Passphrase Generator
A Diceware passphrase is a sequence of words chosen at random from a numbered wordlist, one word per set of dice rolls. DNSX draws from the EFF short wordlist: 1,296 words, four dice rolls each, 10.34 bits of entropy per word. That puts a five-word passphrase at about 51 bits and a seven-word passphrase at about 72.
Easy to Remember
Words are easier for humans to remember than random character strings.
Still Secure
4+ random words provide similar entropy to a 16+ character random password.
Diceware Method
Based on the proven Diceware passphrase generation method for high security.
Command Line
What is a Diceware passphrase?
Arnold Reinhold published the method in 1995. Its value is that you can calculate the strength rather than estimate it. Each word is picked independently and uniformly at random, so the entropy is exactly the word count multiplied by log₂ of the wordlist size, and that figure holds even against an attacker who knows the wordlist and the method. It makes no difference whether the result looks memorable or happens to read like a sentence.
Selection here uses Go's crypto/rand, which reads from the operating system CSPRNG, giving the same uniformity as physical dice.
What is the EFF wordlist, and how big is it?
The Electronic Frontier Foundation published three Diceware wordlists in 2016, curated to remove words that are hard to spell, easy to confuse when spoken, or offensive. Two are in general use:
- EFF short wordlist: 1,296 words (6⁴), four dice rolls per word, 10.34 bits per word. Every word is at most five letters and each is uniquely identified by its first three characters, so it is fast to type and autocomplete-friendly. This is the list DNSX uses.
- EFF long wordlist: 7,776 words (6⁵), five dice rolls per word, 12.93 bits per word. Higher entropy per word, at the cost of longer and less familiar words. DNSX does not use this one.
Which list you use changes the arithmetic, not the method. A short-list passphrase needs roughly one extra word every four words to match a long-list passphrase of the same entropy: seven short-list words (72.4 bits) sit between five and six long-list words (64.6 and 77.6 bits).
How many words should a passphrase be?
Choose the word count by the entropy you need, using the list you are actually drawing from. The figures below are for the EFF short wordlist used by this generator, with the equivalent long-list count shown alongside.
| Words (EFF short) | Entropy | Equivalent random password | Suitable for |
|---|---|---|---|
| 4 | 41.4 bits | ~6 ASCII chars | Not sufficient on its own |
| 5 | 51.7 bits | ~8 ASCII chars | Low-value accounts behind rate limiting |
| 6 | 62.0 bits | ~9 ASCII chars | Ordinary online accounts |
| 7 | 72.4 bits | ~11 ASCII chars | Financial accounts |
| 8 | 82.7 bits | ~13 ASCII chars | Password-manager master password |
| 10 | 103.4 bits | ~16 ASCII chars | Full-disk encryption, long-term keys |
Arnold Reinhold raised his own recommended minimum to six words in 2014. That figure is for the 7,776-word Diceware long list, so the equivalent on the short list used here is eight words. Eight words gives 82.7 bits, comfortably past the ~80-bit threshold for offline cracking resistance, and it is the right default for anything you are protecting seriously.
Capitalising a word or inserting a separator adds almost nothing: an attacker assumes the convention, so a fixed capital is worth a fraction of a bit. Adding one more word adds a full 10.34.
How do I generate a Diceware passphrase with physical dice?
Download the EFF short wordlist. For each word, roll a single die four times (or four dice at once, reading them left to right) and write the four digits down in order, so 3, 1, 6, 2 gives the index 3162. Look that four-digit number up in the list and record the word. Repeat until you have the number of words you decided on, then join them with spaces.
Two rules matter. Never reroll or discard a word because you dislike it, since that makes the selection non-uniform and quietly destroys the entropy calculation. And never substitute mental “random” numbers for dice. Humans are measurably poor at generating uniform randomness, which is why the method uses dice at all.
Are passphrases actually stronger than passwords?
Memorability
Passphrases use real words that form mental images, making them far easier to remember than random character strings of equivalent security.
Typing Ease
Words are natural to type on any keyboard layout. No hunting for special characters or switching between cases repeatedly.
Entropy per Word
Each word from the 1,296-word EFF short wordlist contributes 10.34 bits of entropy. Five words provide 51.7 bits, eight words provide 82.7 bits. Entropy scales linearly with word count and does not depend on how memorable the result looks.
Ideal Use Cases
Passphrases are ideal for master passwords, full-disk encryption, and any scenario where you need to type the password from memory regularly.