Shulou(Shulou.com)06/02 Report--

Common encryption algorithms can be divided into three categories: symmetric encryption algorithm, asymmetric encryption algorithm and Hash algorithm.

Symmetrical encryption

An encryption algorithm that uses the same key for encryption and decryption. The advantage of symmetric encryption algorithm lies in the high speed of encryption and decryption and the difficulty to crack when using long keys. Suppose that two users need to encrypt and exchange data using symmetric encryption, then users need at least 2 keys and exchange them. If there are n users in the enterprise, the whole enterprise needs a total of n × (nmae1) keys. The generation and distribution of keys will become a nightmare for the enterprise information department. The security of the symmetric encryption algorithm depends on the preservation of the encryption key, but it is impossible to require everyone who holds the key in the enterprise to keep the secret. They usually leak the key intentionally or unintentionally-if the key used by a user is obtained by the user, the user can read all the documents encrypted by the user key. If the whole enterprise shares an encryption key Then the confidentiality of the entire enterprise document is out of the question.

Common symmetric encryption algorithms are DES, 3DES, Blowfish, IDEA, RC4, RC5, RC6 and AES

Asymmetric encryption

Refers to encryption algorithms that use different keys for encryption and decryption, also known as public and private key encryption. Suppose that two users want to encrypt and exchange data, and the two sides exchange public keys. When using it, one party encrypts it with the other's public key, and the other party can decrypt it with its own private key. If there are n users in the enterprise, the enterprise needs to generate n pairs of keys and distribute n public keys. Because the public key can be made public, users only need to take good care of their private keys, so the distribution of encryption keys will become very simple. At the same time, because the private key of each user is unique, other users can not only verify the source of the information through the sender's public key, but also ensure that the sender can not deny that the message has been sent. The disadvantage of asymmetric encryption is that the speed of encryption and decryption is much slower than symmetric encryption, and in some extreme cases, it can even be 1000 times slower than asymmetric encryption.

Common asymmetric encryption algorithms are: RSA, ECC (for mobile devices), Diffie-Hellman, El Gamal, DSA (for digital signatures)

Hash algorithm

The special feature of Hash algorithm is that it is an one-way algorithm. Users can generate a unique hash value of a specific length for the target information through the Hash algorithm, but can not get the target information again through this hash value. Therefore, Hash algorithm is often used in irreducible password storage, information integrity check and so on.

Common Hash algorithms are MD2, MD4, MD5, HAVAL, SHA.

The performance of the encryption algorithm can usually be measured according to the complexity of the algorithm itself, the length of the key (the longer the key is, the more secure it is), the speed of encryption and decryption, and so on. Among the above algorithms, except that the length of DES key is not enough and the slow speed of MD2 has been gradually eliminated, other algorithms are still used in current encryption system products.

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