🌘 ShadowSwap

Private Cross-Chain Swaps between Starknet ↔ Zcash

Swap STRK ↔ ZEC with privacy, atomic guarantees, and zero trust assumptions.
ShadowSwap combines the privacy of Zcash with the scalability of Starknet to deliver private, non-custodial, atomic cross-chain swaps.

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🚀 Why ShadowSwap?

Today’s swaps are:

• ❌ Public
• ❌ Traceable
• ❌ Custodial
• ❌ Limited to Ethereum-like chains

ShadowSwap fixes this by bridging two powerful ecosystems:

• 🔗 Starknet — scalable ZK-Rollup
• 🛡 Zcash — industry-leading privacy chain

ShadowSwap enables private, atomic, cross-chain swaps using:

• HTLCs
• Stealth addresses
• Commitments
• Range proofs
• Merkle tree inclusion
• Automated relayer orchestration

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🧠 How It Works (Simple)

1. User locks STRK in a Starknet HTLC

• Includes secret hash
• Private commitment
• Timeout

2. Relayer observes Starknet

• Verifies Merkle inclusion
• Generates stealth parameters
• Creates matching HTLC on Zcash

3. User redeems Zcash HTLC

Reveals the secret.

4. Relayer finalizes Starknet side

HTLC unlocks → STRK released.

5. Atomic refunds if anything fails

Both sides are safe.

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✨ Features

🔒 Private Swaps

• Shielded addresses (Sapling/Orchard)
• Encrypted metadata
• Commitments + nullifiers
• No public link between sender ↔ receiver

⚡ Cross-Chain Atomicity

• HTLCs on both chains
• Refund guarantees
• Fully non-custodial

🤖 Autonomous Relayer

• Observes Starknet & Zcash
• Handles redemptions
• Auto-refunds
• Retry + backoff logic
• Detailed event logging

🌲 Merkle Proof Engine

• Tracks Starknet deposits
• Creates Merkle proofs
• Syncs with on-chain Merkle root

💱 On-Chain/Off-Chain Price Router

• STRK/ZEC/USD pricing
• Multi-source aggregation
• Route through Fast/Standard pools

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🏛 Architecture

flowchart LR
    U[User Wallet] -->|Lock STRK in HTLC| S(Starknet)
    S -->|Deposit Event| R(Relayer)
    R -->|Merkle Proof + Stealth Params| R
    R -->|Deploy HTLC| Z(Zcash)
    U -->|Redeem ZEC HTLC| Z
    Z -->|Reveal Secret| R
    R -->|Redeem STRK HTLC| S

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🔧 Tech Stack

Languages & Frameworks

• 🦀 Rust
• ⚡ Actix Web
• 🔁 Asynchronous Relayer Engine

Cryptography

• ⛓ HTLCs (Hashed Timelock Contracts)
• 🕵️ Stealth Addresses
• 🔐 Range Proofs
• 🧱 Commitments & Nullifiers
• 🌲 Merkle Trees
• ⚙️ ZK-Friendly Hash Primitives

Networks

• ⭐ Starknet (Cairo 1)
• 🛡 Zcash (Sapling / Orchard Shielded Pools)

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📡 REST API Endpoints

POST /swap/initiate

Create a cross-chain swap (STRK → ZEC or ZEC → STRK).

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POST /indexer/event

The indexer sends Starknet/Zcash HTLC events to the backend.

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GET /price

Returns real-time STRK ↔ ZEC ↔ USD pricing.

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GET /stats

Displays global protocol statistics:

• swap volume
• liquidity usage
• completed vs pending swaps

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GET /metrics

Prometheus metrics endpoint for relayer + backend monitoring.

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📬 Team

Mist Labs

👥 Contributors

Okoli Evans

• GitHub: @OkoliEvans

Kolapo Goodness

• GitHub: @Goodness5