Smart Contracts

DPO2U utilizes the Midnight Network and its Compact language to write smart contracts that guarantee compliance immutability without ever compromising sensitive personal data.

Compact, not Solidity

Compact is Midnight's purpose-built smart contract language. Unlike Solidity, Compact compiles to zero-knowledge circuits — every operation is privacy-preserving by default. There are no arbitrary loops or dynamic memory; circuit size is deterministic at compile time.

The zero-knowledge principle

The core principle governing our entire smart contract suite is Privacy by Design. No personally identifiable information (PII) or raw company data is stored on the ledger. We only store:

1. Identifying Hashes (like the hashed CNPJ of the company).
2. The CID (Content Identifier) pointing to the IPFS storage containing the encrypted document.
3. The overall Compliance Score.
4. Timestamps of evaluation.
5. The digital signature / DID of the Agent who emitted the Attestation.

To achieve this, the network uses native zk-SNARKs (Zero-Knowledge Succinct Non-Interactive Argument of Knowledge) to prove that the validation rules were met without disclosing the underlying data that was validated.

Compact example

A simplified view of how a compliance registration might look in Compact:

// Simplified conceptual Compact contract
contract ComplianceRegistry {
  state attestations: Map<Hash, Attestation>;

  transition registerAttestation(
    company_id: Hash,
    agent_did: DID,
    policy_cid: CID,
    score: Uint8
  ) {
    // Agent signature verified via zk-SNARK
    // Only the hash is stored — no PII
    attestations[company_id] = Attestation {
      agent_did, policy_cid, score, timestamp: now()
    };
  }
}

Contract overview

Contract	Purpose	Key function	Status
ComplianceRegistry	Central attestation registry	registerAttestation() — stores score + CID	Deployed (Midnight Testnet)
DocumentTimestamp	Temporal existence proofs	Proves a document existed at a point in time	Deployed (Midnight Testnet)
AgentWalletFactory	Agent wallet creation	Programmatic wallet initialization	Deployed (Midnight Testnet)
FeeDistributor	Agent compensation	Allocates $NIGHT to agents per task	Deployed (Midnight Testnet)
Treasury	Fund management	Receives client payments in $NIGHT	Deployed (Midnight Testnet)
AgentRegistry	Agent identity ledger	Maintains approved did:midnight:agent:* DIDs	Deployed (Midnight Testnet)
PaymentGateway	Client payment interface	Accepts $NIGHT for services	Preprod

Implemented contracts

1. ComplianceRegistry.compact

The central registry. It holds the map of all generated Attestations.

• registerAttestation(company_id, agent_did, policy_cid, score): Validates the signature of the Auditor Agent and stores the score associated with the company hash.

2. DocumentTimestamp.compact

Guarantees the temporal existence of a document via Zero-Knowledge proofs. Useful for demonstrating that a specific privacy policy existed at a specific point in time before a data breach incident.

3. AgentWalletFactory.compact

Facilitates the programmatic creation of network wallets for newly deployed Autonomous Agents.

4. FeeDistributor.compact & Treasury.compact

The financial layer of the protocol. When a company pays for a compliance check, the funds go to the Treasury. The FeeDistributor allocates the correct amount of $NIGHT tokens to the Auditor Agent who processed the operation, acting as an economic incentive for accurate validations.

5. AgentRegistry.compact

Maintains a public ledger of approved did:midnight:agent:<name> identities. Only agents listed here are permitted to interact with the ComplianceRegistry.

6. PaymentGateway.compact

The interface the frontend or external API uses to accept $NIGHT tokens from clients requesting new LGPD Kits or Audits.

Status

PaymentGateway is in preprod — deployed on Midnight testnet but not yet integrated with the production Application Layer. All other contracts are deployed and active on testnet.

What's next

• Architecture — how contracts fit into the 5-layer protocol stack
• Agents — the autonomous agents that interact with these contracts
• Schemas — the dpo2u/lgpd/v1 schema that feeds into ComplianceRegistry