Checksums

3. A Hash Digest. Recall that we spoke about Hash Functions in Topic 4: Cryptography as an effort to ensure data and password confidentiality (e.g., when deciding to save the hash digest of a password, instead of the password itself, in a database) and the non-repudiation of messages (when the hash is used as part of the digital signature, which is a proof that the message was indeed sent by the sender.)
   
   A hash has another wonderful use: it acts as a strong checksum to detect if an error occurred in the data.
   
   Unlike a checksum, which has a relatively-high chance of False Negative, a hash function returns an almost-unique string called digest, which is a 64-byte alpha-numerical string. The chances for a collision (= getting the same digest for two different texts) is very small. As such, a hash function makes a great tool for detecting changes in data!
   
   Many strong (and not so strong anymore) hashing algorithms have been created. One distinguishable example of strong hashing algorithms is SHA-256 (which we already got to use in Topic 4.) Here is a SHA-256 calculator.