Essay on Cryptography

2196 Words 9 Pages
Cryptography

Part one---Why do we need to learn cryptography

Now is a time which the information is extremely development. A lot of datas are stored by the form of electronic messages. The transmission of the information is often through electronic medium such as mobile phone communication, electronic commerce, the on-line chat service etc. Unfortunately, those way of transmit the information are not safe. The message that we delivered is possible be stolen or monitored. If we have no appropriate protect measure, so once the important messages leaks out, the result may be inconceivable.

The safe protection system of any rank all may introduce the concept of encryption. The data encryption has the very vital significance to the
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Modern Encryption System:

・Symmetrical encryption system and asymmetrical encryption system

According to the key whether encryption used and deciphers used is the same one divide the modern encrypt system to symmetrical or asymmetrical encryption system.

Symmetrical encryption system: The symmetrical encryption system is called the private key password system, it means that the encryption key is the same one or decipher key or one key could be educed by another. Who has the ability of encryption means that he has the decipher ability.

The advantages of this system are that the encryption algorithm is quite simple and have high effective, the key used is brief and it's hard to be deciphered.

The disadvantages of this system is that the openness of this system is bad, the key transmission needs to have a reliable channel and this system is hard to resolves the problem of digital signature and signature recognition.

Asymmetrical encrypt system: The asymmetrical encryption system is called the public key password system, it means that the encryption key is public, deciphers key is not public, infers one from another is unfeasible. Under this kind of system the encryption ability is separated from decipher ability.

The advantages of this system: This system is suitable for the open conditions, the key control is simple, but the working efficiency is lower than the
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