The TruthChain Backend serves as the central immutable ledger and orchestration layer for the platform. It acts as a bridge between the secure hardware client (Android) and the decentralized storage network (IPFS/Pinata).

• Trust Bridge: Receives cryptographically signed evidence from trusted Android hardware.
• Decentralized Storage (IPFS): Automatically pins uploaded evidence to IPFS via Pinata, ensuring the media is immutable and uncensorable.
• Verification Engine: Exposes public endpoints to verify asset integrity. If an image hash is queried, it returns the associated hardware signature and metadata.
• Metadata Registry: Stores the "Proof of Presence" data (GPS coordinates, Timestamp, Device ID) linked to the image hash.

• Framework: Spring Boot 3 (Java 17)
• Build Tool: Maven / Gradle
• Database: MySQL
• Storage: IPFS (via Pinata API)
• Deployment: Railway
• Security: SHA-256 Hash Verification

Receives the raw image and the hardware-backed signature.

• Endpoint: POST /api/evidence/upload
• Content-Type: multipart/form-data
• Parameters:
  • file: The image file.
  • signature: The ECDSA signature string from the Android Keystore.
  • metadata: JSON string containing GPS and Timestamp.

Used by the React frontend to check if a file is authentic.

• Endpoint: GET /api/evidence/verify/{hash}
• Path Variable: {hash} - The SHA-256 hash of the file being checked.
• Response:

  {
    "status": "VERIFIED",
    "digitalSignature": "MEYCIQC...",
    "gpsLocation": "26.8467, 80.9462",
    "timestamp": "1735482300000",
    "deviceId": "Pixel_7_Pro_Secure_Enclave"
  }

1. Ingest: Receives MultipartFile and Signature from Android.
2. Hash: Calculates the server-side SHA-256 hash of the received file to ensure integrity during transit.
3. Pin: Uploads the file to Pinata (IPFS) and retrieves the CID (Content Identifier).
4. Persist: Saves the {Hash, CID, Signature, Metadata} tuple to the database.

• Java 17 SDK
• Maven
• Pinata API Keys

1. Clone the repository:

   git clone [https://github.com/yourusername/truthchain-backend.git](https://github.com/yourusername/truthchain-backend.git)

2. Configure Environment Variables (application.properties):

   pinata.api.key=YOUR_KEY
   pinata.secret.key=YOUR_SECRET
   spring.datasource.url=jdbc:postgresql://...

3. Run the application:

   mvn spring-boot:run