Hashing

Hashing converts data of any size into a fixed-length value, called a hash or digest, using a hash function. The same input always gives the same hash, a tiny change in input gives a completely different hash, and it is practically impossible to work out the original input from the hash.

Hashing is one-way, unlike encryption. It is used to verify file integrity, in digital signatures and data structures, and to store passwords. Common algorithms are SHA-256 and SHA-3; MD5 and SHA-1 are no longer safe for security. Passwords should use slow, salted hashes such as bcrypt or Argon2.