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Crypto 101 – Introductory course on cryptography

crypto101.io

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Re: Crypto 101 – Introductory course on cryptography

#141

Post by munin »

mSparks wrote: post #136
kaoD wrote: post #17

Earlier quoted context omitted.

Something tells me a conspirator wouldn't be required anyways. Your security is either sound or broken, i.e. probably broken unless you use proven implementations of proven cryptosystems with proven configurations. E.g. even if RSA is (currenly) safe, as well as its primitives and common configuration... rolling your own implementation will probably be subject to timing attacks.

since im not in the market for downvoting. ill just say. eh. RSA is a simple formula. takes a bit of fiddling and skill to get BigIntegers working. but anyone who passed highschool algebra could roll their own. in fact many high schools even set it as homework. timing attacks you say. erm, not remotely connected.

If you implement RSA from the textbook, as a simple formula, you'll leave yourself vulnerable to padding based attacks that can recover the private key. It turns out that though the formulas are straightforward and the math can be explained after a decent undergraduate education, the implementation is still very subtle.

Re: Crypto 101 – Introductory course on cryptography

#142

Post by mSparks »

munin wrote: post #141
mSparks wrote: post #136

Earlier quoted context omitted.

since im not in the market for downvoting. ill just say. eh. RSA is a simple formula. takes a bit of fiddling and skill to get BigIntegers working. but anyone who passed highschool algebra could roll their own. in fact many high schools even set it as homework. timing attacks you say. erm, not remotely connected.

If you implement RSA from the textbook, as a simple formula, you'll leave yourself vulnerable to padding based attacks that can recover the private key. It turns out that though the formulas are straightforward and the math can be explained after a decent undergraduate education, the implementation is still very subtle.

padding attacks are only really related to encrypting data not sharing the product of two very large primes. You clearly havent got the faintest idea what you are talking about.

Rather than putting the rest of us at risk by putting zero value on the security of anything you make and guessing someone [a spook] will do it for you, why dont you recommend everyone takes some time out to at least learn the basics.

Yes, there are several "mines" you need to be wary of.

But they all pale into insignificance compared to linking openssl and thinking you are done.

Re: Crypto 101 – Introductory course on cryptography

#143

Post by mSparks »

marcosdumay wrote: post #108
stcredzero wrote: post #34

Earlier quoted context omitted.

Something tells me a conspirator wouldn't be required anyways. The conspirator is there to teach about Defense in Depth. Systems that rely on just 1 "impenetrable" membrane tend to be brittle. Their failure is catastrophically sudden and complete, like glass breaking. Glass is way harder than steel, but steel structures are much more robust, because steel's ductility allows for partial failures and continued resistan…

Defense in depth mostly does not work (against willful targeted attacks). Software is not the real world where things bend. If a barrier is sane, it will stand, nobody will break it. But no matter how many non-sane barriers you add, you can not turn them into a sane one. The only thing you will achieve is to increase your system complexity and get more bugs as a result.

only one encryption scheme works against "willful targeted attacks" - the one time pad (and even that has potential for going wrong)

All the others are about making the effort required greater than the will to get there in favor of usability.

All the standard libraries stop at "miniscule effort for a state".

And states aren't even "the big boys" anymore.

Re: Crypto 101 – Introductory course on cryptography

#144

Post by kaoD »

mSparks wrote: post #136
kaoD wrote: post #17

Earlier quoted context omitted.

Something tells me a conspirator wouldn't be required anyways. Your security is either sound or broken, i.e. probably broken unless you use proven implementations of proven cryptosystems with proven configurations. E.g. even if RSA is (currenly) safe, as well as its primitives and common configuration... rolling your own implementation will probably be subject to timing attacks.

since im not in the market for downvoting. ill just say. eh. RSA is a simple formula. takes a bit of fiddling and skill to get BigIntegers working. but anyone who passed highschool algebra could roll their own. in fact many high schools even set it as homework. timing attacks you say. erm, not remotely connected.

> timing attacks you say. erm, not remotely connected.

Fine, I'll trust your overwhelming evidence instead of the many timing attacks described against RSA implementations.

Re: Crypto 101 – Introductory course on cryptography

#145

Post by lethargic_meat »

milansm wrote: post #134
eponeponepon wrote: post #3

This is about to eat my weekend, I think! :) Quite seriously, this is exactly what the tech world needs - personally, I know that in terms of understanding of crypto I'm streets ahead of the average Joe, but orders of magnitude behind people who actually know the field. I'm certain I'm far from alone in that set, but the way the world's going means that we with the generalised technical know-how have a moral impetus…

> I'm streets ahead of the average Joe Has anyone seen "streets ahead" being used by anyone else besides Pierce Hawtorn and the OP? I mean, is it widely used now? (I'm not native speaker, obviously)

I'm using it as much as possible just to push it into language.

Re: Crypto 101 – Introductory course on cryptography

#147

Post by mSparks »

kaoD wrote: post #144
mSparks wrote: post #136

Earlier quoted context omitted.

since im not in the market for downvoting. ill just say. eh. RSA is a simple formula. takes a bit of fiddling and skill to get BigIntegers working. but anyone who passed highschool algebra could roll their own. in fact many high schools even set it as homework. timing attacks you say. erm, not remotely connected.

> timing attacks you say. erm, not remotely connected. Fine, I'll trust your overwhelming evidence instead of the many timing attacks described against RSA implementations.

All those attacks are "theoretical". As opposed to actually having been usefull in the wild - FUD (heartbleed otoh.....).

padding -> irrelevent to an RSA public key, everyone has to know the exact modulus and product, even the bad guys (although I recommend keeping public keys relatively secret)

timing -> irrelevent to an RSA public key, there is nothing you can get from how long it takes to decrypt or encrypt even 1024 bits of data (which is more than most impliementations even send), sometimes the exact same data will take 1ms, sometimes 100ms, it depends what else the machine is doing at the time.

Re: Crypto 101 – Introductory course on cryptography

#148

Post by lvh »

FullyFunctional wrote: post #114
lvh wrote: post #58

Earlier quoted context omitted.

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. unaut…

Isn't this the point of [Twitter]NaCl (Bernstein et al)? To provide a library which, when used correctly, makes it harder to make the obvious mistakes? I think it's great, but it doesn't solve the protocol issue.

Sure! But folks don't always use NaCl; they can have all sorts of stuff currently in play.
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