypto 101 is still useful beyond merely satisfying curiosity now, because most cryptographic libraries _do not_ provide that easy-to-use API. Using regular hashes for password storage, various forms of broken AES-CBC (unauthenticated, key=IV, static IV...), et cetera are very real problems for real code, and Crypto 101 teaches you how to avoid that minefield.

I'm also working on the "better, more accessible" crypto part, but I only have so much free time :)

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