Hashing and checksums

Hashing is an important concept, which is often used to ensure data integrity or lookup values quickly and so it is optimized to be fast. This is why general hashing functions should not be used on their own to securely store passwords. If the algorithm is quick, then the password can be guessed in a reasonably short amount of time. Hashing algorithms vary in their complexity, speed of execution, output length, and collision rate.

A very basic error detection algorithm is called a parity check. This adds a single bit to a block of data and is rarely used directly in programming. It is, however, extensively used at the hardware level, as it is very quick. Yet, it may miss many errors where there are an even number of corruptions.

A Cyclic Redundancy Check (CRC) is a slightly more complex error detecting algorithm. The CRC-32 (also written CRC32) version is commonly used in software, particularly in compression formats, as a checksum.

Tip

You may be familiar with the built...