Chaos

VishwaCTF{CrYpt0_cRyPT0_1g_It_1s_sOm3_7hiNg_t0_D0}

This simple cryptography challenge, we are given a encrypted text file and a python script which was used to encrypt the text file. It was using xor for the encryption. the encrypt function is as follows:

def xor_encrypt(msg):
    transformed = bytearray(msg)
    for i in range(len(transformed)):
        transformed[i] ^= (i % 256)  
    return base64.b85encode(transformed).decode() 

and yes it is very simple to create xor_decrypt function for this. infact you can use the same function to decrypt the message just need to modify input-output encodings.

def xor_decrypt(enc_msg):
    transformed = bytearray(base64.b85decode(enc_msg))
    for i in range(len(transformed)):
        transformed[i] ^= (i % 256)  
    return transformed

After description of text file, we got buch of english lines, 3 fake flags (i hate that) and the real flag.

Perhaps the flag is encoded in Base64? Or maybe hex?Or maybe the real flag is just one character different from all these fakes?VishwaCTF{Fl4g_Or_N0t_Th4t_1s_Th3_QuesT10n}Maybe the flag is hidden elsewhere...VishwaCTF{T00_M4ny_F4k3_Fl4Gs_G00d_Luck}Or inside a comment in the source code?This is not the flag, keep looking!Or maybe there's a script generating multiple fake flags dynamically?VishwaCTF{CrYpt0_cRyPT0_1g_It_1s_sOm3_7hiNg_t0_D0}Maybe it's inside another challenge, cross-referencing flags?Or is it?But wait... isn't this too obvious?What if it's a hash of the real flag?VishwaCTF{NoT_ThE_ReaL_fLaG_K33P_tRy1Ng}Or hidden in an image using steganography?Happy hunting!VishwaCTF{Y0u_WiLl_N3v3r_F1nd_1t}Or maybe the real flag is hidden inside a hidden file?Find_the_real_flag_somewhere_in_this_messOh, did you think that was real? Keep digging!