Update app.py

app.py

@@ -56,4 +56,31 @@ async def relay_txn(payload: dict):
 
 
 
+@app.post("/sign-message")
+async def sign_message(payload: dict):
+    message = bytes(payload["message"])
+
+    # 1️⃣ verify quantum proof (same as your txn logic)
+    proof = base58.b58decode(payload["winternitz_proof"])
+    anchor = base58.b58decode(payload["anchor"])
+    lap = payload["lap"]
+
+    check = proof
+    for _ in range(lap):
+        check = hashlib.sha256(check).digest()
+
+    if check != anchor:
+        return {"success": False, "error": "Quantum auth failed"}
+
+    # 2️⃣ server signs message hash
+    msg_hash = hashlib.sha256(message).digest()
+
+    server_sig = SERVER_KEY.sign_message(msg_hash)
+
+    return {
+        "success": True,
+        "server_signature": base58.b58encode(bytes(server_sig)).decode()
+    }
+
+