Passphrases

A passphrase is an authentication credential consisting of a sequence of words, characters, or other text used to prove identity. Compared with typical short passwords, passphrases are longer and are often designed to be easier to remember while providing greater potential entropy.

The security of a passphrase depends on its length and unpredictability. A passphrase made from common phrases or personal details is vulnerable to dictionary and targeted guessing. A passphrase based on randomly chosen words or uniformly generated text is harder to guess.

Common approaches include diceware, which uses a large wordlist and random dice rolls to select several words, producing a high-entropy passphrase that is still memorable. Another approach is to create a long sentence or concatenated phrases that are not publicly known, optionally with punctuation, case variations, and numbers. If systems restrict characters, adapt by using the longest allowed sequence of symbols.

Practical considerations include compatibility: some systems treat passphrases differently from passwords and may not support spaces or punctuation. If allowed, spaces can increase effective length; if not, use longer sequences of characters. Regardless, using a unique passphrase for each account and storing them in a password manager is recommended. Enabling multi-factor authentication further strengthens access protection.

Limitations and threats include exposure through data breaches, phishing, or keylogging. Never reuse passphrases across sites, and change credentials after a breach. In security practice, the emphasis is on length, randomness, and separation of credentials across services.