$ 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
Compact
#dotsies-cipher
 BYUCTF 2023 – files wu 1
Forgotten_secret
#docker-image-forensics#layer-extraction#leaked-ssh-key
 DCTF 2021 – files wu 1
Oh_Anna_Julia
#discrete-log-oracle#bit-by-bit-leak
 Pwn2Win 2021 83.41 files wu 1
sequoa
#discrete-log
 hxp 2022 – files wu 1
gipfel
#discrete-log
 hxp 2021 99.41 files wu 1
yadlp
#discrete-log
 DownUnderCTF 2021 – files wu 1
Guess_Flag
#digit-oracle
 LakeCTF 2025 Quals – files wu 1
Key_Exchange
#diffie-hellman-key-exchange
 N0PSctf 2025 24.34 files wu 1
MITM
#diffie-hellman#small-parameters#discrete-log-bruteforce
 darkCON 2021 24.06 files wu 1
Secure_Channel
#diffie-hellman#small-key-bruteforce
 COMPFEST 2021 – files wu 1
MiTM
#diffie-hellman#meet-in-the-middle (mitm)
 Securinets 2021 Quals 41.71 files wu 1
Z2kDH
#diffie-hellman#discrete-log#2-adic
 WolvCTF 2023 24.33 files wu 1
Easy_Diffy
#diffie-hellman#degenerate-generator
 PwnMe 2025 Quals 24.95 files wu 1
steps
#diffie-hellman#custom-group-dlp
 corCTF 2024 55.00 files wu 1
RandSubWare
#differential-cryptanalysis#spn
 SekaiCTF 2023 24.86 files wu 1
Crack_a_Mateo
#dictionary-attack
 JerseyCTF 2024 21.26 files wu 1
D
#dickson-polynomial#permutation-polynomial
 VuwCTF 2026 25.00 files wu 1
Fake_Encryption
#des#ecb#block-reordering#known-plaintext
 WORMCON 2021 – files wu 1
SMS
#custom-hash-collision#substitute-mix-shift
 3kCTF 2021 24.14 files wu 1
mathhash
#custom-hash#floating-point#byte-by-byte-bruteforce
 zer0pts 2022 35.97 files wu 1
Mirror_Hash
#custom-hash#birthday-attack#subset-sum#hash-collision
 PwnMe 2025 Quals 24.95 files wu 1
seaside
#csidh#isogeny#oblivious-transfer
 DiceCTF 2023 36.70 files wu 1
Alter_Ego
#csidh#isogeny
 SekaiCTF 2025 55.00 files src wu 1
infinity
#csidh
 hxp 2021 99.41 files wu 1
chinese-lazy-theorem-2
#crt-reconstruction
 LA 2023 – files wu 1
Wifi_Password_of_The_Day
#crime#compression-oracle
 Tenable 2022 22.37 files wu 1
Noisy_CRC
#crc#polynomial#crt
 SekaiCTF 2023 24.86 files wu 1
Noisier_CRC
#crc#crt#polynomial
 SekaiCTF 2023 24.86 files wu 1
cccircus
#crc
 hxp 2024 – files wu 1
circus
#crc
 hxp 2024 – files wu 1
Mersenne_Mayhem
#continued-fractions
 L3akCTF 2025 24.43 files wu 1
NeutronMail
#common-factor-gcd
 LakeCTF 2022 Quals 23.96 files wu 1
Cooking_the_Books
#classical-cipher#rot47#cyberchef#multi-encoding
 DawgCTF 2021 23.29 files wu 1
cbc
#classical-cipher#cbc-mode
 corCTF 2023 36.97 files wu 1
cube_cipher
#cipher-cycle-detection
 BuckeyeCTF 2025 – files wu 1
Export_Grade_Cipher
#chosen-plaintext#custom-cipher
 UofTCTF 2024 23.90 files wu 1
XORDECRYPT
#chained-xor#cipher-feedback
 BlueHens 2026 44.77 files wu 1
Game_of_Secrets
#cellular-automata-keystream
 K3RN3LCTF 2021 24.37 files wu 1
Unlucky_Strike
#cbc-padding-oracle
 b01lers 2021 22.99 files wu 1
Cryptogod
#cbc-mac-forgery
 PatriotCTF 2022 24.52 files src wu 1