A cryptographic hash function works by mapping data to a fixed length string of characters. These types of hash functions are used in many ways. They can be used for authentication, indexing data into hashed tables, checksums, and digital signatures. Two of the most used cryptographic hash functions are MD5 and SHA-3. MD5 was created in 1991 by Ronald Rivest. MD5 uses a 128-bits hash value. At first it was considered secure, but today most experts recommend not using MD5 for authentication, because of the many vulnerabilities found over the years. MD5 works by taking variable length data and converting it into a fixed length hash string of 128-bits. SHA is more secure than MD5. The creators of SHA are Guido Bertoni, Joan Daemen, Michael Peeters, and Gilles Van Assche. The newest version of SHA is SHA-3. It was released in 2015. Most people confuse encryption with hashes. It is important to understand that hashes are digests not encryption. A digest is used by a hash to summarize a compiled stream of data. Hashes are also a one-way function. Encryption converts plaintext data into ciphertext then converts it back to plaintext when the correct keys are given. This is a two-way function unlike hashes, which cannot be reversed. This is an important distinction to make.