Tags: python3
Rating:
# BCACTF WRITEUP
Challenge -->>> Large-Data
In this challange we upto 2700 text file in 27 different folder so we have to do some analysis technique to extract the flag.
![Screenshot_2019-06-17 BCACTF(1)](https://user-images.githubusercontent.com/42002820/59654705-12153a80-91b5-11e9-9aeb-0ed4892cb612.png)
As we can see in above challenge they given a link to download that files for analysis. and they clearly told that flag is 27 character long.
At first i have open file from a folder and get some random characters. that are in every files.then i decided to do something with the characters to extract the flag. so i'm doing trial on one file i have design a solver for one file that read data from file then make sum of each characters ASCII value and finally take average by from counting character emmmmmm... the equation like
#### flagChar = SUM_OF_ALL_CHARACTER(ASCII_CODE)/TOTAL_CHARACTERS_OF_FILE
by doing this i got flags characters like bcactf{.............. then i have created a solver that do this stuff in each file and folder..
## SOLVER.py
------------------------------------------------------------
import os
f = []
root = os.getcwd()
i=0
for filename in os.listdir(os.getcwd()):
f.append(filename)
f.pop()
f1=[]
for i in range(0, len(f)):
f[i] = int(f[i])
f.sort()
flag=[]
st = ""
for i in f:
os.chdir(os.getcwd()+"\\"+str(i))
filelist = os.listdir(os.getcwd())
cntch=0
charcode=0
i=0
for j in range(0, len(filelist)):
filelist[j] = int(filelist[j])
filelist.sort()
for afile in filelist:
if(i<100):
#print(afile)
fp = open(str(afile),"r")
for filedata in fp:
for ch in filedata:
charcode += ord(ch)
cntch = cntch + 1
st += (chr(int(charcode/cntch)))
cntch=0
charcode=0
i+=1
flag.append(st)
os.chdir(root)
st=""
k=0
l=0
flags=""
for i in range(0,100):
for j in range(0,27):
flags += flag[k][l]
k=k+1
l=l+1
print(flags)
flags=""
k=0
By running this solver we got 100 Flags--->
![flags](https://user-images.githubusercontent.com/42002820/59613123-f7eb4600-913b-11e9-9765-30502175cafc.png)
100 flags link -->
https://raw.githubusercontent.com/dhavz/BCACTF-WRITEUP/master/flags
So after that i have found a flag from that list that have good meaningful words like a FLAGGG!!!!!!!!!!!!
## bcactf{crunch1ng_num5_c00l}
c001_dh@\/7_