This is the UTCTF 2021 write up


Small P Problem

I just write two interesting challenge that meaningful to me.

  1. The question require the share secret.
  2. The first steps we would need the secret key of A.
  3. We could use python to brute force the secret key of A.
  4. This is the small problem python that brute force and solve the challenge.
  5. The formula: A=(g**a)%p where a is the secret key. Since it is hard to solve a with mathematic solution, we use brute force method.
  6. Then, we use formula sharesecret=((B**a)%p)
  7. The flag is utflag{53919}.

Peeb Poob

This one is kinda fun.

  1. We open with Ghidra.
  2. Let look at encode();
  3. Let write the exact code in C programming. Source is here.
  4. Let reverse write the process in C programming. Look at the reverse process. It is reverse process.Source is here.
  5. We run it and get the flag! Have fun with this challenge
  6. <
  7. The flag is utflag{b33p_b00p_p33b_p00b}.

Hope you guys enjoy this write up. Thanks to UTCTF for held this challenge.