adding umd ctf 2023 writeup

Author: dreeSec

content/about.md

@@ -8,5 +8,6 @@ author = "Hugo Authors"
 
 Hello! My name's Audrey. Currently a student at the University of Michigan where I study Computer Science.
 
-I am one of the officers for [WolvSec](https://wolvsec.org/), the cybersecurity club at UofM. I paricipate in CTF competitions with them as well. Currently focusing on `Forensics` and `OSINT` challenges, while advancing my skills in other categories. You can find my writeups for challenges in my [blog](https://dree.blog/posts). 
+I am the president of [WolvSec](https://wolvsec.org/), the cybersecurity club at UofM. I paricipate in CTF competitions with them as well. Currently focusing on `Forensics` and `OSINT` challenges, while advancing my skills in other categories. You can find my writeups for challenges in my [blog](https://dree.blog/posts). 
 
+Expect a website redesign soon :)

content/posts/UMD-CTF-2023/Mirror_Unkown.png

@@ -0,0 +1,39 @@
+%Build script to beep-boop (UMDCTF2023, author: Assgent)
+
+%{
+A flag was encoded into a sound file using the script below. 
+Analyze the script and reverse-engineer the flag!
+%}
+
+close
+clear all
+
+flag = fileread("flag.txt");
+
+Fs = 8192;
+sound = string_to_sound(flag, Fs, 1, 0.5);
+
+sound_normalized = sound / (max(abs(sound)));
+audiowrite("sound.wav", sound_normalized, Fs);
+
+function freq = get_frequency_1(char)
+    freq = char * 13;
+end
+
+function freq = get_frequency_2(char)
+    freq = (char - 50) * 11;
+end
+
+
+% Fs is the samples/sec.
+% T is the duration of each key. (in seconds)
+% Tpause is the pause between keys. (in seconds)
+function x = string_to_sound(keys,Fs,T,Tpause)
+    t = (0:fix(T*Fs)).'/Fs ;
+    zp = zeros(fix(Tpause*Fs/2),1) ;
+    x = [];
+    for r = 1:length(keys(:))
+        char = keys(r);
+        x = [x ; zp ; cos(2*pi*get_frequency_1(char)*t) + cos(2*pi*get_frequency_2(char)*t) ; zp];
+    end
+end