PicoCTF 2017 – computeAES #infosec #appsec #crypto #ctf

Another day, another challenge.

Today’s blog post will explore solving the “computeAES” challenge in PicoCTF.

Let’s get started.

Clicking on the challenge we see the following:

PicoCTF_computeAES_1

Clicking on the clue link we see the following:

PicoCTF_computeAES_2

Going back to the challenge and clicking the hints we see:

PicoCTF_computeAES_3

Let’s use the hint of using online tools to solve this challenge.

Doing a Google search for “convert base64 to hex” we get the following link.

Going to this link we put in our base64 input to get the hex equivalent.

Doing this for the key and the input we get the following:

Key = 4f9b95cd8b6e04dbfabf08e886c955e3

Input = b75874a9b70e851405e44e3a6ec34b8a67db708e9e82b28fe0b1ed291de54f851d5a386cb0cf11412053ed2ffcadc472

Doing another Google search for “AES calc hex” we get the following link.

Entering the hex value of the key and input we get the following:

PicoCTF_computeAES_4

We found the flag! Copying the flag and removing the extra space we’ve acquired 50 points!

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