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**Abstract** correcting edit summary

Fast public-key algorithm and the traditional public-key algorithms have wider application than the prospects of a fast public key system is currently a hot topic of public-key system.

**Directory**

- 1 Definition
- 2 History
- 3 Encryption Standard
- 4 Work
- 5 uses
- 6 defects

## Public key algorithm - Definition

Asymmetric encryption algorithm using two different but is perfectly matched pair of keys - a public key and private key. Asymmetric encryption algorithm using the encrypted files, only use a pair of matching public key and private key in order to complete the plaintext of the encryption and decryption process. Plaintext public key encryption used to encrypt, decrypt ciphertext using the private key to complete, and the sender (encryptor) that received one side of the public key , only received one side (decryptor) is the only know the private key people. The basic principle of asymmetric encryption algorithm, if the sender want to send only received one side can interpret the encrypted information is sent by the private key encryption to use their own letters, the recipient's public key to decrypt using the letter the letter. Clearly, using an asymmetric encryption algorithm, the two sides in the communication transceiver before the party must be prepared to receive their long randomly generated public key sent to the sender, while his private key retained. As asymmetric algorithms have two keys, thus suitable for a distributed system of data encryption. Widely used asymmetric encryption algorithm RSA algorithm and a National Bureau of Standards proposed by the U.S. DSA . To an asymmetric encryption algorithm based encryption technology is widely used.

## Public key algorithm - History

Cryptography has a long history. Ancient people did not under high-speed computing equipment, tried a variety of ways, but also contains many clever ideas. As early as 1900 BC, a member of ancient Egyptian writing an inscription on the use of a non-standard hieroglyphs, this is the first recorded human cryptography. Later, the ancient people like to use cryptography reverse the order of the alphabet, to the letter instead, or use the wrong position after a certain number of letters in front of the letter substitution. Some idea of cryptography is also very clever.

Modern cryptography epoch-making breakthrough, Witter Field; Diffie (Whitfield Diffie) and Martin; Hellman (Martin Hellman) the concept of public key encryption system, which is published in 1976. But Witt Field; Diffie and Martin; Hellman knapsack algorithm provide the MH was deciphered in 1984, which lost its practical significance. Truly viable algorithm for public key encryption system is a Long; Rivest (Ronald L. Rivest), Adi; Shamir (Adi Shamir) and Leonard; Adelman (Leonard M. Adlemen) in Witt Field • Diffie and Martin; Hellman's paper inspired the invention in 1977, which is still in use in the RSA algorithm. It was the first not only for data encryption can be used for digital signature algorithms.

## Public key algorithm - Encryption Standard

Public key cryptography standards (PKCS) is RSA Laboratories, and various security systems developer for the global cooperation to develop standards. PKCS standards have been widely accepted, and the standard PKCS series have become standard in many part of the formal and practical, including ANSI X9, PKIX, SET, S / MIME.

## Public key algorithm - works

In 1976, Whitfield Diffe and Martin Hellman to create a public key encryption. Public key encryption is a major innovation because it fundamentally changed the encryption and decryption process.

Diffe and Hellman proposed the use of two keys, instead of using a shared key. A key (called "private key") is confidential. It can only be saved by one party, but not all sharing. The second key (called "public key") is not confidential, and can be widely shared. The two keys (called "key pair") in the encryption and decryption operations with the use. Key relationships with special complementary, so that each key can only be with the key pair used in conjunction with another key. This relationship will be key in the key on the only linked to each other: the public key and its corresponding private key pair, and are not associated with any other key.

As the public key and private key algorithms the mathematical relationship between the specific, making this match possible. Key mathematically related to each other in, for example, can be achieved with the use of two keys on the effect of using the symmetric key. Key must be used with: can not use each individual key to undo its own operation. This means that each individual key operations are one-way operation: You can not use a key to undo its action. In addition, the design of algorithms used in the two keys, specially designed not to use a key to determine the key on to another key. Therefore, the private key can not be determined under the public key. However, making possible the key to the mathematical theory also makes the key on a symmetric key which does not have a shortcoming. That is, the algorithm used must be strong enough to make it impossible to try by force, using the known public key to decrypt the encrypted information through it. Public key used mathematical complexity and characteristics of its way to make up for it is well-known fact that, in order to prevent people from using it to successfully solve encoding information.

If this concept applies to the previous example, the sender will use the public key to encrypt a password in plain text. Then, the recipient will use the private key to decrypt the password back into plain text.

As the key pair in the private and public keys of the special relationship that exists between, so one can when dealing with many people using the same key pair instead of separately with each person using a different key. As long as the private key is confidential, you can freely distribute the public key, and reassured the people that use it. Many people use the same key pair representing the cryptography on a major breakthrough because it significantly reduces the demand for key management, greatly increased the availability of cryptography. Users can share any number of staff a key pair for each person instead of a separate key.

Public key encryption is e-mail security an essential element. If no public key encryption, then the existence of useful e-mail security solution is doubtful, because before the advent of public key encryption, key management is a very troublesome thing. After understanding the basic concepts of public key encryption, the next step is to understand how to implement these concepts through e-mail security. ^{[1]}

## Public key algorithm - Uses

Public key system, the principle is: User A has a pair of key pairs, divided into public and private key, this key pair is unique, is through a huge number for prime factorization proceeds. When the information encrypted with the public key can only be used with its matching private key to decrypt, and vice versa, the private key encrypted message can only be decrypted with the public key. This, A generates the key pair from the certification system, after its private key to save the good, the public key open out, when a user B with A communications, wants to ensure data security, you can use A's public key encrypted information, then pass ciphertext A, so the world is in the hands of the private key that only A can decrypt this ciphertext, thus ensuring information security.

In fact, the information encrypted public key system is one of the purposes, it has a purpose that is the signature of information, anti-denial of this information dissemination, and modification by third parties. Why is this mechanism can achieve this in this function? Very simple, or use the **"public key encryption, private key can only solution; private key encryption, public key can only solution,"** the truth. For example: User A with his own private key to sign messages sent to the (encryption), and then sent out, and later he found his information publicly against him, he will not recognize the information that he made, but he did not may be denied because the information has his private key signature, then the information using his public key authentication, we know that this information is definitely A hair, because only A uses private key signature information received, to use The public key solution. If A is also recognized that he made the message that there is only one possible, it is his private key had been stolen.

Now we know the principle of public-key mechanism, and that it what is the use? On the example above more commonly used, and in our daily work, while others use the public key mechanism, and we may have been used key disk , it U disk is a similar thing, generally provide USB interfaces , it uses the public key mechanism, when we initialize a computer disk, when this key, it will generate a pair of key pair, there is the public key computer, there is the key to set the private key, when the user wants to authenticate to a system though, only insert the key disk though, would the public-private key encryption and decryption of principle, to complete the user authentication process without having to enter account and password for authentication.

## Public key algorithm - disadvantages

In reality, the public key system also has its drawbacks, it is a very low efficiency compared to single-key algorithm used one or two orders of magnitude slower is possible, it often is not suitable for a large number of original information is encrypted using a single password key mechanism of the original information is encrypted, then the single key, we can be encrypted by public key mechanisms.