Difference between revisions of "Checksum"

Revision as of 07:45, 5 June 2015

A checksum or hash sum is a small-size datum from a block of digital data for the purpose of detecting errors which may have been introduced during its transmission or storage.

It is usually applied to an installation file after it is received from the download server.

By themselves checksums are often used to verify data integrity, but should not be relied upon to also verify data authenticity.

The actual procedure which yields the checksum, given a data input is called a checksum function or checksum algorithm.

Depending on its design goals, a good checksum algorithm will usually output a significantly different value, even for small changes made to the input.

• This is especially true of cryptographic hash functions, which may be used to detect many data corruption errors and verify overall data integrity; if the computed checksum for the current data input matches the stored value of a previously computed checksum, there is a very high probability the data has not been accidentally altered or corrupted.

Similar concepts, each with its own applications and design goals, include:

• hash functions
• Fingerprints
• Randomization functions
• Cryptographic hash functions.

Checksums are used as cryptographic primitives in larger authentication algorithms.

Check digits and parity bits are special cases of checksums, appropriate for small blocks of data (such as Social Security numbers, bank account numbers, computer words, single bytes, etc.).

Some error-correcting codes are based on special checksums which not only detect common errors but also allow the original data to be recovered in certain cases.

External links

• Checksum @ Wikipedia