There are a number of one-way hashing algorithms used today for security purposes. The most popular one is SHA-1, a 160-bit message digest which produces a hash 40-characters in-length. These messages are relatively secure by the means of entropy, meaning that there is no deterministic behavior to the hash algorithm.
Other one-way hashes exist, and since 2017, SHA-1 has been declared insecure because hash-collisions in the SHA-1 algorithm have been found. Here are some of them: