Baby Crypt

DESCRIPTION : Give me the key and take what's yours.
AUTHOR : MinatoTW
NOTE : Retired Challenge
FILE : baby_crypt

Basic info

file command

This is a 64 bit elf binary

strings command

There is nothing like password or flag. :(

Run the binary

• It ask for the key.
• And print some string.
• Let analysis the binary in ghidra

Open the binary in ghidra

Just modify the program to understand well

• It ask for 4 byte and store in input.
• Initization a 26 byte, that are store in flag.
• It perform some operation like xor the flag's byte and input's byte.

Let's find the key

• We know that, the flag format is HTB{-------}
• The first three characters of input were xor with flag's byte
• To find the key, just xor the 'H','T' and 'B' with 0x3f, 0x64 and 0x35 respectively

Run the binary with key

The flag is HTB{x0r_1s_us3d_by_h4x0r!}