Hash hash game system development explanation technology -- hash game system development solution analysis

Hash values have the following four characteristics ：

1. High calculation efficiency （ It is very easy to calculate the hash value of any input value ）

2. Anti conflict （ No two input values can give the same hash value ）

3. Hide input information （ The input value cannot be inferred from the hash value ）

4. The output should look random （ But the same input value will get the same hash value ）

1/2. MD4/MD5/HAVAL

MD4：

Ron Rivest Design , Generate 128 Bit message digest value , Software systems for high-speed computing requirements , Optimized for microprocessors .

MD4 First fill in the message , Make sure the message is longer than 512 It's a small multiple 64 position , For example, one 16 Bit message to be filled 432 Bit data , To achieve 448 position （512*1-64）.

MD4 Considered unsafe , Has been largely deprecated .

MD5：

Ron Rivest Design ,MD4 Upgraded version , Generate 128 Bit message digest value ,MD5 and MD4 First fill in the message , But the algorithm is more complex .

Added the fourth round of operation , There are studies that show that MD5 No enemy collision attack , It is no longer applicable to applications that need to resist collision attacks , Such as SSL And digital signatures .

MD5 Very widely used , Even if it proves to be no longer safe , however MD5 Now it is often used for file integrity verification , For example, some intrusion detection systems , And judicial evidence integrity verification Applications for non cryptographic purposes .

HAVAL：

be called Variable length hash , yes MD5 Revised edition , Use 1024 Bit block , Can produce 128、160、192、224 and 256 Bit hash value .HAVAL It also allows the user to specify the number of rounds used to generate the hash （3、4 or 5）.

Unfortunately ,HAVAL Also in the 2004 It was broken around .

2/2. SHA series

Secure Hash Algorithms, secure hash algorithm .

SHA Series is made up of NSA Design 、NIST Release , And digital signature standard （Digital Signature Standard,DSS） Used together hash function —— Federal information processing standards （FIPS）180“ Secure hash standard ”（SHS）.

SHA The original intention of the design is to be used in digital signature . An improvement made to meet the demand of the U.S. government for more secure hash algorithms .

You can't get around it NIST/NSA......

SHA（SHA-0）：

SHA Generate 160 Bit hash value or message digest , The output is then fed into an asymmetric algorithm , Signature of the output message . Be similar to MD4, But more mathematical functions are used to resist brute force attacks , Including birthday attacks . Due to the existence of undisclosed “ Major defects ”, Revised shortly after publication SHA-1 replace .

SHA-1：

SHA-1 yes SHA Improved version ,SHA-1 No enemy collision attack , Therefore, it is not applicable to applications that need anti-collision attacks .

SHA-2/SHA-3：

SHA-2 and SHA-3 As SHA Upgraded version , At present, the industry believes that its security is applicable to any application scenario .

SHA-2 Generate message digest

What needs to be introduced is SHA-3：SHA-3 Use Keccak Algorithm , It supports and SHA-2 Same hash length , But its internal structure is similar to SHA The series is almost completely different .

2012 year Keccak Algorithm in NIST Of SHA-3 In the competition, he beat the famous Rivest It brings MD6 Including many algorithms , a SHA-3 The standard algorithm ,SHA-3 The purpose of is to directly replace... In the current application when necessary SHA-2, And significantly improved NIST Robustness of the overall hash algorithm toolkit （ That is, the ability of the system to resist change without changing the initial stable structure ）.

Keccak Algorithm The sponge structure shown in the figure below is used . Based on wide random functions or random permutations , It allows you to input any number of data , And output any number of data , This brings a lot of flexibility .

The sponge function of unknown force / Sponge structure

MD5/SHA Series hash function attribute table