Crc32 (Cyclic Redundancy Check 32) is a checksum algorithm that hashes byte sequences to 32 bit values.
The algorithm is based on polynomial division. In theory, a variety of polynomials can be used. In practice, only two are widely used. The IEEE polynomial is used by Bzip2, Ethernet (IEEE 802.3), Gzip, MPEG-2, PNG, SATA, Zip and other formats. The Castagnoli polynomial is used by Btrfs, Ext4, iSCSI, SCTP and other formats.
TODO: a worked example.