One major privacy aspect in an anonymous transport protocol is providing Unlinkability, which is
Unlinkability: No non-global entities except the conversation participants can discover that two protocol messages belong to the same conversation.
The level of Unlinkability supported by Waku2-Relay is k-anonymity which holds against a global adversary.
Why k-anonymity? The number of topics transported within the same mesh determines unlinkability level, e.g., if the mesh is used to transport k topics then for every two messages m1 and m2 transported within that mesh, the probability that these two belong to the same conversation is 1/k
Problem
The k-anonymity level is not the highest level of Unlinkability and is not clear how this level compares to the existing private transport protocol of Tor.
Acceptance Criteria
[ ] This is to investigate the Unlinkability of waku2 and provide a clear comparison between Tor.
The comparison shall include different adversarial power:
Local adversary (passive (HbC), active (malicious)): An adversary with the control of local network
Global adversary (passive (HbC), active (malicious)): An adversary with the control of a larger portion of the network e.g., ISPs.
Out of scope
The following items are outside of the scope of the current problem:
In the adversarial model, the end-point security is assumed, hence malware or hardware attacks are precluded.
The adversary has NO Auxiliary Information (background about users). The inclusion of such information would open up all sorts of inference attacks and a countermeasure demands research techniques like differential privacy which is going to be left out of scope for now.
In this analysis, we preclude the metadata included in the WakuMessage, as the unit of data transported using WAKU2-Relay. The waku message is treated as a black box. A privacy-respected application can provide the utmost level of security by encrypting the waku message before transportation. The analysis of the metadata included in the WakuMessage falls into the "conversational security" and deserves a separate issue.
Context
One major privacy aspect in an anonymous transport protocol is providing Unlinkability, which is Unlinkability: No non-global entities except the conversation participants can discover that two protocol messages belong to the same conversation.
The level of Unlinkability supported by Waku2-Relay is k-anonymity which holds against a global adversary.
Why k-anonymity? The number of topics transported within the same mesh determines unlinkability level, e.g., if the mesh is used to transport k topics then for every two messages m1 and m2 transported within that mesh, the probability that these two belong to the same conversation is 1/k
Problem
The k-anonymity level is not the highest level of Unlinkability and is not clear how this level compares to the existing private transport protocol of Tor.
Acceptance Criteria
The comparison shall include different adversarial power:
Out of scope
The following items are outside of the scope of the current problem: