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:
“Nothing is so easy to fake as the inner vision.”
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“You know, whenever women make imaginary female kingdoms in literature, they are always very permissive, to use the jargon word, and easy and generous and self-indulgent, like the relationships between women when there are no men around. They make each other presents, and they have little feasts, and nobody punishes anyone else. This is the female way of going along when there are no men about or when men are not in the ascendant.”
—Doris Lessing (b. 1919)
“People think that if a man has undergone any hardship, he should have a reward; but for my part, if I have done the hardest possible day’s work, and then come to sit down in a corner and eat my supper comfortably—why, then I don’t think I deserve any reward for my hard day’s work—for am I not now at peace? Is not my supper good?”
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“How did reason enter the world? As is fitting, in an irrational way, accidentally. We will have to guess at it, like a riddle.”
—Friedrich Nietzsche (1844–1900)