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(storage, communications)
A computed value which depends on the contents of a block of data and which is transmitted or stored along with the data in order to detect corruption of the data. The receiving system recomputes the checksum based upon the received data and compares this value with the one sent with the data. If the two values are the same, the receiver has some confidence that the data was received correctly.

The checksum may be 8 bits (modulo 256 sum), 16, 32, or some other size. It is computed by summing the bytes or words of the data block ignoring overflow. The checksum may be negated so that the total of the data words plus the checksum is zero.

Internet packets use a 32-bit checksum.

See also digital signature, cyclic redundancy check.
This article is provided by FOLDOC - Free Online Dictionary of Computing (


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.
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References in periodicals archive ?
Since there is only one digital file per title to save for this collection, checksums for the commercially distributed content are run using HashX instead of Bagger.
For instance, Rhian Sasseen, in a March 2014 Al Jazeera article on digital preservation challenges entitled "Bit rot: The Internet never forgets, or does it?" describes how the Library of Congress uses checksums to help maintain and monitor digital materials over time.
In this section, we compare RPFuzzer with Peach, SPIKE and Sulley from generation strategy, monitor, debugger, checksum validation, dimensions, the number of test cases, run time, vulnerabilities on the SNMP protocol and so on.
A possible solution is to extract and to save the documents' checksum and to verify them periodically.
Electronic signatures are possible, along with a checksum (similar to a hash function) to ensure integrity.
* When sending an ASCII message, the two CRC16 checksum bytes were added at the end of it.
System profiles are sophisticated check summing systems that go beyond a simple list of checksums. They verify complete directory structures, e.g., including verification of file attrib-utes, presence or absence of files, and many other characteristics of the entire combination of files present.
The information stored in each entry includes the current document status, a pointer into the repository, a document checksum, and various statistics.
FSP optionally computes its own per-block checksums and uses the same approach to data integrity as GridFTP.
Designed to support econometrics, the FDIC's electronic filing system puts out the cleanest (all the derived calculations and checksums loot) and most immediately useful bulk financial data in the world, far exceeding anything available from any commercial data vendor.
The data path demands of a storage system are additionally taxed by the demands of RAID parity generation for RAID-5 and RAID-6, and by computing data integrity checksums. For instance, a single data port delivering 200MB/s of RAID-5 writes can consume in excess of 2.4GB/s of buffer bandwidth.