Hash function and digital signature (digital handprint)
Hash function, also known as the mixture function, is a password algorithm for extensive and important applications in the field of information security, which has a fingerprint application. In the network security protocol, the mixed function is used to handle electronic signatures, compressing lengthy signature files into a unique digital information, ensuring the legality and security of the original digital signature file like fingerprint authentication. SHA-1 and MD5 mentioned earlier are the most commonly used mixed functions. After the processing of these algorithms, the original information will also become a complete "fingerprint" even if only one letter is only a letter. This guarantees the uniqueness of processing information. Provide digital authentication for e-commerce.
The secure mixture of the conflict function must satisfy two requirements when designing: one is looking for two inputs to get the same output value is not feasible, which is what we usually say; the second is to find an input It can obtain a given output in the calculation, ie, it is not possible to derive its initial state. Important computer security protocols now used, such as SSL, PGP uses a mixed function to sign, once you find two files can produce the same compression value, you can fake signatures, bring huge hazards to the network security field.
MD5 is such a whispering function algorithm with a wide range of applications at home and abroad, which once considered very safe. However, Professor Wang Xiaoyun found that the "collision" of MD5 can be quickly found, which is the same "fingerprint". This means that after you sign a contract on the Internet, it is possible to find another contract with the same signature but a different content, so that the truse of the two contracts is not distinguished. Professor Wang Xiaoyun confirmed the use of MD5 algorithms to seriously threaten information system security, this discovery makes the current electronic signature legal effect and technical system challenged. Therefore, the industry expert Princeton Computer Professor Edward Felten and other strong appeal for information systems replace the signature algorithm as soon as possible, and they emphasize that this is a problem that needs to be resolved immediately.
