[tptacek]

"The javascript is there for the auditing" doesn't mean anything. Javascript is the worst possible environment for running crypto code: it's accepting and running code delivered over a network from untrusted hosts bound in all sorts of unpredictable ways to an extremely complicated markup format optimized for display, and, on top of that, almost every single feature in the language can be overridden from the code.

Even if you were among the 0.00000001% of potential users who could possibly look at a block cipher implemented in Javascript and judge whether it was intact (and among the 0% of people who would actually do this), you can't just look at one piece of code in JS and know what it's actually going to do. You have to have a way of assuring every single bound function in the entire Javascript runtime.

That mechanism of ensuring the entire state of a Javascript context in a browser? It doesn't exist yet in any modern browser.

Your last sentence? What a huge dodge. If your server is compromised, your users lose. My browser trusts your server absolutely. If you'd like me to demonstrate this to you vividly, you can catch me offline and we can arrange terms.

[nickbw]

Your objections seem to boil down to a superstitious distrust of javascript. The web may be a messy platform, but javascript is not a particularly difficult language to read, and (if I may say so) the relevant chunks of bonchat are written in a pretty plain style.

I'm not making any promises of 100% perfect security with no effort and no room for attacks. Bonchat is merely an experiment in securing content against servers as well as network snoops.

I trust Linux more than Windows. I haven't personally audited all the code on my Linux box, and I don't know any one person who even has the skill to do so. But the code is there to be audited, which gives me more confidence than when I use a opaque operating system. The same applies here. Bonchat isn't perfect, it's just trying to be easier to keep honest than a normal web app.

[tptacek]

You say "po-TAY-to", I say "po-TAH-to".

You say "to-MAY-to", I say "no thank you".

You say "supersititious distrust of Javascript", I say "a day job finding, breaking, and fixing the horrible things people try to get away with doing in Javascript". (Or, less charitably: "knowing how Javascript works in browsers.")

Trust me on this one. It's a cool little hack. It's even useful if you get rid of the vanity crypto. But you are asking for someone to write a really mean blog post about you and your actual understanding of how crypto works. That's drama you don't need. Don't bother with the AES stuff.

[nickbw]

If you would like to propose improved crypto code, I would love it. Honestly.

But "javascript is a messy language" is not inherently an attack. You can obfuscate just about any language. Do you actually have an attack in mind based on the fact that it's implemented in the browser?

It's true I don't have a deep understanding of the AES algorithms, and the AES code, as stated in the attribution, isn't even mine. Again, I'd love improved code. But you have yet to make any rational argument that javascript in the browser is inherently unsuited to encryption.

I completely agree that the many attempts to make SSL irrelevant by doing all the encryption in JS (and usually horribly naive JS) are foolish. That's not the point. Bonchat isn't a shopping cart or a mail reader. SSL is for securing communication to the server. Bonchat is an experiment in securing communication against the server. Do you have a better way than client-side encryption?

[SamReidHughes]

Do you actually have an attack in mind based on the fact that it's implemented in the browser?

You, the owner of the server, change the code. That's the attack. There's no way for me to tell my friend Charlie that he can use the service and get secure communication, unless he installs a plugin for his browser to verify that the server has not changed the data it sends the user from the time when I verified the correctness of the code. And if he has to install a plugin to safely use this service, which is now never permitted to change its code, he might as well just install a plugin that has the code, or install a separate application for this purpose.

[tptacek]

You seem intent on evading the point. Most security systems don't depend on me being able to read the code every time I use it.

[nickbw]

Most web security systems don't even give you the option. You sends your data off and you trusts your server. You can't read the code at all because it lives on a box you don't have access to.

Any security system you didn't code yourself does rely on someone you trust having read it at some point.

Is it more secure than some audited local code you compiled months ago and haven't touched and don't have to re-download? No, of course not. Is it more secure than chatting on Facebook? Potentially, yes. The necessary transparency is there.

This is not an innovation in protecting your data from network snoops. In that sense it's no improvement on SSL and it's not trying or claiming to be.

What it does do better than other web apps is protect your conversations from the middleman you can't avoid -- the web server itself.

[tptacek]

Nick. Please. It doesn't do this thing you keep claiming it does, because you left out any mechanism for the client to verify the code the server sends. You keep implying, directly and indirectly, that clients can do this by hand. People keep telling you, no they can't. When I give a specific and unintuitive reason why people can't manually verify your code in a browser, you throw out a smokescreen about how Javascript is a fine language to write things in, which of course has nothing to do with the issue at hand.

(By the way, thing you don't want to hear from the guy offering you super-secure communication system? "You have a superstitious paranoia about Javascript".)

And, as Steve Weis took the time to point out, even if you had invented some new system by which browsers could verify the state of a Javascript interpreter fed by an app that, among other things, had until a few hours ago a bunch of obvious Javascript injection flaws, you still wouldn't have been secure, because you don't really understand how CTR mode works and implemented colliding nonces. (Why did you bother with CTR mode anyways?) You also don't seem to understand the relation between encryption and authentication; not having a MAC would just be an embarassing oversight if you hadn't then argued with Weis about why it wasn't necessary.

The security model behind this application is just a really bad idea, Nick. I know that's tough to hear, since you obviously put some time and effort into it, but you're going to need to zag instead of zig now and come up with something cool about this chat system other than the notion that it's somehow more secure than Campfire or any other https chat.