$ 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
silver-water-industries
#quadratic-residue
 Hack.lu 2021 94.48 files wu 3
TonyAndJames
#python-mersenne-twister#seed-recovery#xor-keystream
 darkCON 2021 24.06 files wu 3
TakeItEasy
#pyc-decompilation#uncompyle6#xor
 darkCON 2021 24.06 files wu 3
Limited_1
#prng-seed-bruteforce#mt19937
 WolvCTF 2024 35.25 files wu 3
result
#pdf-encryption#pdf2john#zipcode-bruteforce
 CyberSecurityRumble 2021 41.60 files wu 3
CipherGauntlet
#multi-layer-encoding#caesar-cipher
 UTCTF 2021 – files wu 3
DiceRoll
#mt19937-prediction
 NahamCon 2021 24.98 files wu 3
SEA_LANGUAGE_1
#morse-code
 TFC 2021 – files wu 3
SEA_LANGUAGE_2
#morse-code
 TFC 2021 – files wu 3
Learning_with_Exploitation
#lwe#lattice#knapsack
 TSG 2023 – files wu 3
minigen
#linear-recurrence#xor#prng
 RaRCTF 2021 24.53 files wu 3
Tyrannosaurus_Rex
#known-plaintext
 HacktivityCon 2021 – files wu 3
interlock
#interlock-mitm
 justCTF 2024 Quals 77.17 files wu 3
Crack_Me
#hash-cracking#salted-sha256#hashcat
 CSAW 2021 Quals 20.54 files wu 3
Wrong_Way_on_a_One_Way_Street
#hash-cracking
 MetaCTF 2021 – files wu 3
Forgery
#elgamal-signature#existential-forgery#unhashed-message#mask-bypass
 CSAW 2021 Quals 20.54 files src wu 3
human_server
#ecdsa#nonce-reuse
 Union 2021 24.34 files wu 3
Break_Me
#ecb-oracle
 DownUnderCTF 2021 – files wu 3
Poor_Megan
#cyberchef-magic#encoding
 DEADFACE 2025 – files wu 3
TrashChain
#custom-hash-collision#multiplicative-hash#modular-arithmetic
 DawgCTF 2021 23.29 files wu 3
stegasaurus-scratch
#combinatorial-encoding#card-trick-protocol
 PlaidCTF 2020 93.15 files wu 3
Julius_ancient_script
#caesar-cipher#shift-cipher
 DCTF 2021 – files wu 3
double-trouble
#caesar-cipher
 HSCTF 2023 – files wu 3
baby-arx
#byte-at-a-time
 DownUnderCTF 2022 – files src wu 3
Transfer
#blockchain-osint
 HeroCTF 2021 35.17 files wu 3
BitFlip1
#bit-flip
 Dragon 2020 98.00 files wu 3
Thnks_fr_th_Pwds
#base64-encoding
 MetaCTF 2021 – files wu 3
The_Conspiracy
#base64#geo-coordinates#country-lookup
 DeconstruCT.F 2021 19.69 files wu 3
back_to_basics
#base-conversion
 UIUCTF 2021 – files wu 3
SizzlingBacon
#baconian-cipher
 UTCTF 2021 – files wu 3
A_to_Z
#atbash-cipher
 MetaCTF 2021 – files wu 3
AES-ABC
#aes-ecb#ecb-penguin#custom-block-chaining#ppm-image
 picoCTF 2019 – files wu 3
malware
#aes-ctr#known-plaintext#keystream-reuse
 UMassCTF 2021 23.56 files wu 3
435
#aes
 TMUCTF 2021 – files wu 3
Just_Take_Your_Time
#3des#time-based-key#pwntools-automation
 DCTF 2021 – files wu 3
CONPASS TSG 2024 – files wu 3
Easy_ECDLP TSG 2024 – files wu 3
Feistel_Barrier TSG 2024 – files wu 3
Mystery_of_Scattered_Key TSG 2024 – files wu 3
Who_is_the_Outlier TSG 2024 – files wu 3