1
$\begingroup$

I'm reviewing some information and possibilities regarding key space size following a unique password requirement, as it were.

This particular requirement is a fixed-length password of 12 characters, with exactly 1 capital letter, and exactly 1 digit.

My understanding is that, let's say we have 26 letters, then we'd take 26^{(number of characters)} so for a 10 character password, your possible key combos is in the neighborhood of 141,167,095,653,376.

If you included all upper case and lower case, that'd be 52^{(number of characters)}, so on and so forth--the question I'm stumped on is how that changes if you have exactly 1 of a UC and exactly 1 of a digit, if it does at all.

$\endgroup$
0
$\begingroup$

Well it's exactly as you've done in your example.

Key space = $26 \times 26^{10} \times 10 = 3.67 \times 10^{16}$ for a capital letter followed by ten lower case letters and one number. The order doesn't matter, and I assume that your input routine enforces the upper and lower case format you've chosen.

And now the standard caveat. I assume that you realise that a password is not a key, and that further work is required to obtain a secure key, including a key derivation function and spices.

$\endgroup$
  • $\begingroup$ Of course! I appreciate the standard advice and caveat--this is more of a concept of calculating all the possibilities that might exist from this kind of restriction, and the address space needed to support it. $\endgroup$ – Jeffrey Johnson Sep 17 '18 at 2:20
1
$\begingroup$

A password space with $n$ lower case letters, 1 upper case letters and one digit in any order is of size: $26^{n+1}*10*(n+2)*(n+1)$

The choice of the letters the times the choice of the digit times location of digit times location of the uppercase letter.

$\endgroup$

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.