Websites that provide downloads will often list accompanying CRC32, MD5, or other hashes to go along with the downloads. You can use these hashes to compare with the file you downloaded to ensure that the file hasn’t been tampered with or wasn’t corrupted during the download. To use the hash, you need to calculate the copy of the file you have to generate your own hash to see if they are identical. Different algorithms can be used to calculate hashes and the results might look like this:
CRC32: c4b80d0e
MD5: ecebaa491750335d604102edd4d39e
SHA-1: fbb90dbf82da3fd4b4b6d539813df895243a2e4a
The application HashTab for Windows makes it a very simple, intuitive process to check the hashes of a file. You just right-click the file and go to Properties. HashTab adds a tab to the Properties window that displays the hash of the file. Instead of eyeballing the results and the provided hash, you can just paste the provided hash into the blank below. The question mark icon will then change into a red X or a green check if the hash doesn’t match any of the calculated hashes or if it does match, respectively.
You can click the Settings link on the tab to change which algorithms are used. There are a number of them available with CRC32, MD5, and SHA-1 selected by default. You can add or remove to your list of hashes to be displayed.
HashTab for Windows is free for home use, students, and charitable organizations. You can get the download link to the installer by providing your email address at http://implbits.com/HashTab/HashTabWindows.aspx
HashTab for Mac is available in the App Store for Mac OS X users.