Passphrase Generator

About Passphrase generator

A passphrase built from several randomly chosen words is much easier to remember and type than a jumble of symbols, and just as hard to guess when enough words are used. This generator draws words from a list of 2,041 common English words, lets you set the length, separator and extras, and shows an entropy figure and a strength estimate.

How to use it

1. A six-word passphrase is already displayed. Select Regenerate for a new one.
2. Drag the Word count slider from 3 to 12. Every change regenerates the passphrase.
3. Choose a Separator: hyphen, period, underscore, space or none.
4. Switch on Capitalize each word, Add a digit or Add a symbol if a site demands them.
5. Check the entropy badge, the strength label and the estimated crack time, then select Copy.

How the entropy adds up

Six words, hyphen separator, no extras

66 bits of entropy, which is six draws of about 11 bits each. Adding a digit raises it to 71.9 bits and a digit plus a symbol to 77.8. Four words alone give 44 bits.

When to use it

• Creating the one master password for a password manager that you have to type from memory.
• Choosing a disk-encryption or backup passphrase that you can read out loud reliably.
• Generating a wifi password for guests that is easy to type on a phone.
• Meeting a site's digit-and-symbol rule while keeping the base of random words.

Questions about Passphrase generator

How is the entropy calculated?

Each word adds log base 2 of the list size, about 10.99 bits. A digit adds log2(10) plus the choice of which word it attaches to, and a symbol works the same way with its 10-character set.

How many words are enough?

Six words, the default, gives about 66 bits, which is sensible for anything that matters. Use more for a master password or an encryption key, since an offline attacker can guess without limit.

Does adding a digit and symbol make it much stronger?

Less than it seems. Together they add roughly 12 bits, about one extra word's worth, because the position and value are the only unknowns. Adding another word is the better improvement.

Can I change a word I dislike?

Do not swap words by hand. Picking your favorites removes the randomness that gives the strength. Regenerate until you get a set you can picture, and then keep it whole.

What is the strength label based on?

It comes from the zxcvbn estimator, which scores from Very weak to Strong and reports a crack time for offline attacks against slow hashing. The entropy number describes the generator's randomness, which is the more reliable figure.

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