My Challenges

I love to make creative and unique challenges that push the players to really think about and investigate potential vulnerabilities, instead of pulling a ready-made exploit from GitHub.

I usually divide my challenges into one of three categories:

  1. TOY challenges are all about analysing and exploiting vulnerabilities in toy cryptographic primitives I make myself. The players will attack these primitives directly. This will test a player’s cryptographic knowledge and their ability to cryptanalyse using the provided source code.

  2. IMP challenges are all about exploiting flaws in the implementation of secure cryptographic primitives. The players will attack the security of these primitives by abusing their flawed implementation. This will test a player’s knowledge on the limitations of the used primitives and their ability to exploit these limitations.

  3. PZL challenges are somewhat looser challenges that challenge the player’s math, logic, and problem solving skills.


In need of Crypto challenges for your CTF? Get in touch!



Overview of Published Challenges


n00bzCTF 2022


Challenge Category Framework Type Primitive Diff Solves
RSA-OOPS Crypto Remote Secure Armoury TOY RSA 4 ?
Hadis Paide Crypto Prime Crimes IMP Paillier 2 ?


HackPack CTF 2022


Challenge Category Framework Type Primitive Diff Solves
Repeating Offense Crypto Prime Crimes IMP RSA + Paillier 4 20
P(ai)^3 Crypto Painful Paillier TOY Paillier 6 15


UMassCTF 2022


Challenge Category Framework Type Primitive Diff Solves
FastCrypt Crypto Mind your Flanks IMP Sub-perm 7 24
MTRSASS Crypto Remote Secure Armoury TOY MSS + RSA 6 6
Tomb of Tutanflagun Crypto Mountain Cipher TOY Hill Cipher 8 3
HatMash Crypto Matrix Mania TOY Hash 4 1
Order of the Eight Apollonii Crypto Circles of Eight TOY Geometric SSS 5 1


K3RN3LCTF 2021


Challenge Category Framework Type Primitive Diff Solves
Twizzty Buzzinezz Crypto Honeycomb TOY XOR 1 116
1-800-758-6237 Crypto 16-byte Nightmares IMP AES-CTR 2 28
Non-Square Freedom 1 Crypto Prime Crimes TOY RSA 1 21
WannaSwirl (Co-Author) Rev WannaSwirl REV Malware 7 19*
Non-Square Freedom 2 Crypto Prime Crimes TOY RSA 4 11
Poly-Proof Crypto Zero-Effort-Proof TOY PCS 2 11
Poly Expo go BRRRRR Crypto Prime Crimes TOY RSA 3 9
Tick Tock Crypto Erratic Elliptics TOY Group Theory 6 6
3Dangerous Commute Misc Hyperspatial Engineering PZL Maze 5 5
Cozzmic Dizzcovery Crypto Honeycomb PZL XOR 4 3
HADIOR Crypto Spinning my Web TOY DSA 9 3*
lightningrod Rev Superweapons REV XOR 4 3
Beecryption Crypto Honeycomb TOY Affine 7 2
Game of Secrets Crypto Cellular Mania TOY Game of Life 8 2
Objection! Crypto Prime Crimes IMP DSA 6 2
Ain’t no Mountain High Enough Crypto Mountain Cipher TOY Hill Cipher 5 1
Mowhock Crypto Submit to Chaos TOY Logistic Map 8 0
Shrine of the Sweating Buddha Crypto Sweating Buddha TOY Paillier 8 0
Total Encryption Crypto Remote Secure Armoury IMP RSA 9 0
WannaSwirl Fixed (Co-Author) Rev WannaSwirl REV Malware 7 0


And more, just waiting to be published ~ !

Recent Posts

  • UMassCTF 2022 - HatMash

    Cryptography – 500 pts (1 solve) – Chall author: Polymero (me)

    What do you mean “We think you spend too much time with matrices.”? It’s just a hash function, jeez…

  • HackPack CTF 2022 - Repeating Offense

    Cryptography – 443 pts (20 solves) – Chall author: Polymero (me)

    One-time oracles using RSA or Paillier are not a great idea due to those slippery mathemagicians… I would like to see them slip their way through RSA AND Paillier! After all, you cannot rob two banks at the same time. … What?

  • HackPack CTF 2022 - P(ai)^3

    Cryptography – 469 pts (15 solves) – Chall author: Polymero (me)

    Pai-ai-ai… My Paillier scheme seems to be broken and I stored my favourite flag in it. Please help me get it back, will you? Who could have guessed this would ever happen? … Me… I- I wrote it… yeah.

  • K3RN3LCTF 2021 - Total Encryption

    Cryptography – 500 pts (0 solves) – Chall author: Polymero (me)

    “To store our most embarrassing secrets, we created a Remote Secure Armoury protected by layered RSA encryption with XOR blinding. Never again will my friends be able to mock me for my use of words!”

  • K3RN3LCTF 2021 - Tick Tock

    Cryptography – 496 pts (6 solves) – Chall author: Polymero (me)

    “I chopped up my flag and hid it behind this simple key exchange. Try dlogging your way in if you are brave enough!”

  • K3RN3LCTF 2021 - Shrine of the Sweating Buddha

    Cryptography – 500 pts (0 solves) – Chall author: Polymero (me)

    “Welcome to the Shrine of the Sweating Buddha. Share the burden of your worries, my child ~~~.”

    Hint: share some (7) of your worries and perhaps your fortune will guide you to the flag.

  • K3RN3LCTF 2021 - HADIOR

    Cryptography – 499 pts (3 solves) – Chall author: Polymero (me)

    “HADIOR will hold the DOOR.”

  • K3RN3LCTF 2021 - Game of Secrets

    Cryptography – 500 pts (2 solves) – Chall author: Polymero (me)

    “John wants to play a game, a game of secrets. Recover his secret or be encrypted.”

  • K3RN3LCTF 2021 - lightningrod

    Reverse Engineering – 499 pts (3 solves) – Chall author: Polymero (me)

    “Warning: Weather Control Device detected! ZAP ZAP [insert conscript_death.mp3 here]”

    “Note: there is a typo in the flag, sorry >m<.”

  • K3RN3LCTF 2021 - Poly-Proof

    Cryptography – 490 pts (11 solves) – Chall author: Polymero (me)

    They asked me to set up a zero-knowledge proof that runs in polynomial time. I don’t know what that means but I assume they want me to use polynomials, right?

  • K3RN3LCTF 2021 - Poly Expo go BRRRRR

    Cryptography – 494 pts (9 solves) – Chall author: Polymero (me)

    “I’m going to say this again: I did not have sexual relations with that polynomial, Miss Polinsky.”

  • K3RN3LCTF 2021 - Beecryption

    Cryptography – 500 pts (2 solves) – Chall author: Polymero (me)

    I was watching the bees and it seemed as if they were trying to tell me something… Have I finally gone crazy?!?

  • K3RN3LCTF 2021 - Twizzty Buzzinezz

    Cryptography – 100 pts (116 solves) – Chall author: Polymero (me)

    “Some bees convinced me to invest in their new cryptosystem. They zzzaid their new XOR keyzztream would revolutionizzze the crypto market. However, they quickly buzzed away so all I have is this weird flyer they dropped. Luckily it has some source code on the back.”
    “Have I just really been scammed by some bees??”

  • K3RN3LCTF 2021 - Objection!

    Cryptography – 500 pts (2 solves) – Chall author: Polymero (me)

    “Looks like Harry is hoarding his flags again… Maybe he will stop if we can convince him both Alice and Carlo dislike hoarding too. Alice and Carlo, being stereotypical CTF admins, are not responding to your complaints. Guess you will just have to answer for them… Luckily, I managed to secure you a channel to the domain controller of the CTF server.”

  • K3RN3LCTF 2021 - Non-Square Freedom (1 and 2)

    Cryptography – 465 pts (21 solves) and 490 pts (11 solves) – Chall author: Polymero (me)

    “What can I say, I just like squares.”

  • K3RN3LCTF 2021 - Cozzmic Dizzcovery

    Cryptography – 499 pts (3 solves) – Chall author: Polymero (me)

    “See that comb over there? It came from that meteorite I mentioned yesterday. Take a look at this, if I send bytes in, different bytes come out! Then there’s this button that seems to just produce random bytes… I’m absolutely stumped :S”

  • K3RN3LCTF 2021 - Ain't no Mountain High Enough

    Cryptography – 500 pts (1 solve) – Chall author: Polymero (me)

    “Hills are easy to climb, but mountains? Hoho, they sure are something else!”

  • K3RN3LCTF 2021 - 1-800-758-6237

    Cryptography – 437 pts (28 solves) – Chall author: Polymero (me)

    “I NEED A PLUMBER ASAP, MY FLAG IS LEAKING ALL OVER THE PLACE!!!”