







A 4 digit combination lock 
20190202 

From Brijanshu: I have a lock that contain only four no. 6,7,8 & 9 . How many possible password of four digit containing these Number. Answered by Penny Nom. 





A lost iPhone pass code 
20170417 

From Sam: I have a locked iPhone and it has all my of my holiday photos on it. I changed the password and then I think I did a incorrect number pattern but anyway I know it ends with 99 and the first 4 digits are 235 and 6 could you please send all of the combinations for this password (without the 99) Thx and plz get back ASAP I need it for school Answered by Penny Nom. 





Sixdigit passwords 
20130319 

From Judy: Hello:
Can you please explain why the answer to the following question is 10^6?
What is the number of possible sixdigit passwords when using the digits 0 through 9, with repetition allowed.
Thank you. Answered by Penny Nom. 





Passwords 
20090708 

From Tim: pretend I have a password that is  9k7d4112p5o
assuming that you continuously guessed wrong until that exact
combination was the only possible answer left;
how many times would you have to guess?
capital letters are not relevant
and you do not know how many digits there are Answered by Stephen La Rocque. 





2 password policies 
20071017 

From Larry: 2 password policies are in question.
Policy 1 states that a password must be between 6 and 8 characters
Policy 2 states that that a password must be exactly 8 characters.
Both policies state that Passwords can contain AZ az 09 (26*2)+ 10 characters to choose from.
Which policy is stronger?
How many potential passwords exist for policy 1 and how many for policy 2? Answered by Penny Nom. 





Nine character passwords 
20070327 

From oliver: suppose a password consisted of a string of nine characters from the
english alphabet(26 characters). if each possible password could be tested
in a microsecond,how long would it take to test all possible passwords? Answered by Penny Nom. 

