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The core of information safety -- password technology
From;    Author:Stand originally

Information security technology is an integrated course, it involves science of information theory, computer and password to learn to wait for many sided knowledge, the protective means that its main task is the information inside all of research computer science department and communication network is the safety with the information inside implementation system, confidential, true and complete. Among them, the core of information safety is password technology.   
Permeate each domains ceaselessly as computer network, the application that the password learns also expands subsequently. Digital sign one's name, identity is differentiated etc is the new technology that is born by password school and application.   
Data adds close principle and system
Data is added close
The data that comes true on the computer is added close, its are added close or decoding commutation control implementation by close key. Close key (Keyword) it is the user is chosen randomly according to system of a kind of password, it is one random string normally, it is control proclaimed in writing and the exclusive parameter that close article alternates.   
Digital sign one's name
Password technology is added besides what provide information close outside decoding, return those who provide pair of news source to differentiate, those who assure information is complete and undeniable wait for a function, and these 3 kinds of functions are to pass digital sign one's name to come true.   
The principle that the number signs is the proclaimed in writing that will convey carries operation of a kind of function (Hash) changeover becomes message summary (the message summary with different correspondence of different proclaimed in writing) , message summary is added close hind convey to accept together with proclaimed in writing square, accept the proclaimed in writing that just will accept to produce new message summary and send square hair to sign up for article summary to decode quite, state proclaimed in writing was not altered consistently as a result quite, if abhorrent state proclaimed in writing already was distorted.   
Add secret system to reach quite
According to close key type cent of technology of different will contemporary password is two kinds: One kind is to be added symmetrically close (secret key is added close) system, another kind is to make public close key to add close (asymmetrical add close) system.   
Symmetrical key adds secret system is to add mix closely decode all use same secret key, and communication both sides must obtain this key, hold the secret of the key.   
The security of symmetrical password system is relied on the following two elements. The first, adding close algorithm must be enough strong, be based on close text body to decode information merely is impossible on practice; The 2nd, the security that increases secret method relies on the secret sex of close key, is not algorithmic secret sex, accordingly, we were not necessary to ensure algorithmic secret sex, and the secret sex that needs to assure close key. The algorithmic implementation rate that increases secret system symmetrically is splitting, await the test that chooses algorithm to look as a result from AES, the rate that software achieves reached every second number or tens of million bit. These characteristics of symmetrical password system make its are having wide application. Because algorithm does not need to keep secret, the chip that so manufacturer can develop low cost is added with realizing data close. These chip are having wide application, agree with mass production.   
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