Simple file verification
This article needs additional citations for verification. (September 2018) |
This article may require cleanup to meet Wikipedia's quality standards. The specific problem is: Needs refocussing on sfv extension rather than overlapping with File verification. (November 2022) |
Filename extension |
.sfv |
---|---|
Internet media type |
text/x-sfv |
Type of format | CRC32 checksums |
Simple file verification (SFV) is a file format for storing
Checksum
Files can become corrupted for a variety of reasons, including faulty
SFV cannot be used to verify the authenticity of files, as CRC32 is not a collision resistant hash function; even if the hash sum file is not tampered with, it is computationally trivial for an attacker to cause deliberate hash collisions, meaning that a malicious change in the file is not detected by a hash comparison. In cryptography, this attack is called a collision attack. For this reason, the md5sum and sha1sum utilities are often preferred in Unix operating systems, which use the MD5 and SHA-1 cryptographic hash functions respectively.
Even a single-bit error causes both SFV's CRC and md5sum's cryptographic hash to fail, requiring the entire file to be re-fetched. The Parchive and rsync utilities are often preferred for verifying that a file has not been accidentally corrupted in transmission, since they can correct common small errors with a much shorter download.
Despite the weaknesses of the SFV format, it is popular due to the relatively small amount of time taken by SFV utilities to calculate the CRC32 checksums when compared to the time taken to calculate cryptographic hashes such as MD5 or SHA-1.
SFV uses a plain text file containing one line for each file and its checksum[1] in the format FILENAME<whitespaces>CHECKSUM. Any line starting with a semicolon ';' is considered to be a comment and is ignored for the purposes of file verification. The delimiter between the filename and checksum is always one or several spaces; tabs are never used. A sample SFV file is:
; This is a comment file_one.zip c45ad668 file_two.zip 7903b8e6 file_three.zip e99a65fb
Command-line utility
An example of an
Many Linux distributions include a simple command-line tool cksfv
to verify the checksums.
See also
References
- ^ ISBN 9781593270940.
- ^ "h (Hash) command", 7-Zip, May 23, 2016
Further reading
- "SFV FAQ ( from isonews.com )", SourceForge, retrieved and archived 29 August 2021.
External links
- Online SFV Calculator
- QuickSFV SFV checksum verifier (Windows Vista or earlier and Linux)
- wxChecksums- Opensource Windows/Linux application
- Check SFV - SFV software for UNIX systems
- checkSum+, Mac OS X, MD5 compatible, free
- isfv sfv checksum verifier for Mac OS X
Windows only
- RapidCRC- Freeware application
- RekSFV - SFV, MD5, SHA1 utility (Multi-Language, Unicode, with batch mode for checking a huge amount of folders)
- RapidCRC Unicode- RapidCRC with Unicode support (v0.3.4 as of 05/27/2012 supports UTF-8 with or without BOM and UTF-16 LE)
- AmoK SFV Utility - CRC32 and MD5 Compatible
- SFV Ninja - SFV, MD5, SHA-1/256/384/512 utility (Freeware for personal use)
- SFV Checker
- SFVManager
- SlavaSoft FSUM - Fast File Integrity Checker
- HashCheck Shell Extension - SFV, MD4, MD5, SHA-1 (Multi-Language)
- Total Commander - supports creation and verification of SFV files
- hkSFV - supports creation and verification of SFV files (crashes on massive SFV files check)
- DySFV - Open Source (free) application for large files
- ilSFV - free and open-source SFV, MD5 and SHA-1 file verification utility.