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
almost_perfect #vigenere #word-frequency-analysis #key-reuse	OMH 2021	–	files wu 1
Rick_Roll #vigenere #rot13	Pearl 2024	23.95	files wu 1
cupcakes #vigenere	HSCTF 2023	–	files wu 1
ShowYourDedication #vigenere	TrollCAT 2021	21.87	files wu 1
Easy1 #vigenere	picoCTF 2019	–	files wu 1
cheap_logs #use-after-free (uaf)	DownUnderCTF 2025	91.66	files wu 1
OTP3 #two-time-pad #key-reuse	BlueHens 2021	22.62	files wu 1
psych #timing-attack #fujisaki-okamoto #kem	DiceCTF 2022	24.82	files wu 1
RSA_Intro #textbook-rsa	NahamCon 2023	34.82	files wu 1
Fly #swipe-typing #keyboard-trace	PatriotCTF 2022	24.52	files wu 1
knapsack #superincreasing-knapsack #greedy #merkle-hellman	PBjar 2021	23.18	files wu 1
FromTheFUTURE #substitution-cipher #futurama-alphabet	VishwaCTF 2021	–	files wu 1
Invisible_Cipher #substitution-cipher #frequency-analysis	WORMCON 2021	–	files wu 1
Subway #substitution-cipher	UMDCTF 2021	–	files wu 1
Knapsack_vs_Backpack #subset-sum #greedy-knapsack #merkle-hellman #superincreasing-sequence	Cryptoverse 2023	24.52	files wu 1
crackme.sol #solidity-smart-contract-reversing #xor	0x41414141 2021	–	files wu 1
HackChain #solidity #delegatecall #function-pointer-jump	RCTF 2021	–	files wu 1
Doe_a_deer #solfa-cipher #music-cipher	DeconstruCT.F 2021	19.69	files wu 1
choreography #slide-attack #feistel	PlaidCTF 2022	93.67	files wu 1
SecureEncodingBase64 #simulated-annealing	ImaginaryCTF 2022	24.65	files wu 1
baba_is_flag #signature-forgery	TSG 2021	–	files wu 1
whatthehecc #signature-forgery	Hack.lu 2021	94.48	files wu 1
S2DH #sidh #castryck-decru #torsion-point	RCTF 2022	–	files wu 1
smoll #shared-prime-factor	ImaginaryCTF 2022	24.65	files wu 1
treasure #shamir-secret-sharing	DownUnderCTF 2021	–	files wu 1
Shamirs_Stingy_Sharing #secret-sharing #polynomial-leak #prng-seed	RaRCTF 2021	24.53	files wu 1
insufficient #secret-sharing #cvp #lattice	SECCON 2022 Quals	97.90	files wu 1
Time_Skip #scytale-cipher	BCACTF 2024	–	files wu 1
snore #schnorr #nonce-reuse #lattice	RaRCTF 2021	24.53	files wu 1
A_Fine_Product #safe-prime-factorization	L3akCTF 2026	34.47	files wu 1
Fractional_Flag #rsa-variant #wiener-lattice-attack #small-private-exponent	Cryptoverse 2023	24.52	files wu 1
FusEd #rsa-signature-forgery #bit-manipulation	CCCamp 2023	25.00	files wu 1
babysign #rsa-signature-forgery	m0leCon 2021 Quals	24.55	files wu 1
Encryptor_Shop #rsa-shared-prime	BCACTF 2024	–	files wu 1
grammar_nazi #rsa-polynomial-root-recovery	MaltaCTF 2025 Quals	24.95	files wu 1
The_oracles_apprentice #rsa-malleability	HeroCTF 2022	51.22	files wu 1
Crypto_101 #rsa-factordb	MetaRed 2021	–	files wu 1
Equality #rsa-common-modulus-attack	1337UP 2022	22.49	files wu 1
CrookedRoulette #rsa-blinding-forgery	KITCTFCTF 2022	–	files wu 1
Fancy_e #rsa #wiener-attack	Srdnlen 2022	24.17	files wu 1