Asymmetric encryption is defined:
Also known as asymmetric encryption algorithm现代加密算法
In 1976, the American scholar Dime and Henman to solve information delivery and public key management problem, a new key exchange protocol that allows communication over an insecure media of both sides to exchange information, agree on the key safely, this is the "public key system."
Symmetric encryption is defined
Symmetric encryption algorithm is applied earlier encryption algorithm, the technology is mature. In symmetric encryption, the sender plaintext data ( raw data ) and the encryption key after the encryption algorithm is a special treatment with (mi yue), so that it becomes complicated sent encrypted ciphertext. After the receiver has received the ciphertext To interpret the original, you need to use the used encryption key is the inverse of the same algorithm Algorithm and decrypt the ciphertext, in order to restore it to a readable plaintext. In symmetric encryption algorithm using the key is only one, hair receivers both use this key to encrypt and decrypt data, which requires decrypting party must know in advance the encryption key.
From the above definition we can see:
A key difference between symmetric encryption and asymmetric encryption: symmetric encryption, a secret key that only the sender and the receiver use a secret key for encryption and decryption; and asymmetric encryption, the sender A: owned 公开密钥(publickey) and私有密(privatekey)，即公钥，私钥，接收方B：也有自己的公钥，私钥；
- Public and private keys are
一对 - Use
公开密钥the data加密only by对应的私有密钥order解密 - Use
私有密钥the data加密only by对应的公开密钥order解密
大致的过程就是这样的，即：
1.A要向B发送信息，A和B都要产生一对用于加密和解密的公钥和私钥
2.A的私钥保密，A的公钥告诉B；B的私钥保密，B的公钥告诉A。
3.A要给B发送信息时，A用B的公钥加密信息，因为A知道B的公钥。
4.A将这个消息发给B（已经用B的公钥加密消息）。
5.B收到这个消息后，B用自己的私钥解密A的消息。其他所有收到这个报文的人都无法解密，因为只有B才有B的私钥。
Characteristics
algorithm complexity strength, security depends on the algorithm and key.
Disadvantages
due to its complex algorithm, such that the speed of encryption and decryption is not decrypted symmetric encryption speed fast.
Compared with symmetric encryption algorithms
- Advantages: its better security, symmetric encryption of communication parties use the same secret key, if one of the keys has been leaked, the entire communication will be cracked. Instead of using a pair of symmetric encryption keys, one for encryption and one for decryption and public key is published, a secret key held by itself, did not like the first synchronization symmetric encryption keys before the communication.
- Disadvantages: asymmetric encryption to encrypt and decrypt the disadvantage that it takes a long time, slow, suitable only for small amounts of data to be encrypted.
The main algorithm used in asymmetric encryption has: RSA, Elgamal, ESA, knapsack algorithms, Rabin, DH, ECC (elliptic curve cryptography) and the like. Different mechanisms to achieve different algorithms, the details may refer to the corresponding algorithm.
大致意思就是这样；作为参考；