Passphrase

A key pair consists of public and secret keys. The secret key must be kept safely, disallowing accesses from other people, in a disk of your computer. But today, people often carry their computers with them, and it would be easy for other people to have access to your computer.

GnuPG lets users decide their passphrases¹ so that their secret keys are only activated when the phrases are typed in.

However, a passphrase is easily broken by a brute-force attack with today's fast computers, if it is short or monotonous, or if it consists of words found in dictionaries.

But if it is random and long, you would not be able to remember it.

There are two very important things about devising a passphrase: 1) you must be able to remember it, and 2) at the same time it should be difficult for others to guess.

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1	A passphrase is like a password, but as a phrase is longer than a word, it suggests that the secret words should be long.