KalmarCTF 2023 - renaissance-flag-music - writeup

Posted on Mar 5, 2023

What we did

It was mostly google-fu or having sufficient previous background knowledge (e.g. someone who has studied music or has played guitar)

Detect that WeirdTable.png maps chords to letters
Detect that FlagMusic.png is some musical notation … renaissance music? … look up renaissance notation => find French lute tablature so it’s essentially a French lute tab empty=X, A=open, B=1st fret, C=2nd, … ok so… what is the tuning?
French lutes are tuned how?
- Find different info on lute tuning
  - Hint “10 course” takes us to a table https://www.lutesociety.org/pages/lute-tuning 10 course Renaissance lute in G
How you play 6 chord music on a 10 chord lute?
- Turns out it’s just the first 6, ez

Start mapping letters

Example:

   Cm  "L"
G  a=0
D  b=1
A  d=3
F  c=2
C  a=0
G
F
Eb
D
C

Spend time mapping letters (@taka mapped the letters)

LOOKMOMIAMAMUSICCOMPOSER

Add the flag format manually

kalmar{LOOKMOMIAMAMUSICCOMPOSER}

Just a few of the links we visited: