🛡️ Sol-Link: Private SOL Sharing via ZK Mixer Links

Sol-Link is a privacy-first application that enables users to send SOL anonymously via secure, shareable links. Powered by Privacy Cash's zero-knowledge proofs and Helius RPCs, Sol-Link ensures that the sender and receiver addresses remain unlinkable on-chain.

🚀 Built for the Solana Privacy Hackathon 2026

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🏗️ The Problem

On public blockchains like Solana, every transaction is visible.

• Sender & Receiver are public: Anyone can trace a payment back to you.
• Transaction History is open: Your financial fingerprint is exposed.
• No private gifting: You can't send money to a friend without them knowing your wallet address.

Sol-Link solves this by breaking the on-chain link between the depositor and the recipient using cryptographic "Notes" and Zero-Knowledge principles.

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🌊 How It Works (The Process)

1️⃣ Shield (Deposit)

The sender connects their wallet and deposits SOL into the Sol-Link protocol.

• The app generates a random Secret Key locally.
• A Note (UTXO) is created representing the deposit amount.
• The SOL is sent to a shared Vault Program.

2️⃣ Link Generation

• The app embeds the Secret Key into a unique, shareable URL.
• Crucial: This key is never sent to the server. It lives only in the link as a URL Fragment (#) and the user's clipboard. This prevents server-side logging of keys.

3️⃣ Share

• The sender shares the link with the recipient via any secure channel (Signal, WhatsApp, Telegram, Email).

4️⃣ Sweep (Claim)

• The recipient opens the link.
• The app extracts the Secret Key from the URL fragments.
• It derives the proofs needed to authorize the withdrawal.
• The funds are "swept" from the Vault directly to the recipient's wallet (or a fresh wallet for max privacy).

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🔄 Flow Diagram

sequenceDiagram
    participant Sender
    participant SolLink as Sol-Link App
    participant Helius as Helius RPC
    participant Vault as Vault/Smart Contract
    participant Recipient

    note over Sender, SolLink: 1. Shielding Phase (Powered by Privacy Cash)
    Sender->>SolLink: Connect Wallet & Enter Amount
    SolLink->>SolLink: [Privacy Cash] Generate Secret & UTXO Note
    SolLink->>Helius: Check Account Balance
    SolLink->>Vault: Deposit SOL (Public Tx via Helius)
    Vault-->>SolLink: Confirm Deposit

    note over Sender, Recipient: 2. Sharing Phase
    SolLink-->>Sender: Generate Magic Link (contains Secret)
    Sender->>Recipient: Share Link (Off-chain)

    note over Recipient, Vault: 3. Sweeping Phase
    Recipient->>SolLink: Click Link
    SolLink->>Helius: Query Chain State
    SolLink->>SolLink: [Privacy Cash] Reconstruct Keypair
    SolLink->>SolLink: [Privacy Cash] Generate ZK Proof
    SolLink->>Vault: Submit Proof & Withdraw Request
    Vault->>Vault: Verify Proof
    Vault-->>Recipient: Transfer SOL (Public Tx)

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🔐 Privacy Cash SDK Integration

Sol-Link relies heavily on the core cryptographic primitives provided by the Privacy Cash SDK. We have integrated key components directly into our application logic to ensure robust privacy.

Core Components Used:

• 🔑 keypair.ts (Shielded Keys):

  • We use the SDK's keypair generation to create ephemeral shielded addresses specifically for each deposit note.
  • This ensures that the keys controlling the funds are distinct from the user's main wallet.

• 🧾 utxo.ts (Note Management):

  • Implements the UTXO (Unspent Transaction Output) model from Privacy Cash.
  • Every deposit is treated as a discrete "Note" object containing the amount, blinding factor, and owner credentials.

• 🌳 merkle_tree.ts (Commitments):

  • Uses Merkle Trees to store commitments of deposited notes.
  • This allows us to prove membership (that a deposit exists) without revealing which deposit is being spent.

• 🕵️ prover.ts (ZK Proofs):

  • Leverages snarkjs and circomlib to generate Zero-Knowledge Proofs client-side.
  • These proofs verify that the user possesses the valid secret key for a note in the Merkle tree without revealing the key itself.

⚡ Helius RPC Integration

Sol-Link requires extremely stable and fast connection to the Solana blockchain to ensure the user experience of "Magic Links" feels instant. We use Helius RPCs exclusively for:

• 🏎️ Instant State Queries: Fetching the latest Merkle Tree state and inclusion paths via getAccountInfo with zero latency.
• ✅ Reliable Confirmations: We heavily leverage Helius's optimized transaction propagation to ensure the "Sweep" transaction (which contains the ZK proof) is confirmed in seconds, preventing users from seeing "Transaction Expired" errors.
• 🛡️ Rate Limit Protection: Privacy operations often require multiple sequential RPC calls; Helius ensures we don't hit public node limits.

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⚡ Technology Stack

• Frontend: Next.js 14, React 19, TailwindCSS, Framer Motion
• Blockchain Interaction: @solana/web3.js, @solana/wallet-adapter
• Privacy & Cryptography: circomlib, snarkjs, ffjavascript
• Infrastructure: Helius RPC for high-speed transaction confirmations and state queries.
• Styling: Custom design system using Syne & Bricolage Grotesque fonts.

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🏃‍♂️ Setup & Run Locally

1. Clone the repository

   git clone https://github.com/NikhilRaikwar/SolLink.git
   cd sol-link

2. Install Dependencies

   pnpm install
   # or
   npm install

3. Configure Environment Create a .env.local file and add your Helius RPC URL:

   NEXT_PUBLIC_HELIUS_RPC_URL=https://devnet.helius-rpc.com/?api-key=YOUR_KEY

4. Run Development Server

   pnpm dev

5. Open in Browser Visit http://localhost:3000 to start shielding SOL!

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🏆 Hackathon Tracks & Bounties

We are targeting the following tracks in the Solana Privacy Hack 2026:

🎯 Primary Tracks

• Track 01: Private Payments: Enabling private, unlinkable value transfer.

💰 Sponsor Bounties

• Privacy Cash: For "Best Integration" by porting and utilizing the core UTXO/Prover SDK logic (src/lib/privacy-cash).
• Helius: For "Best Privacy Project" leveraging Helius RPCs for performant, lag-free user experiences during claim sweeps.

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Built with ❤️ by the Sol-Link Team