Twelve Days of Hackmas


Welcome to the first Thornhill Secondary School Christmas Capture The Flag Hackathon!

Keys are hidden in sneaky riddles, puzzles, scavenger hunts etc. for you to solve and find! Solve the key, and unlock presents :D

One new present will be released each day, for twelve days leading up to Christmas.


Submit keys to the judge for each problem to gain points.

Keys consists of strings that follow this format: key{...}

... may be any non-whitespace alphanumeric characters including dashes and/or underscores. Keys may be encoded in different formats, once the key is decoded however, it will follow the aforementioned format.

Keys will either be very obvious and encased like this: "key{example}", or you will need to put the key in that format.

Submit the key{} to the judge in text or output it in any language.


There will be 12 problems in total, with 1 bonus problem!

One new problem will be added to the contest every day, for... you guessed it, 12 days!

Open a present (solve a problem) by submitting the correct key.

Each person may get 2 hints for presents they are stuck on (except for p0, which is completely trivial). Ask for hints through the computer club Discord server.

Point Bonuses

Every present solved first-try, will reward an additional 10 points. A time bonus is also applied, where one additional point is granted for every 6 hours from the deadline that the AC submission is made.

Clarification requests for the contest must be routed through the clarification system provided on TSSOJ. Note that, in particular, clarification requests must come in the form of yes/no questions.

Any suspicious behaviour will result in being forcibly ranked at the bottom of the scoreboard. As with all contests, sharing answers during the contest is not permitted. Especially with this contest, we kindly ask you to not to share your answers with anyone during the 12 day period.

The contest consists of 12 challenges. It is highly recommended to read all of the available problems. They do not have to be done in order, however, some problems may, or may not require you to solve other problems. You will have the entire length of the contest to complete the questions. After the contest window begins, you may begin at any time, leave during the contest and/or return without incurring any penalties.

After joining the contest, you proceed to the Problems tab to begin. You can also go to Users if you wish to see the rankings.


Problem Points AC Rate Users
Hackathon Present 0 1 9.8% 4
Hackathon Present 1 1 50.0% 26
Hackathon Present 2 1 14.6% 21
Hackathon Present 3 1 18.6% 21
Hackathon Present 4 1 34.5% 19
Hackathon Present 5 1 58.3% 19
Hackathon Present 6 1 24.6% 15
Hackathon Present 7 1 59.1% 12
Hackathon Present 8 1 100.0% 12
Hackathon Present 9 1 100.0% 10
Hackathon Present 10 1 78.6% 10
Hackathon Present 11 1 100.0% 9
Hackathon Present 12 12 72.7% 8


  • 1
    Eric_Zhang  commented on Dec. 13, 2020, 8:52 p.m.

    Imagine getting first try AC

  • 0
    HiroSato  commented on Dec. 13, 2020, 12:28 p.m.

    For present 0, How could we even reverse hash function? Seriously?

  • 0
    EgorGor  commented on Dec. 13, 2020, 11:30 a.m.


  • 3
    Li_Zhang  commented on Dec. 13, 2020, 10:30 a.m.


  • 1
    Henry_Zhang  commented on Dec. 13, 2020, 10:23 a.m.

    Anime Betrayal: present 0 is impossible, if you attempt it you die

  • 5
    Encodeous  commented on Dec. 13, 2020, 12:22 a.m.

    Good luck everyone!