midnight-core-concepts:privacy-patterns

To implement privacy-preserving on-chain logic in Compact, you combine hashes, Pedersen commitments, Merkle trees, and nullifier patterns. This approach keeps your application data private while still enabling verifiable proofs for on-chain state transitions.

On-chain nullifiers prevent double-spending or double-voting by tracking spent commitments, while Merkle trees compactly commit to large datasets. Together, they allow you to prove membership or validity without revealing the underlying private data.

You can build private ballots and confidential asset commitments by composing hashes and Merkle tree proofs within Compact circuits. The Skill provides reference implementations demonstrating how to structure these proofs to keep votes or asset amounts secret yet verifiable.

Yes, you need familiarity with Compact constructs like persistentCommit, MerkleTree types, and nullifier tracking. These constructs are required to properly structure your circuits and generate proofs for private on-chain logic.

Use nullifier tracking when you must prevent an action from occurring twice, such as double-voting in a private ballot or spending a confidential asset twice. Simple hash commitments suffice when you only need to hide data without enforcing spend or vote uniqueness.