Specter — Private Blind Auctions on Solana

"Your bid is real. But until close — it's a ghost."

Specter is a trustless blind-auction platform on Solana powered by Arcium's Multi-Party Computation network. Bids are encrypted on the client, evaluated without decryption by Arcium's MPC nodes, and revealed only after the auction closes.

Built for the Arcium RTG: Blind Auctions.

How it works

[Bidder]            [Solana program]            [Arcium MPC cluster]
encrypt bid ───────▶ store ciphertext  ┐
                                       │
                                  finalize ────▶ evaluate on encrypted data
                                       │              │
                                  callback ◀──── encrypted WinnerResult
                                       │
                            update Auction account
                                       │
                                       ▼
                            [Bidder] decrypts result client-side

• X25519 + Rescue cipher locks bid amounts client-side
• Arcis circuit (encrypted-ixs/src/lib.rs) compares encrypted u64 amounts in MPC and returns an encrypted WinnerResult { winner_index, winning_amount }
• Anchor program (programs/specter/src/lib.rs) coordinates create_auction, place_bid, finalize_auction, the MPC callback, and claim_prize
• Frontend (app/) shows a live "Ghost Leaderboard" (count only, no amounts) and animates a Reveal Ceremony when MPC finishes

Constraints

Max bidders per auction	8 (Anchor's BorshInstructionCoder allocates a 1000-byte instruction buffer; 8 × 80-byte BidData entries fit comfortably)
Output size	65 bytes (winner_index ct + winning_amount ct + nonce) — well under the 1232-byte Solana callback limit
Encryption	X25519 key exchange, Rescue cipher (one ciphertext per encrypted scalar)

Running

You need:

• Rust + cargo build-sbf (via Solana 3.x CLI for builds)
• Solana CLI 2.x for solana-test-validator (3.x crashes on --bind-address 0.0.0.0 that Arcium passes)
• Anchor 0.32.1 (avm install 0.32.1 && avm use 0.32.1)
• Arcium CLI 0.9.7 (arcup install)
• Docker Desktop (Arcium localnet pulls arcium/arx-node and arcium/trusted-dealer)
• Node 18+ and Yarn

Path A — Local end-to-end (recommended for dev)

# 1. Build everything (use Solana 3.x for build-sbf)
agave-install init 3.1.14
arcium build

# 2. Run the integration test (uses Solana 2.x for test-validator)
agave-install init 2.1.0
arcium test --skip-build

# 3. (Optional) Keep localnet running and wire the frontend to it
arcium localnet                                    # in one shell
cd app
cp .env.example .env.local
# set NEXT_PUBLIC_NETWORK=localnet
# set NEXT_PUBLIC_ARCIUM_CLUSTER_OFFSET=0
yarn install
yarn dev                                           # http://localhost:3000

Path B — Devnet (shareable demo)

# Fund the deployer wallet (faucet.solana.com) with ~5 SOL
agave-install init 3.1.14
arcium build
arcium deploy --cluster devnet                     # ~5 SOL
arcium test --cluster devnet                       # optional sanity check

cd app
cp .env.example .env.local
# default NEXT_PUBLIC_NETWORK=devnet works — set NEXT_PUBLIC_RPC_URL if rate-limited
yarn install
yarn dev

The frontend reads the IDL and types from target/idl/specter.json + target/types/specter.ts, so a successful arcium build is required before yarn dev.

Structure

specter/
├── encrypted-ixs/src/lib.rs           ← Arcis circuit (MPC)
├── programs/specter/src/lib.rs        ← Anchor program
├── tests/specter.ts                   ← End-to-end test (passes in 23s)
├── app/                               ← Next.js 14 frontend
│   ├── app/page.tsx
│   ├── components/
│   │   ├── CreateAuctionForm.tsx
│   │   ├── BidForm.tsx
│   │   ├── GhostLeaderboard.tsx       ← live bid count + countdown
│   │   ├── FinalizeButton.tsx         ← triggers MPC computation
│   │   └── RevealCeremony.tsx         ← staged reveal animation
│   └── lib/specter.ts                 ← encrypt / derive / decrypt helpers
├── Anchor.toml
├── Arcium.toml                        ← devnet cluster offset = 456
└── CLAUDE.md / BUILD_GUIDE.md / PHASE_0_CHECKLIST.md

Privacy guarantees

• The auctioneer cannot see bid amounts during the auction
• Other bidders cannot see bid amounts at any point
• Arcium nodes never see plaintext (dishonest-majority MPC security model)
• Only the encrypted result is written on-chain — the holder of bid_0's ephemeral X25519 key (typically the auction creator or first bidder) decrypts it client-side

Known limitations

1. Max 8 bidders per auction (see Constraints)
2. Bid amounts in u64 lamports (max ~18.4M SOL)
3. Sealed bids are final — no cancellation
4. MPC computation takes ~30–60 seconds after finalize_auction
5. The on-chain claim_prize currently only emits an event; real escrow/transfer is mocked for the hackathon

License

MIT