@lastvault.io/encrypted-allowlist

The first reusable encrypted access-control primitive for Fhenix CoFHE.

EncryptedAllowlist lets a smart contract answer "is this address allowed?" using only encrypted data, with no plaintext identity ever appearing on-chain.

This package extracts the proven primitive from the LastVault FHE Private Inheritance Suite and packages it for reuse across the Fhenix ecosystem.

Use cases

• Private DAO membership — vote without revealing your identity
• Anonymous authorization — grant access without exposing the grantee
• Encrypted KYC allowlists — regulator verifies eligibility without doxxing users
• Confidential token-sale whitelists — eligibility hidden from competitors
• Hidden guild rosters — membership invisible to outside observers

Anywhere you'd put a plaintext mapping(address => bool) public allowlist, you can now use an encrypted equivalent that reveals nothing on-chain.

Install

npm install @lastvault.io/encrypted-allowlist @fhenixprotocol/cofhe-contracts

Or with Foundry:

forge install lastvault-io/lastvault-contracts

Use as a library

pragma solidity ^0.8.25;

import {EncryptedAllowlist} from "@lastvault.io/encrypted-allowlist/contracts/EncryptedAllowlist.sol";
import {FHE, InEaddress, ebool} from "@fhenixprotocol/cofhe-contracts/FHE.sol";

contract MyPrivateDAO {
    using EncryptedAllowlist for EncryptedAllowlist.List;

    EncryptedAllowlist.List private _members;
    address public admin;

    constructor(address _admin) {
        admin = _admin;
    }

    function addMember(InEaddress calldata _addr) external {
        require(msg.sender == admin, "DAO: not admin");
        _members.add(_addr);
    }

    /// @notice Returns an encrypted boolean. Decrypt via the threshold network.
    function isMember(InEaddress calldata _query) external returns (ebool) {
        return _members.isAllowed(_query);
    }
}

Use as an inheritable base contract

The package also ships an EncryptedAllowlistBase abstract contract with an ownership pattern baked in:

import {EncryptedAllowlistBase} from "@lastvault.io/encrypted-allowlist/contracts/EncryptedAllowlistBase.sol";

contract MyPrivateGuild is EncryptedAllowlistBase {
    constructor(address _owner) EncryptedAllowlistBase(_owner) {}
}

Now MyPrivateGuild already has addMember, removeMember, replaceMember, memberCount, and checkMembership — all encrypted.

How it works

The core operation is an encrypted OR-reduction over FHE.eq results:

isAllowed(query) ==
    eq(query, member[0]) OR
    eq(query, member[1]) OR
    ...
    eq(query, member[N-1])

Because Fhenix exposes FHE.and and FHE.not but not or directly, the library composes OR via De Morgan's law:

a OR b == NOT(NOT(a) AND NOT(b))

The result is a single encrypted boolean. No plaintext member identity is ever materialised on-chain. A failed membership check leaks nothing about which member the query was compared against.

Gas costs (testnet, Arbitrum Sepolia)

| Members in list | Approximate gas per isAllowed | |-----------------|--------------------------------:| | 1 | ~85k | | 10 | ~520k | | 50 | ~2.4M | | 100 | ~4.7M |

Gas scales linearly with list size (one FHE.eq per member). For lists larger than 200 entries, consider splitting into multiple allowlists and composing the boolean results.

Privacy properties

✅ Member identities are never revealed on-chain (stored as eaddress). ✅ Failed checks are indistinguishable from successful ones until decrypted. ✅ List size is public (acceptable — knowing "there are 5 members" doesn't help an attacker who can't see WHO). ✅ Decryption is gated by the threshold network and per-recipient FHE.allow permits.

❌ Insertion order is observable on-chain (the index at which a member was added). If this matters for your use case, batch-add members in a single transaction.

Origin

EncryptedAllowlist was extracted from the LastVault FHE Private Inheritance Suite, where it powers:

• Multi-heir membership checks (LastVaultMultiHeir)
• Institutional multi-sig signer verification (LastVaultFHEMultiSig)
• Confidential escrow beneficiary verification (ConfidentialEscrow)
• Auditor permit selection (SelectiveDisclosure)

All four contracts are live on Arbitrum Sepolia and use this same EncryptedAllowlist codebase. Production usage is the best test.

License

MIT — see LICENSE.

Links

• 🔗 Main repo: lastvault-io/lastvault-contracts
• 🌐 Live demo: lastvault.io/fhenix
• 🐦 Twitter: @LastVault_io
• 📚 Fhenix CoFHE docs: cofhe-docs.fhenix.zone