Mechanical lock is the simplest and a perfect access control system, and many of the basic concepts of access control system and evaluation methods can be got from the analysis of it. Features carrier, read (recognition) and locking devices consist of the three basic elements of the system.
1. Access control system is used to manage and control people, logistics, information flow. Therefore, system has first to confirm their identity, and determine the legitimacy of their in-and-out (behavior). Here comes a method to give them a sign of status and authority, which we call the characteristics of the carrier, and the information of identity and authority it contains is the characteristics. Mechanical lock key is a kind of feature vector, "its tooth" is the characteristic. There are many carriers can be made used of in the system, such as: magnetic, photoelectric and currently the most commonly used IC card, etc. These carriers have to be used with holders (people or things), but it should at the same time have identity with the holders, which means the feature vector can be used by others (objects). In order to prevent this problem, we can use multiple ways, which means two or more characteristics of the carrier (depending on the requirement of system security).
2. Recognition device: used to exchange information with features carrier. It reads the information of the identity and authority from the characteristics of the carrier in the right way, in order to recognize the identity of the holder and judge the legality of its behavior (and request). Obviously, the characteristics of reading devices are the devices that match the characteristics of carrier, so when carrier technology attribute is different, reading devices also have different properties. Magnetic card reader is magnetoelectricity conversion equipment, photoelectric card reading device is a photoelectric conversion device and IC card reading device is electronic data communication device. Mechanical lock device is to read the "lock", and when the key is in the lock core, it will confirm the identity of the holder and permissions through the match of billiard activities in lock core and the tooth of the key. The process of electronic reading device identification: it will change the characteristics information been read into electronic data, and then compared with data stored in the device memory, to achieve the identity of the qualification and certification authority, which is also known as the "identification". The function of reading device is only reading some information, but some still have the ability to write the information characteristics of carrier, which is called "reading and writing device". To write information feature vector is a process of correction system to the authorization or authorized. This kind of feature vector can be modified and reused. Generally, the key of mechanical lock cannot be changed, so are the permissions it represents. Human biological characteristics cannot be modified, but its permissions can be modified through the system settings.
3. Locking devices: the access control system can only be practical when being added suitable locking devices. When reading device confirms the identity and privileges of the holder, it should make the holder smooth out, and effectively to prevent illegal request. Different forms of locking mechanism will form different access control systems, or achieve the different application of access control technology. For instance, shifter lever of metro charge system, parking lot, the stopper, self-help bank closed out the printing device. Institutions lock is a lock mechanism of access control system, and when the lock matches the key tooth, you can rotate the handle, and recover the open door lock tongue.
The security of the access control system includes the anti-shock strength, namely, resist the destruction of the mechanical force, the performance is mainly determined by the locking mechanism of system. In addition to the mechanical lock, locking mechanism of access control system commonly use electronic locks, its feature vector is mainly all kinds of credit card, and the door opening and closing is controlled by the electromagnetic force.
Above we study the basic elements of the system through the analysis of the mechanical lock, then we are still evaluating its the main technical indicators from the mechanical locks:
A key, its teeth and each tooth of the high and low order number determines the number of tooth to be formed. This is the key quantity. For example: a mechanical lock key is composed of five teeth, and each tooth has 5 (differential), so its key quantity is 55. The key of the credit card is decided by the length of the data representing the characteristics, such as expressed in 8 bit binary number features, and its key content is 28. The greater the system key quantity is, the greater the amount of the greater system capacity is, and the higher the security at the same time, because it is less possible to be deciphered or copied. If each tooth is regarded as a characteristic (T), and the tooth of the high and low order as the difference each characteristic can show(S), then the amount of key system is TS. Credit card can have a large amount of keys (by setting), the key of human creature characteristics is of great amount.
Deterrent rate and false rejection rate: we often encounter situations when other keys can open the lock or the key is not working to lock or unlock, which is especially true for an old lock. That is the concept of deterrent rate and false rejection rate. The error information communication (read) of the system is the cause of the error, while the low key quantity is more likely to cause this problem.
The security of the system includes two aspects: one is mentioned above to prevent from being deciphered and imitated, another is the ability to resist the damage of mechanical force, with which the system locks have a lot to do. Countries have set the standards, and mechanical lock that is in line with the standard is called anti-theft lock.
System friendliness: entrance guard system has two interfaces with people, one is the feature information interaction interface, and another is the process of open/locking door. Door system should be friendly to people, including no compulsive reading characteristics, flow and security process. Some biological characteristics identification and electronic access control system has this kind of friendly, so they can be widely used.