Sorry CSOs Rock, you can be nit-picky, but you also need to be right when you are nit-picky.
Each combination has 15 possibilities:
1
2
3
4
1,2
1,3
1,4
2,3
2,4
3,4
1,2,3
1,2,4
1,3,4
2,3,4
1,2,3,4
Thats a total of 11.4 million possible combinations
I had assumed a 2 button maximum (9 possible combinations per entry), because practically speaking,
1) Few people ever use three or four button entries
2) Three button and four button entries are a pain to remember in a six entry combination
3) Few people will even ever use a pinky alone or more than a four entry combination (that takes time to do)
So....there are 11.4 million POSSIBLE combinations, but practically speaking, if a user can find 9 possibilities they are comfortable with per entry, they can be comfortable that they are protected by 531,441 possible random combinations. I am an engineer, not a scientist or mathematician, so theory is less interesting to me than whether or not someone will actually behave that way. I have hacked Simplex locks for fun and believe me, few people go beyond 3 button-single push cominations (leaving me a whopping 125 tries before I can get in), although theoretically they have 2,162 possible combinations.
BTW, most people use easy combinations they can remember. Consequently, most hackers start at the easy end, and work their way towards the more difficult end. For a good combination, use at least one 3-button entry and you will in-fact be undefeatable.
[Edited by Cruzer on 03-30-2001 at 11:55 AM]