In this challenge we are given a txt file with this description: “We were following a suspect in hot pursuit when he suddenly disappeared. We were left standing in front of a mysterious lab. We didn’t find much, except for a small sheet of paper with this message printed on it. Can you help us decipher it?”

Pretty fast we can see the first part of the flag becomes GTTAAATTCGGT

If we do a quick search of “GTT AAA GTT TTC GGT” and go to images we find a bunch of results talking about DNA

After that we searched for “Dna crypt algorithms” and we find the first article

If we open the table and compare these with the first letters we got we see that they indeed match up

Decoding each character with the table gives us the flag “CYCTF{S0LV1NG_PR08L3M5_1S_1N_Y0UR_DNA}”