Tor trip report to an FBI conference

    The post:

In October I attended an FBI conference, as part of my work to try to keep Tor on good relations with law enforcement. My first goal is to remind them of all the good uses of Tor, so if they ever find themselves lobbying to outlaw anonymity online, they'll understand what they're giving up. The second goal is to make sure they understand what Tor is and how it works, so if they encounter it in their investigations they'll hassle our exit relay operators less. (Here's a great way that one FBI person explained it to me: "I've got 10 leads, and 48 hours before this case doesn't matter anymore. If you can help me understand which leads not to follow, I can do my job better.") My third goal is to help them be able to use Tor correctly for their own jobs — remember that diversity of users is part of what makes Tor safe for everybody to use.

Overall, we've been doing a pretty good job at teaching US-based law enforcement about Tor. At the end of the conference, one of the FBI agents took me aside and asked "surely you have some sort of way of tracking your users?" When I pointed at various of his FBI colleagues in the room who had told me they use Tor every day for their work, and asked if he'd be comfortable if we had a way of tracing them, I think he got it.

I met a nice man from the DEA who worked on the "Farmer's Market" bust. This was in the news a lot back in April, where apparently some people were selling drugs online, and using a Tor hidden service for their website. At the time I thought the news stories could be summarized simply as "idiot drug sellers accept paypal payments, get busted." It turns out they were pretty smart about how to accept paypal payments — they just had random Americans receive the paypal payments, take a cut, and then turn them into a Panama-based digital currency, and the Panama company didn't want to help trace where the money went. The better summary for the news stories should actually have been "idiot drug sellers use hushmail, get busted." Way before they switched to a Tor hidden service, the two main people used Hushmail to communicate. After a subpoena (and apparently a lot of patience since Canada still isn't quite the same as the US), Hushmail rolled over and gave up copies of all the emails. Many more details here: http://www.scribd.com/doc/89690597/Willemsindictment-Filed-0...

I should still note that Tor doesn't introduce any magic new silver bullet that causes criminals to be uncatchable when before they weren't. The Farmer's Market people ran their webserver in some other foreign country before they switched to a Tor hidden service, and just the fact that the country didn't want to cooperate in busting them was enough to make that a dead end. Jurisdictional arbitrage is alive and well in the world.

The host part is the transport layer-dependent permanent hidden service ID. For Tor, which is the primary transport layer supported by cables communication, it is a 16-character Base32 representation of a half of Tor's hidden service RSA-1024 public key fingerprint (an 80-bit part of SHA-1 cryptographic hash), with an .onion domain suffix. For I2P, it is a 52-character Base32 encoding of eepSite's ElGamal-2048 public key SHA-256 fingerprint, with a .b32.i2p suffix.

In this way, message security (inability of the attacker to reveal the message contents) is independent of the transport layer security (inability of the attacker to reveal the contents of network traffc and the location of correspondents). This is important because, at present, Tor appears to disallow “too much” security by design:

- RSA-1024 is universally used as a public key cipher (identity, onion, connection, and private keys, and likely for SSLv3 connections as well; although long-term directory authority identity keys are RSA-3072). This RSA key size is likely inadequate against a resourceful adversary such as the NSA/CSS. RSA-1024 provides only ~80 bits of security (see NIST SP 800-57 Part 1, §5.6.1).

- AES-128 is used as a stream cipher, although this key size is not allowed for highly sensitive data protection in the government of USA (see CNSS Policy №15 FS №1).

- SHA-1 80-MSB are used as the hidden service ID, offering at most 80 bits of security against hidden service impersonation. The security might be weaker than even that, since an MSB section of a cryptographic hash does not automatically inherit the second-preimage attack resistance properties of the original hash.

http://dee.su/cables-security

To the less-proficient ones: Please not that here he is comparing Tor hidden services and i2p eepSites, where both the client and the server use Tor/i2p. In this case all your communication is "magically" encrypted, in a more strong fashion by i2p (this is the tl;dr).

However, when communicating with the regular web none of this apply, and Tor will probably offer better protection as i2p is not by design built to communicate with the outside net.

The realities of the browser environment make it impossible to do what you describe. It's been possible with native clients for a long time, but has always been pretty cumbersome for non-geeks--I've been working on a native client solution that would be easy for non-geeks to use and provide a few different levels of security (which come with varying levels of convenience) that are all better than the "plain-text everywhere" option most people use now.

I posted a link to this yesterday and don't mean to spam, but the topic has come up a few times in the past day, so: http://parley.co

> http://parley.co

Excellent writeup. It really helps when the conversation is steered away from terms like 'amendment', 'advertisers', 'enforcement', 'criminality' and steered back to the central idea of recovering and safeguarding an intuitive and traditional idea of privacy in personal communication (postcard analogy). Lots of people, many with vested interests, insist that this isn't possible, that the genie is out of the bottle. But let's at least try, right?

In fact, PGP was a neat solution for the internet of the '90s with its quaint directory services (Bigfoot, anyone?) and dialup links. I think it had Pretty Good uptake too. So I'm very interested to see what can be done in today's environment.

(Your exchange with jmillikin looked promising too. Did it continue?)