Comment by DanBC | Hacker News Reader

Comment by DanBC | Hacker News Reader

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> Like I said, the developers seem to be earnestly trying to improve their product based on the feedback they are getting.

Cryptographic software isn't something that you can improve by a process of gradual refinement.

Crypto can have small, subtle, bugs. Those bugs could mean that the product is worthless.

A skilled, knowledgeable researcher could audit the code closely, and report any bugs they find. Cryptocat could fix all of those bugs. Does that mean it's secure? No - because crypto is hard.

> What more can you ask of them?

I ask that they make the disclaimers much bolder and bigger. I ask that they emphasise the experimental, untested, unscrutinised nature of Cryptocat.

> "You there. Stop. You shouldn't be building this because we the superior internet community think you're a terrible person who will never learn anything, so we're putting our foot down."

That's a mischaracterisation of the criticism they've got.

"You there. Stop! Cryptography is very hard. Don't roll your own; or do but don't release it as a product for end users."

followed by

"You there. Stop! We suggested that you didn't release it for end users, but you did. Well, here's a list of bugs. Don't just fix these and think everything is good, there are probably other bugs and the whole thing is based on weird wrong ideas."

followed by

"You there. Stop! No, really, just stop. Here's a list of bugs. These are not subtle hard to find bugs. These are obvious bugs that anyone doing crypto really should have been aware of. The presence of these bugs demonstrates lack-of-clue. Please, stop hyping the product as secure, stop distributing as a tool for end users to use."

People get exasperated. It doesn't help that some of the responses from the developers were defensive and aggressive and dismissive.

tl;dr have fun with crypto and building stuff. Just don't think it's secure, and especially don't release it as secure. Especially don't release it as a browser plugin ready for naive end users.

I think I do understand what you're saying Dan, but do you really believe that cryptographic software isn't something you can gradually improve on?

How do you explain the fact that the majority/all of the crypto libraries we rely on today have been gradually improved over time, fixed as bugs have been found, etc?

I think you've severely mischaracterised the way crypto software is developed.

You fix the bugs and you move on. That's the only way to progress, and that's exactly what the developers have been doing. I can't fault them for that.

There is a difference between starting with a reasonably well written core and fixing issues that are discovered, and starting with a product that demonstrates essentially no understanding of cryptography beyond the bare minimum and trying to debug a working cryptosystem into existence. It's bad enough to try that with regular software, but doing it with crypto is insane.

He's not mischaracterizing the way crypto software is developed. You are.

Please characterize the proper way for us of the uninformed...

All software has bugs. There's no piece of real-world general-purpose software that you can't look at and say "this was improved incrementally as bugs were found".

But not all software has the same sensitivity. In the weeks before Netscape Navigator shipped in the mid-90s, Jamie Zawinski slept under his desk at work trying to make it reliable. The builds from the night before launch crashed! Nobody thought they'd make it. That's a story anyone on a commercial dev team can probably tell you; it's the oldest story in product development.

That kind of incremental development works fine when you're shipping the first web browser, or even the first version of a new web browser.

It does not work when you are shipping cryptography. Nate Lawson is fond of saying, "plan to budget 10x for the validation of a new cryptosystem as you to implementation". You probably can't actually be doing that when your whole cryptosystem changes 4 times in 2 years.

The difference is between handling bugs and expecting bugs. Netscape expected bugs. Crypto software can't do that.

You haven't explained anything about how crypto software is developed. You have told us how other software is developed and then told us that it isn't okay for crypto software.

Spend 10x the resources on verification as on implementation. Spend 10x the resources on design as on implementation.

Nobody does this with normal software.

And ultimately the biggest thing to do is that when you find a bug, don't just fix that one bug and call it a day.

If you find a bug in your crypto code through your testing and validation, that means your development process screwed up and allowed that bug to slip through. What you need to do is figure out how that bug got through your development process, change your development process so it wouldn't slip through next time, and then have a thorough audit of your already-written code to make sure no other bugs have slipped through the same way.

Developing must-not-fail critical software is the exact opposite of the traditional launch-fast-and-iterate model that most people use to produce web applications and such. This is a big reason that when web app developers try their hand at developing critical software like cryptography, they get it horribly wrong.

This seems similar to way the people who developed the software for the space shuttle worked. Finding a bug was a huge deal, as it meant something was wrong in their process. It wasn't just fix the bug, but fix what caused the bug, and look to see where that faulty process may have caused other bugs. Google 'they write the right stuff' for a good article on it.

Another domain where you have things like this is embedded systems related to safety, ie, the micro-controller managing pressure equipment.

Reading that it seems as if this space is almost, positively, stacked against any solo or small group dev. Thanks for the insight, but if crypto is hard and there's issues on both ends of the spectrum (commercial space generally ships for monetary reasons, small groups ship for notoriety / political discourse rationale / tinfoil hat.

So who is building great crypto software that's built right from the ground up? OpenSSL AND OpenSSH struggle with this on a continual basis yet they seem to be the prime examples of doing it right. The problem, however seems to be unless every release is a complete rewrite eventually you will be working off of some foundational compromised base component.

Thoughts?

This space is positively stacked against any solo or small group dev.

The way you deal with that is, you pick a credible crypto project with traction and build on top of it.

The world badly needs a GPG UX that ordinary people can use without thinking about it. Bonus: nobody knows what that UX is! It's an open problem! And you can tackle it without getting anyone killed, because the GPG/PGP team has spent decades getting the "might get someone killed" problems addressed.

If the user is placing their trust in the UX's ability to validate that PGP/GPG is working correctly and has not been tampered with, that sounds exactly like something that could get someone killed.

You can say the same thing about any piece of software; if Excel forgets how to multiply numbers, think of the horrible things that could happen! The difference is that multiplying two numbers isn't hard compared to getting a cryptosystem right, and neither is accurately displaying a key fingerprint.

So what you're saying is, for cryptography software, "Agile" development doesn't work. For cryptography software you need very careful, deliberate, up-front design. You need careful, deliberate implementation that does not deviate from the design. You need careful deliberate validation.

What we may be seeing is that we have roughly a decade now where "Agile" has been drummed into developers as the best way to write software. Perhaps it's the only approach they knew to take.

That a much better way to put it than mine.

> The difference is between handling bugs and expecting bugs. Netscape expected bugs. Crypto software can't do that.

I dont know if I believe this. I have never had a software system that was completely bug-free (independent of whether or not it had anything to do with crypto). Furthermore, I would argue that one of the main ideas behind SSL was to expect there to be flaws in the underlying crypto that it used and therefore be able to deal with switching out one algorithm for another. You might argue that there exists a difference between a bug and an algorithmic flaw, but realistically they both have the same effect. Therefore, I argue that the superior method is not to write code expecting no flaws, but to write code which does expect them and has a way to deal with them.

That is not to say that you should release your code knowing that there exists a security flaw, but rather to acknowledge that you're not the smartest guy in the room and that the best way to harden a security system is by letting people attack it. Now, you cant force people who are good at crypto to attack your system in order to improve it. Hopefully though, security through obscurity will help. I.e. if your product is not well known it is not worth it for someone experienced to spend a lot of time to crack it. On the other hand, if it is, you then need to worry about the nature of the person attacking it. Is this person a researcher (in which case he will hopefully reveal his findings) or a threat? If you are a big product, you can hopefully afford to make this person a researcher who will give you his results. For the other case, I think that this is where auditing helps. Even if you have a broken system (which you can almost always safely assume you do), you can at least possibly detect a hack and then try to reverse engineer it. Lastly, to provide a solid example of 'bugs' which have been fixed in crypto code which everyone relied on, you need to look no further than unix's crypt.

Note that, assuming the security model proposed by cryptocat, every time it's broken a few hundred peaceful protesters against a brutal regime end up against the wall. The brutal regime obviously doesn't bother to tell the world to stop using the software in question.

(In reality, it's not that bad because quite a lot of people distrust cryptocat. Still, "patch and move on" doesn't cut it for critical software, which almost all crypto software is.)

My knowledge of this topic is limited but I believe if you are saying that the majority of crypto libraries have had major bugs, in the sense that they are made trivial to break, that you are overreaching.

On the other hand if you are including minor bugs, that have a low impact on security, then you are surely right but this doesn't mean much. Minor bugs get caught even in audits of the code for nuclear power plants.

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