Verra Audit Trail Documentation — Verification Chain of Custody

Purpose

This document serves to outline the compliance requirements and procedures necessary for the end-to-end audit trail from sensor measurement through verification to credit issuance within the framework of the Verified Carbon Standard (VCS). The documentation is intended for use by technical reviewers and compliance auditors associated with Verra and other relevant stakeholders in the carbon markets.

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Table of Contents

1. [Chain of Custody](#chain-of-custody)
2. [Data Integrity](#data-integrity)
3. [Timestamp Verification](#timestamp-verification)
4. [Tamper Detection](#tamper-detection)
5. [Audit Log Format](#audit-log-format)
6. [Conformity Assessment Procedures](#conformity-assessment-procedures)
7. [Appendices](#appendices)

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1. Chain of Custody

1.1 Definition

The Chain of Custody (CoC) refers to the documented process that tracks the movement and handling of carbon data from its point of origin (sensor measurement) through to the final issuance of carbon credits. This process must ensure that all data is accounted for and remains untampered throughout its lifecycle.

1.2 Requirements

• Each data point collected shall be associated with a unique identifier (UID) that links it to the specific sensor and measurement instance.
• The CoC shall document each transition of data ownership, including:
• Data collection
• Data processing
• Data verification
• Credit issuance
• All transitions shall be recorded in a secure, immutable ledger that can be audited.

1.3 Data Field Mappings

The following data fields shall be included in the CoC documentation:

| Field Name | Data Type | Description | |---------------------|-------------|-------------------------------------------------------| | UID | String | Unique identifier for each data point. | | Sensor ID | String | Identifier for the IoT sensor. | | Timestamp | ISO 8601 | Date and time of data capture (UTC). | | Measurement Type | String | Type of measurement (e.g., CO2 concentration). | | Measurement Value | Float | Value of the measurement. | | Data Processor ID | String | Identifier for the algorithm processing the data. | | Verification Status | Enum | Status of verification (e.g., Pending, Verified). | | Credit ID | String | Identifier for the carbon credit issued. |

1.4 API Endpoints

The following API endpoints shall be implemented to facilitate the CoC:

• Data Submission Endpoint
• URL: /api/v1/data/submit
• Method: POST
• Payload: JSON object containing fields as specified in Section 1.3.

• Data Retrieval Endpoint
• URL: /api/v1/data/retrieve
• Method: GET
• Query Parameters: uid, sensor_id, timestamp.

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2. Data Integrity

2.1 Definition

Data integrity refers to the accuracy and consistency of data throughout its lifecycle. The integrity of carbon data is paramount to maintaining trust in the carbon offset market.

2.2 Requirements

• All data captured by sensors shall be transmitted to the processing unit using secure communication protocols (e.g., HTTPS, MQTT with TLS).
• Data shall be stored in a secure database with access controls to prevent unauthorized modifications.
• Data shall be hashed upon capture, and the hash shall be stored alongside the data for verification purposes.

2.3 Verification Chain

The verification chain shall consist of the following steps:

1. Data Capture: Sensors capture environmental data and generate a hash (SHA-256) of the data.
2. Data Transmission: Data and hash are transmitted to the processing unit.
3. Data Processing: Algorithms process the data and generate a new hash for the processed data.
4. Data Storage: Both raw and processed data, along with their hashes, shall be stored in a secure database.

2.4 Data Format

Data shall be formatted as follows:

`json { "uid": "unique-data-id", "sensor_id": "sensor-123", "timestamp": "2023-10-01T12:00:00Z", "measurement_type": "CO2", "measurement_value": 400.5, "data_processor_id": "processor-xyz", "raw_data_hash": "hash-of-raw-data", "processed_data_hash": "hash-of-processed-data" } `

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3. Timestamp Verification

3.1 Definition

Timestamp verification ensures that all data points are accurately timestamped at the moment of capture and that these timestamps are verifiable.

3.2 Requirements

• All timestamps shall be recorded in ISO 8601 format (e.g., YYYY-MM-DDTHH:MM:SSZ).
• Timestamps shall be synchronized with a reliable time source (e.g., NTP server).
• A verification mechanism shall be implemented to ensure that timestamps cannot be altered post-capture.

3.3 Verification Process

1. NTP Synchronization: The system shall synchronize with an NTP server at regular intervals (e.g., every hour).
2. Timestamp Generation: Upon data capture, the system shall generate a timestamp and log it.
3. Audit Trail: The timestamp, along with the UID, shall be included in the audit log for traceability.

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4. Tamper Detection

4.1 Definition

Tamper detection refers to the mechanisms in place to identify unauthorized alterations to data.

4.2 Requirements

• All data entries shall include a hash value for verification.
• Any modification to the data shall trigger an alert and be logged with the details of the modification.
• A tamper-evident logging system shall be utilized to ensure that any unauthorized access is recorded.

4.3 Tamper Detection Mechanism

1. Hash Comparison: Upon retrieval, the system shall compute the hash of the data and compare it with the stored hash.
2. Alerting System: If a discrepancy is detected, an alert shall be sent to the system administrator.
3. Logging Modifications: Any data access or modifications shall be logged with the following information:

• UID
• Timestamp of access/modification
• User ID of the individual accessing/modifying the data
• Action taken (e.g., Read, Modify, Delete)

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5. Audit Log Format

5.1 Definition

The audit log format specifies how all actions taken on the data shall be recorded for compliance and verification purposes.

5.2 Requirements

• The audit log shall be immutable and stored in a secure location.
• Each log entry shall include a timestamp, user ID, action type, and details of the data affected.

5.3 Audit Log Structure

The audit log shall be formatted as follows:

`json { "log_id": "unique-log-id", "timestamp": "2023-10-01T12:00:00Z", "user_id": "user-abc", "action": "MODIFY", "data_uid": "unique-data-id", "details": "Modified measurement value from 400.5 to 405.0" } `

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6. Conformity Assessment Procedures

6.1 Overview

Conformity assessment procedures shall be established to ensure compliance with the VCS requirements and to facilitate third-party verification.

6.2 Assessment Steps

1. Pre-Assessment: Conduct an initial review of the data collection, processing, and verification protocols.
2. Documentation Review: Ensure that all documentation, including audit trails and logs, is complete and accurate.
3. Site Visit: A site visit may be conducted to verify the functioning of sensors and data capture methods.
4. Final Report: A final report shall be generated, summarizing findings and providing recommendations for compliance.

6.3 Third-Party Verification

• Third-party verifiers shall be accredited and shall follow the VCS guidelines for verification.
• The verification process shall include a review of the audit trail and any discrepancies shall be addressed prior to credit issuance.

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7. Appendices

7.1 Appendix A: Glossary of Terms

• UID: Unique Identifier.
• NTP: Network Time Protocol.
• MRV: Measurement, Reporting, and Verification.
• VCS: Verified Carbon Standard.

7.2 Appendix B: References

• Verra VCS Program Document
• ISO 8601 Standard for Date and Time Formats
• SHA-256 Cryptographic Hash Function

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This document is intended to provide a comprehensive framework for ensuring compliance with Verra's standards regarding the audit trail of carbon data. All stakeholders involved in the carbon offset market must adhere to these requirements to maintain the integrity of the carbon credits issued under the VCS.