# zip (300, coding)
> We found a strange zip file. Sadly the content is encrypted. As only criminals encrypt their stuff we need to decrypt this urgently.> Flag format is FLAGB**************S.
In this task we got a zip file containing a couple of other small zip files. All of them were encrypted, but their sizewas only up to 5 bytes - just like in recent [Backdoor CTF task](https://github.com/p4-team/ctf/tree/master/2016-06-04-backdoor-ctf/crypto_crc). See that writeup fordetails.
After decrypting, this is what we got:
```1 main(2 ){int3 n=244 ;whil5 e(n--6 ){put7 char(8 9 10 ]^n);11 }}```Files 8 and 9 were missing. However, basing on flag format from task description, we could guess what should go in theseempty places:```In [1]: s="FLAGB"
In [2]: for i, c in zip(range(23,0,-1), s):   ...:     print chr(ord(c)^i)   ...:     QZTSQ```It might be a bit of guess, but we see that the last letter is the same as the first one, indicating period equal to 4.If we put `"STZQ` in file 8, and `"[n%4` in file 9, then both files have size equal to 5, just like the others, andthe output of compiled program matches flag format.```main(){int n=24;while(n--){putchar("STZQ"[n%4]^n);}}// Prints FLAGBHEC^TY_ZP][V\QWRXUS```