Re: brute-force estimation

"Elenhil" <elenhil@xxxxxxxxx> wrote in message
news:1140599172.853058.63330@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx

Say, I have a 20 character long password consisting of latin
characters (capital and lower-case), numbers and basic punctuation.
That is roughly 80 symbols to play with.

How many combinations one must look through from 1 to 20 (the exact
length is unknown) with unoptimized brute force?

I'm ashamed to admit that I haven't done any mathematics more complicated
than adding up my shopping bill since the second year of University, but I
don't think the problem is as complicated as you are making it.

Assuming 80 valid symbols in the password field and a length of exactly 20
with no limitation on the number of repeats of symbols the number of
combinations is 20^80.

If the password can be of any length up to 20 characters then the number of
combinations is 20^80+19^80+...+1^80.

As for your second point - yes the maximum time for decryption of a message*
is (number of keys)/(time to test each key). This time can be significantly
shortened if the method used to secure the data is weak because it is not
necessary to test every key.

*at least where there is only one key in the domain which produces a valid
output - otherwise you can't be sure that you have the correct message.


.

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