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Tor .onion addresses work by signing a message to a gateway with your RSA-1024 private key, while the actual address is the first half of SHA-1 of the public ke

by yk 13y ago

Tor .onion addresses work by signing a message to a gateway with your RSA-1024 private key, while the actual address is the first half of SHA-1 of the public key. [0] So you have to brute force 80 bit to find a collision for a specific hidden service and you need to break RSA-1024 to actually impersonate a .onion hidden service. In the light of recent news, both seems to be borderline possible. But as far as I understand, brute forcing a SHA collision would lead to strange error messages or some people who can see the original and some who see the FBI version. Since no one reported anything like this, they would need to brute force the RSA key pair for SR in order to hijack the domain. For the other two possibilities, why would DPR's dead man switch pretend to be a FBI note instead of a 'dead man warning,' especially since a hoax FBI message would immediately destroy SR? So I would assume that the FBI managed to get the actual hardware. [0] https://trac.torproject.org/projects/tor/wiki/doc/HiddenServiceNames https://trac.torproject.org/projects/tor/wiki/doc/HiddenServ... Edit: Slight clarification

powertower 13y ago
Didn't SilkRoad transfer ownership some time ago? The guy that got busted was the first one. So the second guy could still be out there, who would be able to post that image.
- shubb 13y ago
  I wouldn't bet on how many guys there are. Big incentive to spread misinformation. Wait for the court case, and then the jail book.
IceyEC 13y ago
While that would let you 'impersonate' a hidden service, you would have to hope the actual hidden service goes down because otherwise the HSDir servers will point requests to the proper host and requests will be encrypted to their key
- makomk 13y ago
  If I recall correctly, it's basically a case of last server to update the dir servers wins, so impersonating hidden services shouldn't be too hard unless the actual service goes down and is restarted.
- yk 13y ago
  AFAIR there is nothing in TOR that prevents races between two servers trying to get a specific .onion address. So my understanding is, that a collision ( or a broken RSA private key) would put the HSDir into a inconsistent state. And in this case, some people would get the real server and some people would get the impersonated server. ( Additionally TOR hopefully warns if the public key of a hidden server suddenly changes.)

by yk 13y ago

powertower 13y ago

Didn't SilkRoad transfer ownership some time ago? The guy that got busted was the first one. So the second guy could still be out there, who would be able to post that image.

shubb 13y ago
I wouldn't bet on how many guys there are. Big incentive to spread misinformation. Wait for the court case, and then the jail book.

IceyEC 13y ago

While that would let you 'impersonate' a hidden service, you would have to hope the actual hidden service goes down because otherwise the HSDir servers will point requests to the proper host and requests will be encrypted to their key

makomk 13y ago
If I recall correctly, it's basically a case of last server to update the dir servers wins, so impersonating hidden services shouldn't be too hard unless the actual service goes down and is restarted.
yk 13y ago
AFAIR there is nothing in TOR that prevents races between two servers trying to get a specific .onion address. So my understanding is, that a collision ( or a broken RSA private key) would put the HSDir into a inconsistent state. And in this case, some people would get the real server and some people would get the impersonated server. ( Additionally TOR hopefully warns if the public key of a hidden server suddenly changes.)