PACTF_2017: XOR 2

Category: Points: 40 Description:

Miles just sent me a really cool article to read! Unfortunately, he encrypted it before he sent it to me. Can you crack the code for me so I can read the article? Article.txt.


Did you know that in typical English writing, a character is the same as the one k characters in front of it about 8% of the time, regardless of k?


A hint of repeated XOR, done easily through XORTool.

$ xortool -x -b -m 1000 Article.txt
$ grep -R 'flag' -i xortool_out/
Binary file xortool_out//000.out matches
xortool_out//032.out:There are infinitely many even numbers, too, but they re much more common: exactly 500 out of the first 1,000. In fact, it s pretty apparent that out of the first X numbers, just about (1/2)X will be even. The flag is primes_are_cool.

Therefore, the flag is primes_are_cool.