feat(blockchain): upgrade to simulated private blockchain with deterministic consensus and multi-node propagation

- Standardized NODE_ID and peer configuration across nodes
- Hardened block propagation with idempotency and loop prevention
- Implemented deterministic round-robin leader consensus (block_height % N)
- Enforced leader-only block creation to prevent conflicts
- Added proposed_by field for block traceability
- Stabilized hash determinism and serialization consistency
- Aligned tests with consensus and propagation rules

Result: system now behaves as a viva-defensible private blockchain simulation

Author: udaycodespace

.gitignore

@@ -182,4 +182,5 @@ htmlcov/
 .coverage
 dist/
 build/
-*.egg-info/
+*.egg-info/
+credify-verify/

app/app.py

@@ -67,14 +67,19 @@ def init_extensions(app):
             blockchain.create_genesis_block()
 
         # P2P multi-node init
-        peer_nodes_env = os.environ.get("PEER_NODES", "")
-        if peer_nodes_env:
-            for peer in peer_nodes_env.split(","):
-                if peer.strip():
-                    try:
-                        blockchain.register_node(peer.strip())
-                    except Exception as e:
-                        logging.warning(f"Invalid peer URI: {peer.strip()}")
+        blockchain.node_id = app.config.get("NODE_ID", "standalone")
+        blockchain.node_address = (app.config.get("NODE_ADDRESS", "") or "").strip().rstrip("/")
+        local_node_address = (app.config.get("NODE_ADDRESS", "") or "").strip().rstrip("/")
+        peer_nodes = app.config.get("PEER_NODES", [])
+
+        if peer_nodes:
+            for peer in peer_nodes:
+                if local_node_address and peer == local_node_address:
+                    continue
+                try:
+                    blockchain.register_node(peer)
+                except Exception:
+                    logging.warning(f"Invalid peer URI: {peer}")
             if blockchain.nodes:
                 threading.Thread(target=_initial_sync, args=(app,), daemon=True).start()
 
@@ -84,7 +89,8 @@ def _initial_sync(app):
     time.sleep(5)
     with app.app_context():
         try:
-            logging.info(f"Syncing with peers: {blockchain.nodes}...")
+            node_id = app.config.get("NODE_ID", "standalone")
+            logging.info(f"Node {node_id} syncing with peers: {blockchain.nodes}...")
             if blockchain.resolve_conflicts():
                 logging.info(f"Synchronized chain. New length: {len(blockchain.chain)}")
         except Exception as e:

app/blueprints/admin/routes.py

@@ -425,7 +425,7 @@ def api_system_stats():
         stats["blockchain"] = {
             "blocks": len(blockchain.chain),
             "peers": len(blockchain.nodes),
-            "node_name": os.environ.get("NODE_NAME", "standalone"),
+            "node_name": current_app.config.get("NODE_ID") or os.environ.get("NODE_NAME", "standalone"),
             "validators": blockchain.VALIDATORS,
         }
 

app/blueprints/api/routes.py

@@ -79,29 +79,19 @@ def receive_peer_block():
         if not block_data:
             return jsonify({"success": False, "message": "No block data provided"}), 400
 
-        # 1. Reconstruct block object
-        new_block = blockchain.block_model(
-            index=block_data["index"],
-            timestamp=block_data["timestamp"],
-            data=json.dumps(block_data["data"]),
-            merkle_root=block_data.get("merkle_root"),
-            previous_hash=block_data["previous_hash"],
-            nonce=block_data["nonce"],
-            hash=block_data["hash"],
-            signed_by=block_data.get("signed_by"),
-            signature=block_data.get("signature"),
-        )
+        required_fields = {"index", "timestamp", "data", "previous_hash", "nonce", "hash"}
+        missing = [field for field in required_fields if field not in block_data]
+        if missing:
+            return jsonify({"success": False, "message": f"Missing required fields: {', '.join(missing)}"}), 400
 
-        # 2. Simple validation against local chain
-        last_block = blockchain.get_latest_block()
-        if last_block and block_data["index"] <= last_block.index:
-            return jsonify({"success": False, "message": "Block already exists or is outdated"}), 409
+        source_node = blockchain.normalize_node_ref(request.headers.get("X-Node-Address") or request.headers.get("X-Source-Node"))
+        origin_node = (request.headers.get("X-Origin-Node") or request.headers.get("X-Source-Node") or "unknown").strip()
 
-        if last_block and block_data["previous_hash"] != last_block.hash:
-            return jsonify({"success": False, "message": "Previous hash mismatch. Sync required."}), 400
+        # Idempotency gate: if already present, ignore safely.
+        if blockchain.has_block(block_data["index"], block_data["hash"]):
+            return jsonify({"success": True, "message": "Duplicate block ignored"}), 200
 
-        # 3. Cryptographic validation (simplified for the model bridge)
-        # Create a Block object for validation methods
+        # 1. Validate block object before any persistence
         from core.blockchain import Block
 
         v_block = Block(
@@ -110,6 +100,7 @@ def receive_peer_block():
             block_data["previous_hash"],
             signed_by=block_data.get("signed_by"),
             signature=block_data.get("signature"),
+            proposed_by=block_data.get("proposed_by"),
         )
         v_block.timestamp = block_data["timestamp"]
         v_block.nonce = block_data["nonce"]
@@ -119,16 +110,50 @@ def receive_peer_block():
         if v_block.hash != v_block.calculate_hash():
             return jsonify({"success": False, "message": "Invalid block hash"}), 400
 
-        if blockchain.crypto_manager and v_block.signature:
+        if v_block.merkle_root and v_block.merkle_root != v_block.calculate_merkle_root():
+            return jsonify({"success": False, "message": "Invalid Merkle root"}), 400
+
+        if v_block.index > 0 and v_block.signed_by not in blockchain.VALIDATORS:
+            return jsonify({"success": False, "message": "Unauthorized block signer"}), 403
+
+        if blockchain.crypto_manager:
+            if not v_block.signature:
+                return jsonify({"success": False, "message": "Missing digital signature"}), 400
             if not blockchain.crypto_manager.verify_signature(v_block.hash, v_block.signature):
                 return jsonify({"success": False, "message": "Invalid digital signature"}), 400
 
-        # All checks passed, add to local DB and chain
+        # 2. Validate against local chain linkage
+        last_block = blockchain.get_latest_block()
+        if last_block and block_data["index"] <= last_block.index:
+            return jsonify({"success": True, "message": "Outdated block ignored"}), 200
+
+        if last_block and block_data["previous_hash"] != last_block.hash:
+            return jsonify({"success": False, "message": "Previous hash mismatch. Sync required."}), 400
+
+        # 3. Persist only after full validation
+        new_block = blockchain.block_model(
+            index=block_data["index"],
+            timestamp=block_data["timestamp"],
+            data=json.dumps(block_data["data"]),
+            merkle_root=block_data.get("merkle_root"),
+            previous_hash=block_data["previous_hash"],
+            nonce=block_data["nonce"],
+            hash=block_data["hash"],
+            signed_by=block_data.get("signed_by"),
+            signature=block_data.get("signature"),
+        )
+
         db.session.add(new_block)
         db.session.commit()
         blockchain.chain.append(v_block)
 
-        logging.info(f"Accepted peer block {block_data['index']} from {block_data.get('signed_by')}")
+        # Controlled gossip propagation: relay accepted blocks, never back to sender.
+        blockchain.broadcast_block(v_block, source_node=source_node, origin_node=origin_node)
+
+        logging.info(
+            f"Accepted peer block {block_data['index']} from signer={block_data.get('signed_by')} "
+            f"source={source_node or 'unknown'} origin={origin_node}"
+        )
         return jsonify({"success": True, "message": "Block accepted and added to chain"})
 
     except Exception as e:

app/config.py

@@ -37,6 +37,16 @@ class Config:
     SECRET_KEY = os.environ.get("SESSION_SECRET", "dev-secret-key-change-in-production")
     DEBUG = True
     PORT = int(os.environ.get("PORT", 5000))
+    HOST = os.environ.get("HOST", "0.0.0.0")
+
+    # Multi-node settings (backward compatible aliases)
+    NODE_ID = os.environ.get("NODE_ID") or os.environ.get("NODE_NAME") or "standalone"
+    NODE_ADDRESS = (os.environ.get("NODE_ADDRESS") or "").strip()
+    PEER_NODES = [
+        peer.strip().rstrip("/")
+        for peer in os.environ.get("PEER_NODES", "").split(",")
+        if peer.strip()
+    ]
 
     # IPFS settings
     IPFS_ENDPOINTS = [