Checksum (New) - PDF

117 Checksum (New) Let's learn about checksum and its usage. Background In a distributed system, while moving data between components, it is possible that * * * * *...

117 Checksum (New) Let's learn about checksum and its usage. Background In a distributed system, while moving data between components, it is possible that * * * * * * the data fetched from a node may arrive corrupted. *** *** This corruption can occur because of faults in a storage device, network, software, *** *** etc. * How can a distributed system ensure data integrity, so that the client receives an ** ** ** error instead of corrupt data? ** * Solution * Calculate a checksum and store it with data. * *** *** * * To calculate a checksum, a cryptographic hash function like MD5, SHA-1, SHA-256, *** *** ** ** ** ** ** ** or SHA-512 is used. ** ** The hash function takes the input data and produces a string (containing letters and *** *** *** *** *** numbers) of fixed length; this string is called the checksum. *** *** *** * * * When a system is storing some data, it computes a checksum of the data and stores * * * * * * * * * *** the checksum with the data. *** * When a client retrieves data, it verifies that the data it received from the server * * * * * * * *** matches the checksum stored. If not, then the client can opt to retrieve that data *** * * *** *** *** from another replica. ***