(third-person singular simple present checksums, present participle checksumming, simple past and past participle checksummed)
A manner of checking the integrity of a set of data by summing all of the bytes of data, or otherwise combining through a series of arithmetic or other logical operations.The originating device appends the result of the calculation to the data set prior to storing or transmitting the data. The device that retrieves the stored data or receives the transmitted data repeats the calculation and compares the two checksums. If the two do not match exactly, it is assumed that the dataset is errored.This process detects many, but not all, errors, and includes no mechanism for error correction. Checksum is employed in an error control mode known as recognition and retransmission. See also cyclic checksum, error control, LRC, and recognition and retransmission.
An integrity protection measure that is used primarily in data storage and networking protocols by adding the bytes or some other string of data components and storing the resulting value. Afterward, an individual having the checksum can confirm that the message was unchanged by performing the same operation on the data—in essence, checking the sum. Some errors—such as reordering the bytes in the message, putting in or taking out zero-valued bytes, and having multiple errors that increase and decrease the checksum in opposite directions—cannot be detected using the checksum integrity protection measure. To avoid this problem, cryptographic checksums have been introduced.
See Also: Bytes; Cryptography or “Crypto.”
A value used to ensure data are stored or transmitted without error. It is created by calculating the binary values in a block of data using some algorithm and storing the results with the data. When the data are retrieved from memory or received at the other end of a network, a new checksum is computed and matched against the existing checksum. A non-match indicates an error. Just as a check digit tests the accuracy of a single number, a checksum tests a block of data. Checksums detect single bit errors and some multiple bit errors, but are not as effective as the CRC method. Checksums are also used by the Sophos antivirus software to determine if a file has changed since the last time it was scanned for a virus. See ECC memory and Sophos.