In Depth Analysis of Communication Security of Intelligent Door Lock

Smart door lock is gradually entering the family with the characteristics of convenience and safety. As the entrance of the family, smart door lock has become the entrance product competed by various giants. All kinds of intelligent door locks are ready to come out. Fingerprint recognition, voice recognition, finger vein recognition, face recognition and other technologies have been added, and the intelligent door lock has become tall.

The smart door lock can also be connected with smart home products such as smart appliances, smart video and audio, and home security through the Internet of things, which realizes the artificial intelligence and human-computer interaction that mechanical locks are difficult to achieve, and can extend more application scenarios and provide richer supporting services. In the industry application market, it can connect with anxinqiao community police cloud system, public rental housing management platform, and campus door lock management platform, Provide community / home / industry market security networking alarm operation services. Therefore, the intelligent door lock of the Internet of things is bound to become the general trend in the future.

NB IOT technology has great potential in the application of intelligent door lock. NB IOT transmission technology further ensures the security of door lock data transmission; Low power consumption overcomes the technical problem of battery powered intelligent door lock; Various types of locks in various areas such as door locks, cabinet locks and traffic locks as the entrance of asset management need to be more widely covered, which is more convenient, more stable and safer than the traditional WiFi communication mode. A door lock that can communicate, think, speak and report in time will play an unlimited important role in asset management, access management and public security management.

Figure 1 block diagram of intelligent door lock

Using the smart door lock, on the one hand, people can not bring the key, saving the trouble caused by forgetting and losing the key before. On the other hand, the smart door lock can also be connected with the safety protection of the family, which solves people's more security demands.

The smart door lock is added to the home smart home application. Once it is connected to the Internet to realize the remote control unlocking application (for example, the owner of the family in the unit can realize the applications such as the entry of the elderly, children or visitors through the remote control door lock), the risk will be greatly increased and a large potential safety hazard will be buried for the family. Responsible smart lock brands will install security chips to ensure the security of the equipment end and the encrypted transmission of information, so as to ensure the user's information security to the greatest extent, but it can not be said that the risk is completely eliminated. It can only be said that they continue to develop and adopt new technologies to continuously improve security.

Intelligent door lock is in the important position of the first guard of family safety, and security is its self-evident core. The purpose of intelligence is to make customers safer and more convenient without deviating from security services. The network security and electronic information confidentiality after the realization of intellectualization, together with the security of the original mechanical lock, are the key problems whether an intelligent door lock is reliable or not.

Mechanical lock cylinder safety

Each smart door lock has a mechanical lock cylinder for emergency opening. The safety level of this mechanical lock is divided into three levels: A, B and C. Intelligent door lock is recommended to be equipped with mechanical lock cylinder of grade C.

The mechanical lock shall be installed normally, and conventional tools such as crowbar, steel bar, screwdriver, pipe wrench, hammer, toggle tool, portable electric drill and hand-held hacksaw shall be used to carry out anti drilling, anti sawing, anti prying, anti pulling, anti impact, anti technical opening test and anti technical opening test of password mechanical anti-theft lock. The lock is damaged The net working hours opened shall not be less than those specified in the table below.

Table 1 minimum net working time of mechanical lock against damage

Anti interference performance of electronic components

On May 26, 2018, on the first day of the 9th China (Yongkang) International Door Expo, a young woman named Wang Haili opened the smart locks of 8 brands on the spot with the small black box shown in the figure below. The fastest time was only 3 seconds! Caused an uproar in the industry circle. People have questioned the security of smart locks.

However, on July 11, 2018, the "Tesla coil" (black box) technology open challenge ", sponsored by Guangdong Mustang Security Technology Co., Ltd., assisted by Guangdong dartson anti-theft equipment Co., Ltd. and supported by many national industry institutions and representatives, was grandly opened at the Crown Hotel in Xiaolan, Zhongshan, Guangdong. The organizer offered a reward of 1 million to challenge the "Tesla coil" (black box) unlocking tool, aiming to escort the national intelligent lock industry. The result of the challenge is the "complete victory" of the domestic brand Mustang intelligent lock.

A few brands of smart lock products are opened by "Tesla coil" (black box) due to lack of anti-interference ability, unreasonable product structure, and unqualified raw materials used by some manufacturers to save costs. More brands with technical strength and ingenuity can not be opened at all.

Security of data interaction

Most of the products on the market have high cost and technical requirements due to a high-level encryption system, so everyone focuses on the intelligent use of functions as the selling point of speculation. Because "safety" is invisible and untouchable, and the high cost is obvious. At present, these smart locks are longer than convenience, but shorter than security.

UART and SPI interfaces are mostly used for data interaction between the main control MCU in the intelligent lock and the external communication module. It is recommended that the data on these channels be encrypted by AES before transmission, and the encrypted key can be agreed with the module manufacturer in advance. In this way, even if the lock is removed as a whole and the data of these communication ports are analyzed, the real original data information cannot be easily obtained without the factory key.

Violent attack is also called exhaustive attack, that is, every possible key is enumerated in turn for decryption operation until the correct key is found. The successful decryption algorithm needs to traverse half of the key space on average. The following table shows the average time of violent attacks corresponding to AES algorithm based on keys of different lengths.

Table 2 average time required for exhaustive attack key