$ 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
3in1
#spectrogram-stego
 K3RN3LCTF 2021 24.37 files wu 2
leaky_block_cipher
#small-multiplicative-order#polynomial-factorization
 PlaidCTF 2021 99.64 files wu 2
Sailing_Thru_Decryption
#signal-flag-decoding#binary#vigenere-cipher
 BCACTF 2021 – files wu 2
Non-textualTroubles
#shift-cipher
 UACTF 2022 – files wu 2
not_quite_caesar
#seeded-prng#operation-inversion
 vsCTF 2024 34.00 files wu 2
Hidden_Frequencies
#run-length-encoding
 BCACTF 2022 – files wu 2
RSASmall
#rsa-low-exponent
 OFPPT 2022 – files wu 2
RSA
#rsa-cube-root-attack
 n00bzCTF 2024 24.23 files wu 2
RSAMod
#rsa-common-modulus
 OFPPT 2022 – files wu 2
Really_Secure_Apparently
#rsa#wiener-attack#small-private-exponent
 1337UP 2023 24.23 files wu 2
Pianoman
#rsa#steganography
 UofTCTF 2024 23.90 files wu 2
john_pollard
#rsa#small-modulus-factoring#x509-certificate
 picoCTF 2019 – files wu 2
RadioStationApocalypse
#rsa#rsactftool
 TrollCAT 2021 21.87 files wu 2
TheMoreTheLess
#rsa#multiprime#factordb
 DaVinciCTF 2021 24.50 files wu 2
lost_modulus
#rsa#modulus-recovery
 SEETF 2022 – files wu 2
Third_Times_the_Charm
#rsa#hastad-broadcast#crt
 UMassCTF 2024 43.10 files wu 2
Slightly_Harder_RSA
#rsa#factordb-factorization
 BCACTF 2021 – files wu 2
Snab_Yes_Snab
#rsa#factordb
 COMPFEST 2021 – files wu 2
CorruptAAAAd
#rsa#corrupted-private-key#public-exponent-bruteforce
 PatriotCTF 2022 24.52 files wu 2
alice_bob_dave
#rsa#common-prime#gcd
 Zh3r0 2021 – files src wu 2
hidE
#rsa#common-modulus-attack
 corCTF 2022 24.92 files wu 2
MultipleExponents
#rsa#common-modulus
 SunshineCTF 2021 23.34 files wu 2
Common_Factor
#rsa#common-factor
 TMUCTF 2021 – files wu 2
small_weiner
#rsa#boneh-durfee#lattice#small-private-exponent
 DaVinciCTF 2022 24.50 files wu 2
easy_rsa
#rsa#bitwise-leak#bit-by-bit-dfs-factoring
 pingCTF 2023 – files wu 2
DesintegratedRSA
#rsa#bit-flip-recovery#prime-reconstruction
 DaVinciCTF 2023 29.26 files wu 2
rsa-apprentice
#rsa
 TJCTF 2022 – files wu 2
Skipping_the_Ropes
#rot13
 eHaCON 2021 – files wu 2
PrimeGuesser1
#rlwe-key-recovery
 KITCTFCTF 2022 – files wu 2
PrimeGuesser2
#rlwe-key-recovery
 KITCTFCTF 2022 – files wu 2
flagprinter
#reversing#base3-digit-sum#xor-keystream
 CyberSpace 2024 24.83 files wu 2
BinomialWays
#reversible-stream-cipher#modular-addition
 1337UP 2022 22.49 files wu 2
Keyless
#reversible-arithmetic-cipher#no-key-encoding
 1337UP 2023 24.23 files wu 2
very_hot
#related-primes
 LA 2024 – files wu 2
base64
#radix-conversion
 ImaginaryCTF 2024 49.81 files src wu 2
bank
#quantum-cryptography#bb84
 corCTF 2021 24.92 files src wu 2
MediumExpectations
#python-random-prediction
 BSidesTLV 2022 23.94 files wu 2
RANDOM_SEED_RANDOM
#prng#cycle-length-attack
 TSG 2023 – files wu 2
supercomputer
#prime-power-modulus-factorization
 corCTF 2021 24.92 files wu 2
Badseed
#predictable-rand
 K3RN3LCTF 2021 24.37 files wu 2