You work in a security dep of a bank websit. to access their accounts, customers
ID: 3294593 • Letter: Y
Question
You work in a security dep of a bank websit. to access their accounts, customers of the bank must create an 8-digit password. it is your job to determine the password req for these accounts. Security guidlelines stat taht for the website to be secure the probabilty than at 8 digit password is guessed on one try must be less than 1/60e8 asssuming all passwords are equally likely.
how would you investigate the quesiotn of what passwork req should be to meed guidelines?
what password req would you set?
show probabilty that a password is guessed on one try is less than 1/60e8 when req in part (a) are used and all passwords are equally likely.
Additional sec would be to ask for a 5 digit pin. to discourage customers from using predictable pins you sould consider prohibiting PINs that use the same digit more than once.
How would this req. affect the number of poss 5 digit pins?
would you decide to prohibit PINS that use the same digit more than once? Exlpain.
Explanation / Answer
password should be 8 digit long
1)use of alphabets , small and capital - 26 *2 = 52
2)use of digits - 10
3)use of special characters - like ! ,@ ,$ ,%.^.&.* ,(.) - 10
total 52 +10 +10 = 72 option for each place
probability of guessing password = 1 / (72^8)
which << 1/(60*10^8)
b) number of 5 digit that don't use the same digit more than once.
= 10P5
= 10C5 * 5!
= 252 *120 = 30240
i would not decide to prohibit PINS that use the same digit more than once
as this would reduce the total number of combination ,
earlir it 10^5 >> 30240
hence it can be brute-forced.
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