One way to check if a downloaded file is correct, damaged, or tampered with is to compare the hash value. The hash value is a data (string) calculated from the contents of the file based on an algorithm, and is used to check the identity of the file, since even a single bit difference in the contents of the file can make a big difference.
By calculating the hash value of the downloaded file and comparing it with the publicly announced hash value, you can see that the file is identical to the original. Also, if a free software file is distributed through a third party's website, you can check if the file is really the same as the original by comparing the hash value.
In the following sections, we will show you how to check the hash value of a file.
There are different types of algorithms for calculating hash values, as follows. (From PeaZip HP)
The CRC is called a checksum and is a simple algorithm to check for bit errors, but it cannot be used to check for malicious file tampering. To check for tampering, more secure hashing algorithms are used, such as MD5 and SHA-1, which are still in use in many cases. However, due to the news that Google successfully created two different files with the same hash value, it is now recommended to use the more powerful SHA256 or SHA-3.
You can obtain checksum/hash values of a file using PeaZip.
Right click on a file you want to check, and select "PeaZip" > "CRC, hash and file tools".
Select "Checksum/Hash (common algorithms)", then press OK.
Checksum and hash windows will appear. Then select "Clipboard" tab.
There you can find many types of checksums/hash values. (ex. CRC32, CRC64, MD5, RIPEMD160, SHA1, SHA256, SHA3_256)
If you want to see other types of hash values, select "Checksum/Hash (all supported algorithms)" in previous window.
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