Show HN: aes.io - secure storage/collaboration with client-side JS crypto

by trekkin • 14 years ago

10 38 14 years ago

Piskvorrr4• 14 years ago

Oblig: JavaScript crypto considered harmful. http://www.matasano.com/articles/javascript-cryptography/

The site doesn't address any of the concerns. Why? Well, because they can't. Client-side JS is fundamentally, unfixably insecure.

ch0wn• 14 years ago

This is no longer true. There exists the Stanford JavaScript Crypto Library authored by known experts, including Emily Stark, Mike Hamburg and Dan Boneh:

http://crypto.stanford.edu/sjcl/

I also suggest reading the paper that comes along with the library, addressing several of the common issues like randomness and entropy generation and integer calculations in JavaScript: http://crypto.stanford.edu/sjcl/acsac.pdf

tinco6• 14 years ago

Matasano refers to SJCL in his article, it does not invalidate many of his points. If you had read his article you would know that it cannot simply be 'no longer true'. The article shows fundamental problems with security on the web and in javascript.

tptacek10• 14 years ago

Did you actually read the SJCL page before you wrote this comment? Because it rebuts you.

trekkin9• 14 years ago

The article has many points, but it seems that they can be grouped together around three themes:

1. very easy for MITM-type attacks: this is negated by using SSL

2. JavaScript is too "malleable" for crypto - this argument is not very clear; yes, JS is "malleable" - so what, if we can be reasonably sure it is not "infected", by using server-side tools like signatures and SSL? This is highly debatable...

3. server breaches easily propagate to users: this is a real issue, but it is a real issue with many products that auto-update themselves, such as OSes (with patches/updates), browsers, anti-viruses, etc. Thus although this is a valid concern, it is part of everyday life of most Internet users,and not something JS crypto is specifically bad at.

Piskvorrr4• 14 years ago

In other words, "I don't understand #2, so let's assume it's not a problem and handwave it away." Alas, it is a problem, and a critical one. Pray tell, how do you check the VM, from inside the VM sandbox? Guess what: you have no way to do that, not in JavaScript. That's another chicken-and-egg problem which is insurmountable with client-side, in-page JS.

tptacek10• 14 years ago

By "malleability", we mean that code loaded in the future can monkey patch away the random number generator or AES block cipher function. I'm pretty sure that isn't debatable.

You keep saying that you mitigate this problem by controlling your pages 100%. Congratulations, you have gone farther than many of the JS crypto apps I've looked at; many of those bug their pages with Google Analytics, or with Typekit.

But that doesn't mitigate the problem that your users can't police you. They are relying entirely on your promise not to deploy code that will surreptitiously defeat the security of AES (or whatever ciphers you're using). And because JS is malleable, it is untenably hard even for an expert to attempt to validate your code by hand.

tinco6• 14 years ago

Even though client-side JS has some fundamentally insecure properties it does not mean it can't be used for establishing reasonably secure communication. HTTPS suffers from some of those properties too and we rely on https for almost everything we do that requires some sort of security.

If your site is entirely self-contained and transported in full over https with a trustable ssl certificate and your users are using reasonably secure passwords and run browsers with addons that respect the confidentiality of https communication then client-side js encryption might be a nice extra layer of data protection.

It won't protect against the government probing, and it won't protect against a passionate lulz hacker.

The government can always subpoena the host website, and force it to fetch the password from the user, thereby comprimising their data. The government also has access to ssl certificates so it could even do this without notifying the host website. You may assume that lulz hackers have similar capabilities.

If you think about it straight, the only way this can be truly secure is with a browser extension that digitally signs and versions _all_ javascript on a website, and the signing is done by a fully trusted third party (which arguably don't exist).

tinco6• 14 years ago

There is one thing client side js does protect you against very well and that is simple sql-injection style vulnerabilities.

Any database exposure vulnerability that does not compromise the host is fully mitigated by client side encryption. This is a very large class of vulnerabilities in the real world, so this is actually a very good case in favor of client side encryption.

justauser• 14 years ago

Trekkin posted yesterday in the discussion regarding Microsoft's SkyDrive (http://news.ycombinator.com/item?id=4265621) and not being familiar with the project I asked him to post a ShowHN so more folks could chime in regarding the use of clientside JS cryptography.

I asked about the library/implementation used and it is BouncyCastle compiled/convertered to JS using GWT.

The common discussion/blog references I've also pointed out but for everyone else have a look at these: http://rdist.root.org/2010/11/29/final-post-on-javascript-cr... and http://www.matasano.com/articles/javascript-cryptography/ .

trekkin9• 14 years ago

Thank you! The Matasano article, as I mentioned in another comment, for some reason assumes that SSL is not used, which is not the case with aes.io.

Piskvorrr4• 14 years ago

You are misrepresenting the article. SSL is only a mitigating factor.

eli• 14 years ago

If you're already using SSL, why do you need client-side JS in the first place? I'm not sure I understand the use case.

tptacek10• 14 years ago

The article does not assume SSL isn't used. The article addresses JS cryptosystems in the presence of HTTPS/TLS from top to bottom.

But we also go out of our way to discuss JS cryptography as an alternative to HTTPS, because that is how many people use it; for instance, to do challenge-response authentication for "secure login" without needing SSL.

But that's a sideshow on this thread. The article squarely addresses exactly the application you've built, and in detail.

pwpwp• 14 years ago

Interesting. How difficult was it to get the Bouncy Castle crypto lib to compile with GWT?

trekkin9• 14 years ago

Not difficult in theory - classes not supported by GWT (such as iostreams) are easily cut out; but in practice many array operations inside BigInteger needed to be carefully tweaked to work well when compiled into JS.

abemassry• 14 years ago

I went full server side encryption with https://truefriender.com I relied on SSL for the client to server communication. However the user holds a key that is not stored on the server, so without that key the text on the server is unreadable, if you try entering an incorrect PIN you can see what I mean.

I've submitted to HN but didn't make the front page, check it out if you're interested in this stuff.

Toshio• 14 years ago

This site more or less does the same thing as deadrop.us so why do I need to sign up?

trekkin9• 14 years ago

deadrop.us seems to be focused exclusively on short messages. aes.io, in addition to messages, supports file uploads and sharing, for example...

Show HN: aes.io - secure storage/collaboration with client-side JS crypto

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