Introduction to three encryption algorithms

Encryption technology is a technology for encoding and decoding information. Encoding is to translate the original readable information (also known as plaintext) into code form (also known as ciphertext), and the inverse process is decoding (decryption). The key point of encryption technology is encryption algorithm, which can be divided into three types: symmetric encryption, asymmetric encryption and irreversible encryption.

Symmetric Encryption Algorithm Symmetric encryption algorithm is an earlier encryption algorithm with mature technology. In the symmetric encryption algorithm, the sender of the data processes the plaintext (original data) and the encryption key together with a special encryption algorithm to turn it into a complex encrypted ciphertext and send it out. After the recipient receives the ciphertext, if he wants to interpret the original text, he needs to decrypt the ciphertext using the encryption key and the inverse algorithm of the same algorithm to restore it to readable plaintext. In the symmetric encryption algorithm, only one key is used, and both sender and receiver use this key to encrypt and decrypt data, which requires the decryptor to know the encryption key in advance. The characteristics of the symmetric encryption algorithm are that the algorithm is open, the calculation amount is small, the encryption speed is fast, and the encryption efficiency is high. The disadvantage is that both parties of the transaction use the same key, and the security is not guaranteed. In addition, each pair of users needs to use a unique key that no one else knows about each time they use the symmetric encryption algorithm, which will increase the number of keys owned by both sender and receiver exponentially, and key management will become a burden for users. Symmetric encryption algorithms are difficult to use in distributed network systems, mainly because of the difficulty of key management and the high cost of use. Symmetric encryption algorithms widely used in computer private network systems include DES and IDEA. AES, advocated by the National Bureau of Standards, is about to replace DES as the new standard.

Asymmetric Encryption Algorithms Asymmetric encryption algorithms use two completely different but perfectly matched pairs of keys - a public key and a private key. When encrypting a file using an asymmetric encryption algorithm, the encryption and decryption process of plaintext can only be completed by using a matching pair of public and private keys. Public key encryption is used to encrypt plaintext, and private key is used to decrypt ciphertext, and the sender (encryptor) knows the recipient's public key, and only the recipient (decryptor) is the only one who knows his private key people. The basic principle of the asymmetric encryption algorithm is that if the sender wants to send encrypted information that only the receiver can interpret, the sender must first know the receiver's public key, and then use the receiver's public key to encrypt the original text; After the recipient receives the encrypted ciphertext, it can decrypt the ciphertext by using its own private key. Obviously, with the asymmetric encryption algorithm, before the sender and receiver communicate, the receiver must send the public key that has been randomly generated to the sender, and keep the private key. Since asymmetric algorithms have two keys, they are particularly suitable for data encryption in distributed systems. The widely used asymmetric encryption algorithms include the RSA algorithm and the DSA proposed by the US National Bureau of Standards. Encryption technology based on asymmetric encryption algorithm is widely used.

Irreversible Encryption Algorithm The characteristic of the irreversible encryption algorithm is that no key is required in the encryption process. After the plaintext is input, the system directly processes it into ciphertext through the encryption algorithm. This encrypted data cannot be decrypted. After being processed by the same irreversible encryption algorithm again, the same encrypted ciphertext can be obtained and re-identified by the system before it can be truly decrypted. Obviously, in this type of encryption process, the encryption is oneself, and the decryption must be oneself, and the so-called decryption is actually a re-encryption, and the applied "password" is the input plaintext. The irreversible encryption algorithm has no key storage and distribution problems, and is very suitable for use in distributed network systems. However, due to the complex encryption calculation and heavy workload, it is usually only used when the amount of data is limited, such as widely used in computer systems. The password encryption in , uses an irreversible encryption algorithm. In recent years, with the continuous improvement of computer system performance, the application field of irreversible encryption is gradually increasing. The MD5 algorithm invented by RSA Company and the irreversible encryption standard SHS (Secure Hash Standard: Secure Hash Standard) proposed by the National Bureau of Standards are used in computer networks.