Ethereum co-founder Vitalik Buterin 'vibe-codes' anonymous billboard demo with onchain moderation on Aztec

Vitalik Buterin has released a working demo of an anonymous message board on Aztec, pairing fully private posting with an onchain moderation layer.

The Ethereum co-founder shared the project Sunday on Farcaster, calling it a "vibe-coded" toy version of the "anon billboard with moderation" concept he outlined in a 2022 blog post. The code is public on GitHub under his vbuterin account.

Buterin’s onchain message board

The billboard is built on Aztec. Users deposit ETH on Ethereum's (ETH) base layer, post messages anonymously on Layer 2, and later withdraw their ETH back to Layer 1, according to the repository. Posts carry no sender address in public call data and no link to the original deposit.

Buterin also noted that Aztec had reached stage 2 — the most decentralized tier on the Layer 2 maturity scale — in a follow-up cast, otherwise known as a post on the Farcaster platform.

The design attaches a censor role, set at deployment, that can flag posts as "immoral." Flagged posts are hidden from the default feed and impose a time-lock penalty on the poster's next message.

A local LLM daemon watches the board, evaluates each post against an onchain moderation policy, and flags anything that violates it, per the documentation. The policy itself is stored onchain and readable by the app, the CLI, and the daemon.

Posting is rate-limited through a cooldown that shrinks as the deposit grows, meaning 0.001 ETH buys one post per hour, while 0.01 ETH buys ten, according to the repo.

Part of the system also carries formal verification. The security properties covering rate limits, censorship screening, privacy, and deposit safety are proven in Lean 4 across 70 theorems with zero unproven gaps, the documentation said.

The repository lists the work as early and incomplete, with open items including access-control fixes and untested browser flows. Buterin said in his cast that the demo can already do "very interesting nontrivial stuff."