This is solutions of a problem "Problem: Crypto#1 “-.-”" from TAMUctf 19

Files

Attachment flag.txt

Problem statement

Our coworker Bob loves a good classical cipher. Unfortunately, he also loves to send everything encrypted with these ciphers. Can you go ahead and decrypt this for me?

Problem solution

The attached file "Attachment flag.txt" looks like a sequence of "dah", "di", "dit", "-", " ":

dah-dah-dah-dah-dah dah-di-di-dah di-di-di-di-dit dah-dah-di-di-dit dah-dah-di-di-dit dah-dah-dah-dah-dah di-di-dah-dah-dah di-dah dah-di-di-di-dit dah-di-dah-dit di-di-di-di-dit dah-dah-dah-di-dit dah-dah-di-di-ditdi-di-di-di-dah di-di-di-di-dah dah-dah-di-di-dit di-di-di-di-dit di-dah-dah-dah-dah di-di-di-dah-dah dah-dah-dah-di-dit dah-di-di-di-dit di-di-di-di-dit di-di-di-dah-dah dah-dah-dah-di-dit dah-dah-di-di-dit di-dah-dah-dah-dah dah-di-di-di-dit dit dah-di-di-di-dit dah-di-dit di-di-di-di-dah dah-di-dit di-di-di-...

When we try to google this sequence "dag-di-dit" we found that simbols is used for Morse code encryption, for example "A" is "di-dah", "B" is "dah-di-di-dit" etc.

A piece of theory. Usually the Morse code is consist of "dots" = "." (for now called "dit") and "dash" line = "-" (for now called "dah").

In our case "di" is ".", "dah" is "-", "dit" is "di" before space. Let's encode the attached file using this Morse code. The full decode message is:

0X57702A6C5874475138653871696D4D59552A737646486B6A49742A5251264A705A766A6D2125254B446B667023594939666B346455346C423372546F5430505A516D4351454B5942345A4D762A21466B386C25626A716C504D6649476D612525467A4720676967656D7B433169634B5F636C31434B2D7930755F683476335F6D3449317D20757634767A4B5A7434796F6D694453684C6D38514546695574774A4049754F596658263875404769213125547176305663527A56216A217675757038426A644949714535772324255634555A4F595A327A37543235743726784C40574F373431305149

Due to the message starts from "0X" it might be Hexadecimal representation of the data. Using any decoder (for example https://gchq.github.io/CyberChef/) to decoder message text after "0X" we will get the next full message:

Wp*lXtGQ8e8qimMYU*svFHkjIt*RQ&JpZvjm!%%KDkfp#YI9fk4dU4lB3rToT0PZQmCQEKYB4ZMv*!Fk8l%bjqlPMfIGma%%FzGgigem{C1icK_cl1CK-y0u_h4v3_m4I1} uv4vzKZt4yomiDShLm8QEFiUtwJ@IuOYfX&8u@Gi!1%Tqv0VcRzV!j!vuup8BjdIIqE5w#$%V4UZOYZ2z7T25t7&xL@WO7410QI

So, the flag is here:

gigem{C1icK_cl1CK-y0u_h4v3_m4I1}

Original writeup (https://github.com/c00c00r00c00/writeups/blob/master/TAMUctf/crypto1/Crypto-1.md).