Cracking the Vigenere Cipher knowing the keyword length - Space included

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I am trying to write java code to break the Vigenère Cipher and i already done the first part of that which is finding the expected length of the keyword now i have 2 questions about this the first one is how i automatically decide the proper key length for example for this output i can see that key length 13 is the proper one, how can i get a way to differentiate this in the program

KeyLength = 6, Ic = 0.03859048320776436
KeyLength = 7, Ic = 0.038461776361534486
KeyLength = 8, Ic = 0.04127335450717369
KeyLength = 9, Ic = 0.038126854785976556
KeyLength = 10, Ic = 0.04081510015219356
KeyLength = 11, Ic = 0.037334117453444116
KeyLength = 12, Ic = 0.038540774334425126
KeyLength = 13, Ic = 0.07911004714981987
KeyLength = 14, Ic = 0.036578630064582195
KeyLength = 15, Ic = 0.03787057034466581
KeyLength = 16, Ic = 0.041064246637608465

And second of all i how would i generate the the key letters assuming that i know the length and considering that i include space in the alphabetic probability table -i didn't find frequency table that includes space so far-? Any suggestions.

asked 45 secs ago

user3038489

8

Cracking the Vigenere Cipher knowing the keyword length - Space included