A cryptographic hash value can be thought of, and is often referred to as, a fingerprint. They are also referred to as simply hashes or check-sums. What they are though are alphanumeric identifiers produced by a cryptographic function being run on a file.
In addition to just being plain cool, this can be very useful if you have an occupation where you may need to verify updated versions of a particular file, or if you need to differentiate unique files of the same name.
- Download the fciv.exe installer from Microsoft. This utility is not included in Windows by default.
- Double-click the “Windows-KB841290-x86-ENU.exe” file and choose where to extract its contents. I chose the Desktop. You will now see two new files on your Desktop, “fciv.exe” and “ReadMe.txt.”
- Drag fciv.exe to your Windows directory at C:\Windows\
- Now let’s open up Command Prompt and set the working directory to the Desktop. To do this, follow these steps:
- Click the Windows button in the lower left and search for “cmd.exe” then click it.
- Enter the following into the window:
- cd C:\Users\%USERNAME%\Desktop
- Note: “cd” is the command to change directory and %USERNAME% is a Windows environment variable referring to your username, whatever that happens to be.
- Now we’re ready to run a cryptographic hash on any file located in the Desktop. For the purposes of this example, I made a “test.docx” file.
- The great thing is, so long as this document is unaltered, the fingerprint will be the same. For example, I added a single character to the doc, the fingerprint now becomes: 89bfc27dfad3ef4b1b5f147fcb3a8290
- Up to this point, all of the fingerprints generated have been produced by the MD5 algorithm. However, as noted in the title, you can generate SHA-1 fingerprints as well. To do so add the -sha1 or -both options after fciv.exe
- Remember that “ReadMe.txt” that was generated back in step 2? It has even more details and options, like how to use fciv.exe to recursively run through an entire directory and then export the results to an XML file. Enjoy!