Monday, May 18, 2009

The Importance of Case-Sensitive Passwords

It is rare that I encounter a web application that doesn't support case-sensitive user passwords. But it still happens. In my experience this often occurs not because the application developers weren't cognizant of security, but because the authentication is actually processed by an old, backend system that doesn't support case-sensitive passwords. Let's review why implementation of case sensitive passwords is so important.


At first you might think that having case-sensitive passwords would double the number of possible passwords. Of course, that is not how it works. Let's say a user decides he wants a password of "orange7". Without case sensitivity, the number of possible passwords for this user is exactly one. But with a case-sensitive password, the user can choose from sixty-four possible passwords:

orange7 Orange7 oRange7 orAnge7 oraNge7 oranGe7
orangE7 ORange7 OrAnge7 OraNge7 OranGe7 OrangE7
oRAnge7 oRaNge7 oRanGe7 oRangE7 orANge7 orAnGe7
orAngE7 oraNGe7 oraNgE7 oranGE7 ORAnge7 OrANge7
OraNGe7 OranGE7 OrAnGe7 OrAngE7 OraNgE7 ORaNge7
ORanGe7 ORangE7 oRANge7 oRaNGe7 oRanGE7 oRAnGe7
oRAngE7 orANGe7 orAnGE7 orANgE7 oraNGE7 oRaNgE7
orANGE7 oRaNGE7 oRAnGE7 oRANgE7 oRANGe7 OraNGE7
OrAnGE7 OrANgE7 OrANGe7 ORanGE7 ORaNgE7 ORaNGe7
ORAngE7 ORAnGe7 ORANge7 oRANGE7 OrANGE7 ORaNGE7
ORAnGE7 ORANgE7 ORANGe7 ORANGE7


So, having case-sensitive passwords vastly increases the universe of possible passwords and sets the bar significantly higher for hackers running brute force or dictionary attacks on a web application. For example, 64 passwords must be checked versus only one in the scenario presented here.

As an end-user, be sure to take advantage of case sensitivity to strengthen the security of your account. Use a mixture of upper and lower case letters, plus numbers. It may prevent a lazy or time-crunched attacker -- who checks lower case passwords only -- from compromising your account.

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