My CTF Challenges

This is some challenges I created for CTF competitions.

The difficulty is rated by me, and it is only consistent within a single competition. While I tried to keep it consistent by it does not really work 😞, so don't be surprised if you find a challenge with lower rating that is harder than a challenge with higher rating.

TSJ CTF 2022

Also published here for better math rendering.

Name	Category	Tags	Difficulty
Futago	Crypto, CSC 1	RSA	★
RNG++	Crypto	LCG	★★
babyRSA	Crypto	RSA, ECC	★★
Top Secret	Crypto	GF, dlog	★★☆
Cipher Switching Service	Crypto	RSA, ElGamal	★★☆
Signature	Crypto	ECDSA, LLL, AES-CTR	★★★
RNG+++	Crypto	LCG, LLL	★★★☆
Nim Notes	Web	Script Gadgets, CSRF, CRLF Injection, CSP	★★★☆
Genie 2	Web, Crypto	Path traversal, AES-CBC, Deserialization	★★★☆
Just a pyjail	Misc	Pyjail	★★★

HITCON CTF 2022

Name	Category	Tags	Difficulty
BabySSS	Crypto	SSS, CRT	★☆
Superprime	Crypto	Binary Search, Prune and Search	★★☆
Chimera	Crypto	ECM, LLL, ECDLP, HSSP	★★★★
LemMinX	Misc	LSP, XXE	★★★
Secure Paste	Web, Crypto	JSONP, Key Confusion, DOMPurify, CSP	★★★★

HITCON CTF 2023

Name	Category	Tags	Difficulty
Share	Crypto	SSS, CRT	★★
EZRSA	Crypto	ECC, Wiener, ECM	★★☆
Echo	Crypto	RSA, Index Calculus, LLL	★★★
Random Shuffling Algorithm	Crypto	Noisy CRT, Coppersmith	★★★☆
Collision	Crypto	Collision	★★★☆
Lisp.js	Misc	Node.js Jail	★★★
Login System	Web	TE.TE, JSON Injection, YAML	★★★
Canvas	Web	JS Jail, Worker, CSP	★★★☆
Harmony	Web	Electron	★★★★☆

HITCON CTF 2024

Name	Category	Tags	Difficulty
ZKPoF	Crypto	Python, Coppersmith	★★
BrokenShare	Crypto	SSS, LLL	★★★
Hyper512	Crypto	LFSR, FCA	★★★☆
ECLCG	Crypto	ECDSA, LCG, LLL	★★★★
MatProd	Crypto	Matrix, LLL	★★★★
Flag Reader	Misc	Tar	★☆
RClonE	Web	CSRF, RCE	★★
Truth of NPM	Web	Deno, LFI, RCE	★★★
Private Browsing+	Web	XSS, Response Splitting	★★★★

HITCON CTF 2025

Name	Category	Tags	Difficulty
wp-admin	Web	PHP, LFI, RCE	★★★★
Pedantic	Crypto	ZKP, LLL	★★★
BabyLWE	Crypto	LWE	★★★☆
MRSA	Crypto	RSA, LLL	★★★☆
Paranoid	Crypto	ZKP, k-list	★★★★

ImaginaryCTF 2023

Name	Category	Tags	Difficulty
Tan	Crypto	LLL	★★
Wasteful	Crypto	RSA, Coppersmith	★★
Sus	Crypto	RSA, Algebra	★★☆
Imaginary Casino	Crypto	CSIDH, RNG	★★☆
Login	Web	PHP	★☆
Sanitized	Web	DOMPurify, XHTML	★★★
Sanitized Revenge	Web	DOMPurify, XHTML	★★★
Typechecker	Reverse	TypeScript, Linear	★★
Get and set	Misc	Pyjail	★★

ImaginaryCTF 2024

Name	Category	Tags	Difficulty
lf3r	Crypto	LFSR	★★☆
coast	Crypto	Isogeny	★★☆
notitle	Crypto	Algebra, DLP, LLL	★★★
pacap	Crypto	Coppersmith	★★★
vokram	Reverse	Markov Algorithm	★★★
readme	Web	Path Normalization	★
readme2	Web	Bun, HTTP	★★
calc	Misc	Pyjail	★★★

ASIS CTF Finals 2024

Name	Category	Tags	Difficulty
LiveMD	Web	XSS	★★★☆

AlpacaHack Round 9

Name	Category	Tags	Difficulty
ffmac	Crypto	Linear, GB	★★★

ImaginaryCTF

Name	Category	Tags	Difficulty
Really Simple Algorithm	Crypto	RSA, Continued Fractions	★★
Minimal	Pwn	Stack pivoting, read(2) return value, SROP	★★

These two challenges are created before I became a board of ImaginaryCTF.

Round 26

Name	Category	Tags	Difficulty
Box	Crypto	Affine function	☆
pqqp	Crypto	RSA, Number Theory	★
First RSA	Crypto	RSA	★☆
No modulus	Crypto	RSA, LLL	★★★
Login Please	Web	JavaScript, Prototype	★
Read	Pwn	Shellcoding	★☆
Not a kernel pwn	Misc	Privilege Escalation	★☆
Free Shell	Misc	Bash	★★
Here's some Rev v2	Reverse	Pyc	☆
Here's some Rev v3	Reverse	LCG	★

Round 27

Name	Category	Tags	Difficulty
RSA-CBC	Crypto	RSA	☆
RSA-CBC v2	Crypto	RSA, Coppersmith	★☆
Mobius	Crypto	Rational Function, LLL	★★☆
Hello World as a Service	Misc	Java, Quirks	★☆
Baby Shell	Pwn	C++, std::string_view, UAF	★

Round 28

Name	Category	Tags	Difficulty
Substitution	Crypto	RSA, Search	★☆
Unchanged	Reverse	pthread, LCG	★☆
Filter Master	Web	PHP, filter	★★
Half FFT	Misc	FFT, LLL	★★☆

Round 29

Name	Category	Tags	Difficulty
Strong Prime	Crypto	DLP, CRT	★☆
Web3	Crypto	Ethereum, ECDLP	★★
Req Bin	Web	Python Format String, Flask	★☆
Generic Flag Checker	Reverse	Signal Handler	★☆
xkcd 835	Pwn	UAF	★★

Round 30

Name	Category	Tags	Difficulty
PowerRSA	Crypto	RSA	★
Easy DSA: LCG	Crypto	ECDSA, LCG, LLL	★★☆
Fake Flags	Web	Trolling	☆
Echo	Web	Request Smuggling	★☆

Round 31

Name	Category	Tags	Difficulty
KVIN	Web/Misc	JavaScript	★★

Round 32

Name	Category	Tags	Difficulty
Poly RSA	Crypto	RSA, GCD	★★
Old School	Web	Bash, CGI	★☆

Round 33

Name	Category	Tags	Difficulty
Vault	Web	XSS, Cache	★★☆

Round 34

Name	Category	Tags	Difficulty
Integrity	Crypto	CRT-RSA, Coppersmith	★☆

Round 35

Name	Category	Tags	Difficulty
Encrypted Command Executor	Crypto	ECB	★

Round 37

Name	Category	Tags	Difficulty
You can't reverse me	Misc/Reverse	Hook	★☆

Round 39

Name	Category	Tags	Difficulty
Safe Pickle	Misc	Pickle	★☆

Round 40

Name	Category	Tags	Difficulty
Leet Universe	Crypto	Number Theory	★★

Round 43

Name	Category	Tags	Difficulty
Three Pieces	Crypto	Number Theory	★☆

Round 44

Name	Category	Tags	Difficulty
Flag Server	Web	HTTP Cookie	★★☆
FLT-1337	Misc	Sage Trivia	☆

Round 48

Name	Category	Tags	Difficulty
readme3	Web	HTTP, Bun	★★

Round 49

Name	Category	Tags	Difficulty
MDLP	Crypto	DLP, LLL	★★
MDLP v2	Crypto	Coppersmith	★★☆

Round 54

Name	Category	Tags	Difficulty
MLFSR	Crypto	Stern's Attack, LLL	★★★

Round 55

Name	Category	Tags	Difficulty
MagicHash	Crypto	CRC, MD5, Collision	★★

AIS3 Pre-exam 2022

Name	Category	Tags	Difficulty
JeetQode	Misc	PPC, JQ	★☆
B64DLE	Misc	AES-CTR, Pickle, Python Format String	★★☆
SC	Crypto	Classic	☆
Fast Cipher	Crypto	Modular Arithmetic	☆
shamiko	Crypto	SHA1, DSA	★☆
Really Strange orAcle	Crypto	GCD, Binomial Theorem	★☆
pettan	Crypto	RSA, MT19937	★★☆
pekobot	Crypto	Invalid Curve Attack	★★★
Flag Checker	Reverse	ROP, Pickle, RSA-like	★★
Private Browsing	Web	SSRF, Redis, PHP, Deserialization	★★
UTF-8 Editor	Pwn	C++, std::vector, OOB, GOT overwrite	★★
SAAS	Pwn	C++, Copy Constructor, UAF	★★☆

AIS3 Pre-exam 2023

Name	Category	Tags	Difficulty
ECC	Crypto	ECC	★
Not Wiener	Crypto	RSA, Coppersmith	★★
Media Server	Misc	Python http, procfs	★★
Gitly	Web	0day	★
Password Generator	Pwn	Number Theory, ROP	★☆

AIS3 EOF 2023 - koh-jeopardy

Name	Category	Tags	Difficulty
Shamiko no fukushuu	Crypto	ECDSA, HMAC	★
onelinecrypto	Crypto	RSA, LSB	★
NotLFSR	Crypto	LFSR	★☆
magicRSA	Crypto	RSA	★☆
Neo RSA	Crypto	RSA, coppersmith	★★

AIS3 EOF 2024

Name	Category	Tags	Difficulty
Baby Side Channel Attack	Crypto	SCA, RSA	★
Baby ECDLP	Crypto	Linear, ECDLP	★☆
Baby XOR	Crypto	Linear, LLL	★★★
Internal	Web	Nginx, CRLF Injection	★

AIS3 EOF 2025

Name	Category	Tags	Difficulty
prsa	Crypto	RSA, Paillier	★★
zkdlp	Crypto	ZKP, MT19937	★★☆

Security BSides Ahmedabad CTF 2022

Name	Category	Tags	Difficulty
A complex number	Crypto	LLL	★★★

Footnotes

1. CSC refers to Cursed Shaman Challenges, just kind of a trolling/guessing category for this CTF. ↩

2. This challenge is made by both @splitline and me. ↩