- File verification
File verification is the process of using an
algorithmfor verifying the integrity or authenticity of a computer file. This can be done by comparing two files bit-by-bit, but requires two copies of the same file, and may miss systematic corruptions which might occur to both files. A more popular approach is to also store checksums (hashes) of files for later comparison.
File integrity can be compromised, usually referred to as the file becoming corrupted. A file can become corrupted by a variety of ways: faulty
storage media, errors in transmission, write errors during copying or moving, software bugs, and so on.
Hash-based verification ensures that a file has not been corrupted by comparing the file's hash value to a previously calculated value. If these values match, the file is presumed to be unmodified. Due to the nature of hash functions,
hash collisions may result in false positives, but the likelihood of collisions is often negligible with random corruption.
It is often desirable to verify that a file hasn't been modified in transmission or storage by untrusted parties, for example, to include malicious code such as
viruses or backdoors. To verify the authenticity, a classical hash function is not enough since they are not designed to be collision resistant; it is computationally trivial for an attacker to cause deliberate hash collisions, meaning that a malicious change in the file is not detected with by a hash comparison. In cryptography, this attack is called the collision attack.
For this purpose,
cryptographic hash functions are employed often. As long as the hash sums cannot be tampered with — for example, if they are communicated over a secure channel — the files can be presumed to be intact. Alternatively, digital signatures can be employed to assure tamper-resistance.
Simple file verification
Comparison of file verification software
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Simple file verification — (SFV) is a file format for storing CRC32 checksums of files in order to verify the integrity of files. SFV can be used to detect random corruptions in a file, but cannot be used for checking authenticity in any meaningful way. Typically, the .sfv … Wikipedia
Simple File Verification — Die Simple File Verification (kurz SFV, engl., Einfache Dateiverifikation) ist ein Verfahren zur Überprüfung der Integrität von Dateien über CRC32 Prüfsummen. Die übliche Dateiendung für SFV Dateien ist .sfv. Inhaltsverzeichnis 1 Funktionsweise 2 … Deutsch Wikipedia
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