This year, I was happy to be part of the organization committee for the GreHack conference and I created a few challenges for the CTF. Thanks to all the participants and organizers, the event was once again awesome 🔥 💚

For this year, we really wanted to make custom beers for the event, but we don’t had a graphic designer for that and not also a brewery that was willing to make custom beers… But guess what? We found these two extraordinary people this year and managed to make some unique GreHack beers! How classy is that ? 😎

And how to make it more classy ? Of course we need to make challenges on this beer !!

Real thanks to Yuyu for the design of the beers and La Canute Lyonnaise who create beers ! 🍻

Hold My B33r 1

  • Name : Hold My B33r 1
  • Category : Steganography
  • Solves : 23
  • Points : 50
  • Authors : Nishacid, Yuyu

Have you seen it ?? We have wonderful customized beers ! These beer labels are so beautiful…

These challenges are designed to be easter eggs, they don’t need to be really difficult, and also, who really wants to do steganography ? ^^

The first challenge is to scan the barcode on the left of the label, with the flag simply inside.

  • Flag : GH{s0m3_b33r}

Hold My B33r 2

  • Name : Hold My B33r 2
  • Category : Steganography
  • Solves : 11
  • Points : 150
  • Authors : Nishacid, Yuyu

Have you really seen it ?? Are you sure of that ?? We have wonderful customized beers ! These beer are so delicious…

For the second challenge, it’s a bit more steganoguessing, but if you take a closer look at the beer’s ingredients, there’s something weird about it.

Take the first character and the first digit (case-sensitive), and decode it in base64 to obtain the flag.

Ingrédients : Raisins 0°, houblon, 7 Yuzu jaunes, Malts, zestes citron, miel, Infusions zestes, Mandarine, 3 Jasmins, 9 Céréales grenobloises
» echo 'R0h7YjMzcmIzM3J9Cg' | base64 -d

  • Flag : GH{b33rb33r}