The Importance of File Checksum/Hash

A checksum or hash is an error-detecting code with the purpose of detecting error which may happened during transmission or storage of data. A checksum is computed from whole blocks of data and results in fixed-length check value which later may be compared to the original data.

Checksum (courtesy of Wikipedia)

Checksum hashes and its sensitivity against data input

There are numerous implementation of checksum algorithm are in data storage and data transport implementation (i.e: Harddisk, Ethernet, Bluetooth). Most of them use cyclic redundancy check (CRC) as its checksum algorithm because of CRC are simple to implement and good at detecting unintentional error made during transmission and storage of data.

A specific implementation in the management of data integrity could be observed in the anime-sharing communities, where checksum/hash of CRC32 is embedded in suffix of the filename.

Such example are [Group] Title – Episode [89BD123A].mkv where 89BD123A is a CRC32 hash of said file. While CRC32 hash embedding are made redundant by inherent implementation of hash algorithm of file in BitTorrent networks, the tradition still lives on because of other modes of file transmission which did not have such file hash algorithm feature (i.e: HTTP and IRC networks).

There are few Windows application which could embed or verify the data against CRC32 hash and one of them are RapidCRC.

RapidCRC 0.6.1 User Interface

RapidCRC has simple interface with features that is useful in file verification management. Although RapidCRC is an old application (last update on 2005), it is still reliable for simple file verification. Beside computing for CRC32 hash, RapidCRC could also compute MD5 hash for stronger file verification (note that both CRC32 and MD5 algorithm are NOT suitable for protection against intentional alteration data).

Using RapidCRC is simple because you only need to drag files or folder you want to verify to the main window. After finished computing for CRC32 of said files, RapidCRC will tell you whether CRC32 computed from file data stored against CRC32 hash embedded in the filenames are correct or not. Other action beside file verification includes embedding CRC32 hash to the filename and store CRC32 hashes into a separate (SFV) files for later verification.

RapidCRC can be downloaded in its download page. As of version 0.6.1, RapidCRC is confirmed working in Windows 7.

Besides RapidCRC, there are a simple application (CRC32finder.exe) which could verify file against its CRC32 hash but unfortunately i cannot find download links for said application.

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