Sealed — Vickrey NFT Auctions on Solana × Arcium MPC

Live: https://sealed-rayasa07s-projects.vercel.app · Network: Solana Devnet

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What is Sealed?

Sealed is a trustless, privacy-preserving NFT auction protocol built on Solana, powered by Arcium's Multi-Party Computation (MPC) network. It implements a Vickrey (sealed-bid second-price) auction: the highest bidder wins, but pays only the second-highest bid price. Bid amounts are encrypted client-side using the Arcium MXE public key before ever touching the blockchain — no one, including the auction creator, can see individual bids until the winner is decided. Losing bids are never revealed.

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How It Works

1. Create Auction — Seller escrows a Metaplex NFT into the on-chain auction PDA and sets the auction window (start_ts, end_ts)
2. Place Sealed Bid — Each bidder publicly locks max_collateral SOL on-chain and submits an encrypted bid amount, encrypted client-side using x25519 Diffie-Hellman key exchange + RescueCipher (Arcium's ZK-friendly cipher) against the real MXE public key fetched from devnet
3. Encrypted Commitment — The two ciphertexts (bid amount + active flag) are stored in the bidder's BidderRecord PDA on Solana devnet, referencing the deployed Sealed MXE program ID
4. Resolve Auction — After end_ts, anyone can trigger the Arcium MPC find_winner circuit, which scans all encrypted bids, enforces bid_amount ≤ max_collateral per slot, and computes both the highest bidder index and the second-highest price — all without revealing individual bid values. Only the winner index, second price, and validity flag are decrypted on-chain.
5. Settle — Winner receives the NFT, seller is paid the second-highest price, the winner's excess collateral is refunded, and losing bidders permissionlessly reclaim their full collateral

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Real Arcium Integration

Component	Details
MXE Program	6K6aykKN8vrBg8RQDtpeJXm6KUo5hG3KFYfyWdi5YS1e
MXE Account	7t2Z6MBuWKfTWaUtHNj5LRwcuDbMJdvQ2ujNjUZa84SR
Comp Def Account	EumEzPVoJwdWvM9f2Pmm568SFPGsRBQtNNmTU9SXK4hi
Cluster Offset	456 (Arcium devnet cluster)
Encryption	x25519 key exchange + RescueCipher via @arcium-hq/client SDK
MPC Circuit	find_winner (compiled .arcis circuit, single computation per auction)
Network	Solana Devnet

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MXE Program Features

• create_auction — Validates the Metaplex NFT (supply 1, decimals 0, rejects programmable NFTs), escrows it into the auction PDA, and stores the auction config
• submit_bid — Stores the bidder's encrypted bid ciphertexts in their lazy BidderRecord PDA and locks max_collateral SOL on-chain
• init_find_winner_comp_def — One-time setup that registers the find_winner MPC computation definition with the Arcium program- queue_find_winner — Builds an ArgBuilder payload of up to 8 encrypted bids + 8 public collaterals (sentinel-padded) and queues the MPC computation- find_winner_callback — Receives SignedComputationOutputs<FindWinnerOutput>, verifies the BLS-signed result, and stores winner_index, second_price, has_valid_winner on-chain- settle_auction — Permissionless. Transfers the NFT to the winner, pays the seller the second-highest price, and refunds the winner's excess collateral- refund_loser — Permissionless. Each losing bidder reclaims their full collateral- emergency_refund / emergency_reclaim_nft — Recovery path if the MPC computation fails or times out past end_ts + EMERGENCY_TIMEOUT

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Tech Stack

• Frontend: Next.js 14, TypeScript, Tailwind CSS
• Blockchain: Solana Web3.js, Wallet Adapter (Phantom)
• MPC: Arcium SDK (@arcium-hq/client 0.9.3), Anchor 0.32.1
• Program: Rust + arcium-anchor macros
• Encrypted Circuit: Rust + arcis framework (compiled to .arcis MPC bytecode)
• Deployment: Vercel (frontend), Solana Devnet (program)

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Project Structure

sealed/
├── app/                         # Next.js frontend (App Router)
│   ├── auction/[address]/       # Auction detail page (bid + settle UI)
│   ├── create/                  # Create auction page
│   ├── components/              # WalletProvider, AuctionCard, BidForm, etc.
│   ├── lib/                     # PDA helpers, Arcium encryption, program hooks
│   └── idl/                     # Anchor IDL for the deployed program
├── programs/
│   └── vickreynftauction/
│       ├── src/lib.rs           # Anchor program (9 on-chain instructions)
│       └── Cargo.toml
├── encrypted-ixs/
│   └── src/lib.rs               # Arcis MPC circuit (find_winner Vickrey logic)
├── tests/
│   ├── vickreynftauction.ts     # Localnet end-to-end test
│   └── vickreynftauction_devnet.ts # Devnet end-to-end test (verified passing)
├── scripts/
│   ├── init_devnet_comp_def.ts  # One-time devnet circuit upload script
│   └── mint-nft.ts              # Test NFT minting helper
├── devnet_e2e_proof.txt         # Captured output proving devnet flow works end-to-end
├── Anchor.toml
└── Arcium.toml

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Running Locally

git clone https://github.com/rayasa07/sealed
cd sealed
yarn install
arcium build
arcium test

Then start the frontend:

cd app
yarn install
yarn dev

Open http://localhost:3000 and connect a Phantom wallet on Solana Devnet.

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Deployed Program

The Sealed MXE program is deployed and verified on Solana Devnet:

• View Program on Solana Explorer
• View MXE Account

A captured end-to-end test run against real Arcium devnet MPC nodes is preserved in devnet_e2e_proof.txt — proving the Vickrey settlement (winner_index=1, second_price=3 SOL) was computed entirely inside the MPC network without revealing individual bids.

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Team

Built for the Arcium RTG by asa ray