STAC Merkle Tree CLI Tool

A Command-Line Interface (CLI) tool for computing and adding Merkle Tree information to your SpatioTemporal Asset Catalog (STAC) directory structure. This tool ensures metadata integrity for your STAC Items, Collections, and Catalogs by encoding them in a Merkle tree via hashing.

Table of Contents

• Overview
• Features
• Prerequisites
• Installation
• Directory Structure
• Usage
  • Basic Usage
  • Example
• Merkle Tree Extension Specification
• Output
• Contributing

Overview

The STAC Merkle Tree CLI Tool automates the process of computing and embedding Merkle Tree information into your STAC catalog. By integrating this tool into your workflow, you can:

• Ensure Metadata Integrity: Verify that your STAC objects (Items, Collections, Catalogs) have not been tampered with.
• Facilitate Verification: Enable users to verify the integrity of STAC objects using the Merkle hashes.
• Maintain Consistency: Automatically compute and update Merkle information across your entire catalog hierarchy.

Features

• Recursive Processing: Traverses the entire STAC catalog, including Catalogs, Collections, and Items.
• Merkle Hash Computation: Computes merkle:object_hash for each STAC object based on specified hashing methods.
• Merkle Root Calculation: Builds Merkle trees for Collections and Catalogs to compute merkle:root.
• Extension Compliance: Adheres to the Merkle Tree Extension Specification for STAC.
• User-Friendly CLI: Built with the Click library for an intuitive command-line experience.
• Customizable Hash Methods: Supports various hash functions and field selections.

Prerequisites

• Python 3.6 or higher
• pip (Python package installer)

General Installation

pip install stac-merkle-tree-cli

Building for Development

1. Clone the Repository

   git clone https://github.com/stacchain/stac-merkle-tree-cli.git
   cd stac-merkle-tree-cli

2. Install the Package

   pip install -e .

Directory Structure

Ensure your STAC catalog follows the directory structure below for optimal processing:

catalog/
├── catalog.json
├── collections/
│   ├── collection1/
│   │   ├── collection.json
│   │   ├── item1.json
│   │   ├── item2.json
│   │   └── ...
│   ├── collection2/
│   │   ├── collection.json
│   │   ├── item1.json
│   │   └── ...
│   └── ...

• Catalog Level:
  • catalog.json: Root catalog file.
  • collections/: Directory containing all collections.
• Collections Level:
  • Each collection has its own directory inside collections/, named after the collection.
  • Inside each collection directory:
    • collection.json: Collection metadata.
    • item.json, item2.json, ...: Items belonging to the collection.

Usage

Basic Usage

After installing the package, you can use the stac-merkle-tree-cli command to compute and add Merkle information to your STAC catalog.

Navigate to the directory containing your catalog.json file and run the command as follows:

stac-merkle-cli path/to/catalog.json

Example

Assuming your directory structure is as follows:

my_stac_catalog/
├── catalog.json
├── collections/
│   ├── collection1/
│   │   ├── collection.json
│   │   ├── item1.json
│   │   └── item2.json
│   └── collection2/
│       ├── collection.json
│       ├── item1.json
│       └── item2.json

Run the tool:

stac-merkle-tree-cli ./my_stac_catalog/catalog.json

Expected Output:

Processed Item: /path/to/my_stac_catalog/collections/collection1/item1.json
Processed Item: /path/to/my_stac_catalog/collections/collection1/item2.json
Processed Collection: /path/to/my_stac_catalog/collections/collection1/collection.json
Processed Item: /path/to/my_stac_catalog/collections/collection2/item1.json
Processed Item: /path/to/my_stac_catalog/collections/collection2/item2.json
Processed Collection: /path/to/my_stac_catalog/collections/collection2/collection.json
Processed Catalog: /path/to/my_stac_catalog/catalog.json
Merkle info computation and addition completed.

Merkle Tree Extension Specification

This tool complies with the Merkle Tree Extension Specification, which outlines how to encode STAC objects in a Merkle tree to ensure metadata integrity.

Fields Added

• merkle:object_hash (string, REQUIRED in Items, Collections, Catalogs)
  • A cryptographic hash of the object's metadata, used to verify its integrity.
  • For Items: Located within the properties field.
  • For Collections and Catalogs: Located at the top level.
• merkle:hash_method (object, REQUIRED in Collections and Catalogs)
  • Describes the method used to compute merkle:object_hash and merkle:root, including:
    • function: The hash function used (e.g., sha256).
    • fields: Fields included in the hash computation (e.g., ["*"] for all fields).
    • ordering: How child hashes are ordered when building the Merkle tree (e.g., ascending).
    • description: Additional details about the hash computation method.
• merkle:root (string, REQUIRED in Collections and Catalogs)
  • The Merkle root hash representing the Collection or Catalog, computed from child object hashes.

Extension URL

All STAC objects processed by this tool will include the Merkle extension URL in their stac_extensions array:

"stac_extensions": [
  "https://stacchain.github.io/merkle-tree/v1.0.0/schema.json"
]

Output

After running the tool, each STAC object will be updated with the appropriate Merkle fields.

Catalog (catalog.json)

{
  "type": "Catalog",
  "stac_version": "1.1.0",
  "id": "my-catalog",
  "description": "My STAC Catalog",
  "links": [],
  "stac_extensions": [
    "https://stacchain.github.io/merkle-tree/v1.0.0/schema.json"
  ],
  "merkle:object_hash": "abcdef1234567890abcdef1234567890abcdef1234567890abcdef1234567890",
  "merkle:root": "1234567890abcdef1234567890abcdef1234567890abcdef1234567890abcdef",
  "merkle:hash_method": {
    "function": "sha256",
    "fields": ["*"],
    "ordering": "ascending",
    "description": "Computed by excluding Merkle fields and including merkle:object_hash values in ascending order to build the Merkle tree."
  }
}

Collection (collections/collection1/collection.json)

{
  "type": "Collection",
  "stac_version": "1.1.0",
  "id": "collection1",
  "description": "My STAC Collection",
  "extent": {},
  "links": [],
  "stac_extensions": [
    "https://stacchain.github.io/merkle-tree/v1.0.0/schema.json"
  ],
  "merkle:object_hash": "fedcba0987654321fedcba0987654321fedcba0987654321fedcba0987654321",
  "merkle:root": "0987654321fedcba0987654321fedcba0987654321fedcba0987654321fedcba",
  "merkle:hash_method": {
    "function": "sha256",
    "fields": ["*"],
    "ordering": "ascending",
    "description": "Computed by excluding Merkle fields and including merkle:object_hash values in ascending order to build the Merkle tree."
  }
}

Item (collections/collection1/item1.json)

{
  "type": "Feature",
  "stac_version": "1.1.0",
  "id": "item1",
  "properties": {
    "merkle:object_hash": "0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef",
    "merkle:hash_method": {
      "function": "sha256",
      "fields": ["*"],
      "ordering": "ascending",
      "description": "Computed by excluding Merkle fields and including merkle:object_hash values in ascending order to build the Merkle tree."
    }
  },
  "geometry": {},
  "links": [],
  "assets": {},
  "stac_extensions": [
    "https://stacchain.github.io/merkle-tree/v1.0.0/schema.json"
  ]
}

Contributing

Contributions are welcome! If you encounter issues or have suggestions for improvements, please open an issue or submit a pull request on the GitHub repository.