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The Proof struct contains all the components of a Groth16 zero-knowledge proof and the public inputs required to verify a private transaction.

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Structure Definition

All public inputs are encoded in big-endian format.
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proof_a
[u8; 64]
required
First component of the Groth16 proof (G1 point)
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proof_b
[u8; 128]
required
Second component of the Groth16 proof (G2 point)
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proof_c
[u8; 64]
required
Third component of the Groth16 proof (G1 point)
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root
[u8; 32]
required
Merkle tree root at the time the proof was generated. Must match a root in the tree’s history to be considered valid.
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public_amount
[u8; 32]
required
The public amount being transacted, calculated as ext_amount + fee. This value is part of the zero-knowledge circuit’s public inputs.
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ext_data_hash
[u8; 32]
required
Hash of the external data (ExtData) that accompanies this transaction. Used to bind the proof to specific transaction parameters like recipient and fee.
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input_nullifiers
[[u8; 32]; 2]
required
Array of two nullifiers corresponding to the two input notes being spent. Each nullifier can only be used once, preventing double-spending.
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output_commitments
[[u8; 32]; 2]
required
Array of two commitments corresponding to the two output notes being created. These are added to the Merkle tree.

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Usage

The Proof struct is used in both transact and transact_spl instructions: 
pub fn transact(
    ctx: Context<Transact>, 
    proof: Proof, 
    ext_data_minified: ExtDataMinified, 
    encrypted_output1: Vec<u8>, 
    encrypted_output2: Vec<u8>
) -> Result<()>

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Verification Process

  1. Root Verification: The proof.root must exist in the Merkle tree’s root history
  2. ExtData Hash: The proof.ext_data_hash must match the hash of the provided ExtData
  3. Public Amount: The proof.public_amount must equal ext_amount + fee
  4. Cryptographic Proof: The Groth16 proof components (proof_a, proof_b, proof_c) are verified against the circuit’s verifying key
  5. Nullifiers: The input_nullifiers must not have been used before (enforced by PDA account creation)
  • ExtData - External transaction data that is hashed and verified against ext_data_hash

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