### Advantages and disadvantages of symmetric and asymmetric cryptographic systems

The advantages and disadvantages of symmetric and asymmetric cryptographic systems are as follows:

Symmetric encryption:

Advantages: fast, symmetric encryption is usually used when the sender of the message needs to encrypt a large amount of data, the algorithm is public, the amount of computation is small, the encryption speed is fast, and the encryption is efficient.

Disadvantages: before the data is transmitted, the sender and receiver must agree on the secret key, and then enable both parties to save the secret key. Secondly if the secret key of one party is compromised, then the encrypted information is not secure. In addition, each pair of users needs to use a unique secret key that no one else knows every time they use a symmetric encryption algorithm, which can make the number of keys owned by the receiving and sending parties huge, and key management becomes a burden for both parties.

Asymmetric encryption:

Advantages: secure.

Disadvantage: slower.

### Advantages of Asymmetric Algorithms

First, the key set and the number of keys required for confidential message transmission between multiple people is small; second, the distribution of keys is not a problem; and third, a public key system enables digital signatures. Disadvantages: public key encryption is slower than private key encryption in encryption/decryption.

Differences in encryption and decryption key: from the above description of symmetric key algorithms and asymmetric key algorithms can be seen, symmetric key encryption and decryption using the same key, or from the encryption key can easily launch the decryption key symmetric key algorithms have encryption processing is simple, encryption and decryption speed is fast, the key is shorter, the development of the history of a long period of time and so on, asymmetric key algorithms have the encryption and decryption The asymmetric key algorithm is characterized by slow speed, large key size, and a short history of development.

asymmetricencodingalgorithm asymmetric encoding algorithm requires two keys: public key and private key. The public key and the private key are a pair; if the data is encrypted with the public key, it can only be decrypted with the corresponding private key; if the data is encrypted with the private key, it can only be decrypted with the corresponding public key. Because encryption and decryption use two different keys, this algorithm is called asymmetric encryption algorithm. Asymmetric encryption algorithm to achieve the basic process of confidential information exchange is: Party A to generate a pair of keys and one of them as a public key to other parties; get the public key of Party B to use the key to encrypt confidential information and then send it to the Party A; Party A and then use their own preservation of the other special key to the encrypted information to be decrypted. On the other hand, Party A can use Party B’s public key to encrypt the confidential information and send it to Party B. Party B will use its own private key to decrypt the encrypted information. Party A can only use its private key to decrypt any information encrypted by its public key. Asymmetric encryption algorithms provide better confidentiality, and they eliminate the need for end users to exchange keys. Characteristics of asymmetric cryptosystems: algorithm strength is complex, security depends on the algorithm and key but due to the complexity of the algorithm, the speed of encryption and decryption is not as fast as symmetric encryption and decryption. Symmetric cryptosystems have only one key, and it is non-public, if you want to decrypt, you have to let the other party know the key. So to ensure its security is to ensure the security of the key, while the asymmetric key system has two kinds of keys, one of which is public, so that you can not need to transmit the other party’s key like symmetric cipher. This is much greater security.

### Advantages and disadvantages of asymmetric encryption

Asymmetric encryption has better security than symmetric encryption: symmetric encryption uses the same secret key for both sides of the communication, and if one side’s secret key is leaked, then the whole communication will be broken. Asymmetric encryption uses a pair of secret keys, one for encryption and one for decryption, and the public key is public and the secret key is kept by itself, so you don’t need to synchronize the secret keys before communicating like symmetric encryption.

The disadvantage of asymmetric encryption is that encryption and decryption take a long time and are slow, and are only suitable for encrypting small amounts of data.

The main algorithms used in asymmetric encryption are RSA, Elgamal, Backpack Algorithm, Rabin, D-H, ECC (Elliptic Curve Cryptography), and others.

Different algorithms have different implementation mechanisms, so you can refer to the detailed information of the corresponding algorithms.

### Advantages and disadvantages of RSA and DES algorithms, comparison

DES algorithm:

Advantages: key is shorter, encryption processing is simple, encryption and decryption speed is fast, suitable for encrypting a large amount of data occasions.

Disadvantages: a single key, can not be deduced from one of the keys to another.

RSA algorithm:

Advantages: widely used, encryption key and decryption key is not the same, generally encryption key is called the private key. The decryption key is called the public key, the private key encryption can only be decrypted with the public key, of course, can also be encrypted with the public key, decrypted with the private key.

Disadvantages: The key size is large, the encryption and decryption speed is slow, generally used to encrypt a small amount of data, such as the DES key.