Confidential Token Deploy (fhEVM)

Deploy fully homomorphic encryption (FHE) tokens on fhEVM-compatible networks. Balances and transfers are encrypted on-chain — only authorized parties can decrypt them.

Supported Standards

Standard	Description
CONFIDENTIAL_ERC20	Encrypted ERC-20 with private balances and transfers
CONFIDENTIAL_ERC20_VOTES	Encrypted ERC-20 with private voting delegation
CONFIDENTIAL_ERC721	Encrypted metadata ERC-721

Prerequisites

1. fhEVM-enabled network — deploy to a network where is_fhevm = true (e.g., Zama devnet, Inco Rivest)
2. Network configuration — the target network must have all fhEVM fields populated:
   • confidential_factory_address
   • acl_address
   • coprocessor_address
   • kms_verifier_address
   • gateway_url
3. API key — secret key (sk_...)

tip

Use GET /v1/networks and filter by is_fhevm: true to discover available fhEVM networks.

1. Check Network Support

import Urblock from "@urblock/sdk";

const client = new Urblock({ apiKey: "sk_test_..." });

const networks = await client.networks.list();
const fhevmNetworks = networks.data.filter((n) => n.is_fhevm);
console.log("fhEVM networks:", fhevmNetworks.map((n) => n.name));

Or with curl:

curl https://api.urblock.io/v1/networks \
  -H "Authorization: Bearer sk_test_..." | jq '.data[] | select(.is_fhevm == true) | .name'

2. Deploy a Confidential ERC-20

const token = await client.tokens.create({
  name: "Private Stablecoin",
  symbol: "pUSD",
  standard: "ERC20",
  network_id: "net_zama_devnet",  // or chain_id
  initial_supply: "1000000000000000000000000",
  confidential: true,  // ← enables fhEVM encryption
  features: {
    mintable: true,
    burnable: true,
    pausable: true,
  },
  idempotency_key: "deploy-pusd-001",
});

console.log("Token deployed:", token.id);
console.log("Contract:", token.contract_address);
console.log("Tx hash:", token.deploy_tx);

curl -X POST https://api.urblock.io/v1/tokens \
  -H "Authorization: Bearer sk_test_..." \
  -H "Content-Type: application/json" \
  -d '{
    "name": "Private Stablecoin",
    "symbol": "pUSD",
    "standard": "ERC20",
    "network_id": "net_zama_devnet",
    "initial_supply": "1000000000000000000000000",
    "confidential": true,
    "features": { "mintable": true, "burnable": true },
    "idempotency_key": "deploy-pusd-001"
  }'

3. Deploy Confidential ERC-20 with Votes

caution

CONFIDENTIAL_ERC20_VOTES requires networks with full coprocessor support. Some fhEVM testnets may not yet support encrypted delegate/vote flows.

const govToken = await client.tokens.create({
  name: "Private Governance",
  symbol: "pGOV",
  standard: "ERC20_VOTES",
  network_id: "net_zama_devnet",
  initial_supply: "10000000000000000000000000",
  confidential: true,
  features: { mintable: true, burnable: true },
  idempotency_key: "deploy-pgov-001",
});

4. Deploy Confidential ERC-721

const nft = await client.tokens.create({
  name: "Private Art",
  symbol: "pART",
  standard: "ERC721",
  network_id: "net_zama_devnet",
  confidential: true,
  features: { mintable: true, burnable: true },
  idempotency_key: "deploy-part-001",
});

How It Works

1. The API detects confidential: true and validates the target network is fhEVM-enabled
2. The token is deployed via UrblockConfidentialFactory instead of the standard factory
3. Constructor args include the network's acl_address, coprocessor_address, and kms_verifier_address
4. All balance and allowance state is stored as FHE ciphertexts on-chain
5. Only the token owner and approved addresses can decrypt balances via the fhEVM gateway

Contract ABIs

Get the full ABIs for integration:

const abi = await client.contracts.getAbi("confidential_erc20");
// Also available: confidential_erc20_votes, confidential_erc721, confidential_factory

See the Contracts & ABIs reference for the full list.

Error Handling

Error Code	When
network_not_fhevm	Target network does not support fhEVM
incomplete_fhevm_config	Network is fhEVM but missing required addresses (acl, coprocessor, kms_verifier)
confidential_votes_unsupported	ERC20_VOTES with confidential: true not supported on this network