Algorithm, because as long as you have enough time, you can explore by exhaustive method. If an encryption algorithm is robust, it generally means that it will take a long time to succeed exhaustively under the existing computing conditions (for example, 100 years). 1. Active attack and passive attack data, if not protected by password during transmission or in daily work, can easily lead to file leakage, resulting in more serious consequences. Generally speaking, attacks are divided into active attacks and passive attacks. Passive attack refers to illegally obtaining information from transmission channels or disk media, resulting in information leakage. Active attacks are much more serious, not only obtaining information, but also deleting and tampering with information, with extremely serious harmful consequences. Second, symmetric encryption key-based algorithms are usually divided into symmetric encryption algorithms and asymmetric encryption algorithms (public key algorithms). Pairwise encryption algorithm means that the encryption key and decryption key are equal. For example, the famous Caesar password, its encryption principle is that all letters are shifted backwards by three digits, so 3 is the key of this algorithm, and cyclic right shift is the encryption algorithm. Then the decryption key is also 3, and the decryption algorithm is to circularly shift 3 bits to the left. Obviously, this algorithm is easy to understand, easy to implement and fast in encryption, but the security of symmetric encryption depends entirely on the key. If the key is lost, the whole encryption will not work at all. The well-known symmetric encryption algorithm is DES. Its block length is 64 bits, the actual key length is 56 bits, and the check code is 8 bits. DES algorithm has a short key, and with the continuous improvement of computer speed, it is possible to crack it by exhaustive method. Third, asymmetric encryption The core of asymmetric encryption algorithm is that the encryption key is not equal to the decryption key, and another key cannot be derived from any key, which greatly strengthens the strength of information protection. It is easy to realize digital signature and electronic envelope based on the key pair principle. The typical asymmetric encryption algorithm is RSA algorithm, whose mathematical principle is the decomposition of large prime numbers, and the keys appear in pairs, one is the public key and the other is the private key. The public key is public. You can use a private key to decrypt information encrypted by a public key, or you can use a public key to decrypt information encrypted by a private key. For example, A sends information to B. Since B's public key is public, A encrypts the information with B's public key and sends it out. Because only B has the corresponding private key, the information can only be read by B. A robust RSA algorithm requires its key length to be 1024 bits, and its weakness is the slow encryption and decryption speed. Another typical asymmetric encryption algorithm is ECC algorithm, which is based on the mathematical principle of elliptic curve discrete logarithm system. The standard of this algorithm has not been determined in China, but only 192 bit is needed to realize solid encryption. So it should be better than RSA algorithm. Advantages: ECC > RSA> data encryption standard.