This page offers a better way to create a strong, yet easy to remember passphrase for use with encryption and security programs. Weak passwords and passphrases are one of the most common flaws in computer security. Take a few minutes and learn how to do it right. The information presented here can be used by anyone. No background in cryptography or mathematics is required. Just follow the simple steps below. If you'd like to know even more about passphrases, see the Frequently Asked Questions (FAQ).
This page is also available in Chinese, Finnish, French, Italian, Japanese, Polish and Spanish. There are also Dutch, Finnish, German, Italian, Polish, Russian, Spanish, Swedish and Turkish word lists.
Try our free Big Number Calculator
Java
applet. It lets you perform many
of the calculations used in
public key cryptography. It should work on most modern
browsers.
A passphrase is a bunch of words and characters that you type in to your computer to let it know for sure that the person typing is you. Most newer security programs allow you to enter a passphrase instead of just a short password for added protection against attackers. Some programs also use your passphrase to form a cryptographic key to encrypt your data:
You should follow the Diceware instructions and have your passphrase ready before installing a WiFi router, creating your PGP or GPG key, opening a new Hushmail account or setting up an encrypted disk.
Passphrases differ from passwords only in length. Pass words are usually short -- six to ten characters. Short passwords are OK for logging onto computer system that are programmed to detect a large number of incorrect guesses and protect the stored passwords properly, but they are not safe for use with encryption systems. Passphrases are usually much longer -- typically 20 to 40 characters, sometimes more. Their greater length makes passphrases more secure. Modern passphrases were invented by Sigmund N. Porter in 1982. If all you need right now is a login password, click here. Otherwise, read on.
Picking a good passphrase is one of the most important things you can do to preserve the privacy of your computer data and e-mail messages. A passphrase should be:
Diceware™ is a method for picking passphrases that uses dice to select words at random from a special list called the Diceware Word List. Each word in the list is preceded by a five digit number. All the digits are between one and six, allowing you to use the outcomes of five dice rolls to select one unique word from the list.
Here is a short excerpt from the Diceware word list:
16655 clause
16656 claw
16661 clay
16662 clean
16663 clear
16664 cleat
16665 cleft
16666 clerk
21111 cliche
21112 click
21113 cliff
21114 climb
21115 clime
21116 cling
21121 clink
21122 clint
21123 clio
21124 clip
21125 clive
21126 cloak
21131 clock
The complete list contains 7776 short English words, abbreviations and easy-to-remember character strings. The average length of each word is about 4.2 characters. The biggest words are six characters long. The list is based a longer word list posted to the Internet news group sci.crypt by Peter Kwangjun Suk. An alternative list, edited by Alan Beale, contains fewer Americanisms and obscure words. And there are lists for several other languages. You can also download the Diceware word list in PDF format or in PostScript format.
To use the Diceware list you will need one or more dice. Dice come with many board games and are sold separately at toy, hobby, and magic stores. Toys"R"Us sells a package of five dice for about a dollar. Braille dice are also avaliable. You can purchase five casino-grade dice online from Casinocom.com for about $11, but they are overkill for this purpose. Do not use a computer program or electronic dice generator.
Suppose you want a five word passphrase, as we recommend for most users. You will need 5 times 5 or 25 dice rolls. Let's say they come out as:
1, 6, 6, 6, 5, 1, 5, 6, 5, 3, 5, 6, 3, 2, 2, 3, 5, 6,
1, 6, 6, 5, 2, 2, and 4
Write down the results on a scrap of paper in groups of five rolls:
1 6 6 6 5
1 5 6 5 3
5 6 3 2 2
3 5 6 1 6
6 5 2 2 4
You then look up each group of five rolls in the Diceware word list by finding the number in the list and writing down the word next to the number:
1 6 6 6 5 cleft
1 5 6 5 3 cam
5 6 3 2 2 synod
3 5 6 1 6 lacy
6 5 2 2 4 yr
Your passphrase would then be:
cleftcamsynodlacyyr
Third Roll
1 2 3 4 5 6
F 1 ~ ! # $ % ^
o 2 & * ( ) - =
u 3 + [ ] \ { }
r 4 : ; " ' < >
t 5 ? / 0 1 2 3
h 6 4 5 6 7 8 9
There are many different recommendations available on the Internet about how to pick a passphrase. Many are good, a few are bad, but almost all require the user to judge what will be hard for someone else to guess. Some give no guidance on how to do that, others have you make complex mathematical calculations. By contrast, the Diceware method of generating passphrases is:
The prescriptive nature of Diceware is very important for new users of encryption. Here is one person's experience, as posted to the Internet newsgroup alt.security.pgp:
"I just wanted to relate a personal story about how hard it is to convince a novice how important it is to select a secure password, and get them to understand what constitutes a secure password. I am an old-timer at both the Internet and security issues. My sister, however, is brand new to it having just opened an Internet account. She lives in [the mid-west] while I live [on the west coast]. As a result, we exchange quite a bit of very personal email.
Recently, she wanted to give her Internet password to her husband so that he could get on line. However, she still wanted to be able to exchange private messages with me that he would not be able to read. I, of course, introduced her to PGP.
I gave her the usual lecture about how important it is to select a password that nobody else can easily guess, and that the ideal password would be some obscure and nonsense word that would have meaning only to here. I told her all about not selecting birthdays, anniversaries, names, and the like. I didn't suggest a random combination of letters and numbers because we were not after world class security, we just wanted to keep her husband out of our private letters. So, after she selected her PGP password, I decided to give it a try at cracking it. The VERY FIRST password I tried worked! She was totally surprised at how easily I had found it, but it was a word that anyone knowing her would have access to. So, after giving her some more tips on good password selection, I let her try again. This time, it took me only 3 attempts before I found the right word. Finally, she gave up and let me pick a password for her."
Had she used Diceware, the author's sister's very first passphrase would have been totally secure and known only to her. Remember: in public key cryptography, the security of your message depends on the recipient's passphrase. Spread the word about Diceware!
For more information on passphrases and Diceware see the following:
Diceware FAQ Questions and answers for people who want to know more about Diceware and passphrase generation.
Diceware Word List, the list in PostScript format, Beale word list, Diceware8k list for computer generation
A Survey of PGP Passphrase Usage A small poll I ran to find out what PGP users actually do to make passphrases, and some suggestions for improvement.
Diceware for Passphrase Generation and Other Cryptographic Applications Includes info on other uses of Diceware and an analysis of Diceware security.
Protecting Passwords by Gary McGraw and John Viega, An article in the IBM Developerworks Security Library that discuss passwords, pasphrases and Diceware.
Passgen: A Password Generator Java Applet Uses keyboard latency to generate random passwords based on a selectable format. Not as secure as the diceware method, but adequate for login passwords and similar applications. Includes source code.
Random Noise Sources A collection of information on sources of randomness for use with computers.
CipherSaber Home Page Learn how to build your own strong encryption program. It's easier than you think!
Other Papers on Cryptography by Arnold Reinhold P=?NP -- who Cares?, Cryptanalysis of Histocompatibility, etc.
S.
N. Porter, A Password
Extension for
Improved Human Factors,
Advances in Cryptology: A Report on CRYPTO 81, Allen Gersho, editor,
volume 0, U.C. Santa Barbara Dept. of Elec. and Computer Eng., Santa
Barbara, 1982. Pages 81--81. Also in Computers & Security, Vol.
1. No. 1, 1982, North Holland Press.
Oren Tirosh has a site on using wordlists to represent large numbers for cryptographic and other purposes. He has references to a number of interesting wordlists.
CN -- Chinese translated by Lian.
DE -- A German word list (pdf format) provided by Benjamin Tenne under the terms of the GNU General Public License. Here is a sample German passphrase:
distel ist landen kammer puffen
ES -- Spanish translated by Manuel Palao, including a Spanish word list. Here is a sample Spanish passphrase:
multa h64 quien enero tubo
FI ---Finnish translated by Kai Puolamaki, including a Finnish word list. Here is a sample Noppaware ("noppa" means a dice in Finnish) passphrase:
olli kukot hoveli hintaa airoja
FR -- French translated by Joachim Dubuquoy-Portois.
IT -- Italian translated by Tarin Gamberini with an Italian word list (pdf format). Here is a sample Italian passphrase:
casi botole stadi maglia venivo
JP -- Japanese translated by Hiroshi Yuki.
NL -- A Dutch word list provided by Bart Van den Eynde under the terms of the GNU Free Documentation License. Here is a sample Dutch passphrase:
ijler 100 leperd akolei kolkje
PL -- Polish translated by Piotr (DrFugazi) Tarnowski, Computer Science Techniques Centre, University of Silesia, Katowice, PL, including a Polish word list. Here is a sample Polish passphrase:
plewka szpieg raban pruski ibi
RU -- Russian word list provided by "kitten." Here is a sample passphrase. You need a Cyrillic font to read it.
ÍËðýÒý Ò¸Ïãý âÂðÒÚý ÊÛõÎûÈ ÁÂâÓÚý
SV -- Swedish word list provided by Magnus Bodin. Here is a sample Swedish passphrase:
ark altan rodel lamm kyot
TR -- Turkish word list provided by Mert Dirik. Here is a sample Turkish passphrase:
derz permi turba um beniz
The Diceware Kit contains instructions on how to create a Diceware word list for other languages.
Special thanks to all the translators!
Internet Gurus Central -- Introduction to PGP
MIT's Distribution Site for PGP
Fran Litterio's Cryptography, PGP and Your Privacy Page
Here are some other sites with recommendations on how to make your passphrase. I do not suggest that the information at these sites is wrong, just that it may be too complex for most people. Take a look and judge for yourself.
Passphrase FAQ by Randall T. Williams
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