Easy To Remember, Hard To Guess
A password that is easy to remember is generally also easy for an attacker to guess. Passwords which are difficult to remember will reduce the security of a system because (a) users might need to write down or electronically store the password, (b) users will need frequent password resets and (c) users are more likely to re-use the same password. Similarly, the more stringent requirements for password strength, e.g. "have a mix of uppercase and lowercase letters and digits" or "change it monthly", the greater the degree to which users will subvert the system.
In "The Memorability and Security of Passwords", Jeff Yan et al. examine the effect of advice given to users about a good choice of password. They found that passwords based on thinking of a phrase and taking the first letter of each word are just as memorable as naively selected passwords, and just as hard to crack as randomly generated passwords. Combining two unrelated words is another good method. Having a personally designed "algorithm" for generating obscure passwords is another good method.
However, asking users to remember a password consisting of a “mix of uppercase and lowercase characters” is similar to asking them to remember a sequence of bits: hard to remember, and only a little bit harder to crack (e.g. only 128 times harder to crack for 7-letter passwords, less if the user simply capitalises one of the letters). Asking users to use "both letters and digits" will often lead to easy-to-guess substitutions such as 'E' → '3' and 'I' → '1', substitutions which are well known to attackers. Similarly typing the password one keyboard row higher is a common trick known to attackers.
Read more about this topic: Password Cracking
Famous quotes containing the words easy to, easy, hard and/or guess:
“It is as easy to deceive oneself and not be aware of it, as it is hard to deceive others without their being aware of it.”
—François, Duc De La Rochefoucauld (1613–1680)
“If learning to read was as easy as learning to talk, as some writers claim, many more children would learn to read on their own. The fact that they do not, despite their being surrounded by print, suggests that learning to read is not a spontaneous or simple skill.”
—David Elkind (20th century)
“It was hard for an American to understand the contented acceptance by English men and women of permanent places in the lowest social rank.”
—Virginia Crocheron Gildersleeve (1877–1965)
“The line of separation was very distinct, and the Indian immediately remarked, “I guess you and I go there,—I guess there’s room for my canoe there.” This was his common expression instead of saying “we.” He never addressed us by our names, though curious to know how they were spelled and what they meant, while we called him Polis. He had already guessed very accurately at our ages, and said that he was forty-eight.”
—Henry David Thoreau (1817–1862)