EVID-DGC — Blockchain Evidence & Digital Chain of Custody

• Broken chain of custody in traditional evidence room handling
• No public auditability — evidence integrity only checkable by the court
• Missing multi-hash verification (MD5, SHA-1, SHA-256)
• No immutability — files can be silently modified

• 8-role RBAC + ABAC enforcement applies to every action
• Blockchain anchoring on Polygon Amoy — write the evidence hash, immutably
• IPFS pinning via Pinata — full file, permanent storage
• Forensic Lab — generates multiple hashes per evidence, highlights tamper
• 3D evidence model — an STL digital twin of the evidence document

• 8 roles: Admin, Officer, Investigator, Analyst, Evidence Manager, Reviewer, Judge, Public
• Evidence create → register → store → transfer → verify lifecycle
• Audit logging of all custody events
• Real-time dashboard via Socket.IO
• Subordinate re-upload anti-tamper via multi-hash comparison

• EVID-DGC.sol — anchorEvidence, verifyEvidence, getEvidenceHistory
• Won the chain (deployed address in Deployment section)
• Files pinned to Pinata IPFS, hash recorded on-chain

• Forensic analyzer: MD5 / SHA-1 / SHA-256, entropy, file-type detection
• 3D Evidence Viewer — STL model rendered in-app (asset: assets/evidence-cube.stl)
• Forensic report generator — planned
• AI-based evidence triage — research

flowchart TD
    subgraph Client
        A[Browser] --> B[Dashboard / Public Pages]
    end
    subgraph Server
        C[Express API] --> D[(PostgreSQL / Supabase)]
        C --> E[Pinata IPFS]
        C --> F[Polygon Amoy node]
    end
    subgraph Contract
        F --> G[EVID-DGC contract]
    end
    B -->|REST + Socket.IO| C
    B -->|3D viewer| H[THREE.js/STL]

ABAC rules enforce context: only the owning investigator/team may transfer evidence; Public role is restricted to verification endpoints.

// contracts/EVID_DGC.sol (simplified)
contract EVID_DGC {
    mapping(bytes32 => EvidenceRecord) public records;

    function anchorEvidence(
        string memory evidenceId,
        bytes32 evidenceHash,
        address officer
    ) external returns (bytes32) {
        record.evidenceHash = evidenceHash;  // SHA-256 of file
        emit EvidenceAnchored(evidenceId, evidenceHash, block.timestamp);
        return recordHash;
    }
}

Deployed Address (Polygon Amoy):

EVID-DGC: 0x39453ED8CF79Fe56150fe1E8348e75894e3dD9e3
Explorer : https://amoy.polygonscan.com/address/0x39453ED8CF79Fe56150fe1E8348e75894e3dD9e3

sequenceDiagram
    autonumber
    participant O as Officer
    participant S as Server
    participant C as EVID-DGC (Amoy)
    participant I as Pinata IPFS
    O->>S: Upload file + metadata
    S->>I: Pin file → CID
    S->>C: anchorEvidence(evidenceId, keccak(file))
    C-->>S: emit EvidenceAnchored { block }
    S-->>O: Evidence ID + tx hash

• Files pinned on Pinata IPFS at upload time — permanent & deduplicated
• CID stored in PostgreSQL, hash stored on-chain
• Public-dashboard verification compares stored file hash vs. on-chain hash

erDiagram
    USERS ||--o{ EVIDENCE : submits
    USERS ||--o{ AUDIT_LOG : performs
    EVIDENCE {
        uuid id PK
        string case_number
        string description
        string file_hash "SHA-256"
        string ipfs_cid
        string onchain_tx
        string custody_actor
    }
    AUDIT_LOG {
        uuid id PK
        uuid evidence_id FK
        uuid actor_id FK
        string action
        timestamp time
    }

Full schema: complete-database-setup-fixed.sql (repo root).

flowchart LR
    C[Evidence Capture] --> R[Registration]
    R --> L[Lab Analysis]
    L --> A[Anchoring on Amoy]
    A --> V[Verification by Reviewer]
    V --> T[Transfer / Trial]
    T --> D[Disposal or Archive]

A genuine 3D model asset is included: assets/evidence-cube.stl. The interactive viewer (view-evidence3d.html) renders it with notes/rotation; miniature interactive application elements (e.g., adjustable lighting) are planned.

npm test          # unit + integration
npm run test:e2e  # Playwright E2E (planned configuration in progress)

• Evidence CRUD multi-hash detection
• Auth + RBAC role gating
• IPFS & chain mocks

• Node.js 18+, npm
• Supabase project (or docker run postgres)
• (Optional) Pinata account + JWT

git clone https://github.com/Gooichand/blockchain-evidence.git
cd blockchain-evidence
npm install

cp .env.example .env

npm run dev
# http://localhost:3000

Seed the DB first with complete-database-setup-fixed.sql (creates 8 roles & demo users).

Anyone can enter an Evidence ID, SHA-256 hash, or on-chain tx hash on the Public Dashboard and receive VERIFIED ✅ / TAMPERED ❌ instantly — cross-checked against PostgreSQL, the Amoy ledger, and IPFS.

• docs/API.md – REST endpoints
• docs/DEPLOYMENT.md – Render + PostgreSQL setup
• docs/SECURITY.md – security model & checklist
• PHASES.md – phases, roadmap, status
• CONTRIBUTING.md – how to contribute

render.yaml provisions the web service + managed PostgreSQL.

See CONTRIBUTING.md — issues welcomed, PRs reviewed. Help wanted tags: 3d-viewer, ai-analysis, mainnet.

MIT — see LICENSE. © 2025-2026 EVID-DGC.

• Pinata for IPFS pinning
• Polygon Amoy testnet
• Render hosting
• Supabase PostgreSQL + Auth
• GitHub Actions for CI status badge

⚖️ EVID-DGC — Immutably anchored. Forever provable.

⭐ If you find this project useful, **give it a star**!

_{© 2025-2026 EVID-DGC · Immutably anchored. Forever provable. ⚖️}