$ 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

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Challenge CTF Weight Has
nom_nom
#rsa#franklin-reiter#related-message
 VuwCTF 2026 25.00 files wu 1
Noob_RSA_Returns
#rsa#fermat-little-theorem
 BITSCTF 2025 – files wu 1
PQ
#rsa#fermat-factorization#close-primes
 VolgaCTF 2024 Quals 35.91 files wu 1
RSA_School_7th_Grade
#rsa#fermat-factorization
 BlueHens 2023 24.61 files wu 1
RSA_School_8th_Grade
#rsa#fermat-factorization
 BlueHens 2023 24.61 files wu 1
pqqp
#rsa#factorization-from-hint
 WaniCTF 2023 24.99 files wu 1
factor-master
#rsa#factorization
 TJCTF 2022 – files wu 1
minimalist's_private
#rsa#factorization
 TSG 2021 – files wu 1
Not_Baby
#rsa#factordb#multi-prime-rsa
 PBjar 2021 23.18 files wu 1
RSA2
#rsa#factordb
 BYUCTF 2023 – files wu 1
RSA_School_2nd_Grade
#rsa#factordb
 BlueHens 2023 24.61 files wu 1
Baby-RSA
#rsa#factordb
 S4CTF 2021 24.52 files wu 1
Defective_RSA
#rsa#eth-root#crt
 BuckeyeCTF 2021 24.81 files wu 1
not_mordell_primes
#rsa#elliptic-curve#resultant#point-recovery
 zer0pts 2021 24.56 files wu 1
ezcoppersmith
#rsa#ecm-factorization
 CyberSpace 2024 24.83 files wu 1
RSA_School_4th_Grade
#rsa#d-to-factorization
 BlueHens 2023 24.61 files wu 1
RSA_Recycle
#rsa#cycling-attack
 ToH 2025 24.27 files wu 1
RSA5
#rsa#common-modulus-attack
 BYUCTF 2023 – files wu 1
RSA_School_3rd_Grade
#rsa#common-modulus-attack
 BlueHens 2023 24.61 files wu 1
Office_Secrets
#rsa#common-modulus-attack
 UMDCTF 2021 – files wu 1
beginners_crypto_2021
#rsa#common-modulus#low-exponent
 TSG 2021 – files wu 1
escrime
#rsa#common-factor#gcd
 Securinets 2022 Quals 50.11 files wu 1
RSA3
#rsa#common-factor
 BYUCTF 2023 – files wu 1
DamaS
#rsa#boneh-durfee#small-private-exponent#coppersmith
 ASIS 2021 Quals 89.22 files wu 1
really-small-algorithm
#rsa
 HSCTF 2023 – files wu 1
asr
#rsa
 UIUCTF 2022 – files src wu 1
ShakespeareAndEncoding
#rot47
 Engineer 2022 22.65 files wu 1
Attack_of_the_Clones
#rlwe-error-reuse
 LakeCTF 2025 Quals – files wu 1
learning-without-errors
#rlwe#ckks#lattice#key-recovery
 DiceCTF 2022 24.82 files wu 1
Cowsay
#repeating-key-xor#xortool
 PatriotCTF 2022 24.52 files src wu 1
OTP1
#repeating-key-xor#xortool
 BlueHens 2021 22.62 files wu 1
A2S
#reduced-round-aes#differential-cryptanalysis
 Pwn2Win 2021 83.41 files wu 1
Tabula_Recta
#rc4-fms
 InCTF 2021 70.41 files wu 1
BabyRC4
#rc4#keystream-reuse
 SEETF 2023 – files wu 1
would-you-wordle
#rc4
 JerseyCTF 2022 25.00 files wu 1
Off_the_Rails
#rail-fence-cipher
 DEADFACE 2023 – files wu 1
Fake_Medallion
#quantum-cloning#mersenne-twister#quantum-money
 PlaidCTF 2021 99.64 files wu 1
two_wrongs
#quantum-circuit-reversal#brute-force
 corCTF 2024 55.00 files wu 1
Quantum_vernam
#quantum-change-of-basis
 LakeCTF 2025 Quals – files wu 1
RandomseniorAdleman
#prng-seed-rsa
 KnightCTF 2025 18.78 files wu 1