Damjan Cvetko

Damjan Cvetko

Developer, System Architect, Hacker.

1 minute read

Challenge: Someone send an image to Santa but it got corrupted during the transfer or did it? Maybe someone intentionally did this and hidden a message inside?

A picture, bsides.png, was attached.

First, I took a common online stego tool to try to analyse the image. Found quickly, by using “Browse Bit Planes”, that the starting pixles were hiding something:

I did try to decode it myself, pulled all the firs bits and put them together in various ways and didn't get anything obvious. I found another nice tool and the online version: https://aperisolve.fr/

Throwing in the picure, one of the results was the hit:

imagedata .. text: "\t?#\tE&\tC%"
b1,b,lsb,xy .. text: "rp}9~U:W"
b1,bgr,lsb,xy .. text: "#xmas{d0_TH3y_KnOw_its_chr1stmas???}"
b3,g,lsb,xy .. file: GLS_BINARY_MSB_FIRST

b1 means bit plane 1, so, first bit. bgr means sequence, blue green red. lsb is Least Significant Bit, for bit order. And xy means the direction of pixel processing, but that has no effect here.

Flag: xmas{d0_TH3y_KnOw_its_chr1stmas???}

What did I learn: Don't bother installing python and downloading tools. Ther's alway a webpage to run it in the browser.

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