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Yona implements a UTXO-based privacy model with Groth16 zk-SNARKs on Solana, providing strong anonymity guarantees while maintaining full on-chain verifiability. Program uses a modified version of the Tornado Nova circom circuits, adapted for Solana’s architecture. A modified version of the circom is used to create a dual-token circuit. The circom schemes are currently undergoing a security audit, and we will publish details soon. Program: 6Uok9UsjztPC9VJ3a8ZpawzKmgrD2VvMKQGb64FYjhnx Code for the program is open source and available here.

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UTXO Model

Yona uses a Unspent Transaction Output model similar to Bitcoin/Zcash:

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Structure

interface UTXO {
    amount: bigint;        // Token amount
    mintAddress: string;   // SPL token mint
    blinding: bigint;      // Random value for privacy
    publicKey: bigint;     // Owner's public key (BN254 curve)
}

Commitment = Hash(amount, mintAddress, blinding, publicKey)
Nullifier = Hash(commitment, privateKey, merkleProofPathIndex)

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Privacy Properties

  • Hiding: Commitments reveal nothing about contents
  • Binding: Cannot change UTXO after commitment
  • Unlinkability: Cannot link commitments to nullifiers without private key

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Transaction Logic

Every instruction consumes 2 input UTXOs and creates 2 output UTXOs:

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Public Inputs & Data Integrity

All transaction data is cryptographically bound to the zero-knowledge proof through 10 public inputs. This means no transaction data can be modified without invalidating the proof:

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Public Inputs to Proof Verification

publicInputs = [
    root,                    // Merkle tree root
    publicAmount0,           // Token A amount (deposit/withdraw)
    publicAmount1,           // Token B amount (for swaps)
    extDataHash,            // Hash of external data
    mintAddressA,           // SPL token mint A
    mintAddressB,           // SPL token mint B
    inputNullifier[0],      // First spent UTXO nullifier
    inputNullifier[1],      // Second spent UTXO nullifier
    outputCommitment[0],    // First new UTXO commitment
    outputCommitment[1]     // Second new UTXO commitment
]

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External Data Hash

The extDataHash itself is computed from additional transaction parameters: 
extDataHash = Hash(
    recipient,           // Withdrawal address
    extAmount,          // External amount
    encryptedOutput,    // Encrypted UTXO data
    fee,               // Relayer fee
    feeRecipient,      // Fee collector address
    mintAddressA,      // Token mint A
    mintAddressB       // Token mint B
)
Security Guarantee: Since all this data is part of the proof’s public inputs, any attempt to modify transaction parameters (amounts, recipients, fees, nullifiers, commitments) will cause proof verification to fail. This ensures complete data integrity without revealing private information.

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Program Components

The Yona program serves as the core verification system that stores all private transaction data and validates zero-knowledge proofs. It maintains the complete state of the privacy pool, including all commitments and nullifiers, while ensuring that only valid proofs can modify this state.

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Merkle Tree State

  • Height: 26 levels
  • Capacity: 67 million commitments
  • Structure: Sparse binary tree with Poseidon hashing
  • Purpose: Stores cryptographic commitments of all UTXOs without revealing amounts or owners

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Nullifier Registry

  • Function: Prevents double-spending, stored on-chain in Solana network to prevent double-spending
  • Mechanism: Each spent UTXO generates a unique nullifier that is permanently recorded

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Proof Verification System

  • Provider: Light Protocol’s Groth16 verifier
  • Curve: BN254 elliptic curve
  • Proof Size: 256 bytes (compressed)

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Private UTXO Storage

Yona stores all private UTXOs in on-chain events with highly optimized compression. This approach allows efficient retrieval through the indexer while minimizing on-chain storage costs. The protocol achieves exceptional efficiency through multiple compression techniques:

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Commitments Compression

We store encrypted Commitments in on-chain events using highly optimized serialization:
  • Minimal Serialization: Data is compressed to the smallest possible size using custom binary packing
  • Dual UTXO Optimization: Two UTXOs are packed into a single on-chain record, reducing storage costs by 50%
  • Partial Mint Storage
Result: Each commitment entry uses only ~100 bytes instead of traditional 200+ bytes

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Data Retrieval

Private UTXO data is stored in Solana events and can be efficiently retrieved through the Yona indexer. The indexer monitors on-chain events, decrypts relevant UTXOs for users, and provides fast access to transaction history without requiring full chain scanning.
If needed, you can send transactions directly through the local frontend with any custom encryptedOutput format that suits your requirements.

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Audit Status

Protocol is experimental and under active development. No formal audit completed yet. Use with caution.