# Device Registration and SAS Token Generation for Azure IoT Hub

## 🔧 Prerequisites

- Azure Subscription
- Azure IoT Hub created
- Azure CLI installed
- Device created in IoT Hub

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## 1️⃣ Register a Device

```bash
az login
az account set --subscription "<your-subscription-id>"

az iot hub device-identity create --hub-name <your-hub-name> --device-id <your-device-id>

2️⃣ Get Device Connection String
az iot hub device-identity show-connection-string --hub-name <your-hub-name> --device-id <your-device-id>

3️⃣ Generate SAS Token

import base64, hmac, hashlib, time, urllib.parse

def generate_sas_token(uri, key, expiry=3600):
    ttl = int(time.time()) + expiry
    sign_key = f"{urllib.parse.quote_plus(uri)}\n{ttl}"
    signature = base64.b64encode(hmac.new(base64.b64decode(key), sign_key.encode(), hashlib.sha256).digest())
    return f"SharedAccessSignature sr={uri}&sig={urllib.parse.quote_plus(signature.decode())}&se={ttl}"

4️⃣ Use SAS Token in Firmware
Set the Authorization header in MQTT/TLS to the token string.