Hash functions can be used to take a file and generate a much smaller string that represents, and presumably only represents, the given file. These are often used to help determine if a transferred file is coming from a reputable source, and contains exactly the information that it is supposed to contain. By comparing hash values, you can more quickly make these determinations than if you had to compare files bit-by-bit.

For example, some online virus scanners let you search for previously-scanned files by their hash values, allowing you to possibly determine if a popular file has already been uploaded and tested. This way you can see (with a reasonable degree of certainty ) if the file has a virus or has been scanned as "clean" without having to upload the entire file yourself.

So how can one generate file hash values? One option is HashTools by Binary Fortress Software. The software generates a variety of hashes using functions CRC32, MD5, SHA1, and the more-secure SHA256, SHA384, and SHA512.

After installing or unpacking the application, simply run it, select a file to open, and select a hash function. Click the "Copy Hash" button to place the value in the Windows Clipboard for pasting into other applications. If desired, paste a hash value to compare the file hash with in the "Hash Compare" textbox and click the "Compare" button. If the values do not match, the textbox will turn red.

HashTools runs on Windows 2000 and up. Note that you may have to install the Microsoft.NET Framework V2.0 framework if it is not already installed on your system.

The software can be downloaded at the following address. Note that the file can be downloaded with or without an installer:

* HashTools: http://www.binaryfortress.com/hashtools/

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