Thread by @dominic_w

1/ To design a web-speed blockchain computer:

—That can scale without bound
— Is efficient enough for mass market usage

You must observe a key design principle:

Your network protocol suite must separate key blockchain concerns, such as mediating participation, and consensus...

2/ Bitcoin was the first blockchain design, so naturally it tightly coupled concerns

For example, Proof-of-Work hashing must create "Sybil resistance" that mediates participation by making it costly *and* generate random numbers to drive consensus by selecting block proposals...

3/ At a Stanford Security Seminar, a long time ago, I proposed “Puzzle Tower” cryptography, which transformed Proof-of-Work into a membership scheme to obtain:

(i) Stronger Sybil resistance
(ii) Anon identities for faster consensus

Bitcoin cannot be so easily reworked.

But...

4/ For me, this affirmed the power of decoupling concerns:

—If Proof-of-Work only has to mediate miner participation (Sybil resistance), security can be increased

—If consensus only need form agreement, and dedicated crypto generates randomness, consensus can be vastly faster…

5/ Separation of concerns is the most obvious principle at work in the design of the Internet Computer blockchain.

Its ICP protocol has four main layers: Execution, Message Routing, Consensus and P2P.

Consensus is broken into three further layers...

6/ Consensus layers 1-3:

L1. Threshold Relay efficiently produces a sequence of unmanipulable random numbers


L2. Probabilistic Slot Consensus creates a blockchain using the perfect randomness

L3. Asynchronous Negative Attestation Finalization anoints permanent blocks...

7/ Meanwhile, consensus is decoupled from updating on-chain state:

First "Consensus" produces a globally consistent final ordering of messages

Only then are messages (e.g function calls) applied to update state

Hence on-chain state doesn't fork, avoiding the cost of rewinds...

8/ Sybil resistance is decoupled thus:

—The participation of network nodes is controlled by a dedicated system (the NNS)

—Which means fixed rewards can be disbursed to standard node machines in return for compute power the network can repurpose for users, instead hashing…

9/ Of course, separating concerns is nothing new in networking. Both the TCP/IP and the OSI stacks have rigorously layered architectures

But the need for scalable, fast and more efficient blockchains, behoves architects to take separation of concerns principles to the next level