Android phones often have a pattern authentication mechanism. each dot can be selected no more than once and they can be selected in any order. what is its strength (both number of possible patterns and the bit strength)

The Android pattern lock comes with around 389,112  number of possible patterns. And this is much more than 4 digit pin code which is 10000 in all. We have a tendency to choose the easy ones but it can be dangerous definitely. Also for the bit strength, one dot holds one bit, and so 3 x 3 grid can hold 3 x 3 =9 bits. If you chose n out of then it will be 9CN like 9C2= 9!/2!*7!, and likewise we can calculate the bit strength, which is 9*8/2= 36 bits.

Explanation:

The answer is self explanatory.