Node.js + viem

A single example demonstrating the full @fhevm/sdk lifecycle using viem: encryption, reading public values, and private decryption.

Prerequisites

• Node.js >= 22
• SDK dependencies installed (npm install in the repo root)

Setup

Optionally provide a wallet private key:

cp .env.local.example .env.local

Without .env.local, a random wallet is used. The full flow still runs but decryption will fail (encrypted values are not on-chain).

Run

npx tsx ./test-run.ts

Notes

• This example uses the viem adapter (@fhevm/sdk/viem). The API is identical to the ethers adapter — only the import path and provider type differ.
• The viem adapter uses PublicClient<Transport, Chain> instead of ethers' ContractRunner.
• EIP-712 signing uses walletClient.signTypedData() instead of ethers' wallet.signTypedData().
• The E2E transport key pair is generated locally and never leaves the client. Only the corresponding public key is shared (embedded in the EIP-712 permit).
• The Zama Protocol processes decryption requests and returns encrypted shares that only the holder of the transport key pair can decrypt.
• ACL permissions are checked on-chain before decryption. If FHE.allow() was not called for the user + encrypted value pair, decryption will fail.