$ ctf42

Crypto CTF challenges

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

Top crypto techniques

#rsa 106 #xor 16 #lattice 16 #known-plaintext 12 #substitution-cipher 12 #lll 11 #crt 10 #diffie-hellman 9 #ecdsa 9 #discrete-log 9 #meet-in-the-middle 8 #caesar-cipher 8 #lfsr 8 #padding-oracle 8 #hastad-broadcast 7

Challenges

Filter and sort these in the challenge browser →

Challenge CTF Weight Has
At_Home UIUCTF 2023 – files src wu 3
Dragon_Tyrant Paradigm 2023 25.00 files wu 3
JohnTheRocker VishwaCTF 2022 20.79 files wu 3
Jumble KnightCTF 2022 17.38 files wu 3
Passwd KnightCTF 2022 17.38 files wu 3
SecureSlotsI KITCTFCTF 2022 – files wu 3
BabyDefi N1CTF 2021 53.54 files wu 3
HOLIDAY TFC 2021 – files wu 3
IllegalPrime UTCTF 2021 – files wu 3
Leaky_Blinders FwordCTF 2021 24.42 files wu 3
RAS ASIS 2021 Finals 89.22 files wu 3
babycrypt RaRCTF 2021 24.53 files wu 3
factorize 0x41414141 2021 – files wu 3
fibinary corCTF 2021 24.92 files src wu 3
sRSA RaRCTF 2021 24.53 files wu 3
this_is_dsa TSG 2021 – files wu 3
Zodiac_Killer
#zodiac-cipher#homophonic-substitution
 BroncoCTF 2024 22.51 files wu 2
bivalves
#z3#state-recovery
 PlaidCTF 2023 100.00 files wu 2
ss_puzzle
#xor-secret-sharing
 LINE 2022 – files wu 2
X_Marked_the_Spot
#xor#repeating-key
 UIUCTF 2024 – files wu 2
XQR
#xor#qr-code
 BYUCTF 2022 – files src wu 2
Ring_Of_Fire
#xor#logic-gates
 TAMUctf 2021 – files wu 2
Lowkey_RSA
#wiener-attack
 L3akCTF 2025 24.43 files wu 2
New_Technology
#weak-key-derivation
 ImaginaryCTF 2021 – files wu 2
Vencryption
#vimcrypt
 HacktivityCon 2021 – files wu 2
Vinegar_2
#vigenere-cipher
 n00bzCTF 2024 24.23 files wu 2
Vietas_Poly
#vietas-formulas
 K3RN3LCTF 2021 24.37 files wu 2
pow-pow
#vdf#rsa-group#repeated-squaring
 DiceCTF 2022 24.82 files wu 2
Random
#unseeded-rand-prng
 n00bzCTF 2024 24.23 files wu 2
chinese-lazy-theorem-1
#unbounded-modulus-leak
 LA 2023 – files wu 2
Broken_OTP
#time-seeded-prng
 N0PSctf 2024 24.34 files wu 2
Nameless
#sum-of-squares-rsa
 idekCTF 2021 24.56 files wu 2
A_Simple_SP_Box
#substitution-permutation-network#block-cipher#chosen-plaintext#key-recovery
 DCTF 2021 – files wu 2
greek-cipher
#substitution-cipher
 LA 2023 – files wu 2
trios
#substitution-cipher
 HSCTF 2023 – files wu 2
VariousVernacular
#substitution-cipher
 UTCTF 2021 – files wu 2
aptenodytes-forsteri
#substitution-cipher
 HSCTF 2021 – files src wu 2
Sunset
#subset-sum#convolution
 UTCTF 2022 – files wu 2
Real_Smooth
#stream-cipher#known-plaintext
 BuckeyeCTF 2023 34.50 files wu 2
Hide_n_Seek
#steganography#morse-code#steghide
 BlueHens 2023 24.61 files wu 2