If you’ve just downloaded a file from the Internet, you may want to verify that the downloaded file hasn’t been tampered with. After all, who knows that kind of nefarious fiddling a hacker might have been up to? By checking the MD5, SHA-1 or SHA-256 checksum of a file, you can verify its integrity and ensure the file hasn’t been corrupted or changed.
What’s a Checksum?
A checksum is a short, unique string that results from running an encryption algorithm on a given file. The algorithm looks at all the bits that make up a file and, based on those unique bits, creates a checksum. This checksum will change if even a single bit in the file changes. This means that by comparing two checksums, you can make sure your file hasn’t been damaged or modified. It’s a useful way to defend against file corruption or malicious interference in your downloads.
The most commonly used algorithms for checksums in MD5. SHA-1 and SHA-256 are also available and are based on cryptographically-secure algorithms. If you can choose from among the three, use SHA-256.
How Do You Use a Checksum?
To use a checksum, you’ll first need to know what a given file’s checksum is. This will have to be provided to you by the same source that provided the file. You’ll run your downloaded file through the same checksum algorithm using one of the tools below. Once you’ve done that, you’ll compare the two strings. If the strings match, the file hasn’t changed. If the strings don’t match, something about your file is different from the original file.
Verify MD5, SHA-1 and SHA-256 Checksums in Windows 10
The best way to run checksums in Windows 10 is with a tool called MD5 & SHA Checksum Utility. It will calculate the MD5, SHA-1 and SHA-256 checksums for a given file simultaneously and allow you to compare your result against the provided data.
Download MD5 & SHA Checksum Utility from the developer’s website.
Double-click the downloaded file to launch the program.
Click the “Browse” button to select the file you want to check.
Locate the provided checksum for your downloaded file. Not all downloaded files have checksums available, but open-source or security-conscious developers will frequently provide a checksum. Copy that checksum to the clipboard, then click the “Paste” button in MD5 & SHA Checksum Utility.
If the checksum is the same as the checksum the application calculated, you’ll receive a success message. This means that the file you have is identical to the file that was previously checked.
If the checksum is different, you’ll get an error message. This means the file has somehow changed since the last checksum was calculated.
Verifying Checksums Within File Explorer
If you verify checksums frequently, you might be interested in HashTab. The application installs an additional tab in the Properties window of File Explorer. Thanks to being embedded in Explorer, Hashtab can calculate checksums in place without requiring a separate application. By default, it calculates CRC32, MD5 and SHA-1 hash values. Additional hashing algorithms can be enabled in Hashtab’s settings.
Download and install HashTab from the developer’s website.
Right-click on the file you want to run a checksum against and choose “Properties” from the context menu.
Click the tab labelled “File Hashes” at the top of the window to see the MD5, SHA-1 and CRC32 hashes for the file you selected.
Copy and paste the checksum you want to compare against in the “Hash Comparison” dialog box.
If the hash checks out, you’ll see a green checkmark.
If the hash doesn’t match, you’ll see a red X.
Conclusion
If you want to check the integrity of a file you’ve downloaded, checksums will help you get it done. You can use MD5 & SHA Checksum Utility as a standalone application for calculating and comparing MD5, SHA-1 and SHA-256 checksums or use HashTab for a checksum checking tool that’s integrated into File Explorer.
Image credit: Beyer Cryptographic Watch via Wikimedia Commons
Alexander Fox is a tech and science writer based in Philadelphia, PA with one cat, three Macs and more USB cables than he could ever use.
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