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How I implemented my own crypto

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Re: How I implemented my own crypto

#301

Post by lisper »

tptacek wrote: post #295
lisper wrote: post #293

Earlier quoted context omitted.

> Is it possible that you are expecting the cryptography community to be one organized around being newbie-friendly and encouraging to beginners? Not at all. I'm not actually expecting anything. All I'm saying is that as a matter of common courtesy (in any field) if you're going to say, "You just have to know X" then you should do at least one of the following: 1. Check that if someone doesn't know X that they can ge…

If someone posted a message on HN about doing DIY appendectomies with Arduino-controlled robots and I pointed out that you need to go to med school to do surgeries, you would not in fact be harping on me for not having explained why.

Not at all.

If I don't know how to sign up for med school, I can find out by searching for "How do I sign up for med school?" or even "How do I become a doctor?"

If I search for "How do I sign up for crypto school" the results are far less helpful.

Re: How I implemented my own crypto

#302

Post by TylerE »

lisper wrote: post #298
brians wrote: post #273

Earlier quoted context omitted.

Carry propagation is one pixel in the 4K movie that is safe crypto implementation. One reason not to link to trivia and factoids about safe crypto implementation is that it builds a dangerous false sense of competence. There are programs that teach this, but they take years. Nobody who's passed through that is interested in creating an easy scaffolding whose levels are unclear.

> Carry propagation is one pixel in the 4K movie that is safe crypto implementation This is exactly the sort of thing I'm talking about. This is semantically equivalent to, "If you don't already know this, then you are too stupid, and my time is too valuable, for me to do anything beyond pointing out that you are stupid and my time is valuable." That may be true, but it's not helpful. > There are programs that teach…

With all due respect, some things should only be done by trained professionals.

Crypto is one of them.

Flying a commercial airliner is another.

Re: How I implemented my own crypto

#303

Post by tptacek »

lisper wrote: post #301
tptacek wrote: post #295

Earlier quoted context omitted.

If someone posted a message on HN about doing DIY appendectomies with Arduino-controlled robots and I pointed out that you need to go to med school to do surgeries, you would not in fact be harping on me for not having explained why.

Not at all. If I don't know how to sign up for med school, I can find out by searching for "How do I sign up for med school?" or even "How do I become a doctor?" If I search for "How do I sign up for crypto school" the results are far less helpful.

I think you are arguing yourself into an absurd corner here, because I know for a fact that you can name off the top of your head five university crypto programs, and I'm sure you realize that for each of the ones you can name, there are 10 more that others can name.

And: for what it's worth, I don't think going to school is the only way to learn this stuff. I just don't think putting end-users at risk, especially since they can't possibly be expected to tell the difference between Dan Boneh and some guy who assembled a broken ECDH out of random npm libraries.

Re: How I implemented my own crypto

#304

Post by [deleted] »

chubot wrote: post #261
lisper wrote: post #258

Earlier quoted context omitted.

> You just have to know what a carry propagation bug is This is one of the things that drives me nuts about the crypto community. The natural response upon reading, "You just have to know X" if you don't already know is to go search for X. Well, if you go search for "carry propagation bug" you will find lots of examples of carry propagation bugs being found and fixed, but no explanation of what one is. The thing that…

Being able to Google unfamiliar terms is table stakes for participating in HN :) http://www.urbandictionary.com/define.php?term=table%20stake...

[deleted]

Re: How I implemented my own crypto

#305

Post by tptacek »

lisper wrote: post #258
tptacek wrote: post #240

I would like to clarify: The thing that I said was "table stakes" for implementing cryptography was passing the algorithm test vectors , which this author's previous post claimed as a security feature. If you're unfamiliar with the concept, a test vector is a series of strings and intermediate values used to ensure that your (say) OCB3 is the same as everyone else's OCB3. Had he asked, I'd further claim that not havi…

> You just have to know what a carry propagation bug is This is one of the things that drives me nuts about the crypto community. The natural response upon reading, "You just have to know X" if you don't already know is to go search for X. Well, if you go search for "carry propagation bug" you will find lots of examples of carry propagation bugs being found and fixed, but no explanation of what one is. The thing that…

Give me a fucking break.

Sean, Marcin, and I spent the better part of a year individually replying to tens of thousands of emails from people doing the Cryptopals challenges that we wrote and published for free. Do you know how much work that was? Here's a hint: it was a lot of work.

There are a lot of charges you can level at me to try to win a dumb message board argument, but the one where I want cryptography to be a secret priesthood known only to the anointed select is not one of them --- nor is the argument that I haven't taken the time to help make these kinds of cryptographic attacks easier for people to learn about.

Please immediately find one of those other arguments to substitute for this one, and, if you have it in you, take a moment to retract.

Thanks in advance.

Re: How I implemented my own crypto

#306

Post by dfox »

thaumasiotes wrote: post #296
Piskvorrr wrote: post #133

Earlier quoted context omitted.

Thank you, that's my point exactly. Nothing wrong with what you wrote - but note the subtle difference between "XORing a stream of random number s " (potentially viable, even unbreakable when using a OTP) and "XORing a random number" (essentially a Caesar cipher, kid-sister encryption).

> note the subtle difference between "XORing a stream of random numbers" (potentially viable, even unbreakable when using a OTP) and "XORing a random number" (essentially a Caesar cipher, kid-sister encryption) No, that's not a difference. A "stream of numbers" is just one very large number. What you're worrying about is how large the numbers are, not whether there's one or more than one.

Original point was certainly to point out the most common mistake of typical homegrown cryptosystems. Even programmers who know that XORing stuff with constant byte is not viable encryption can produce systems that do essentially the same thing (usually by XORing everything with RC4 output with long lived or even constant key)

Re: How I implemented my own crypto

#307

Post by baby »

tptacek wrote: post #289
baby wrote: post #281

Earlier quoted context omitted.

> I would suggest that for each of them, a 10+ year career in academic cryptography, in each case accompanied by significant new research results, is what helped them get there. Implementing a library, not so much. I believe that what made them exceptional (for most of them) is the combination of theoretical learning and hands-on programming. That's my entire point. I think we can agree to disagree. But that's an opi…

Why don't you ask them? Most of these people aren't hard to get ahold of. One of them you even share a Slack with. I would be surprised to learn that any of them believed doing a library implementation of pre-existing crypto constructions was an important part of their education, but I like to be surprised.

I did ;) surprise

Re: How I implemented my own crypto

#308

Post by [deleted] »

tptacek wrote: post #289
baby wrote: post #281

Earlier quoted context omitted.

> I would suggest that for each of them, a 10+ year career in academic cryptography, in each case accompanied by significant new research results, is what helped them get there. Implementing a library, not so much. I believe that what made them exceptional (for most of them) is the combination of theoretical learning and hands-on programming. That's my entire point. I think we can agree to disagree. But that's an opi…

Why don't you ask them? Most of these people aren't hard to get ahold of. One of them you even share a Slack with. I would be surprised to learn that any of them believed doing a library implementation of pre-existing crypto constructions was an important part of their education, but I like to be surprised.

[deleted]

Re: How I implemented my own crypto

#309

Post by [deleted] »

davidw wrote: post #297
tptacek wrote: post #295

Earlier quoted context omitted.

If someone posted a message on HN about doing DIY appendectomies with Arduino-controlled robots and I pointed out that you need to go to med school to do surgeries, you would not in fact be harping on me for not having explained why.

I think it's perfectly normal to be curious about a field and want to know more without necessarily wanting to charge off and do it yourself.

[deleted]

Re: How I implemented my own crypto

#310

Post by jacobolus »

Tomte wrote: post #264
lisper wrote: post #258

Earlier quoted context omitted.

> You just have to know what a carry propagation bug is This is one of the things that drives me nuts about the crypto community. The natural response upon reading, "You just have to know X" if you don't already know is to go search for X. Well, if you go search for "carry propagation bug" you will find lots of examples of carry propagation bugs being found and fixed, but no explanation of what one is. The thing that…

"Table stakes" in competetive Poker means that all you can bet is what's on the table, in front of you. So this old movie cliché where the protagonist has lost almost all his chips and needs a huge win, so he casually throws in his car keys and the title to his house in the middle of play is not allowed. Neither is grabbing your wallet and throwing cash in. The idea is that (a) rich people cannot bully others around…

You’re getting confused between two different things with the same name. This use of “table stakes” means something like the minimum buy-in to join the table or the table’s minimum bet to play a hand.

When used as an analogy, the table stakes are just features expected of anyone, not something special to advertise. For example, you wouldn’t say “I’m the best driver because I have a driver’s license and car insurance” – those things are just “table stakes” for drivers.

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