Key - Derivation function (password to key)

Key derivation function transform a password or passphrase into a key.

The fastest function to transform a password into a key is to ignore the password and return the zero key.

• PBKDF2 (with a work factor of > 100,000) is fine, if aging.
• Better are scrypt or argon2, again with appropriately-sized work factors.
• bcrypt (Password/Passphrase hash)

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