What's the Matter?By Ben Eatts On 02/01/2024
Matter, an open-source protocol in the Internet of Things (IoT) world, merges different IoT protocols, such as Thread & Zigbee, with traditional Wi-Fi and Ethernet networks.
Matter, an open-source protocol in the Internet of Things (IoT) world, merges different IoT protocols such as Thread & Zigbee with traditional Wi-Fi and Ethernet networks. It does this by creating a fabric, a "network", on top of the traditional IPv6 TCP/UDP stack.
Matter is standardized by the same organization as ZigBee, previously known as the Zigbee Alliance, and now renamed to the Connectivity Standards Alliance.
Because Matter sits over IPv6, it is agnostic of the lower layers. This allows the protocol to communicate across Ethernet, Wi-Fi, Thread, and even Bluetooth Low Energy (BLE) if the IPv6 for BLE adaptation layer is used. A device (typically within the Smart Home realm) utilizing Matter can be a member of multiple fabrics, allowing it to be controlled by components from different vendors.
The Matter Topology
A typical Matter topology consists of the following objects:
- Bridge: Exposes devices between Matter and non-Matter networks.
- Controller: Used for commissioning and control of the devices on the fabric.
- Edge Router: Ensures interoperability of different IPv6 networks.
- Node: A Matter device that can belong to multiple Matter fabrics.
These components form the Matter fabric, as shown in Figure 1. Here, the Thread Border router & Wi-Fi Access Point are acting as edge routers. The Master Controller is also assuming the role of bridge. These components are what the different Nodes are connecting to.
Devices are commissioned onto a fabric through a set process.
When a device is first added to a fabric, it undergoes a series of steps.
1. Device Discovery
The discovery process will occur over BLE, Wi-Fi, or IP if already on an IP network. If utilizing Thread as the medium, the device must also support BLE for the discovery purposes. When using BLE, the discovery method is the Generic Access Profile (GAP). For Wi-Fi, it uses a Soft-AP function. An out-of-band password is obtained, usually via a QR code, which is used in the next step.
2. Security Setup using Passcode-Authenticated Session Establishment (PASE)
The outcome of this step is to establish encryption keys between the device being commissioned and the commissioner. Additionally, a challenge is created for the next stage, the Attestation phase. The image below illustrates the PASE process at a high level (Figure 2.)
3. Device Attestation Verification
The commissioner verifies that the device is a certified device and will notify the user if it is not certified.
4. Information Configuration
The commissioner provides the device with relevant information such as regulatory domain information, UTC time, network interface configurations, and certificates.
5. Join Network
The commissioner instructs the device to connect to the operational network. The IPv6 address is either already known or discovered by the commissioner.
6. Security Setup with Certificate Authenticated Session Establishment (CASE)
Encryption keys are derived to ensure secure communication between the commissioner and the device. All unicast messages between the commissioner and the device are encrypted using these keys.
7. Commissioning Complete Message Exchange
An encrypted exchange of messages is performed over the operational network to indicate successful commissioning.
Matter promises to revolutionize the Smart Home IoT world by unifying different wireless protocols and creating a versatile fabric over IPv6 networks. The Matter fabric enables simplicity, interoperability, reliability, and security. By embracing Matter, we are promoting a future where IoT devices of different vendors can work harmoniously in a connected environment.
Ben Eatts, CWNE #315
Blog Disclaimer: The opinions expressed within these blog posts are solely the author’s and do not reflect the opinions and beliefs of the Certitrek, CWNP or its affiliates.