Hashing is a cryptographic operation that is performed on variable-length data strings, such as email addresses or phone numbers, to convert them from plaintext to bit strings of a fixed length through the use of a specific algorithm. Hashing of a particular data string with a particular algorithm always produces the same result. Hashing is designed to be a one-way function, so that it is very difficult to reverse. 

Common hashing algorithms include MD5, SHA-1, and SHA-256.

See "Hashing Identifiers" for more information.

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Updated 10/18/18.