Find the message is a crypto challenge that was part of the MetaRed CTF 2022 (4th STAGE).

``````Sy@t{N_f0yq13e fubBg\$, n uNpx3E t!irf 3agrE}
``````

We were give no other information.

## First look

To solve this challenge, we need to find the encryption method used.

The website dcode.fr pointed us to the `Vigenere cipher`.

## Solution

Now we had to find the key.

Using the same website www.dcode.fr/vigenere-cipher, with the `Knowing a plaintext word` option, and word `FLAG` as a first guess, got us these results:

``````YLAJBV	Un@t{E_e0ds13t flaGi\$, c uEoc3G i!iie 3figE}
NNTHC	Fl@a{G_d0ld13l ysoOn\$, g sAce3X r!vem 3teeR}
ENNNKM	Ol@g{A_v0mm13r shrPc\$, a hAfl3A g!vev 3oceR}
YLDGFU	Un@q{H_a0es13t cowHi\$, c rHkd3G i!fla 3gigB}
AJBV	Sp@s{S_f0pp13j flaGg\$, e tSpo3D y!iie 3fgiD}
TTCNNS	Zf@r{A_s0gx13l dhoJn\$, u sAcf3L a!ges 3inyC}
NNTHNQ	Fl@a{G_s0id13r mnoLt\$, a bGch3R g!pks 3kteL}
...
``````

Turns out that `FLAG` is not in the message. But we weren’t that far off. `NNTHNQ` seems to be very close.

The first and second letter of our plaintext should be `F` and `L` (from `FLAG{...`) and the first two letters of `NNTHNQ` are `N` which gave us `Fl@a{G_s0id13r mn...`.

So we tried the `Knowing the Key/Password` option with `N`:

``````Fl@g{A_s0ld13r shoOt\$, a hAck3R g!ves 3nteR}
``````

That’s it!

## Flag

The flag is “Fl@g{A_s0ld13r shoOt\$, a hAck3R g!ves 3nteR}”.