Mark Clowes (38M 🇬🇧)

Index - 2013 Xmas Cipher Challenge Part 2 Solution

Plenty of clues for this one. Big hint it's simple morse code. The file:

It's a safe presumption the red and green notes represent dots and dashes.

rrgr grg rg g ggrg rg gr rrg rg rrg ggr 
grg ggrg grg grrg g grg rrg grrg rggg 
rrgr grg gggr ggrg grg ggggr rgr gg rg 
rrgr rggg rrg gggg grrg rgr g ggggr ggg 
g rggg rrgg rrgg g rrgg rggg g ggrg grg

If we interpret the red as dash this morse decodes to:

QRNEFNAGNGURFRPERGPBQRVFR4KINQBGHPKE4SEBZZEZBEFR

We were warned that the message was both encoded and encrypted. I merrily went off down a rabbit hole at this point trying all sorts of different approaches (including looking in the PNG file metadata and raw hex for a key), but it turned out to be but the simplest ROT13:

DEARSANTATHESECRETCODEISE4XVADOTUCXR4FROMMRMORSE

And the solution is revealed.