Checksum

Method for detecting bit errors on digital signals. In simplest form, a data sender adds up the values of all the bytes in a block of data (such as a packet header) and calculates the total. This total is sent along with the data and called the checksum. At the receiving end of the data, the same addition operation is performed on the data block, generating a received checksum. The received checksum is then compared with the checksum that was sent with the original data. If the two checksum values don’t match, then at least one bit of the data block has changed value, and the data block will be designated as corrupted. Note that in most cases, a more complicated mathematical process is used instead of addition so as to make the checksum more robust.