On 2010-12-06 09:18, John Case wrote:
On Mon, 6 Dec 2010, grarpamp wrote:
[...]
Maybe there would also be benefit in a web of trust amongst nodes not unlike a keysigning party. As with social networking, people vouch for each other in various ways and strengths based on how they feel that person meets them. I don't see any reason why node operators [descriptors] could not keysign and have that web encoded into the descriptors, directories, DHT, etc.
I proposed early in the previous thread that not only should a web of trust be considered, but that this was indeed a classic case of a web of trust ... I didn't see any comment on this from the Big Names on the list, though...
The Web of Trust (WoT) concept provides for marginal security benefits and then only in a very narrow set of circumstances that are unlikely to hold true for the larger community of Tor node operators. Starting with the second point, the WoT concept presumes that trust between its members precedes the codification of that trust into attestations attached to digital certificates. In other words, the WoT might provide (but likely will not) security benefits to a group of users that have pre-existing social relations and trust. For example, members of a human rights group that have personally known each other, or at least the bulk of each other, for years. The WoT cannot provide security benefits to a group of users with no pre-existing social trust relationship, such as the set of "Tor node operators". The thousands of Tor node operators, a tiny percentage of which have an existing social relationship, have no inherent trust amongst each other. And how could they? Absent an existing real-life WoT, there is no digital WoT to codify. Even within a group that has a strong existing trust and social graph in real life, the digital codification of a WoT offers security benefits only at the extreme margins. This fact is easiest explained by example: o Fire up your preferred OpenPGP software. (If you don't have OpenPGP software, then your understanding of how a WoT works is likely different from what a WoT actually does). o Eliminate all public keys for users with whom you do not intend to communicate. (No communication security system can provide security benefits to communications that will never take place). o List the public keys that show as valid. (Meaning they are signed by one or more keys that you trust to some degree). o Eliminate all the public keys that are signed by your key. (Those keys are not authenticated by the WoT, they were authenticated by you directly). o Eliminate all the public keys that are signed by keys that you chose to trust because they are the equivalent of CA root keys. This includes Debian distribution signing keys, the keys of any commercial CA, and the signing keys of auto-responder key servers such as the PGP Global Directory. (Signatures performed by such keys do not employ the WoT). o Look at the small number of public keys remaining. The keys are likely from deep inside your social circle. Now eliminate all the public keys that you could trivially authenticate directly, such as by asking a key holders, who are well known to you, to provide you with their key's fingerprint at work, at the next security conference, or the next time you meet at the pub. (The WoT may have authenticated those keys, but the WoT was not necessary to do so since you could have trivially authenticated those few keys yourself). o Lastly, count the remaining public keys. The number will likely be zero (no real life benefit to the WoT) or close to zero (benefit only in the extreme margins). In summary, the WoT is not a suitable solution to increasing the security of the Tor network. --Lucky Green *********************************************************************** To unsubscribe, send an e-mail to majordomo@torproject.org with unsubscribe or-talk in the body. http://archives.seul.org/or/talk/ ----- End forwarded message ----- -- Eugen* Leitl <a href="http://leitl.org">leitl</a> http://leitl.org ______________________________________________________________ ICBM: 48.07100, 11.36820 http://www.ativel.com http://postbiota.org 8B29F6BE: 099D 78BA 2FD3 B014 B08A 7779 75B0 2443 8B29 F6BE