Prerequisites
Required tools
| Tool | Version | Purpose |
|---|---|---|
| Node.js | 20+ | Runtime for scripts and tooling |
| npm or pnpm | Latest | Package management |
| Hardhat | 2.28+ | Smart contract development framework |
| Solidity | 0.8.24+ | Smart contract language |
Required packages
These are installed automatically as peer dependencies:
@fhevm/solidity(^0.11.1) — Zama’s FHE Solidity library@openzeppelin/contracts(^5.6.1) — Standard contract utilities
For proof generation (optional)
If you plan to generate ZK proofs in your application (client-side or server-side):
| Package | Purpose |
|---|---|
@aztec/bb.js | Honk SNARK proof backend |
@noir-lang/noir_js | Noir circuit execution |
@aztec/foundation | Poseidon2 hashing and field arithmetic |
ethers | ABI encoding and hex utilities |
Conceptual background
You don’t need to be a cryptography expert, but familiarity with these concepts will help:
Zero-Knowledge Proofs (ZK)
A ZK proof lets you prove a statement is true without revealing the underlying data. In Cipher, ZK proofs are used to prove:
- You are a member of the DAO (without revealing which member)
- Your vote is within the valid range (without revealing your vote)
- Your nullifier is correctly derived (preventing double voting)
Fully Homomorphic Encryption (FHE)
FHE allows computation on encrypted data. In Cipher, votes are encrypted using FHE so the smart contract can:
- Add encrypted votes together (homomorphic addition)
- Store encrypted tallies that no one can read
- Decrypt only the final aggregate when voting ends
Merkle Trees
Cipher uses a Poseidon2 Merkle tree (height 32) to represent DAO membership. Each member has an identity secret whose hash is a leaf in the tree. The tree root is stored on-chain, and voters prove membership by providing a Merkle path — without revealing their position in the tree.
Nullifiers
A nullifier is a deterministic value derived from hash(proposal_id, identity_secret). It uniquely ties a voter to a proposal. Since the same inputs always produce the same nullifier, the contract can reject duplicate votes — without knowing who voted.