HACKvent 2020 – Day 1

01-01-2021 - 0 minutes, 36 seconds - CTF

Happy HACKvent 2020

Welcome to this year’s HACKvent. Attached you can find the “Official” invitation to the HackVent. One of my very young Cyber Elves cut some parts of the card with his alpha scissors.

Have a great HACKvent,

– Santa

Image of the invitation card


Those alpha scissors are clearly a hint. So lets set the alpha channel fully opaque with some C# code:

using System;
using System.Drawing;

Console.WriteLine("Enter path to image: ");
var path = Console.ReadLine();

var image = new Bitmap(path);
for (int x = 0; x < image.Width; x++)
    for (int y = 0; y < image.Height; y++)
        Color clr = image.GetPixel(x, y);
        image.SetPixel(x, y, Color.FromArgb(byte.MaxValue, clr));

image.Save(path + "1.png");

Unsurprisingly, this made the hidden flag HV20{7vxFXB-ItHnqf-PuGNqZ} visible:

Image of the solution

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