SFV
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SFV is an abbreviation for simple file verification, a checksum format using the CRC32 algorithm to verify the integrity of files.
Flaws
CRC32, and thus also SFV, is not an ideal format for securely verifying data integrity, since the CRC32 format is vulnerable to intentional modification that cannot be detected. Other formats, such as SHA512, are better suited for ensuring the authenticity of files.
MD5 has also been used for this purpose, but it's now prone to the same attacks (after the discovery of an MD5 hash collision in August 2004, claimed to be found in only 1 hour on a low-grade computing cluster).
Check sum
Files can become corrupted for a variety of reasons including: faulty storage media, errors in transmission, write errors during copying or moving, and so on. SFV allows a person to ensure that a file has not become corrupted by comparing a hash applied a file to see that they are equal. SFV also allows users to verify the authenticity of files, since if a file was changed (say, with the addition of malicious code) the hash 'fingerprint' of the file would change and alert the user that the authenticity of the file is in question.
One of the first programs to use the SFV format was WinSFV.
SFV uses a plain-text file containing one line for each file and its checksum in the format FILENAME CHECKSUM. Any line starting with a semicolon ';' is considered to be a comment line and is ignored for the purposes of file verification. A sample SFV file appears as follows:
file1.zip c45ad668 file2.zip 7903b8e6 file3.zip e99a65fb
External links
- QuickSFV (http://www.quicksfv.org/)
- Check SFV (http://www.fodder.org/cksfv/)
- hkSFV (http://www.big-o-software.com/products/hksfv/)
- SFV Checker (http://www.traction-software.co.uk/SFVChecker/)
- WinSFV FAQ (in Dutch!) (http://members.lycos.nl/winsfvfaq/)
- Yet another SFV Checker (http://www.irnis.net/soft/xcsv/)
- SFV (and also MD5) Creator and Checker (http://www.irnis.net/)
- dsSFV (http://members.ozemail.com.au/~nulifetv/freezip/freeware/)
- Pure-SFV (and PAR) (http://pure-sfv.sourceforge.net)
- wxChecksums (http://wxchecksums.sourceforge.net/) (Free software for Microsoft Windows)