Welcome to tkbctf5!

tkbctf5 is a Jeopardy-style CTF organized by TPC, CTF team from University of Tsukuba. It features a wide range of challenges spanning beginner to advanced levels across the following categories: Web, Crypto, Reversing, Pwn, and Misc.

tkbctf was a CTF organized by CTF players at University of Tsukuba. With a renewed organizing team, we are excited to bring it back after 10 years. For archives of past events, please visit tkbctf.info.

All announcements will be made on the tkbctf official Discord server. Please make sure to join.

How to Participate

1. Sign up as a user of AlpacaHack by clicking the 'Sign Up' button at the top right.
2. After signing up, click the 'Create Team' button on this page to create a team.
3. If you want to join an existing team, get an invite link from a team member. The invite link can be found on the 'team' tab page.

Competition rules

• This is a team competition.
• The challenges will be assigned points based on dynamic scoring.
• There is no limit to the number of people in one team. Of course you can participate alone though.
• The flag format is tkbctf{...}, unless otherwise specified.
• Players need to submit a flag to the score server in order to get points.
• A team that gets more score, ranks higher. If some teams get the same score, a team that made the last submission of a valid flag earlier, ranks higher among them.
• If there arise situations which are not covered by these rules, the organizers may make decisions on them as needed. The decisions made are absolute.

Important Notes

• While we will also notify you of updates on this web service, the Discord server is our primary communication channel.
• If you encounter any issues, you can ask questions or report them in the #ticket channel in Discord. Please note that hints for the challenges will not be provided.
• If you take the following actions, you will be disqualified.
  • To attack or disturb other teams.
  • To attack servers unrelated to challenges.
  • To share flags, solutions, or hints with anyone outside your team.
  • To try insane amount of brute-force attacks to challenges servers.
  • To share account. (i.e. Each participant MUST use their own account)
• 3/13 Update
  • Unless otherwise specified, all instances are hosted on e2-highcpu-16 machines in region asia-northeast1-b. The source image is debian-12-bookworm-v20260310.
  • The intended difficulty for each challenge will not be disclosed. The challenge order on the challenge page is not related to difficulty.
  • All challenges will be released at the start of the competition. However, until 18 hours after the start, new challenges may be added to address unintended solutions.