Diceware is a method for creating passphrases, passwords, and other cryptographic variables using ordinary dice as a hardware random number generator. For each word in the passphrase, five dice rolls are required. The numbers that come up in the rolls are assembled as a five digit number, e.g. 43146. That number is then used to look up a word in a word list. In the English list 43146 corresponds to munch. Lists have been compiled for several languages, including English, Finnish, German, Polish, Russian, Spanish and Swedish. A Diceware word list is any list of 6⁵ = 7,776 unique words, preferably ones the user will find easy to spell and to remember. Image File history File links This is a lossless scalable vector image. ... A passphrase is a sequence of words or other text used to control access to a computer system, program or data. ... A password is a form of secret authentication data that is used to control access to a resource. ... Two standard six-sided pipped dice with rounded corners. ... In computing, a hardware random number generator is an apparatus that generates random numbers from a physical process. ... The English language is a West Germanic language that originates in England. ...

The level of unpredictability of a Diceware passphrase can be easily calculated: each word adds 12.9 bits of entropy to the passphrase (that is, log₂(6⁵) bits). Five words (slightly over 64 bits) are considered a minimum length. This article is about the unit of information. ... Entropy of a Bernoulli trial as a function of success probability. ...

Diceware passphrases can be difficult to remember and some may prefer other methods, such as using the initial letters of a memorable phrase (for instance, "To be, or not to be, that is the question" becomes "2bor~2b,titq"). Estimating the entropy of the phrase using the latter approach is more difficult. // The phrase to be, or not to be comes from Shakespeares Hamlet, Prince of Denmark, Act III, scene I, and it is often used in reference to the whole speech the line opens. ... Negation (i. ...

If the length of Diceware passphrases are assumed to be known to an attacker, then the passphrases yields less entropy than the ideal 64.62 bits when used with dictionaries containing variable-length words. This is because the length of the resulting passphrases "leak" information about their composition.

Reference

• Internet Secrets, 2nd Edition, John R. Levine, Editor, Chapter 37, IDG Books, 2000, ISBN 0-7645-3239-1

John R. Levine is an Internet consultant specializing in email infrastructure, spam filtering, and software patents. ... IDG (International Data Group) is a publisher of magazines which focus on information technology. ...

See also

• Brute force attack
• Key size discusses how many bits of key are considered "secure".

The EFFs US$250,000 DES cracking machine contained over 1,800 custom chips and could brute force a DES key in a matter of days — the photograph shows a DES Cracker circuit board fitted with several Deep Crack chips. ... In cryptography, the key size (alternatively key length) is a measure of the number of possible keys which can be used in a cipher. ...

External links

• English diceware page has the complete description and a word list.
• Dialdice has a nicely-formatted word list.