Passwords, passwords
To restrict the access to or the usage of something only to an individual or to a group of people, we employ keys, in the broadest sense of the word. Keys can be classic keys on a keychain, smart cards, biometric identifiers or just secrets like passwords, passphrases or passcodes. Two additional concepts should be distinguish: authentication, where we want to prove the identity of someone, and authorization, where we check if someone is allowed to do some action. Usually, both processes are important for security.
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https://www.passwordstore.org/ https://en.wikipedia.org/wiki/Authentication https://en.wikipedia.org/wiki/Password