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ESPILON-CTF-2026-Writeups/Hardware/Serial_Experimental_00/solve/solve.md
Eun0us 6a0877384d [+] Writeups v2 — sync solves, real points, scoreboard stats, cleanup 
- Remove undeployed challenges: Phantom_Byte, Cr4cK_w1f1, Lain_Br34kC0r3 V1,
  Lain_VS_Knights, Lets_All_Love_UART, AETHER_NET, Last_Train_451, Web3/
- Sync 24 solve/ files from main CTF-Espilon repo
- Update all READMEs with real CTFd final scores at freeze
- Add git-header.png banner
- Rewrite README: scoreboard top 10, edition stats (1410 users, 264 boards,
  1344 solves), correct freeze date March 26 2026
2026-03-27 21:27:45 +01:00

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Serial Experimental 00 -- Solution

Overview

The challenge provides a split UART interface:

  • TX (read): 1111
  • RX (write): 2222

Goal: recover token and run unlock <token>.

Steps

  1. Open both channels:
nc <host> 1111
nc <host> 2222
  1. Query diagnostics from RX:
diag.uart
diag.eeprom
diag.order
  1. Recover fragments:
  • frag_a_hex=4c41494e -> LAIN
  • frag_b_xor_hex=4056415a525f with xor_key=0x13 -> SERIAL
  • frag_c_hex=3030 -> 00
  1. Build token:

LAIN-SERIAL-00

  1. Unlock:
unlock LAIN-SERIAL-00
  1. Flag is returned on TX.