Basic knowledge of network security - password (I)

Properties of information

Usability 、 Authenticity 、 Confidentiality

Usability ： The ability of information system to provide services , Information can be served normally or obtained

Confidentiality ： A secret

Authenticity ： Distinguishable （ Who sent the message ）、 integrity （ Are the files before and after sending the same ）、 Non-Repudiation （ If you really sent this message , Can't deny ）

Information security means that the owner can understand and control information in three states （ transmission 、 Storage 、 Handle ） Security properties under （CIA）.

Information and data

Data is the symbolic representation of objective things .

Data is the carrier of information , But information is not equal to data .

The value of information ———— Digital survival .

The weakness of information system

Internal cause ：

（1） Design problems ： From the beginning, the establishment of the system lacks the overall concept and design of security .

（2） Implementation problems ： There is a backdoor or unintentional bug.

（3） Configuration problems ： The default service .

（4） Management problems ： Insiders operate unintentionally or maliciously .

The carrier of information security is data security .

We should ensure the security of information in the information system represented by computer system and network system , Provide information security services .

Cryptography classification

Password credits for coding 、 Decipherment

Code credits for modern passwords 、 Classical code

Classical passwords are divided into substitution 、 Transposition method

Modern passwords are divided into symmetric encryption 、 Asymmetric encryption 、Hash

Symmetric encryption is divided into stream ciphers 、 Block code

According to the country, it is divided into national secret algorithm 、 International algorithm

Four key points in cryptography are data encryption 、 digital signature 、 A summary of the news 、 Key management

Use cryptography to protect the confidentiality and authenticity of information .

encryption and decryption

Ciphertext = encryption algorithm （ Plaintext + Encryption key ）

Plaintext = Decryption algorithm （ Ciphertext + decryption key ）

Two cryptosystems

Symmetric cryptography 、 Asymmetric cryptography

Symmetric cipher algorithm ： The encryption key is the same as the decryption key , Or they can deduce from each other （ For example, replace the password ）, They pass keys over secure channels

Asymmetric cipher algorithm ： The encryption key and decryption key are different , And cannot be deduced from each other ( Pairs of , One-to-one correspondence ), for example RSA Algorithm . The encryption key transmission channel of asymmetric cryptosystem is not afraid of eavesdropping . The decryption key is confidential , such , People who don't know each other can also encrypt communication . Can guarantee integrity 、 Confidentiality , But there is no guarantee of identifiability and non repudiation .

Double key encryption decryption key public application —— digital signature 、 digital certificate

digital signature ： Based on the data content cannot be forged .

One way hash function

One way hash function is also called message digest function , One way hash function or hash function , It is a function that changes the input message string of any length into a fixed output string, and it is difficult to get the input string from the output string . This output string is called the hash value of the message . Generally used to generate message summaries , Key encryption, etc

Classical algorithms include :MD4\MD5\SHA1\SHA256\SHA512 etc.

Be careful ： Hash is neither encryption nor encoding

National secret algorithm

In order to ensure the security of commercial passwords , The State Password Bureau has formulated a series of password Standards , Include ：SM1、SM2、SM3、SM4、SM7、SM9、 Zu Chongzhi's cryptographic algorithm （ZUC) etc. .
among SM1、SM4、SM7、 Zu Chongzhi password （ZUC） It's a symmetric algorithm .
SM2、SM9 It's an asymmetric algorithm .
SM3 It's a hash algorithm .
among SM1、SM7 The algorithm is not public , When the algorithm is called , It needs to be called through the interface of the encryption chip .