A
passphrase is a sequence of words or other text used to
control access to a computer system, program or data. A passphrase is similar to a
password in usage, but is generally longer for added security. Passphrases are often used to control both access to, and operation of,
cryptographic programs and systems. Passphrases are particularly applicable to systems that use the passphrase as an
encryption key. The origin of the term is by analogy with
password. The modern concept of passphrases is believed to have been invented by Sigmund N. Porter in 1982.