Feature codes are used to determine which computer domain a piece of data belongs to. * * * 40 characters. It is impossible to simply take out a piece of code, but it is segmented, which can contain anything in the middle, that is, add some "mask bytes" that do not participate in the comparison, and nothing will participate in the comparison where the "mask bytes" appear.
Hash is to convert an input of any length into an output of fixed length through a hash algorithm, and the output is a hash value. This transformation is a kind of compressed mapping, that is, the space of hash value is usually much smaller than that of input, and different inputs may be hashed into the same output, so it is impossible to determine the unique input value from hash value. This is a function of compressing messages of any length into message digests of fixed length.
The embodiment of hash algorithm in information security
1, file verification
We are familiar with parity and CRC. Neither of these checks has the ability to resist data tampering. They can detect and correct channel errors in data transmission to a certain extent, but they cannot prevent malicious destruction of data.
The "digital fingerprint" feature of md5 hash algorithm makes it the most widely used file integrity checksum algorithm at present, and many Unix systems provide commands to calculate MD5 checksum.
2. Digital signature
Hash algorithm is also an important part of modern cryptography. Because of the slow operation speed of asymmetric algorithm, one-way hash function plays an important role in digital signature protocol. Digitally signing the hash value, also known as "digital digest", can be considered as equivalent to digitally signing the file itself. There are other benefits to such an agreement.