Checksum Validator is a simple to use progam that allows you to calculate and validate checksums for files that you have downloaded (or will upload).

More sites are including either MD5 or SHA-1 checksums on their files. By comparing a site's checksum with your calculated one, you can be sure your copy matches their official release copy and that there was not corruption of the data or tampering by anyone else. Checksum Validator can calculate either type of checksum.

Of the two checksums MD5 is more common and it will be 32 characters long (written in hexadecimal notation, so that is 16 bytes or 128 bits), but SHA-1 is 40 characters long (20 bytes, 160 bits) and is considered a little more secure.

For more information on checksums and the MD5 and SHA-1 digests head over to Wikipedia, they have many good articles explaining the details on message digests or the "official" term of, cryptographic hash functions, and articles on the MD5 and SHA hash functions

It is extremely easy to create and validate checksums with Checksum Validator:

• To create a checksum just drag any file onto the Checksum Validator application icon or into its Drag Well window. You can also use the typical MacOS "Open…" item from the "File" menu or use ⌘-O.
• To validate a checksum, merely copy it in your browser from the web site where you downloaded your file and then paste that into the file's Checksum Validator window.