TISC @ DEF CON Singapore 2026 finals

Just took part in TISC @ DEF CON Singapore finals today. Super fun.

The online qualifier ran a month ago over the weekend of 27 to 29 March. I was lucky enough to place in the top 50 and qualify for the on-site finals at the inaugural DEF CON Singapore. As a bonus, I also got a free DEF CON SG ticket out of it. Thanks CSIT. :)

The finals

50 of us, seated on the spot, allocated 6 hours from 10am to 4pm to solve 5 challenges.

I spoke to a few of the organizers and they put in a ton of effort to make sure the challenges are not easily solved by LLMs, especially Claude Opus or Mythos. The challenges spanned a very wide range of areas, and the fact that this was held in a physical location rather than online let the organizers do things that would otherwise be impossible:

• An ESP32 hardware trinket running a customized mesh chat protocol over BLE. Each participant was handed one to reverse engineer, with the goal of gaining unauthorized access into an administrative system broadcasting over the protocol.

  

• A reverse engineering challenge on a physical Windows kiosk. Only 7 minutes per attempt, and we couldn't bring our own laptops or devices to the machine. I eventually solved it after a few tries, having to pick up Windows and the relevant tools for the first time.

Solved 3.5 out of 5 in the end. Did okay. I'm probably one of the oldest contestants in the finals; most are in their 20s/early 30s.

Claude Code now blocks Opus for exploits

Interesting moment during the competition: Claude Code started refusing my Opus requests for exploit work. I don't recall seeing this in the past, definitely something new:

⎿  API Error: Claude Code is unable to respond to this request, which appears
   to violate our Usage Policy (https://www.anthropic.com/legal/aup). Please
   double press esc to edit your last message or start a new session for
   Claude Code to assist with a different task. If you are seeing this refusal
   repeatedly, try running /model claude-sonnet-4-20250514 to switch models.

I later learned that some participants who work in the cybersecurity industry have access to unblocked Claude Opus.

DEF CON Singapore

It's now day 2 of the inaugural 3-day DEF CON Singapore. Glad to see CSIT, HTX, and the Singapore government overall putting more emphasis on the cybersecurity industry.

I was initially skeptical about the world's largest hacking conference being co-organized with a government, but the vibe turned out to be really good. Smaller scale than Vegas, sure, but the feel isn't far off. Many villages, parallel talks and demos. Many eager participants. Jeff Moss, the founder of DEF CON, agreed. Also good to know that he's now a Singapore resident.