Diving into hash algorithms and message digests

- Encryption uses a key or pair of keys.…When we encrypt a message, we can decrypt the message…as long as we have a key.…A hash is different in that it is one way.…You can not generate the original message from the hash.…We use hash in a number of different applications,…including authenticating a message,…monitoring data integrity,…and storing passwords.…

A hash takes a variable length input…and generates a fixed length output,…depending on the algorithm…and the compression function used.…Now there are certain cryptographic requirements…for a hash algorithm.…It can be applied to a block of data of any size.…It creates a fixed-sized output.…It is easy to compute.…And it has a strong collision resistance…in that no two hashes will be the same.…

There are two popular hash algorithms.…One is Secure Hash Algorithm, or SHA.…This was developed by NIST and produces…a hash value of 160 bits.…It's used frequently on the internet.…Message Digest Algorithm, MD5,…is a widely used cryptographic hash…which produces a hash value of 128 bits.…