Diceware Passphrase Generator

Arnold Reinhold proposed Diceware in 1995: roll five dice to choose a word from a numbered list of 7,776 words, repeat several times, and you have a passphrase that is easy to remember and hard to guess. The idea fits a brain much better than x7#Kp2$q. The Electronic Frontier Foundation published improved lists in 2016 with words that are easier to spell and distinguish. This page uses those lists and a software random generator in place of dice.

Where the strength comes from

A passphrase is secure because of how many equally likely possibilities it has. With the 7,776-word large list, each word adds log2(7,776), which is 12.9 bits. Six words give 77.5 bits, so about 2 to the power 78 possible passphrases. An attacker who knows your method must try them all, and the page translates the figure into time: at ten billion guesses per second, about 350,000 years on average for six words. Five words give 64.6 bits, four 51.7 bits, three 38.8 bits.

A worked example

Press Sample for the sample settings. The page generated unheated-commodore-tinsmith-request-craftsman-skilled, six words joined by hyphens, and reported entropy of 77.5 bits, about 2 to the power 78 possible phrases and about 350,270 years on average at ten billion guesses a second. Your own result will differ, since each press draws new random words. Each word is chosen independently of the others, so repeated words are possible, and the arithmetic still holds.

The three lists

The large list has 7,776 words, enough for five dice, and gives the most bits per word. Short list 1 has 1,296 words, which suit four dice, and 10.3 bits each; its words are shorter and easier to type, at the price of needing more of them. Short list 2 has 1,296 words with unique three-letter prefixes, so you can type just the first three letters and an autocomplete or a careful reader can recover the word; useful on a phone.

Options and their value

Capitalising each word and choosing the separator change how the phrase looks and not how many possibilities it has, unless the attacker does not know your habit. Adding a number between 0 and 99 adds about 6.6 bits and a symbol a few more, which together is less than half of one extra word. The page includes them because some sites require them. If you can, add another word instead.

How many words to use

For a master password that protects a password manager or an encrypted disk, use six words or more. For an account behind a second factor and rate limiting, five may be enough. Never reuse a passphrase, and do not change one that is strong unless it leaks.

Limits

Strength depends on the words being random. Choosing words yourself, or rerolling until you like the result, reduces it. A site that caps length or rejects spaces may force a different separator. The passphrase appears only on this page and is not saved or sent.

Related tools

• Password Strength Checker tests a phrase against real guessing patterns.
• Password Generator creates random character passwords.
• AES Encryptor and Decryptor turns a passphrase into encryption.
• Shamir Secret Sharing splits a master passphrase between trustees.