3 ms·

How do we know that Tor is reliable? It's the de facto standard, but, barring bugs, is it provably NSA-resistant?

by ISL 14y ago

deleted 14y ago
[deleted]
- ISL 14y ago
  I'm less concerned for the encryption. In principle, Tor guarantees anonymity - my question is really, "How guaranteed is that anonymity, assuming Tor's implementation is correct?" I concur that, if anyone has been able to break Tor, they haven't made use of it in any public way. You can only really do that once. Put another way: Suppose I want to know who is sending messages to the New Yorker's strongbox, but I don't have physical access to their isolated system. Can I figure it out? How many Tor nodes would I need to compromise to have a ~5% shot at discovering interesting information about the sender?
  - 616c 14y ago
    I am not sure you can put down a real number, but the developers are in concert with power users, and they are well aware of when something is fishy and they patch quickly, specifically for the very well-known state actors that Tor irks (e.g., China and Iran). See one such recent example: https://blog.torproject.org/blog/iran-blocks-tor-tor-releases-same-day-fix https://blog.torproject.org/blog/iran-blocks-tor-tor-release... And yes, I know this supposes it is an obvious attack vector, and this is not really disastrous; they got blocked. I encourage you to read the Tor Project blog. They did, for example, an excellent writeup of how BEAST was not impacting them, and did a very detailed layman's article on how, even if their implementation did not pad TLS the way it did, would still not be exploitable with the BEAST exploit. https://blog.torproject.org/blog/tor-and-beast-ssl-attack https://blog.torproject.org/blog/tor-and-beast-ssl-attack There are a lot of eyeballs, and all the usual cathedral and bazaar quotes will tell you I trust their implementations, despite its dubious origin with a Naval Postgraduate School thesis, than other systems that are not open source.
deleted 14y ago
[deleted]
shabble 14y ago
Even if it is already entirely broken by them, there's the question of whether they'll risk revealing that fact by going after you (publicly) c.f. Ultra[1] level intelligence from breaking Enigma. [1] https://en.wikipedia.org/wiki/Ultra_%28cryptography%29#Safeguarding_of_sources https://en.wikipedia.org/wiki/Ultra_%28cryptography%29#Safeg...
- acheron 14y ago
  Yes, we all read Cryptonomicon too.
wiml 14y ago
Pedantic response: There's surprisingly little provable (in the mathematical sense) security in the crypto world. It's possible, though rather unlikely, that the NSA has a cheap way to factor large numbers and has been laughing at us all for decades. Less pedantic response: Tor does use good strong crypto and has been examined by many experts, both practical and theoretical; I'd be surprised if the crypto, protocol design, or even the implementation is the weakest spot. One weak spot it does have is traffic analysis. Any low-latency anonymity network has this problem: if someone can observe the traffic in and out of enough nodes on the network (even if they can't decrypt any of it) they can statistically correlate arrival times and figure out who is talking to whom pretty reliably. Even if you can't read the data, reading the envelopes is enough to plug leaks, find dissidents, etc.. (Consider the Associated Press phone records affair.) If the attacker can experiment by causing brief interruptions or delays on the circuits between nodes they can extract even more information. Google will find you many cites on this subject. The Tor project tries to mitigate this but considers a full solution out-of-scope (for fairly good reasons, I think). There aren't many projects that really do try to address it --- the old cypherpunk Mixmaster network is the only one I know of offhand. And even there, the best you can do really is up the constant factors of the attack, or push the attack one level up into the greater network of human communication ("who knew X, at a time they could have communicated it to Y? Who knew Z, at such a time?").

How do we know that Tor is reliable? It's the de facto standard, but, barring bugs, is it provably NSA-resistant?

by ISL 14y ago

How do we know that Tor is reliable? It's the de facto standard, but, barring bugs, is it provably NSA-resistant?

deleted 14y ago

[deleted]

ISL 14y ago
I'm less concerned for the encryption. In principle, Tor guarantees anonymity - my question is really, "How guaranteed is that anonymity, assuming Tor's implementation is correct?" I concur that, if anyone has been able to break Tor, they haven't made use of it in any public way. You can only really do that once. Put another way: Suppose I want to know who is sending messages to the New Yorker's strongbox, but I don't have physical access to their isolated system. Can I figure it out? How many Tor nodes would I need to compromise to have a ~5% shot at discovering interesting information about the sender?
- 616c 14y ago
  I am not sure you can put down a real number, but the developers are in concert with power users, and they are well aware of when something is fishy and they patch quickly, specifically for the very well-known state actors that Tor irks (e.g., China and Iran). See one such recent example: https://blog.torproject.org/blog/iran-blocks-tor-tor-releases-same-day-fix https://blog.torproject.org/blog/iran-blocks-tor-tor-release... And yes, I know this supposes it is an obvious attack vector, and this is not really disastrous; they got blocked. I encourage you to read the Tor Project blog. They did, for example, an excellent writeup of how BEAST was not impacting them, and did a very detailed layman's article on how, even if their implementation did not pad TLS the way it did, would still not be exploitable with the BEAST exploit. https://blog.torproject.org/blog/tor-and-beast-ssl-attack https://blog.torproject.org/blog/tor-and-beast-ssl-attack There are a lot of eyeballs, and all the usual cathedral and bazaar quotes will tell you I trust their implementations, despite its dubious origin with a Naval Postgraduate School thesis, than other systems that are not open source.

deleted 14y ago

[deleted]

shabble 14y ago

Even if it is already entirely broken by them, there's the question of whether they'll risk revealing that fact by going after you (publicly) c.f. Ultra[1] level intelligence from breaking Enigma. [1] https://en.wikipedia.org/wiki/Ultra_%28cryptography%29#Safeguarding_of_sources https://en.wikipedia.org/wiki/Ultra_%28cryptography%29#Safeg...

acheron 14y ago
Yes, we all read Cryptonomicon too.

wiml 14y ago

Pedantic response: There's surprisingly little provable (in the mathematical sense) security in the crypto world. It's possible, though rather unlikely, that the NSA has a cheap way to factor large numbers and has been laughing at us all for decades. Less pedantic response: Tor does use good strong crypto and has been examined by many experts, both practical and theoretical; I'd be surprised if the crypto, protocol design, or even the implementation is the weakest spot. One weak spot it does have is traffic analysis. Any low-latency anonymity network has this problem: if someone can observe the traffic in and out of enough nodes on the network (even if they can't decrypt any of it) they can statistically correlate arrival times and figure out who is talking to whom pretty reliably. Even if you can't read the data, reading the envelopes is enough to plug leaks, find dissidents, etc.. (Consider the Associated Press phone records affair.) If the attacker can experiment by causing brief interruptions or delays on the circuits between nodes they can extract even more information. Google will find you many cites on this subject. The Tor project tries to mitigate this but considers a full solution out-of-scope (for fairly good reasons, I think). There aren't many projects that really do try to address it --- the old cypherpunk Mixmaster network is the only one I know of offhand. And even there, the best you can do really is up the constant factors of the attack, or push the attack one level up into the greater network of human communication ("who knew X, at a time they could have communicated it to Y? Who knew Z, at such a time?").