Write up — Code On (500) — Crypto-Bio — Rice Tea Cat Panda CTF

Igo0r
2 min readJan 25, 2020

#RATF

The challenge give us a sequence of mRNA and a “Key”:

My houseplant and I were working on a biology assignment together. Yes, my houseplant. Don’t question it. Anyways, she ended up giving me a new cipher to use in my next project! So I’m giving it to my biology friends to see if they can solve it. They are, after all, studying DNA and mRNA right now.

AUGCAAGGUCUCUUGACCCAGUGGAUACUAAAUGCCUGGAAGGUAGCAUACUAG

Key: 6, 3, 4, 3, 1, 9, 8, 3, 3, 2, 7, 4, 1, 2, 4, 1

Table of amino acids:

So removing the first and the last codons AUG (Start) and UAG (Stop), we have:

CAA GGU CUC UUG ACC CAG UGG AUA CUA AAU GCC UGG AAG GUA GCA UAC

1.Glutamine,2.Glycine,3.Leucine,4.Leucine,5.Threonine,6.Glutamine,7.Tryptophan,8.Isoleucine,9.Leucine,10.Asparagine,11.Alanine,12.Tryptophan,13.Lysine,14.Valine,15.Alanine,16.Tyrosine

Each numbers of Key corresponds with each number of letter of name of amino acids respectively

Key: 6, 3, 4, 3, 1, 9, 8, 3, 3, 2, 7, 4, 1, 2, 4, 1

6º letter of Glutamine = m
3º letter of Glycine = y
4º letter of Leucine = c
3º letter of Leucine = u
1º letter of Threonine = t
9º letter of Glutamine = e
8º letter of Tryptophan = h
3º letter of Isoleucine = o
3º letter of Leucine = u
2º letter of Asparagine = s
7º letter of Alanine = e
4º letter of Tryptophan = p
1º letter of Lysine = l
2º letter of Valine = a
4º letter of Alanine = n
1º letter of Tyrosine = t
mycutehouseplant

Hint: “Make sure to encase the plaintext with rtcp{} Spaces are represented by a underscore, (_)”

Flag: rtcp{my_cute_houseplant}

Reference: Dario Floreano, Claudio Mattiussi, Bio-Inspired Artificial Intelligence Theories, Methods, and Technologies. 1. ed. Cambridge, Massachusetts: The Mit Press, 2008.

--

--