CRC32

CRC32 is a cyclic redundancy check that produces a 32-bit checksum used to detect accidental data corruption in digital networks and storage. The most widely used 32-bit CRC in practice is the IEEE 802.3 CRC-32, defined by the polynomial 0x04C11DB7, with input and output reflected, an initial value of 0xFFFFFFFF, and a final XOR of 0xFFFFFFFF. Examples of systems that rely on this CRC include Ethernet frames, ZIP archives, and PNG image files.

Computation can be done bit-by-bit or with a precomputed 256-entry lookup table, which speeds processing by handling one byte at a time. The calculation updates a 32-bit remainder as data bytes are processed. After all data are processed, the CRC value is the final remainder, often expressed as the 32-bit value after applying the final XOR.

Other 32-bit CRC variants exist, such as CRC-32C (Castagnoli) and CRC-32K, which use different polynomials and parameters. CRC32 is not a cryptographic hash and is not intended to provide security against deliberate tampering; it is designed to detect accidental errors in data transmission or storage with high probability.