What is the electronic signature?

Coding began beret in extreme antiquity. Thus, already Caesar created the classical cipher, which bears his name. But about the history of electronic signature to here say separately something which, however, is not surprising, indeed to people since olden times was sufficient press and stroke of a pen, so that to the mind comes only papyrus with the sealing-wax press, and therefore let us limit to the present.

In the algorithms of electronic signature and asymmetric coding secret and open keys are used. Moreover secret must be taken absolutely randomly, for example from the random-number generator, and opened - be calculated from the secret in such a way as to obtain the second of the first it was impossible. Thus, let us suppose you with the friend decided to place electronic signature under all their communications. It is theoretically necessary to make the following.

First create the keys of electronic signature. As in the case of coding, they usually are stored in the files, in particular on the diskettes. Each of you must have their secret and open keys.

Keep secret keys, and exchange those opened.

Sign the letter to friend by secret key and send your message together with the signature. Electronic signature is the sequence of several numbers. At first glance it appears chaotically; in fact it is calculated from the following simplified formula:

f(.M.ks),

M - text of letter; and ks - secret key.

After obtaining the letter, supplied with electronic signature, addressee with the aid of your open key checks its authenticity. Result of checking - one of the answers: "it is accurate - it is incorrect". Electronic signature confirms the veracity of the report. If any changes were introduced in it in the process of sending, even entirely insignificant, then substitution will be revealed.

Secret key you must thoroughly keep secret, indeed any, who learns it, he will know how to counterfeit your signature. If you nevertheless lose your key, then compulsorily undertake the specific measures and, most importantly, you will report to all your potential addressees about the fact that your signature, which they considered accurate, from now on should be considered incorrect. But until you this make, count, as if recently signed the bundle of empty sheet paper.

One more, not less important designation of electronic signature - confirmation of the authorship of communication. Usually into the files of keys ETSP besides strictly the key are written different further news like FIO and place of the work of its owner, period of the action of signature, etc. But into the signature, which stands under the communication or the document, is copied the given from the secret key, and, first of all, information about its owner, which makes it possible to establish authorship. It means, it will not be necessary to memorize, who precisely sent the open key, with the checking which showed that ETSP was accurate, and this is very important, indeed actually it can be not one hundred open keys. By the way, "correct" programs with the calculation strictly of the electronic signature of communication include information about the author so that it would come to mind to change no one it. The result of checking ETSP usually is placed on screen in this, for example, form:

The signature of file compromat.bmp is accurate

Like any cryptographic algorithms with the open key, ETSP are convenient for distributing the keys "in flight", what is especially good in the Internet - you can send your open key to any addressee directly before the sending to it the signed by you communication or, which is still simpler, to place it on any resource in the Internet. However, I will allow itself to quote the classicists of the protection of the information: "the principles of accessibility, convenience, speed and functionality of computing system are antagonistic to the principles of its safety". On the whole, for the convenience it is necessary to pay by the considerable weakening of safety. Here, as with the asymmetric coding, are possible the substitution of the open keys, truth leading to other consequences.

This is how this is: you with the friend created on the pair of keys and exchanged those opened. Everything it would be a good thing, but malicious hacker here interfered. He intercepted the sent correct open key, moreover in such a way that the key so did not reach your friend, he read your OF FIO, and then created the new pair of keys (secret plus opened), after writing down there the information about you. Criminal kept secret key, and that opened sent to friend from your name. Now hacker will be able to send any letters to it, and friend will consider your signature under its false communications accurate until fraud swims out outside, but in you with your comrade serious problems can arise.

Fortunately, there is a method of fight with the substitution of the open keys - this is their certification.