Measure the quality of unobservability

[youngjoon-lee]

This is just a naive idea for evaluating the quality of unobservability that our mixnet implementation provides.

Of the requirements listed in Notion, we're currently targeting the "sender unobservability" first. We have an intuition that our approach achieves the sender unobservability, but we don't have any way to see if it's true.

For example, it would be great if we can check

• how much traffic is coming in and out of each node, for each timeframe
• whether there is any pattern difference between timeframes.
  • and whether this difference degrades the sender unobservability (e.g. Even if there is an noticeable pattern, it may not provide important information with the adversary, or it may provide obfuscated information.).
• or any others useful

This will also help us maintaining the quality of unobservability while adding/modifying mixnet features.

[youngjoon-lee]

Closing this because we can start from #542 first.