$ 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
CrackSSH
#rsa#weak-ssh-key
 TsukuCTF 2021 – files wu 1
RSA
#rsa#symmetric-polynomial#vieta
 Srdnlen 2023 24.17 files wu 1
Special
#rsa#special-primes
 Securinets 2021 Quals 41.71 files wu 1
RSA1
#rsa#small-modulus-factorization
 BYUCTF 2023 – files wu 1
Little_e
#rsa#small-exponent-e=3#cube-root-attack
 BCACTF 2021 – files wu 1
miniRSA
#rsa#small-e#cube-root
 picoCTF 2019 – files wu 1
rsa
#rsa#signing-oracle#blinding
 WRECKCTF 2022 – files wu 1
squishy
#rsa#signature-oracle
 TJCTF 2023 – files wu 1
signme
#rsa#signature-forgery#weak-prng#seed-bruteforce
 zer0pts 2021 24.56 files wu 1
not_baby_fixed
#rsa#polynomial-factorization
 PBjar 2021 23.18 files wu 1
pqpq
#rsa#polynomial
 SECCON 2022 Quals 97.90 files wu 1
forgetful
#rsa#phi-multiple-leak#factoring
 plfanzen 2026 25.00 files wu 1
Big_RSA
#rsa#phi-leak-factorization
 TeamItaly 2023 24.88 files wu 1
RSAGoneWrong
#rsa#phi-factorization#prime-combination
 RITSEC 2022 – files wu 1
Private_Encryption_Mistake
#rsa#partial-private-key-recovery#ocr
 DCTF 2021 – files wu 1
babyrsa
#rsa#partial-prime-recovery
 corCTF 2021 24.92 files wu 1
Bro-key-n
#rsa#partial-key-recovery
 UIUCTF 2022 – files wu 1
Modulus_RSA
#rsa#multiprime#residue-recovery#bruteforce
 CyberSpace 2024 24.83 files wu 1
EZDORSA-Lv3
#rsa#multiprime#factorization
 WaniCTF 2023 24.99 files wu 1
symmetric
#rsa#multi-prime
 UIUCTF 2025 – files wu 1
too_many_primes
#rsa#multi-prime
 UIUCTF 2025 – files wu 1
MRSA
#rsa#modular-oracle#p-mod-r-leak
 PBjar 2021 23.18 files wu 1
this_is_not_lsb
#rsa#lsb-oracle#lll (lll-lattice-reduction)
 SECCON 2022 Quals 97.90 files wu 1
The_Accursed_Lego_Bin
#rsa#low-public-exponent#prng-seed-recovery
 UMassCTF 2026 65.95 files wu 1
EZDORSA-Lv2
#rsa#low-public-exponent#nth-root
 WaniCTF 2023 24.99 files wu 1
RSA_School_5th_Grade
#rsa#low-exponent#cube-root
 BlueHens 2023 24.61 files wu 1
Small_Inscription
#rsa#low-exponent#coppersmith#stereotyped-message
 DanteCTF 2023 24.44 files wu 1
Damn_Randomware
#rsa#leaked-private-key
 BSidesTLV 2021 23.94 files wu 1
BBBB
#rsa#lcg#coppersmith
 DiceCTF 2023 36.70 files wu 1
baby-rsa
#rsa#known-prime#factorization
 WRECKCTF 2022 – files wu 1
RSA_School_1st_Grade
#rsa#known-prime
 BlueHens 2023 24.61 files wu 1
TwoFifty
#rsa#known-factorization
 PatriotCTF 2022 24.52 files src wu 1
Uncommon_Factors_II
#rsa#implicit-factoring#lll (lll-lattice-reduction)
 RCTF 2021 – files wu 1
baby-rsa
#rsa#higher-power-residue#nth-root#crt
 DiceCTF 2022 24.82 files wu 1
RSASSS
#rsa#hastad-broadcast-attack#crt
 b01lers 2021 22.99 files wu 1
BBB
#rsa#hastad-broadcast#prng
 SECCON 2022 Quals 97.90 files wu 1
RSA_School_6th_Grade
#rsa#hastad-broadcast#crt
 BlueHens 2023 24.61 files wu 1
RSA4
#rsa#hastad-broadcast
 BYUCTF 2023 – files wu 1
iheartrsa
#rsa#hastad-broadcast
 TJCTF 2023 – files wu 1
Reasonable_Security_Ahead
#rsa#franklin-reiter-related-message#coppersmith
 b01lers 2021 22.99 files wu 1