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About

Passphrase Generator

A passphrase of five random words is ready as the window opens, drawn from the Electronic Frontier Foundation’s list of 7,776 by your browser’s cryptographic random generator. Each word adds 12.9 bits, so five give 64.6 bits, and the time a rack of graphics cards would need to guess it is shown beside it.

What it does

  • Three to twelve words, joined by a hyphen, a space, a full stop, an underscore or a comma.
  • Capitals add no strength, since every word gets one and knowing the method gives them away, and the count says so.
  • A digit after one of five words adds 5.6 bits, for a site that insists on a number.
  • Six words give 77.5 bits and seven 90.5, past what any rack of graphics cards will guess in a lifetime.
  • The words are 3 to 9 letters long, about 7 on average, and every one is as likely as any other.

How to use it

  1. Pick the number of words; five is where it starts.
  2. Choose the separator, and capitals or a digit if a site demands them.
  3. Copy the passphrase, or make a new one.

What it does not do

  • Words of your own choosing: a phrase a person picks is far easier to guess than words drawn at random, which is the whole point of the list.
  • Word lists in other languages: the EFF list is English, and the strength shown only holds for words drawn from all 7,776.

Questions

How many words do I need?

Five, 64.6 bits, for most accounts: against a site that stored it badly, a rack of graphics cards needs about half a year. Use six or seven for a password manager’s master password or disk encryption, which an attacker can work on offline for years.

Why the EFF list and not a dictionary?

Its 7,776 words, the number five rolls of a die can pick from, were chosen to be common and easy to spell and remember. The strength shown assumes exactly that list.

Can I roll dice instead?

Yes, that is what the list was made for: five dice give a number from 11111 to 66666, which picks one word. This window does the same with your browser’s random generator, as unpredictable as dice and faster.

Everything here runs in your browser. Nothing you type, paste or open is uploaded, and there is no account and no queue. How that works.

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