Hacker News Reader

Comment by sneak | Hacker News Reader

A reminder: bitcoin, like tor, is useless if the government has a realtime analysis of the L3 network traffic of a majority of the participants, as we have learned they do in the US under NSA's MAINWAY and MARINA programs.

View on HN

Not true: A new transaction in the bitcoin network isn't linked to any IP address, since transactions diffuse through the network haphazardly: There's nothing to distinguish between a transaction coming from elsewhere and a new transaction originating in the client. The only way to figure out the originating IP address would be to collect all data on close to 100% of the network and analyse the data in a sophisticated way.

Hunting down a money trail through the block chain by getting user data from exchanges or points of purchases without trying to determine the raw IP for a particular transaction is much more tractable, as others have pointed out.

EDIT: User "sneak" has changed the wording of his original comment, so this reply now doesn't make as much sense)

I'm pretty sure an eavesdropper can simply watch for outgoing transactions which you never recieved and deduce that they originated from you. No fancy network analysis needed.

Exactly right. However, it means they would have to have direct access to 100% of the traffic from the user in question, while the original comment referred to having just a percentage of the backbone (user "sneak" has since edited the original comment to use different wording)

True, but that depends if you want to go from Bitcoin addresses to IP address or vice versa.

The avarage Bitcoin trade is not ananymous. You have to provide identification with most exchanges and you'd have to invest a lot of effort to stay really anonymous.

The primary benefit of Bitcoin is it's speed utility (you can send money to anywhere within minutes and low fees) and the inability to freely create infinite amount of it (scarcity).

I don't think the entire usefulness of Bitcoin is related to staying anonymous as it's actually pretty hard to stay anonymous when using Bitcoin.

Also, wouldn't the government need to be operating a certain percentage of the Tor nodes to do effective traffic analysis?

"Also, wouldn't the government need to be operating a certain percentage of the Tor nodes to do effective traffic analysis?"

Not if they can conduct surveillance on the entire Internet.

You establish a random circuit through the Tor network when you first connect. Even if the NSA is analyzing every packet between every node, they're not going to be able to distinguish your packet from anyone else's. I think they would need to control some of the nodes to keep track of packet sources and destinations.

You are wrong. Tor does not include any latency, so a passive global adversary who can watch every packet can correlate your input to the Tor network with the traffic between nodes and the outputs of the exit nodes, and thus break the anonymity property. The reason this does not apply to anonymous remailers is that they randomly permute the messages they receive, sending them out in a different order than they were received; this creates far too much latency for use with HTTP or IRC or other common protocols, so Tor sacrifices security against a global adversary.

http://www.cs.usfca.edu/~ejung/courses/f11683/lectures/tor.p...

http://mice.cs.columbia.edu/getTechreport.php?techreportID=5...

It's still useful, just less anonymous.

From bitcoin.org: "Bitcoin is not anonymous"

  http://bitcoin.org/en/you-need-to-know

Yeah I should have been more specific: less pseudononymous.

Eavesdroppers (local, ISP, or NSA) can link specific addresses to your IP address when you make a transaction.

One workaround is to use a hosted online wallet or submit pre-signed transactions to the network through a third party like https://blockchain.info/pushtx (assuming the connection is secure, including resistance to traffic analysis isn't possible)

Why pasting as code making it impossible to click on it?

Is there any theoretical way to defeat these programs and ensure anonymity? I'm even suspect of SSL given private keys can probably be demanded through FISA court.

The 100% theoretically guaranteed method is the zerocoin extension: http://zerocoin.org/

Caveat, much higher bandwidth and data storage requirement.

One ZeroCoin transaction takes the bandwidth/storage space of something like 100 (or was it 1000?) Bitcoin transactions. That could add up fast.

Well, not fully defeat, but you could make yourself less of a target by using a series of shell accounts and effectively laundering the money.

Just Google laundering. Techniques are widely publicized and accessible.

Use separate hardware on public wifi. Take the battery out when you're done.

Was that a joke?

What does public WiFi have to do with anything? We're talking about the NSA wiretapping Internet backbones and forging SSL certificates.

We're not talking about forging ssl certs and never have been. NSA doesn't do that and never will, for reasons which are totally obvious if actually think about what would happen if they did.

By "forge" I meant using the private keys (obtained through FISA, or possibly cracked) to either decrypt or MITM SSL sessions, not using one of their own CAs to create a valid but obviously fake certificate, which I assume is what you thought I meant.

Maybe "forge" was the wrong word.

I think (not an expert) that with elliptic curve Diffie-Hellman (which e.g. Google uses), even with the private key and the whole session, you still can't decrypt the session (Diffie-Hellman provides a secure channel, public/private proves the server is who it says it is).

That is correct. These are referred to as ECDHE, or DHE for the non-ECC variant (vanilla DH). The last e is "ephemeral", referring to the lifetime of the session key.

The property that this provides is known as "forward secrecy".

Assume they have access to the original pricate keys.

We're talking about anonymity, not secrecy.

Oh I see. That works as long as nothing you do online can identify you. That rules out the vast majority of things people do online.

Why taking the battery out? Are you talking about a smartphone or a laptop?

It's only as useless as the stock market and SWIFT.

Reply on news.ycombinator.com