A checksum is a series, unique string derived from a digital file for the purpose of detecting errors that may have been introduced during its transmission or injected by malware. It’s one of the most effective ways to verify the integrity of the file you download from the internet to make sure the file is not tempered in any way. The most commonly used algorithms used to generate the checksum are MD5 and SHA family (SHA1, SHA256, SHA384, and SHA512). Obviously, The higher bit used in the algorithm, the better.
To use a checksum to verify a file’s integrity, you need to get the original checksum from the source that provides the file first. And then, compare it to the one you generate from the downloaded file using the same algorithm. If both strings match, the downloaded file hasn’t changed. But if not, something has happened to the file to corrupt the file. In that case, redownloading the file will be the best practice for you.
Now, the question is, how do I generate the checksum of the file I downloaded?
Here are 5 ways that will help you overcome this gap and do the job relatively easy for you.
A command-line way
CertUtil is a Windows built-in command line installed as part of certificate services, but it also offers a switch -hashfile that allows you to generate the hash string using a specified algorithm. For example, running the following command generates an SHA-512 checksum for an executable file called lsr.exe.
certutil -hashfile z:desktoplsr.exe SHA512
A PowerShell way
In PowerShell 4.0, there is a new cmdlet called Get-FileHash that lets you generate the file hash without any coding involved.
Get-FileHash -Path z:desktoplsr.exe -Algorithm SHA512
From the right-click context menu
Hash Generator is a tool that adds a new item in the context menu that lets you easily generate hashes for any given file.
3rd Party tools
If command-lines are not your thing, here are 3 free tools that can also do the job very well.
Hash Generator is the FREE universal hash generator tool which automates the generation of 14 different type of hashes or checksums. It supports most of the popular hashes including MD5 family, SHA family, BASE64, LM, NTLM, CRC32, ROT13, RIPEMD, ALDER32, HAVAL, WHIRLPOOL, etc.
MD5 & SHA Checksum Utility
MD5 & SHA Checksum Utility is a tool that allows you to generate CRC32, MD5, SHA-1, SHA-256, SHA-384 and SHA-512 hashes of single or multiple files. You can also verify hashes with the matching file to ensure the file integrity is correct.
HashMyFiles is another small and portable tool from NirSoft that also displays the hashes for CRC32, MD5 and the SHA family (SHA1, SHA256, SHA384, and SHA512). If you need to check the hashes for a bunch of files, HashMyFiles is your best friend.
A tab from File’s properties
HashTab is a free tool that adds a separate tab in File Properties dialog box to display the hash strings for any given file. It would be my go-to tool if it offered more algorithms for SHA family. SHA-1 is apparently not enough these days to ensure the integrity of the file.