Re: [tor-dev] Questions about "Tor Messenger CONIKS integration"

Hi,

Thanks for you quick reply. I still have few questions:

1. If one CONIKS server has been compromised, and I happen to register to this server; I guess the server can see my username in this case, Âright?Â

2. I found the ticketÂhttps://trac.torproject.org/projects/tor/ticket/17961. The answer for the second question says "We can ask for a proof of ownership of the name...". So when doÂCONIKSÂneed to do proofÂof account ownership? Could please anyone give me some concreteÂscenarios? My concern is that in order to do proof of ownership, we have to hand out the real accounts to CONIKS.Â

Sorry for being paranoid.Â

Thanks!

On Tue, Apr 19, 2016 at 4:57 PM, Ismail Khoffi <ismail.khoffi@xxxxxxxxx> wrote:

Hi there,

I don't know about much about the concrete plans for the Tor Messenger and CONIKS but I'm quite familiar with the original CONIKS design. First of all: Iâm sure no one would force you to give your "real" identity, you could for instance use large Âidentity provider which is rather difficult to compromise, at least for non-state actors (for example gmail and the pseudonymÂsimplesmtptest123 ;-). Maybe, for the Tor messenger integration there will be/people might choose some other identity providers (with a stronger focus on privacy and more freedom to choose pseudonyms instead of real names).Â

If an identity provider (one of the several "CONIKS servers") is compromised, the attacker is able to read the provider's local directory (containing public key of already registered providers), he would basically see a more or less ârandomly' looking Merkle tree. Theoretically, the attacker would still need to know all the user real-names beforehand to (for instance) query for their public keys. (This is achieved using the following "crypto-tricks": identities are stored at a private âindex" in the tree; computed using a verifiable unpredictable function from a cryptographic commitment/hash of the username instead from the username itself). Of course one would also need to make sure that the stored public-key material (in the leaf-nodes) is pruned from user identifying data (like an identity in GPG); otherwise the attacker could guess the identities from that information.Â
Also, in general, the attacker wonât be able to see that you used Tor Messenger from the mere fact that you use a certain identity provider, even if he still could recompute your user-name from the directory.

Hope that helps?
Ismail

On 19 Apr 2016, at 21:28, Go <simplesmtptest123@xxxxxxxxx> wrote:

Hi,Â

CONIKS seems to be a very useful system. Just curious: do Tor messenger users need to hand out their real identities (facebook account, twitter account, etc.) to CONIKS servers? If so it seems dangerous to put all the identities in a centralized service.Â If the CONIKS servers have been compromised, will the attacker be able to figure out theÂsocial networking profiles of TorÂmessenger users?Â

Thanks!
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