File Extension SFV
File extension SFV is associated with a Simple File Verification file, which uses checksum data to determine whether or not a file or folder structure has been altered through corruption or modification by a third party. SFV files are most commonly used in conjunction with files downloaded from the Internet, or when burning data to optical media.
SFV files are usually contained within a compressed archive such as a ZIP or RAR file, and are used to verify the integrity of the files contained within the archive. SFV files contain a CRC32 (Cyclic Redundancy Check) checksum for each file within the archive, which is a 32-bit integer, calculated using the original file size. If the checksum of any of the files within the archive do not match those specified in the SFV file, then it can be assumed that the archive is corrupt. This may be due to incomplete transmission, or a file in the archive being missing or different from the original.
Though SFV files can determine whether or not a file is incomplete or missing, it should not be used to verify the authenticity of a file as it is possible to modify the contents whilst still retaining the same checksum. Additionally, SFV files are only suitable for relatively small files, as the 32-bit limitation means that different files could conceivably generate the same checksum. For larger files, such as ISO images, MD5 hashes are more commonly used as they support 128-bit values.
SFV files can be opened using any Simple File Verification application, such as MooSFV, QuickSFV, RapidCRC or SFV Checker on Windows, MacSFV or SuperSFV on Mac or CheckSFV on Linux. Opening the file in any of these applications will result in the associated files having a checksum calculated and any which differ from the expected value will be flagged.