Serial (150 pts)

Question:

Run and capture the flag!

Write-Up:

Analyze the file by Trid.

$ ./trid_Linux64 serial 

TrID/64 - File Identifier v2.20 - (C) 2003-15 By M.Pontello
Definitions found:  5988
Analyzing...

Collecting data from file: serial
 49.7% (.) ELF Executable and Linkable format (Linux) (4025/14)
 49.4% (.O) ELF Executable and Linkable format (generic) (4000/1)
  0.7% (.CEL) Lumena CEL bitmap (63/63)

So this is an ELF file. Analyze the file by IDAPro! Unfortunately, you can not get usefull information by reversed code! It seems the app used anti-disassembling techniques! So, lets debugging it. Use gdb for debugging the app. In this question you should use debugger instead of disassembler. After giving input, set a breakpoint and follow the instructions, there are many simple comparing instruction. The flag is EZ9dmq4c8g9G7bAV.