Cryptographic hash functions are commonly used to guard against malicious changes to protected data in a wide variety of software, Internet, and security applications, including digital signatures and other forms of authentication. Two of the most common cryptographic hash functions are the Secure Hash Algorithm (SHA) and Message Digest Algorithm-5 (MD5). Checksum utilities are used to verify the integrity of generated hashes. There are two basic types, those that calculate checksum values and those that also validate them by checking them against a list of values for the protected data, which is the only way it can be done. Raymond Lin's MD5 & SHA-1 Checksum Utility is a standalone freeware tool that generates and verifies cryptographic hashes in MD5 and SHA-1.
The program has a basic, utterly functional interface that should pose no trouble for anyone with the knowledge and skill to actually need it. To generate or verify a hash, you simply browse to the file of choice, select either MD5 or SHA-1, and click either Copy to generate the hash or Verify to check its integrity. A Paste function automatically enters the generated hash for verification at the click of a button.
MD5 & SHA-1 Checksum Utility is free to download and use, though Ray accepts donations from satisfied users. At a mere 57k, his checksum tool is about as small as a useful, functioning utility can be in this age of bloatware, and even more so considering that it's certified to work in Windows Vista and 7.