![]() ![]() Alternatively, digital signatures can be employed to assure tamper resistance.Ī checksum file is a small file that contains the checksums of other files. 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. In cryptography, this attack is called a preimage attack.įor this purpose, cryptographic hash functions are employed often. ![]() To verify the authenticity, a classical hash function is not enough as 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 by a hash comparison. 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. 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. If these values match, the file is presumed to be unmodified. ![]() HASHTAB COMPARE A FILE VERIFICATIONHash-based verification ensures that a file has not been corrupted by comparing the file's hash value to a previously calculated value. 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. File integrity can be compromised, usually referred to as the file becoming corrupted. ![]()
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