Stego: BitsNBytes WriteUp: Challenge

BitsNBytes Stego WriteUp

Tools:

1. compare, crop, python
2. binary to ascii converter
3. base64 decoder

Steps:

1. download the zip file
2. extract it with password "hackthebox"
3. compare intercepted.png original.png diff.png
4. crop diff.png left side with red dots
5. Invert the python image to BnW and convert the dotted code on the left corner
6. black dot for 1 and white dot for 0
result is
010100110100011001010010010000110110010101111010010001100110110101011000001100100100011001100110011001000111101001000001011101110101101001000110001110010110101001100001010010000101011001101010011000010011000100111001011010100100110101001000010101100111001101011010010001100011100101101010011000010100100001010110011010100110000100110001001110010011001101001101010001000100001001101011011001100101000100111101001111010
7. convert binary to ascii using https://www.binaryhexconverter.com/binary-to-ascii-text-converter
8. decode: SFRCezFmX2FfdzAwZF9jaHVja19jMHVsZF9jaHVja193MDBkfQ==
9. base64 decode the flag
HTB{1f_a_w00d_chuck_c0uld_chuck_w00d}

Commands:

1. compare -extract '1x550+0+0' original.png intercepted.png -highlight-color white -lowlight-color black -compose src gray:- | perl -lpe '$_=pack"B*",$_' | base64 -id

Flag:

HTB{1f_a_w00d_chuck_c0uld_chuck_w00d}

Reference:

1. https://forum.hackthebox.eu/discussion/345/hint-with-bitsnbytes
2. https://pwning.re/2015/09/17/enei-ctf-writeups-forensics/
3. https://forum.hackthebox.eu/discussion/1919/stego-challenge-bitsnbytes-write-up-by-alamot

Video: