Choosing "good" passwords

• "Foiling the Cracker": A Survey of, and improvements to, Password Security by Daniel V. Klein
• Password Security: A Case History by Robert Morris and Ken Thompson

Knowing what a "bad" password is helps you choose a "good" one. According to the experts, a "good" password is one that (among other criteria):

• Doesn't use your login name in any form (e.g., as-is, reversed, capitalized, doubled, etc.)
• Doesn't use your first, middle, or last name in any form
• Doesn't use your spouse's, significant other's, children's, parent's, etc. name
• Doesn't use any information that can be easily obtained, such as information provided by the finger program, your Social Security number, license plate, make of car, driver's license, the street you live on, building name, etc.
• Isn't formed from all numbers, all letters, all lower/upper case, or all the same character repeated
• Isn't a common dictionary word (of any language, or specific to a discipline like Chemistry or Medicine)
• Does mix upper/lower case randomly
• Does include punctuation, numbers, and/or control characters or spaces
• Is seven or more characters in length
• Is easy enough to type quickly so someone cannot "snoop" over your shoulder and see what you type
• Is formed by a method that is easy to learn and remember (which means people are more likely to use it), such as one of these methods:
  • Choose a line (or lines) from a song or poem and form the password from the first letter of each word. For example, "Itsy bitsy, teeny weeny, yellow Polka Dot bikini" would become "IbtwyPDb"
  • Alternate between one consonant and one/two vowels, producing a word that is pronounceable and thus easily remembered, e.g. "FobyLufa" or "BooLWadi"
  • Take two non-related words and separate them with a punctuation character; for added security, mix in some upper-case characters, numbers, and perhaps reverse one of the words, e.g.,
    • "DOg.tenT" (mixed upper/lower case)
    • "t00l%p0nd" (zeros instead of "O")
    • "p33l*BOARd" (substitute numeric for alpha)
    • "tned-Pile" (reversed first word)