(1) Fingerprint Fingerprint was used to prove identity instead of signature in ancient China. It can be roughly divided into three basic types: "bow", "basket" and "bucket", which are different from person to person and remain unchanged for life. Fingerprint identification is the most mature, convenient, reliable, non-invasive and cheap biometric technology solution, which has been widely used in many industries. Advantages: First, it has strong specificity and high complexity: fingerprint is a unique feature of human body, and its complexity is enough to provide sufficient features for identity recognition. The second is high reliability: if you want to increase the reliability, you only need to register your fingerprints and identify ten fingers at most, and each fingerprint is unique. The most reliable way to read human biometric features is for users to directly contact the fingerprint collection head. Third, fast and easy to use: scanning fingerprints is fast and easy to use; Fourthly, the equipment is small and the price is low: the fingerprint acquisition head is more miniaturized and can be easily combined with other equipment, and with the rapid development of electronic sensing chips, its price will be lower. Disadvantages: The fingerprints of some people or certain groups are difficult to image because of the few fingerprint features. In addition, because the current fingerprint authentication technology can not store any data containing fingerprint images, it can only store encrypted fingerprint feature data obtained from fingerprints; Every time fingerprints are used, fingerprints will be left on the fingerprint collection head, which may be used to copy fingerprints. (2) The palm geometry is based on the fact that almost everyone's hand shape is different, and this hand shape will not change obviously after a certain age. When the user puts his hand on the hand reader, a three-dimensional image of his hand is captured. Next, measure the shape and length of fingers and knuckles. According to the different data used to identify people, hand shape reading technology can be divided into the following three categories: the application of palm, the pattern of hand blood vessels and the geometric analysis of fingers. Drawing different features of the hand is very simple and will not produce a large number of data sets. However, even if there are a considerable number of records, palm geometry may not necessarily distinguish people, because the characteristics of hands are very similar. Compared with other biometric methods, palm geometry can not obtain the highest degree of accuracy. When the database is increasing, it is necessary to increase the obvious characteristics of hands in quantity in order to clearly identify and compare people with templates. (3) The biometric technologies for analyzing the complex and unique features of eyes mainly include iris recognition technology, retina recognition technology and cornea recognition technology. Iris is a layer of colored cells around the pupil. Each iris contains a unique structure, which is based on features such as crowns, lenses, filaments, spots, structures, pits, rays, wrinkles and stripes. The iris scanning security system includes a fully automatic camera to find your eyes. When the iris is found, it begins to focus. After collecting iris samples, the software compares the obtained data with the stored templates. Blinking can't fool the system. Iris recognition is more convenient for users; Good reliability, no physical contact between users and equipment; However, its equipment is large, and the camera used for focusing is very expensive, which is extremely difficult for black eyes to read. In addition, a better light source is needed. The retina is the blood cell layer at the bottom of the eye. Retinal scanning uses low-density infrared rays to capture the unique characteristics of retina, so it only captures the pattern of blood cells. Some people think that retina is more unique than iris. The advantage of retina recognition is that it is an extremely fixed biological feature, because it is "hidden", so it can not be affected by wear and aging; Users don't need direct contact with the equipment; At the same time, it is also the most difficult system to cheat, because the retina is invisible, so it will not be forged. On the other hand, there are some imperfections in retina recognition, such as: retina technology may bring health damage to users and need further research; The equipment investment is relatively expensive, and the requirements of identification process are also high, so it is difficult to popularize and apply corneal scanning identification. (4) The facial recognition system recognizes people by analyzing the unique shape, pattern and position of facial features. The acquisition and processing methods are mainly standard video and thermal imaging technology. Standard video technology takes an image or a series of images of the face through a standard camera. After capturing the face, record some core points, such as the positions of eyes, nose and mouth and their relative positions, and then form a template. Thermal imaging technology produces facial images by analyzing the hot lines generated by the blood of facial capillaries. Unlike video cameras, thermal imaging technology does not need good light source conditions, so it can be used even in the dark. The attraction of face biometric technology lies in its human-computer interaction, and users don't need to touch the device directly. But relatively speaking, this system is unreliable. The position of the user's face and the surrounding light environment may affect the accuracy of the system, and the equipment is very expensive. Only relatively advanced cameras can capture facial images effectively and at high speed, and it is also difficult to miniaturize the equipment. In addition, the facial recognition system needs artificial intelligence to compensate for the changes of human face, such as hair, ornaments, aging and so on. The machine knowledge learning system must constantly compare the images obtained before with the images obtained now. To improve the core data and make up for minor differences. In view of the above factors, there are still some difficulties in the popularization and application of this technology. (5) Speech recognition mainly includes language and sound. Speech recognition is the application of the speaker's voice and language model based on physiological and behavioral characteristics. Unlike language recognition, it does not recognize the spoken words themselves. But by analyzing the unique characteristics of speech, such as the frequency of pronunciation, to identify the speaker. Speech recognition technology enables people to control whether they can enter or leave restricted areas through their voices. For example, dial-in banking, database services, shopping or telephone voice mail, and access to security devices. Language recognition is to recognize the content of speech, which can be mainly used in information input, database retrieval, remote control and so on. At present, voice recognition is used for identity recognition. Speech recognition is also a non-contact recognition technology, which can be naturally accepted by users and is convenient to use. However, it is unreliable because of the risk of dehumanization, remote control and low precision. Moreover, the wide range of sound changes (such as volume, speed and sound quality) will directly affect the accuracy of collection and comparison, and a person with a cold may be wrongly rejected and unable to use the speech recognition system. At the same time, with the development of digital technology, audio digital processing technology is likely to deceive speech recognition system, and its security has been challenged. (6) Signature signature identification, also known as signature mechanical identification, is based on the strength of the signature. It analyzes the motion of the pen, such as acceleration, pressure, direction and stroke length, rather than the signature image itself. Like speech recognition, signature recognition is also a behavior measurement. The key of signature mechanics is to distinguish different signature parts, some are habitual, and some are different every time. As a means of identity authentication, signature has been used for hundreds of years, and its application scope can be seen from the declaration of independence to credit cards. It is a mature identification technology that is easily accepted and recognized. However, there are still problems in signature recognition in terms of measurement methods and signature repeatability used in the process of obtaining the logo. The signature system has been controlled to accept variables in some way. However, if the acceptance rate does not decrease, it cannot continuously measure the strength of the signature. Because the speed of signature is not fast, it is not convenient to use on the Internet. (7)DNA DNA in the human body is unique (except for twins who may have the same structure) and is permanent in the whole human range. Therefore, this method is absolutely authoritative and accurate, but the identification of twin individuals may lose its due role. The method of DNA identification is mainly based on the characteristics that the molecular structure of DNA in human cells varies from person to person. The accuracy of this method is better than any other identification method, and it has good anti-counterfeiting. However, the method of obtaining and identifying DNA (DNA identification must be carried out in a certain chemical environment) limits the real-time performance of DNA identification technology; In addition, some special diseases may change the structural composition of human DNA, and the system cannot correctly identify such people. (8) In addition to the above biometric technology, there are also identification technologies based on vein, ear shape, key rhythm, body odor and walking gait.