200 points
Category: Forensics
Tags : #image ##steganography
This image passes LSB statistical analysis, but we can't help but think there must be something to the visual artifacts present in this image...
The description and name of challenge suggests data may be hidden in the Most Significant Bit (MSB) of the RGB pixels values within the image.
Rather than writing a program to do this analysis, a quick google search found a python tool sigBits.py that can extract data from both LSB and MSB for analysis.
$ wget https://artifacts.picoctf.net/c/306/Ninja-and-Prince-Genji-Ukiyoe-Utagawa-Kunisada.flag.png
$ pip install Pillow
$ wget https://raw.githubusercontent.com/Pulho/sigBits/master/sigBits.py
$ python3 sigBits.py -t=msb Ninja-and-Prince-Genji-Ukiyoe-Utagawa-Kunisada.flag.png
The generated output outputSB.txt was searched for picoCTF locating the flag (actual flag value redacted for the purposes of this write up) :
picoCTF{........redacted........}
Flag is located at offset 0x3CD6E in the file, viewed from a Hex exitor such as ImHex, if you having trouble locating it within a text editor.
Alternatively, grep can be used and the output restricted to the matched string and using regex to add 50 characters after the "picoCTF" prefix
$ cat outputSB.txt | grep -o -E "picoCTF.{0,50}"
picoCTF{........redacted........}"Thou h