Hedera HCS Audit Layer

Hedera Consensus Service (HCS) is AsiliChain’s independent, append-only audit log. It records every stage event from the protocol — a permanent, tamper-proof chain of custody that neither AsiliChain nor any cooperative can alter.

Why HCS, Not Mantle Alone

Mantle is where the economic logic lives — contracts, tokens, loans. HCS is where the audit trail lives — readable by any regulator or EU buyer without understanding Solidity or querying a smart contract.

Requirement	Mantle	Hedera HCS
Smart contract execution	✅	❌
Token minting and ownership	✅	❌
Lending vault operations	✅	❌
Append-only immutable audit log	Partial (events)	✅ Purpose-built
Governance credibility (IBM/Google/FedEx/Boeing)	Ethereum ecosystem	✅ HCS governing council
Human-readable JSON messages	Requires decoder	✅ Native
Queryable without Solidity knowledge	Requires ABI	✅ REST API
Regulatory acceptance (EU auditors)	Growing	✅ Established

HCS Topic Structure

AsiliChain uses one primary HCS topic per cooperative deployment:

Topic: 0.0.XXXXXXX   (created once per cooperative)
  │
  ├── Message: REGISTERED    (farm GPS verified)
  ├── Message: DELIVERED     (batch submitted, BatchToken minted)
  ├── Message: GRADED        (quality assessment passed)
  ├── Message: MILLED        (processing complete)
  ├── Message: WAREHOUSED    (storage confirmed)
  ├── Message: COMMITTED     (PurchaseOrder confirmed)
  ├── Message: EXPORTED      (shipment confirmed)
  ├── Message: SETTLED       (loan repaid, net disbursed)
  └── Message: DDS_GENERATED (DDS IPFS CID recorded)

Message Format

Every HCS message follows a consistent schema:

{
  "protocol": "asilichain",
  "version": "1.0",
  "event": "DELIVERED",
  "batch_id": "BATCH-2026-004821",
  "farmer_id": "UG-KAS-2024-001234",
  "cooperative_id": "COOP-MBALE-001",
  "timestamp": "2026-04-17T10:23:00Z",
  "mantle_tx_hash": "0xabc123...",
  "mantle_block": 14782341,
  "data": {
    "weight_kg": 67.5,
    "collection_point_gps": { "lat": 1.0656, "lng": 34.1772 },
    "collector_agent_id": "AGENT-001"
  },
  "recorded_by": "0xCOOP_WALLET_ADDRESS"
}

Integration Code

packages/api/lib/hedera.ts

import { Client, TopicMessageSubmitTransaction } from '@hashgraph/sdk';

const client = Client.forMainnet();
client.setOperator(
  process.env.HEDERA_ACCOUNT_ID!,
  process.env.HEDERA_PRIVATE_KEY!
);

export async function writeHCSEvent(event: AsiliChainEvent) {
  const message = JSON.stringify({
    protocol: 'asilichain',
    version: '1.0',
    ...event,
    timestamp: new Date().toISOString(),
  });

  const tx = await new TopicMessageSubmitTransaction()
    .setTopicId(process.env.HEDERA_TOPIC_ID!)
    .setMessage(message)
    .execute(client);

  const receipt = await tx.getReceipt(client);
  return receipt.topicSequenceNumber?.toString();
}

Querying HCS for DDS Generation

The DDS pipeline fetches the complete stage history for a batch by querying HCS:

// Fetch all messages for a batch from HCS mirror node
const response = await fetch(
  `https://mainnet-public.mirrornode.hedera.com/api/v1/topics/${topicId}/messages?limit=100`
);
const messages = await response.json();
const batchHistory = messages.messages
  .map(m => JSON.parse(atob(m.message)))
  .filter(m => m.batch_id === batchId)
  .sort((a, b) => new Date(a.timestamp).getTime() - new Date(b.timestamp).getTime());

Immutability Guarantee

HCS messages are submitted to Hedera’s Hashgraph consensus — finality in 3–5 seconds. Once confirmed:

• The message cannot be deleted
• The message cannot be modified
• The sequence number is permanent
• The timestamp is consensus-verified (not self-reported)

This is why EUDR auditors can trust the stage timestamps — they are not from AsiliChain’s database. They are from a consensus network governed by IBM, Google, FedEx, and Boeing.