Mature case and source code of hash quiz game system development technology

　　 Hash algorithm is to transform any length of input into a fixed length of output , Each byte affects the output value , And the input cannot be obtained by reverse calculation of the output .

　　 Hash algorithm mainly includes constructor and conflict resolution .

　　 The constructor criterion of hash algorithm is relatively simple 、 uniform , That is, the constructor can quickly calculate the hash value , At the same time, the constructor can distribute the keyword set evenly in the output address set {0,1,…,n-1} On , Keep the possibility of conflict to a minimum .

　　 Common construction methods include ： direct addressing 、 Digital analysis 、 Square with the middle method 、 Folding method 、 Random number method 、 Divide and leave the remainder, etc .

　　Hash,generally translated as hash or transliterated as hash,is generally called hash function.It is the processing of hash algorithm of input(also known as pre mapping pre image)of any length into output of fixed length,and the output data can be called hash value or hash value.This conversion is a kind of compression mapping,that is,a reasonable compression process.The space occupied by the output hash value is much smaller than the input space,but different inputs may be hashed into the same output.In other words,the output value is unique,but it is impossible to find the one-to-one corresponding input value.

　　 Application direction

　　 Due to the diversity of hash function applications , They are often designed for a particular application .

　　 Error checking

　　 Using a hash function, you can intuitively detect errors in data transmission . At the sender of the data , Apply hash functions to unsent data , And send the calculation results together with the original data . that , At the receiver of the data , The received data is processed using the same hash function , If the results of two hash functions are different , Then it means that there are errors in the process of data transmission . This is called redundancy check .

　　 Information security

　　Hash Algorithm is one of the most secure methods in modern cryptography . Because the asymmetric algorithm is time-consuming and laborious , So in the digital signature protocol , The one-way hash function completely replaces the traditional encryption method .

　　 Blockchain technology is also interested in it. It can only “ A one-way ” This feature of the operation , To bring it under his command , To verify all blocks extended by the entire blockchain based on the underlying blocks , To ensure the accuracy and consistency of subsequent uplink blocks .

　　 Hash discreteness refers to two very similar files , Or a long data with only one digit difference between us , The value of the hash we calculated is very different , There is no similarity whatsoever , The discreteness of hash is mainly to avoid some characteristic attacks .

　　 If the difference between your two files is only one , If the calculated hash is also very similar , It is more vulnerable to attack , So the normal hash has these three characteristics , Hash its length is 32 Bytes , Each byte is eight digits , Now the general hash is 256 Digit number , The hash value is 0-2 Of 256 Power , that 2 Of 256 How big is the power , It has more atoms than the universe .