What is the development of block hash quiz game system? Hash quiz game system development (case mature)

　　01.Hash function

　　 One way hash function , Also known as one-way Hash function 、 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 .

　　 Hash algorithm is widely used in many scenarios , For example, secure encryption and hash table lookup in data structures , Bloom filter and load balancing （ Consistent Hashing ） wait .

　　02. common Hash function

　　 common Hash Function has MD series 、SHA series 、MAC and CRC etc. .

　　MD series

　　MD Full name Message Digest, According to the Standard Version, it is divided into MD2、MD4、MD5 Three algorithms , At present, the most commonly used is MD5 Version algorithm .

　　MD4 Algorithm

　　1990 year , stay MD2 On the basis of the development of MD4 Algorithm .

　　MD5 Algorithm

　　1991 year ,MD4 Its founder developed MD5 Algorithm . No matter how long the string is , Use MD5 The calculated length is the same , It is convenient for the statistics and management of information at ordinary times .

　　 after MD5 Encryption generates a fixed length of 128bit String of . because 128 position 0 and 1 The binary string expression of is not friendly , So it turns into 16 Base number ,128/4=32 Bit 16 Base number . take 32 Before removing bit 8 Position and back 8 Bit gets 16 position . So there will be MD5 Of 32 Bit and 16 Bit encryption .

　　SHA series

　　SHA(Security Hash Algorithm) It's American NIST and NSA A standard of design Hash Algorithm ,SHA Standard algorithm for digital signature DSS in , It is also a kind of high security Hash Algorithm .

　　SHA-1

　　SHA-1 The input message length of the algorithm is less than 264bit, The final output value is 160 Bits,SHA-1 And MD4 By comparison , It mainly increases the extension transformation , Add the output of the previous round to the next one , This increases the avalanche effect , And because of it 160 Bits Output , More resistant to exhaustive attacks .

　　 The general implementation process ： Convert the message digest into a bit string , Carry on the place filling operation to the converted bit string , Attach the length value and initialize the cache , Then calculate the message digest .

　　SHA-256

　　SHA-256 The maximum length of algorithm input message does not exceed 264 Bits, Enter the 512 Bits Work in groups , The output produced is a 256 Bits Message summary of .

　　SHA-2 Other derivative algorithms of

　　 Include SHA-224、SHA-256、SHA-384、SHA-512, Together these versions make up SHA big family .

　　SHA-224：SHA-256 Of “ Castration plate ”, Can generate length 224bit A summary of the information .

　　SHA-512： Can generate length 512bit A summary of the information .

　　SHA-384：SHA-512 Of “ Castration plate ”, Can generate length 384bit A summary of the information .

　　SHA The newest member of the family SHA-3 Already in 2015 It came out in .

　　MAC

　　MAC Algorithm (Message Authentication Codes) With a secret key Hash function .

　　MAC There are two forms of Algorithm , Namely CBC-MAC Algorithm and HMAC Algorithm . stay HTTP Most used in MAC The algorithm is HMAC Algorithm .

　　HMAC（Hash-based Message Authentication Code） The algorithm uses Hash Algorithm as encryption primitive ,HMAC combination Hash There are many variations of the algorithm , such as HMAC-SHA-1、HMAC-SHA256、HMAC-SHA512. Don't mistake HMAC The algorithm is Hash The algorithm adds a key ,HMAC The algorithm is just based on Hash Algorithm , The internal implementation is quite complicated .

　　CRC

　　CRC(Cyclic Redundancy Check)： Cyclic redundancy test . It is a hash function that generates a short fixed digit check code based on data packets on the Internet or computer files , It is mainly used to detect or verify the possible errors after data transmission or saving . The generated number is calculated and appended to the data before transmission or storage , The receiver then checks to see if the data has changed . Generally speaking , The values of cyclic redundancy check are 32 An integer . Because this function is easy to use binary computer hardware 、 Easy to do mathematical analysis and especially good at detecting errors caused by transmission channel interference , So it's widely used .

　　 list （Hash table, Also called hash table ） It's a search algorithm , With the list 、 Tree algorithm is different from , Hash table algorithm does not need to do a series of search and keyword search （ A keyword is the value of a data item in a data element , To identify a data element ） Comparison operation of .

　　 Hash table algorithm wants to be able to do as much as possible without any comparison , You can get the data elements you are looking for in one access , Therefore, the storage location of the data element and its keyword must be specified （ You can use key Express ） Establish a definite correspondence between , Make each keyword correspond to a unique storage location in the hash table . So in the search , Just find the position of the given keyword in the hash table according to the corresponding relationship . This correspondence is called a hash function ( You can use h(key) Express ).

　　 The methods used to construct hash functions are ：

　　（1） direct addressing ： Take the key or a linear function value of the key as the hash address . namely ：h(key)=key or h(key)=a*key+b, among a and b Constant .

　　（2） Digital analysis

　　（3） The square method ： Take the middle digits after the square of the keyword as the hash address .

　　（4） Folding method ： Divide keywords into parts with the same number of digits , Then take the sum of these parts as the hash address .

　　（5） Division and remainder ： The keyword is not longer than the hash table m Number of numbers p The remainder after division is the hash address , namely ：h(key)=key MOD p p≤m

　　（6） Random number method ： Choose a random function , Take the random function value of the keyword as its hash address , namely ：h(key)=random(key)

　　 So construct a useful hash table , The most important thing is to do the following two things well ：

　　 To design a " good " Hash function to calculate Key value .( A good hash function should avoid conflicts as much as possible , And the calculation should be as simple and fast as possible )

　　What is a block hash?

　　The block hash value is the DNA of a piece of data,and each block hash value is unique,random and unbreakable."Hashfun"is hello DAPP,the SK application launched by fun blockchain ecology in the gamefi stage,has a mission to implement the"interesting investment and mining"mechanism and attract millions of Genesis residents.

　　What is blockchain?

　　In essence,blockchain is a shared database of data or information stored in it.It has the characteristics of unforgeability,full trace,traceability,openness and transparency,collective maintenance,etc