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Comment Eh.... (Score 5, Informative) 59

Two datacenters owned by the same company using MPC is a really dumb use case. That won't help at all. The point of Google encrypting cross-dc communications is a forcing manoeuvre - it forces intelligence agencies to go via Google Legal to get information where the request can be analyzed and pushed back on. Even in countries where the legal system is flimsy and corrupt, that's an issue that can be improved significantly just with a single act of Congress or Parliament, whereas undoing their wiretapping infrastructure will prove somewhat harder because there's no adversarial lawyer standing in the way.

A better example might be two datacenters owned by different companies, where they don't mutually trust each other. Or, to give an actual use case, the OTR chat encryption protocol uses MPC to authenticate connections. They call it the socialist millionaires protocol. The two parties agree on a secret word (typically by one user posing a question to the other), and then a variant of MPC is used to verify that both parties selected the same word. The word itself never transits the wire and it's only used for authentication, so it's relatively strong even if the secret word is short or predictable.

Now, for some background. The paper can be found here if you want to skip the million+1 links and registration crap.

The basic idea behind MPC is that you write your shared computation in the form of a boolean circuit, made up of logic gates as if you were making an electronic circuit. The inputs to the program are represented as if they were electronic signals (i.e. as one and zero bits on wires). Once done, there are two protocols you can follow. The original one is by a guy named Andrew Yao. Each wire in the circuit is assigned a pair of keys. The details I'll gloss over now, but basically given the circuit (program) as a template, lots of random keys are created by party A, then the entire "garbled circuit" is sent to party B who will run it. Party A also selects the keys for his input wires and sends them to party B, who doesn't know whether they represent 0 or 1, only party A knows that.

Now party B wants to run the program with his input, but he doesn't want party A to know what his input is. So they use a separate protocol called an oblivious transfer protocol to get party A to cough up the right keys for B's input wires, without A finding out what they were. Finally, party B can run the program by progressively decrypting the wires until the output is arrived at.

What I described above is Yao's protocol. There is also a slightly different protocol called BGV. In BGV you don't send the entire program all at once. Instead, as party B runs through the program, each time they encounter an AND gate they do an oblivious transfer with party A. XOR gates are "free" and don't require any interaction. I forgot what happens for other kinds of gates. Basically, BGV involves both parties interacting throughout the computation, however, it can result in much less network traffic being required if your OT protocol is cheap, because if your circuit is very wide and shallow then most of the garbled program never has to even get transferred at all.

From what I can tell, most of the best results in MPC these days are coming from BGV coupled with new, highly efficient OT protocols. SPDZ appears to work on yet another design, but the basic reliance on circuit form remains.

Comment Re:Meaningless ... (Score 1) 248

Eh, you realise that Google has lots of engineers who don't live in the USA, have no ties to the USA, even strongly dislike the US government, right? Some of them are even working in China or Russia.

The idea that every Google employee is a slave to the NSA is absurd. The vast majority wouldn't even qualify for basic security clearance.

Comment Re:UK Has that now! (Score 1) 298

The link you provided makes no mention of any such thing. In fact it says the UK government refused to prosecute because the evidence was too vague. However, a film industry body was able to do so and the guy was found guilty. It seems he didn't really try to argue that he ran the websites in question but tried to rely on technicalities all the way, and the judge didn't buy it.

I'm all for being worried about abuses of due process and excessive government power. But what we have here is an asshole who was apparently making nearly $80k per month off advertising on a site dedicated to piracy and illegal downloading of films. The film industry was able to bring a private criminal prosecution (I didn't know that was possible), and won. Almost by definition a private prosecution couldn't have had access to material obtained via GCHQ or the NSA so the point you're trying to make is lost.

Comment Re:About Tor versions (Score 1) 236

What's more, this analysis is very fresh. Remember that right now huge chunks of Tor traffic appear to be botnet control circuits. The botnet runs on 0.2.3.x - so that's going to bias the sample somewhat.

BTW - not surprised to learn that Linux distributors are screwing their users with stale repos yet again. Anyone who is using distributor repositories to get security sensitive software is just asking to be compromised.

Comment Re:Question about Google's HTTPS (Score 1) 607

Not all Google searches are encrypted. Only if you're logged in, or specifically visit encrypted.google.com. The reasons are complicated and stupid - to do with US schools with political clout that outsourced their internet filtering and couldn't filter searches (for the children!) if SSL was enabled for everyone. A bunch of companies/orgs in similar positions also complained.

If you use Chrome at least then Chrome-Google communication is forward secure (compromise of the private key let's you MITM but not passively decrypt).

Comment Re:Uh... okay (Score 3, Informative) 607

There's nothing in the articles that implies this. Backdooring a CA only helps if several things hold:

1) They can not only intercept but also rewrite traffic on the fly. Possible, but if so, not yet mentioned in any leaks.

2) They're willing to take the chance that someone might notice.

So an operation against a single site, definitely possible. But they are clearly desperate to grab everything, all the time! Their whole MO is not targeted investigations but to spy on everyone simultaneously. You can't use a rogue CA to do that. They'd be detected immediately, if only by geeks setting up SSL for their new personal VPS and suddenly noticing the CA their browser gets isn't the one they installed.

The problems with SSL are not that CAs exist. The model holds against the global adversary who wants to decrypt everything. The problems with SSL are almost certainly more prosaic - many websites can be automatically hacked and their keys stolen without the owners ever knowing. In the default config that allows you to then decrypt all past traffic as well. Some implementations will use old, weak keys that were strong once upon a time but have since become obsolete. Some implementations will have bad random number generators. Some implementations will run on VPS providers and are subject to side channel attacks by colocated VMs. Some keys can be subpoenad and others can be obtained by covert agents. And of course you still leak traffic metadata even when SSL works perfectly.

There are lots of ways to attack SSL that will work some of the time, and that's exactly what the leaks imply - they can beat encryption sometimes but they don't have a magic skeleton key to everything.

Comment Re:SSH? (Score 5, Informative) 607

Certificate authorities never see private keys so you are dead wrong about that. What's more, even if a rogue CA was minting bad certs on the fly to attest that the NSA was really foobar.com, that would have been noticed. Remember that secrecy is something they value insanely highly. They wouldn't ever do something so easily noticed and the articles do not imply any kind of CA compromise.

In fact if you read all the stories (they overlap largely but not entirely) you can get a vague picture of what's going on. Firstly, they record all encrypted traffic in case they can decrypt it later. Secondly, they have a database of public to private keys, populated via any means they can. Thirdly, they obtain keys in lots of ways (hacking, subversion, bogus court orders, brute forcing old/weak keys etc) but they don't seem to have a magical solution to all strong crypto. The closest that the leaks come to this is discussion of some amazing cryptoanalytic breakthrough, which could possibly mean they're able to break some kinds of RSA? Perhaps they're ahead of Joux et al by some years?

Regardless, what it is, it can't be a solution to all crypto, because these governments apparently asked the newspapers not to publish on the grounds that people might switch to stronger systems that worked.

Comment Re:Botnets and Tor (Score 2) 55

No offence, but there absolutely is reason to believe you're incorrect. The reasons are in the Tor mailing lists which I've been keeping up with for the past few weeks.

Firstly, exit traffic has hardly moved, despite massive increase in Tor usage overall. This is consistent with the bots getting instructions from a hidden service. So exit node operators can't do much here.

Secondly, the whole point of the hidden service protocol is that relays don't know the IP of the hidden service. That's why there are rendezvous nodes that join user and service together via two 3-hop circuits. De-anonymizing such a service is very hard and requires you to control large numbers of nodes over a period of many months, according to the latest research. It's not something the Tor community can just do.

If you think you know of a slick way to resolve this problem, I suggest taking it to the Tor developers, because all the evidence I see from their lists is that right now they don't have any great ideas.

Comment Re:Botnets and Tor (Score 4, Informative) 55

I believe you are making an incorrect assumption that these botnet nodes are actually relaying on behalf of the network. I've not seen any reason to believe this is correct. Rather than just act as normal clients of the Tor network - placing extreme load on existing relays.

In fact, this botnet appears to be basically breaking Tor with many node operators reporting that their relays cannot keep up. The Tor developers recently started developing code to prioritise the more efficient NTOR handshake over the older protocol, and because the botnet runs older code people who upgrade to the latest code (once they are finished) should take priority over the botnet traffic. Until the botnet also upgrades, of course.

To make it worse, when a circuit fails to build because of overloaded relays, Tor retries. I'm not sure there's any kind of exponential backoff. Thus the network goes into a death spiral in which clients constantly try to build circuits and fail, placing even more load on the already overloaded system and making it impossible to recover.

Unfortunately we may be looking at the end of Tor here, at least temporarily. The botnet operator doesn't seem to realise what's happening, otherwise they'd be backing off. Tor is effectively experiencing a massive, global, accidental denial of service attack by this botnet. Many relays don't have enough CPU power to weather the circuit storms. It will be very interesting to see what the Tor developers do next - they don't have any effective way to fight off this botnet because almost by design they can't detect or centrally control the network. They practically have to ask nicely for the operators to go away.

Comment Re:How to crack: (Score 1) 183

I think this speaks to the fact that post-Snowden, the game has entered a new stage.

Pre-Snowden the NSA or whoever would not have been willing to do such a thing, due to the very high likelyhood of detection. Yes, 99.9% of people aren't going to notice their phone doing something unexpected. But if you apply it to everyone because you want the ability to grep their communications for keywords a.k.a. selectors then you need all of it, all the time. There are over a billion Android activations now. Even 0.01% of users being tech savvy and using custom/modified ROMs or analyzing their phone more carefully would notice what's up, and then their secrecy (the most prized asset) is blown. Secrecy is a double edged sword, it protects them but also limits them. So - not feasible.

Unfortunately, post-Snowden, the intelligence agencies know two things. Firstly, their secrecy is blown. Everyone knows they spy on every person alive, all the time. Most of their secrets are now ex-secrets. There's nothing to defend anymore there. The second thing they know is that it seems people don't give a shit. There were no protests in the streets. There were no diplomatic repercussions. It went in front of Congress and got voted down. The UK didn't even get to have a vote, the government just went full Orwell and other than some angry newspaper columns jack shit happened. Time to invade Syria? Parliamentary recall. Journalists have their materials seized? Stay on vacation. Generally they learned, totalitarian surveillance ranks lower in the priority stack than whether to invade Syria or not.

The combination of these two things means they're going to get really aggressive now. Automatically MITM every SSL connection using a FISAd CA? Unthinkable before, too easily detected. Post-Snowden, why not, it's just another way to do what people already know about. Force Google to back door every Android? Why not! They already track peoples movements everywhere, including people who switch phones to try and avoid detection. They apparently have the ability to turn phones into bugs, even if they appear to be switched off. Automatic, global backdooring of every mobile device wouldn't surprise people.

In short I think we may have lost as much as we gained from Snowden's leaks. Sure, the veil of secrecy was torn down. But society failed to rise up. The secret police have won. Now they can do anything without fear, and there's literally nothing to stop them.

Comment Re:Very little utility here (Score 2) 183

Er, what? We just learned this summer that governments are sucking up EVERYTHING and storing it for god knows how long, and you think it's useless because you would need to obtain the device to read the content?

No way! At this point any kind of crypto, even the unauthenticated kind, is a good step forward.

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