What is the transmission principle of Bluetooth? Are there loopholes in Bluetooth technology?

Bluetooth is very common after birth. As residents of the information age in the 21st century, we are naturally no stranger to Bluetooth. In order to enhance everyone’s understanding of Bluetooth technology, this article will discuss the transmission principle of Bluetooth and the “BLESA” loopholes in Bluetooth. If you are interested in Bluetooth-related content, you might as well read it down with the editor.

Bluetooth is very common after birth. As residents of the information age in the 21st century, we are naturally no stranger to Bluetooth. In order to enhance everyone’s understanding of Bluetooth technology, this article will discuss the transmission principle of Bluetooth and the “BLESA” loopholes in Bluetooth. If you are interested in Bluetooth-related content, you might as well read it down with the editor.

What is the transmission principle of Bluetooth? Are there loopholes in Bluetooth technology?

1. Bluetooth application

Bluetooth technology has been widely used in actual life and work, but people do not know much about Bluetooth technology. In addition to the application of Bluetooth transmission function and voice function in mobile phones, it is used for wireless printers, wireless conferences, etc. There is not enough knowledge about Bluetooth applications. Therefore, in the future development of Bluetooth technology, the Bluetooth technology should be promoted, and the low-cost and technologically advanced Bluetooth technology should be promoted in a wider application platform.

The application field of Bluetooth technology should develop in breadth. The first stage of Bluetooth technology is to support mobile phones, PDAs and laptops, and the next development direction will be expanded to all walks of life, including automobiles, information plus points, aviation, consumer electronics, military and so on.

2. Bluetooth transmission principle

1 Master-slave relationship:

Bluetooth technology stipulates that when each pair of devices performs Bluetooth communication, one must be the master and the other must be the slave in order to communicate. During communication, the master must find and initiate the pairing. After the link is established, the two parties must Can send and receive data. In theory, a Bluetooth master device can communicate with 7 Bluetooth slave devices at the same time. A device with Bluetooth communication function can switch between the two roles. It usually works in slave mode and waits for other master devices to connect. When necessary, it switches to master mode and initiates calls to other devices. When a Bluetooth device initiates a call in the master mode, it needs to know the other party’s Bluetooth address, pairing password and other information. After the pairing is completed, the call can be initiated directly.

2 Calling process:

When the Bluetooth master device initiates a call, the first step is to find out the Bluetooth devices around which can be found. After the master device finds the slave Bluetooth device, it will pair with the slave Bluetooth device. At this time, the PIN code of the slave device needs to be entered, and some devices do not need to enter the PIN code. After the pairing is completed, the slave Bluetooth device will record the trust information of the master device. At this time, the master can initiate a call to the slave device, and the paired device does not need to be paired again during the next call. A paired device, as a slave Bluetooth headset, can also initiate a link establishment request, but the Bluetooth module for data communication generally does not initiate a call. After the link is successfully established, two-way data or voice communication can be carried out between the master and the slave. In the communication state, both the master and slave devices can initiate link disconnection and disconnect the Bluetooth link.

3 Data transmission

In Bluetooth data transmission applications, one-to-one serial data communication is one of the most common applications. The Bluetooth device sets the pairing information between the two Bluetooth devices in advance before leaving the factory. The master has pre-stored the PIN code of the slave device, Address, etc., when the devices at both ends are powered on, the link is automatically established, and the serial port is transparently transmitted, without the intervention of peripheral circuits. In one-to-one applications, the slave device can be set to two types. One is the silent state, that is, it can only communicate with the designated master and cannot be searched by other Bluetooth devices; the second is the development state, which can be searched by the designated master. , It can also be searched and established by other Bluetooth devices.

What is the transmission principle of Bluetooth? Are there loopholes in Bluetooth technology?

3. “BLESA” makes reconnection unsafe

The “BLESA” vulnerability is different from the “BLURtooth” vulnerability in the pairing operation. It is a security issue that occurs when Bluetooth is reconnected. “BLESA” is a Bluetooth low energy spoofing attack. The vulnerability is numbered CVE-2020-9770, which affects devices running the BLE protocol (Bluetooth Low Energy).

BLE is designed to save battery power and extend the duration of Bluetooth connection. In the past ten years, this technology has been widely adopted, and it will be used in almost all battery-powered devices.

The security vulnerabilities in this technology were discovered by a security research team from Purdue University, and BLE is a research project of this 7-person team of experts, who focused on the process of “reconnecting”. Two BLE devices (client and server) perform a pairing operation, and after they have mutually authenticated, there will be a “reconnection” step.

When the Bluetooth device moves out of range and then moves back into range, the device will reconnect. When reconnecting, the two BLE devices should check each other’s encryption keys negotiated during the pairing process, then reconnect and continue to exchange data via BLE.

However, the security research team discovered some security issues in this process:

During device reconnection, authentication is optional, not mandatory;

If the user’s device cannot force the IoT device to authenticate the communicated data, the authentication may be bypassed.

Therefore, hackers can use this security “Bug” to carry out BLESA attacks. Nearby attackers bypassed the reconnection verification and sent spoofed data with incorrect information to the BLE device, and tricked the operator and the automated process into making a wrong operation decision.

The Links:   LTM170ET01 EW24210GLY

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