Crypto CTF challenges

4,483 Crypto CTF challenges from 404 CTFs (2011–2026), 708 with writeups.

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Challenges

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Challenge	CTF	Weight	Has
The_Deterministic_Fog #lcg-lattice-recovery	KubSTU 2026	24.83	files wu 1
pwgen #lcg #z3	TAMUctf 2021	–	files wu 1
lcvc #lcg	HSCTF 2022	–	files wu 1
signature-sheep-scheming-signature-schemes #lattice-signature #mask-recovery	DiceCTF 2021	24.82	files wu 1
oneline6ryp7o #lattice #modular-arithmetic #mersenne-modulus	SekaiCTF 2026	79.25	files wu 1
Duality #lattice #lll (lll-lattice-reduction)	TeamItaly 2023	24.88	files wu 1
Spooky_Safebox #lattice	Hack.lu 2023	94.73	files wu 1
the_swirl #lattice	hxp 2022	–	files wu 1
Substitution_Cipher_II #lagrange-interpolation	DownUnderCTF 2021	–	files wu 1
Cryptoclock #known-plaintext-xor	NahamCon 2025	53.77	files wu 1
Scrambled_Pizzeria #known-plaintext #keystream-recovery	TeamItaly 2023	24.88	files wu 1
Baby_Sharingan #known-plaintext	H7CTF 2025	22.56	files wu 1
1_10 #knapsack #merkle-hellman #lll (lll-lattice-reduction)	1337UP 2023	24.23	files wu 1
my_array_generator #keystream-recovery	DownUnderCTF 2024	68.04	files src wu 1
Poem #keyboard-shift-cipher	BYUCTF 2023	–	files wu 1
I_got_my_drivers_license_last_week #keyboard-shift-cipher	MetaRed 2021	–	files wu 1
Cryptografie #java-reflection #filesystempreferences-encoding	plfanzen 2026	25.00	files wu 1
spring #java-random	HSCTF 2023	–	files wu 1
Last_Flight #isogeny #supersingular-elliptic-curve	SECCON 2025 Quals	–	files wu 1
Pwn_Chall #isogeny #sqisign	TeamItaly 2023	24.88	files wu 1
not_csidh #isogeny	hxp 2022	–	files wu 1
kipferl #invalid-curve	hxp 2021	99.41	files wu 1
What_the_HECC_2 #hyperelliptic-curve #divisor-arithmetic	TRX 2026	–	files wu 1
RepeatingOffense #homomorphic	HackPack 2022	35.11	files wu 1
hill-easy #hill-cipher	LA 2023	–	files wu 1
Aint_No_Mountain_High_Enough #hill-cipher	K3RN3LCTF 2021	24.37	files wu 1
Magical_Oracle #hidden-number-problem	L3akCTF 2025	24.43	files wu 1
3_spies #hastad-broadcast #rsa #crt	Pearl 2024	23.95	files wu 1
RSAEncrypter #hastad-broadcast	BCACTF 2024	–	files wu 1
minithorpe #hash-reversal	hxp 2020	94.00	files wu 1
I_Like_McDonalds #hash-length-extension-attack #mac-forgery	BackdoorCTF 2024	–	files wu 1
TagSeries3 #hash-length-extension #sha1	WolvCTF 2024	35.25	files wu 1
Merkle-Derkle #hash-length-extension #sha1	PatriotCTF 2022	24.52	files wu 1
JAM #hash-length-extension #md5	TFC 2021	–	files wu 1
ForgeMe_2 #hash-length-extension	NahamCon 2023	34.82	files wu 1
Diffecientwo #hash-collision #z3 #murmurhash3	SekaiCTF 2023	24.86	files wu 1
mac-master #hash-collision #md5	TJCTF 2022	–	files wu 1
Diffecient #hash-collision #bloom-filter #murmurhash3	SekaiCTF 2022	24.86	files wu 1
octothorpe #hash-collision	hxp 2020	94.00	files wu 1
Aes-1 #hardcoded-password	n00bzCTF 2023	15.12	files wu 1