Rating:
# VC - 50
Problem:
```
There are files A.png and B.png. But where's the flag?
A.png
B.png
```
For file A.png and B.png I've checked for file type and [Exiftool](http://www.sno.phy.queensu.ca/~phil/exiftool/) but there are nothing suspicious.
```
root@AIRBUS:# exiftool A.png
ExifTool Version Number : 10.47
File Name : A.png
Directory : .
File Size : 17 kB
File Modification Date/Time : 2017:03:24 16:19:58-04:00
File Access Date/Time : 2017:03:26 09:06:54-04:00
File Inode Change Date/Time : 2017:03:25 08:55:06-04:00
File Permissions : rw-r--r--
File Type : PNG
File Type Extension : png
MIME Type : image/png
Image Width : 370
Image Height : 370
Bit Depth : 1
Color Type : Grayscale
Compression : Deflate/Inflate
Filter : Adaptive
Interlace : Noninterlaced
Image Size : 370x370
Megapixels : 0.137
root@AIRBUS:# exiftool B.png
ExifTool Version Number : 10.47
File Name : B.png
Directory : .
File Size : 17 kB
File Modification Date/Time : 2017:03:24 16:20:02-04:00
File Access Date/Time : 2017:03:26 11:33:38-04:00
File Inode Change Date/Time : 2017:03:25 08:55:06-04:00
File Permissions : rw-r--r--
File Type : PNG
File Type Extension : png
MIME Type : image/png
Image Width : 370
Image Height : 370
Bit Depth : 1
Color Type : Grayscale
Compression : Deflate/Inflate
Filter : Adaptive
Interlace : Noninterlaced
Image Size : 370x370
Megapixels : 0.137
root@AIRBUS:#
```
Both of them are Grayscale image that mean no color applied to the images. I check for color by reading the images and printing the pixel value of them using python code.
```python
from PIL import Image
im = Image.open("A.png","r")
pix_val = list(im.getdata())
for x in pix_val:
print x
```
I found that there are only 2 values 0 and 255. I merge 2 images using python again.
```python
import Image
with open('pixA.txt') as f:
linesA = f.read().splitlines()
with open('pixB.txt') as f:
linesB = f.read().splitlines()
int_listA = [int(i) for i in linesA]
int_listB = [int(i) for i in linesB]
int_listC = []
for i in range(0,len(int_listA)):
C = 255
if int_listA[i] != int_listB[i]:
C = 0
int_listC.append(C)
# print int_list
im = Image.new('L', (370, 370))
im.putdata(int_listC)
im.save('solve.png')
```
Now I found the flag.
The flag was:
* VolgaCTF{Classic_secret_sharing_scheme}
