Development of block hash game guessing system (mature code)

The four core technologies of blockchain are cryptography 、 Distributed ledger 、 Consensus mechanisms and smart contracts . Cryptography is one of the most important parts , It can be said to be the cornerstone of blockchain , Other technologies are high-rise buildings that build blockchain based on cryptography . There are two main cryptographic algorithms used in blockchain ：

　　 One is hash algorithm ,

　　 Second, asymmetric encryption .

　　 First , It's decentralized . The database originally maintained by one party , It has become a database maintained by many parties . Everyone writes data together by consensus , No one can control the data alone .

　　 secondly , It allows everyone to change from a separate account to a joint account , This brings consistency and transparency to the data .

　　 in addition , Blockchain is only allowed to write data , Deleting and modifying... Are not allowed , It can prevent data from being tampered with secretly . Simply speaking , Hash algorithm is a special function . No matter how long the string is entered , You can get a fixed length output value through this function . It's like the ID number , Always the 18th , It is also the only one in China . The output value of hash algorithm is called hashing value . Hash algorithm has three characteristics .

　　 The first characteristic of hash algorithm is anti-collision ability . The so-called collision , Is to enter two different data , You end up with the same input . It's like we hit the shirt when we were shopping , The pit collision is that most of the inputs can get the only output . In the world of blockchain , The address of any transaction or account is completely generated by the hash algorithm . This also ensures the uniqueness of the transaction or account address in the blockchain network . The second feature is that it is unidirectional . for example , If you enter a string of data , You can get a hash value through the hash algorithm , But there is no way to invert the hash value to get the input data string . It's one-way , Based on that , Blockchain effectively protects the security of our information . The third characteristic of hash algorithm is anti tamper ability . For any input , Even small changes , The hash value can also vary greatly . This feature plays a key role in the connection between blocks . Each block of the blockchain is marked by the hash value of the previous block . Unless someone can crack all the hash values in the whole chain , Otherwise, once the data is recorded on the chain , It's impossible to tamper . Hash property ：

　　(1) One way .Thatis,givenaninputnumber,itiseasytocalculateitshashvalue,butgivenahashvalue,theoriginalinputnumbercannotbeobtainedaccordingtothesamealgorithm.

　　(2) Weak anti-collision .Thatis,givenaninputnumber,itiscomputationallyinfeasibletofindanotherhashvaluetogetagivennumberwhenusingthesamemethod.

　　(3) Strong collision resistance .Thatis,foranytwodifferentinputnumbers,itisnotfeasibletocalculatethesamehashvalueaccordingtothesamealgorithm.

　　 Simple explanation ： Hash (Hash) Algorithm , Hash function . It's a one-way cryptosystem , That is, it is an irreversible mapping from plaintext to ciphertext , Only the encryption process , No decryption process . meanwhile , Hash function can change the input of any length to get fixed length output . This one-way feature of the hash function and the fixed length of the output data make it possible to generate messages or data .