hidden word is a crypto challenge that was part of the MetaRed CTF 2022 (5th STAGE). We were given the string:

ACTCATGAG CCCOTTGATAACAATCTGCGCGTTG AGTATTACAUGCGACTATTOAAT ATAAAT ACCCATGAA TGGOAGACTGGAT ATTTCA TGCOATGCCTCTCATTTGTGCGACTGAGGAC ACTCATGAG TTCTTGGCGGGG ATATCG TGGGCACGC AACGAGACTTGGGAAGAAAAC CGCUTCCTCTATCGCA GCCAACGAC UAAGCGTGCGATTAATGAA CATGCATCC TGTGCGUTCCGAGGAT GCC TGCOATGATGOACCATCOAAC ATCAAT ACCCATGAG TGGOCGACTCGAC

and the following hint:

the format the flag is: flag{WORDFIND}

Solution

We took the same approach as the last MetaRed CTF (Find the message) to solve this challenge.

First we asked dcode.fr to identify the cipher. It identified it as a Codons (Genetic Code) cipher.

Using the Automatic Detection option, we got the following result:

Method Decoded text
RNA→A.A₁ ACTCATE POTTGATNAATCTACGTTG AGTATTTCDTATTOAAT ATKT TCATE TGGORCTGT ATTTCA TGCOATATCTCATTTGTAACTED ACTCATE TTCTTGGG ATATCG TGHGC NEACTTGKKAC RUTCCTCTATRA AND *ATAATTAATE CATATCC TGTAUTPRAT A TGCOATGATGOTATCON ATQT TCATE TGGORCTRC
DNA→A.A₁ THE POLITICAL SITUATION IN THE WORLD IS CO(M/Start)PLICATED THE FLAG IS WAR NETWEEN RUSSIA AND UKRAINE HAS CAUSED A CO(M/Start)(M/Start)OTION IN THE WORLD
A.A₃→A.A₁ ACTCATGAG CCCOTTGATAACAATCTGCGCGTTG AGTATTACAUGCGACTATTOAAT ATAAAT ACCCATGAA TGGOAGACTGGAT ATTTCA TGCOATGCCTCTCATTTGTGCGACTGAGGAC ACTCATGAG TTCTTGGCGGGG ATATCG TGGGCACGC AACGAGACTTGGGAAGAAAAC CGCUTCCTCTATCGCA GCCAACGAC UAAGCGTGCGATTAATGAA CATGCATCC TGTGCGUTCCGAGGAT GCC TGCOATGATGOACCATCOAAC ATCAAT ACCCATGAG TGGOCGACTCGAC
… …

The DNA→A.A₁ method gave us a readable text that said:

… THE FLAG IS WAR …

Flag

The flag is “flag{WAR}”.