README.md

IceCTF 2016 – Vape Nation

Problem

Go Green!

Solution

Mathematica can download the image with Import[].

image = Import["https://play.icec.tf/problem-static/vape_nation_7d550b3069428e39775f31e7299cd354c721459043cf1a077bb388f4f531d459.png"]

But this problem likely involves steganalysis of the pixel data of the image. We can specify "Data" in the Import[] call to download the image. Or we can convert the image data to byte data after downloading with ImageData[].

imageData = Import[
  "https://play.icec.tf/problem-static/vape_nation_7d550b3069428e39775f31e7299cd354c721459043cf1a077bb388f4f531d459.png",
  "Data"];

Let's try previewing the least significant bit (LSB) of each channel of the image.

First we extract the LSB of each channel by calling BitAnd[] with 1. Then reconstruct an Image[] and ImageAdjust[] the image to make the minute differences of each pixel visible.

flagImage = ImageAdjust@Image[BitAnd[imageData, 1], "Byte"]

The flag is easily readable. The flag is green in the image because it is in the green channel. The green channel is the second channel of the image and can be extracted with ColorSeparate[] if desired.

Additionally, we can attempt to extract the text from the image by OCR using TextRecognize[] for easy copy pasting to submit the flag.

TextRecognize@ColorSeparate[flagImage][[2]]

IceCTF{420_CuR35_c4NCEr}