$ 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
fancynotes
#hash-length-extension
 m0leCon 2022 Quals 36.00 files wu 2
Rabin_To_The_Rescue
#fermat-factorization
 niteCTF 2021 – files wu 2
What_an_Enigma
#enigma-machine
 RITSEC 2021 – files wu 2
janken_vs_yoshiking
#elgamal#quadratic-residue#legendre-symbol
 zer0pts 2021 24.56 files wu 2
Morphing_Time
#elgamal#malleability
 UIUCTF 2023 – files src wu 2
flag_is_win
#ecdsa#ehnp#lattice
 TSG 2021 – files wu 2
TagSeries1
#ecb#mac-forgery
 WolvCTF 2024 35.25 files wu 2
nDLP
#discrete-logarithm#composite-modulus#pohlig-hellman#crt
 ASIS 2021 Finals 89.22 files wu 2
dividing_secrets
#discrete-log#quadratic-residue
 corCTF 2021 24.92 files wu 2
basic_sums
#digit-sum-crt
 KalmarCTF 2025 33.89 files wu 2
dhke_adventure
#diffie-hellman#pohlig-hellman
 UIUCTF 2021 – files wu 2
dhke_intro
#diffie-hellman#discrete-log
 UIUCTF 2021 – files wu 2
keyexchange
#diffie-hellman#chosen-exponent
 WolvCTF 2023 24.33 files wu 2
TheMostWorthyDistinctionOfPain
#dictionary-encoding
 BYUCTF 2022 – files wu 2
Celebration
#dancing-men-cipher#substitution-cipher
 UMDCTF 2021 – files wu 2
RITSEC_Hash
#custom-hash#bruteforce#rockyou
 RITSEC 2021 – files wu 2
FailedHashFunction
#custom-hash#bit-manipulation
 UTCTF 2022 – files wu 2
CRC_Recursive_Challenge
#crc
 Dragon 2021 99.33 files wu 2
CRC_Recursive_Challenge_warmup
#crc
 Dragon 2021 99.33 files wu 2
dyrpto
#coppersmith-short-pad#franklin-reiter#rsa#small-e
 PlaidCTF 2020 93.15 files wu 2
ClassicCrypto
#classical-cipher#substitution
 Tenable 2021 22.37 files wu 2
ZKPoD
#chosen-ciphertext-attack
 ImaginaryCTF 2021 – files wu 2
Baby_MAC
#cbc-mac-forgery
 Dragon 2021 99.33 files wu 2
babycrypto2
#cbc-iv-bit-flip
 LINE 2021 – files wu 2
Flip_Flops
#cbc-bit-flipping
 ImaginaryCTF 2021 – files wu 2
Wheel_Barrow
#burrows-wheeler-transform
 UofTCTF 2024 23.90 files wu 2
baby-baby-rsa
#brute-force
 HSCTF 2022 – files wu 2
CrossingTheRedSea
#brainfuck#esolang#substitution-cipher
 VishwaCTF 2023 22.69 files wu 2
easy_pseudo_random
#blum-blum-shub#lll (lll-lattice-reduction)#lattice#msb-recovery
 zer0pts 2021 24.56 files wu 2
BitFlip2
#bit-flip
 Dragon 2020 98.00 files wu 2
BitFlip3
#bit-flip
 Dragon 2020 98.00 files wu 2
This_one_is_really_basic
#base64#encoding
 DCTF 2021 – files wu 2
Recovery
#base64#constraint-solving
 vsCTF 2022 23.32 files wu 2
Whose_Base_Is_It_Anyway
#base-conversion
 UMDCTF 2021 – files wu 2
Preschool_Lessons
#baconian-cipher
 BroncoCTF 2024 22.51 files wu 2
mfine
#affine-cipher#brute-force
 VULNCON 2021 – files wu 2
staple-AES
#aes-ecb#block-shuffling
 0x41414141 2021 – files wu 2
You_AES_Me_Up
#aes-decryption-oracle
 COMPFEST 2021 – files wu 2
caBalS_puking
#aes-ctr
 hxp 2021 99.41 files wu 2
babycrypto1
#aes-cbc-malleability
 LINE 2021 – files wu 2