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Welcome

Introduction

shh is a privacy L3 on Base, built on the OP Stack. It ships in two profiles that share one cryptographic core — a full shielded-UTXO chain, and an open EVM L3 with a compliance-compatible Privacy Pool.

shh gives you private value transfer with a single, audited-by-construction cryptographic core: Poseidon commitments in a fixed-depth Merkle tree, spent through Groth16 zero-knowledge proofs. The same circuits, tree, and verifiers power both of its profiles — you choose how much privacy the chain exposes by default.

Profile A — Full privacy chainEvery transfer is a shielded UTXO note. Balances live as commitments; transfers are join-split proofs. No transparent transfers in the default UX.Profile B — Open L3 + Privacy PoolA transparent EVM L3 with an opt-in, fixed-denomination Privacy Pool. Withdrawals require an Association Set proof — privacy that stays unlockable.

It runs locally with a single sequencer via Docker Compose, and deploys to Base Sepolia or mainnet by swapping the settlement endpoint and keys. Both profiles reuse the same circuits, Merkle tree, and verifier infrastructure; the difference is which contract is the default value path and what the genesis/predeploys set.

What you get

  • A zk privacy core — Circom circuits (@shh/circuits) for UTXO join-split and Privacy-Pool withdrawals, with Groth16 trusted-setup tooling and generated Solidity verifiers.
  • Production-shaped contracts — @shh/contracts: pools, an on-chain Poseidon Merkle tree, and a bidirectional shielded bridge to Base.
  • An isomorphic SDK — @shh/sdk: notes, the Merkle tree, witness building, and proof generation, split into a browser-safe entry and a Node proving entry.
  • A turn-key local stack — pnpm dev boots a chain, deploys the core, copies circuit artifacts, and runs the wallet backend with a relayer.
  • An OP Stack devnet + explorer — single-sequencer Docker Compose and a Blockscout instance.

How the pieces fit

packages/
  circuits/   Circom circuits + trusted-setup tooling (the zk core)
  contracts/  Hardhat: pools, Poseidon Merkle tree, bridges, verifiers
  sdk/        TypeScript: notes, Merkle tree, witness + proof generation
infra/
  op-stack/   Docker Compose single-sequencer L3 devnet
  explorer/   Blockscout
apps/
  web/        Next.js UI + wallet backend (deposit / transfer / withdraw)
The monorepo at a glance — see Project layout for the full map.

Where to start

Quick startInstall, run the trusted setup, and boot the full local stack in three commands.ArchitectureThe L1 → L2 → L3 picture and how the two profiles share one core.Concepts & glossaryNotes, commitments, nullifiers, anonymity sets, ASPs — the vocabulary.

New to zero-knowledge value layers? Read Concepts & glossary first, then The two privacy profiles. Want to build now? Jump to the Quick start.