This article describes the basics about USB protocol enough to overcome my usual fear of dappling into USB hacking. The author demonstrated the means to use libusb (user-space) to interact with an unsupported USB RGB light.

A non-interactive zero-knowledge proof scheme: The prover commits (shuffle+lock) the graph N times: s[0..N]. He then calculate r=hash(s[0] || s[1] || .. || s[N]). And then he use the random bits in r generate N pseduorandom numbers c[0..N]. For each i=0..N, use c[i] to select a fixed edge in s[i] and reveal the keys k[i][0] and k[i][1] for the two nodes of the edge. The final message consists of s[0..N] and k[0..N][0..1]. The verifier is able to use these information to replay the steps to verify the prover's claim.

Another thing I learned from the video is how to "lock" messages cryptographically and allow the verifier to verify any message without revealing the others. First, the prover calculate h[i] = hash(m[i] || nounce[i]) and send h[0..N] to the verifier. The verify choose any integer t between 0 and N and send to prover. The prover will then send back (m[t], nounce[t]) to the verifier that h[t] is indeed calculated from m[t]. Here h[t] is the locked message m[t] and nounce[t] is the key.

A refreshing viewpoint: when we use UDP as an unreliable protocol, we often actually wants its "timeliness" property, which is to say if we have to choose from dropping two versions of a data, we want to drop the old one. This is why real-time video streaming and gaming choose UDP. The datagram extension in QUIC offers a nice solution. Data are split into streams, within each stream data is ordered. Each stream has a priority attached that is used to determine which packet to drop.

However, how do you choose which to drop without having a bloating buffer that hurts latency? The author suggests using delay-based congestion control like BBR that uses network metrics to probe the bandwidth and RTT.

The design of HTTP/3 by Daniel Stenberg.

The design of HTTP/2 by Daniel Stenberg.

This article explained the ActivityPub protocol (used by Mastodon and others) by describing the essential endpoints which may be served simply in static json.

I love this approach of explaining things by reducing a complex thing into the minimalist essentials.