Hashing
A one-way operation that produces a fixed-length digest from data that cannot be reversed; it is used to store passwords and to verify that files have not changed.
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Why it matters
Passwords must never be kept in the database as plain text; only their digests are stored and compared at sign-in. Slow algorithms designed specifically for passwords, plus a random salt added to each password, make cracking the passwords in a leaked database much harder.
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Example
An application's database leaks, but the passwords were hashed with an algorithm designed for passwords and with a salt. The attackers cannot crack strong passwords; the company still asks all users to change theirs.
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Common mistake
Storing passwords with a fast, general-purpose hash and no salt. Such digests can be cracked quickly with precomputed tables and powerful hardware.
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Related terms
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