Knight's Droid CTF Complete Writeup KnightCTF 2025

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Knightctf2k25_knight's_Droid_writeup....


Category :- Reverse Engineering


Solutions :-


Step 1 :- 


Download the task file [knights_droid.zip].


Step 2 :-


Decompile the [.apk] using an online decompiler. Alternatively, you can use another tool.

 

knightdroid - Decompile the [.apk] using an online decompiler


After decompiling, navigate to knights_droid > sources.

 

Step 3 :-

 

examine the SecretKeyVerifier function




Look in com > knightctf.knights_droid and examine the SecretKeyVerifier function.

 

 

Step 4 :-


We can see an encrypted string

 


We can see an encrypted string:

GYPB{ykjcnwp5_GJECDP_u0q_c0p_uKqN_Gj1cd7_zN01z}, which appears to use a Caesar cipher encryption. I decrypted it using Cryptii. By shifting the encrypted string [-4], I decrypted it successfully.

 

we decrypted it successfully and find the flag -Dp1h3r0x

 



Flag :-

KCTF{_congrat5_KNIGHT_y0u_g0t_yOuR_Kn1gh7_dR01d_}



Thank You For Reading This Writeup




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