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3. Market Mechanics3.1 Sealed-Bid Auctions

3.1. Sealed-Bid Auctions

Traditional blockchain auctions operate in a state of forced transparency. Every transaction, including bid values and participant addresses, is broadcast in plaintext to the mempool before confirmation. This architectural flaw enables MEV front-running, bid sniping, and seller shill bidding, fundamentally corrupting market fairness.

Fhenix-FairMarket v2.0 replaces “trust in transparency” with “trust in cryptographic proof”. By implementing a Sealed-Bid architecture powered by Fully Homomorphic Encryption (FHE), the protocol ensures that bid values remain mathematically concealed from validators, node operators, and even the protocol developers until the exact moment of asynchronous settlement. All on-chain interactions are reduced to opaque ciphertext hashes, achieving O(1) gas complexity while preserving absolute economic privacy.

Core Cryptographic Principles

PrincipleTechnical Implementation
Client-Side EncryptionBids are encrypted locally via @cofhe/sdk ^1.2.0 before transmission. The plaintext value never enters the mempool, RPC layer, or node infrastructure.
O(1) On-Chain StorageThe contract accepts the ciphertext but persists only its bytes32 cryptographic hash in the ciphertextHashes mapping. Full FHE objects are never stored on-chain.
Encrypted Solvency GateFHE.lte(encryptedBid, escrowBalances[msg.sender]) validates financial capacity homomorphically. No balance or bid amount is exposed during verification.
Async Resolution TriggerfinalizeAuction() emits a DecryptionRequested event at endTime, delegating all comparative FHE math to off-chain FHEOS coprocessors. Zero on-chain computation occurs.
Event Log NeutralityZero plaintext bid values, intermediate states, or comparative results are emitted in Events. Only auctionId, bidder address, and cipherHash are logged.

️ Technical Implementation

1. Client-Side Encryption Flow

The encryption process occurs entirely within the user’s secure execution environment (browser/extension) before any network call.

// packages/frontend/src/lib/cofhe/encryption.ts
import { cofheClient, Encryptable } from '@cofhe/sdk';
 
export async function encryptBid(amount: number): Promise<InEuint32> {
 // 1. Range validation (euint32 max: 2^32 - 1)
 if (amount < 0 || amount > 2 ** 32 - 1) {
 throw new Error('Bid amount exceeds euint32 range');
 }
 
 // 2. Local encryption via CoFHE SDK
 const encryptedPayload = await cofheClient.encryptInputs([
 Encryptable.uint32(amount)
]);
 
 return encryptedPayload[0]; // Returns InEuint32 Ciphertext
}

2. On-Chain Submission & O(1) Hash Storage

The smart contract acts as a stateless cryptographic registry. It validates solvency, records the hash, and emits a neutral event.

// packages/contracts/core/FhenixFairMarket.sol
function placeBid(uint256 auctionId, InEuint32 calldata encryptedBid) external {
 require(state == AuctionState.ACTIVE, "Auction not active");
 require(block.timestamp < auctions[auctionId].endTime, "Expired");
 
 // Encrypted Solvency Check: Executes without decryption
 FHE.lte(encryptedBid, FHE.asEuint32(escrowBalances[msg.sender]));
 
 // O(1) Storage: Only cryptographic hash is persisted
 bytes32 bidHash = keccak256(abi.encode(encryptedBid));
 auctions[auctionId].ciphertextHashes.push(bidHash);
 
 emit BidPlaced(auctionId, msg.sender, bidHash);
}

Sealed-Bid Data Flow

️ Security & Privacy Guarantees

Threat VectorTraditional AuctionFhenix Sealed-Bid Mechanism
MEV Front-RunningBots read pending txs, outbid instantlyPayload is opaque ciphertext; value cannot be parsed by validators
Bid SnipingSnipers wait to see current highest bid & increment”Current highest bid” is never computed or visible until endTime
Plaintext LeakageEvents/Storage expose bid historyOnly bytes32 hashes stored; zero plaintext in logs or state
Gas-Based DoSHigh FHE computation per bid blocks networkplaceBid costs flat ~15k–25k gas; heavy math offloaded
Solvency Oracle DependencyRequires external price feeds or plaintext checksFHE.lte verifies capacity homomorphically without revealing balances

Architectural Impact

  • Market Fairness Restoration: Participants can bid their true maximum valuation without fear of strategic manipulation or information leakage.
  • Linear Scalability: The O(1) storage model decouples participant count from on-chain state bloat. Auctions can scale to thousands of bidders without triggering block gas limits.
  • Deterministic Finality Costs: By eliminating synchronous FHE comparisons, gas consumption becomes predictable and independent of bid volume or network congestion.
  • Trustless Verification: The cryptographic hash registry provides an immutable audit trail. Post-audit verification is possible by cross-referencing off-chain FHEOS outputs against on-chain stored hashes.

Audit Gate Compliance (P0)

The protocol enforces strict sealed-bid verification gates. Progression to subsequent phases is blocked until all P0 items pass:

  • [] Zero Plaintext in Events/Storage: CI lint rules fail the build if any uint or bytes plaintext bid values are emitted alongside BidPlaced.
  • [] FHE.lte Solvency Check: Encrypted bids strictly cannot exceed escrowBalances[msg.sender]; invalid bids revert pre-dispatch.
  • [] Adapter Isolation: Zero direct import @fhenixprotocol/cofhe-contracts in core logic; all FHE calls route through ICofheAdapter.
  • [] O(1) Gas Enforcement: hardhat-gas-reporter confirms placeBid() consumes < 25k gas across varying participant counts (1 → 1,000).
  • [] State Transition Guard: Bids submitted after endTime or during RESOLVING/FINALIZED states revert instantly with "Expired" or "Invalid state".

Next Steps

Market Mechanics3.2 Vickrey Price Sharing