Reverse engineering challenges
Work out what a compiled program does without its source, then work backwards from the check to the input that passes it.
2,324 in the index. The 200 below are ranked by how many independent published solutions exist - which is the right order for learning, not for difficulty. A challenge with nine writeups gives you nine explanations of the same technique to compare; a harder one nobody documented gives you none.
RE4:unVM me
AlexCTF 201719 writeupsRE2: C++ is awesome
AlexCTF 201716 writeupsRE1: Gifted
AlexCTF 201713 writeupsbeginner
Google Capture The Flag 2020 202012 writeupsunknown
TUCTF 2017 201712 writeupsno-calm
BackdoorCTF 2017 201711 writeupsRE5: packed movement
AlexCTF 201711 writeupsRev Rev Rev
Tokyo Westerns CTF 3rd 2017 201711 writeupsfuture
TUCTF 2017 201710 writeupsRE3: Catalyst System
AlexCTF 201710 writeupsGetit
SharifCTF 7 201610 writeupsChasing a lock
RaziCTF 2020 20209 writeupsCheesy
TAMUctf 19 20199 writeupsGuess The String
noxCTF 2018 20189 writeupsFunmail2.0
TUCTF 2017 20179 writeupstableEZ
CSAW CTF Qualification Round 2017 20179 writeupsRev 60 File Checker
Internetwache CTF 2016 20169 writeupsRev 80 - Eso Tape
Internetwache CTF 2016 20169 writeupsPassphrase
Cyber Apocalypse 2021 20218 writeupsandroid
Google Capture The Flag 2020 20208 writeupsKey generator
Syskron Security CTF 2020 20208 writeupsnot_malware
CSAW CTF Qualification Round 2020 20208 writeupsreee
PlaidCTF 2020 20208 writeupsropes
redpwnCTF 2020 20208 writeupsSMarT-solver
redpwnCTF 2020 20208 writeupsFaker
TUCTF 2019 20198 writeupsSecrets
TAMUctf 19 20198 writeupsBabyReverse
Hack.lu CTF 2018 20188 writeupsbaby-re
DEF CON CTF Qualifier 2016 20168 writeupsconsul
Hack The Vote 2016 20168 writeupsIll Intentions
Google Capture The Flag 2016 20168 writeupsReversing 500
CSAW CTF Qualification Round 2013 20138 writeupsflag checker
Nullcon Goa HackIM 2025 CTF 20257 writeupssnek
RITSEC CTF 2021 20217 writeupsdanger-Live-and-Malicious-Code
WPICTF 2020 20207 writeupsNotWannasigh
WPICTF 2020 20207 writeupsToo Slow
rgbCTF 2020 20207 writeupsWindows of Opportunity
ångstromCTF 2020 20207 writeupsKeyGenMe
TAMUctf 19 20197 writeupsDanger Zone
TUCTF 2018 20187 writeupsJuggle
35C3 CTF 20187 writeupskvm
CSAW CTF Qualification Round 2018 20187 writeupsBackdoor Pi
Kaspersky Industrial CTF Quals 2017 20177 writeupsSkipper
BSides San Francisco CTF 20177 writeupsLogmein
RC3 CTF 2016 20167 writeupsRev 50 - SPIM
Internetwache CTF 2016 20167 writeupsReverse Box
Tokyo Westerns/MMA CTF 2nd 2016 20167 writeupsSCrack
SharifCTF 7 20167 writeupsReversing 100
CSAW CTF Qualification Round 2013 20137 writeupsbacktrack
Nullcon Goa HackIM 2025 CTF 20256 writeupsscrambled
Nullcon Goa HackIM 2025 CTF 20256 writeupsThe Flag Vault
KnightCTF 2022 20226 writeupsWIDE
Cyber Apocalypse CTF 2022: Intergalactic Chase 20226 writeupsbabymix
DiceCTF 2021 20216 writeupsFREE FLAGS!!1!!
ångstromCTF 2021 20216 writeupsInfinity Gauntlet
ångstromCTF 2021 20216 writeupsverybabyrev
RaRCTF 2021 20216 writeupswstrings
redpwnCTF 2021 20216 writeupsCandroid
NahamCon CTF 20206 writeupsFirmware update
Syskron Security CTF 2020 20206 writeupsMoM's Touch
2020 Defenit CTF 20206 writeupsReverse-ing
TSG CTF 2020 20206 writeupsRevving Up
ångstromCTF 2020 20206 writeupsz3_robot
SharkyCTF 20206 writeupsbeginner_reverse
Insomni'hack teaser 2019 20196 writeupsCrackme
UTCTF 2019 20196 writeupsDiscount VMProtect
X-MAS CTF 2019 20196 writeupsEasy Crack Me
TokyoWesterns CTF 5th 2019 20196 writeupsElementary
CONFidence CTF 2019 Teaser 20196 writeupsLicense
HSCTF 6 20196 writeupsLocal News
TAMUctf 19 20196 writeupsSanta's crackme
X-MAS CTF 2019 20196 writeupsSnakes over cheese
TAMUctf 19 20196 writeupsbabyre
RCTF 2018 20186 writeupsC6: gates of hell
Square CTF 2018 20186 writeupsRansomware
DefCamp CTF Qualification 2018 20186 writeupsre06
WhiteHat Grand Prix 2018 – Quals 20186 writeupsRev3
ångstromCTF 2018 20186 writeupsShall we play a game?
Google Capture The Flag 2018 (Quals) 20186 writeupsYeahright
TUCTF 2018 20186 writeupsFunmail
TUCTF 2017 20176 writeupsF#ck
EKOPARTY CTF 2016 20166 writeupsHidden In Plain Sight
IceCTF 2016 20166 writeupsRev 70 - ServerfARM
Internetwache CTF 2016 20166 writeupsoscilloscope
Nullcon Goa HackIM 2025 CTF 20255 writeupsBaby Rev
FooBar CTF 2022 20225 writeupsClick Me!
NahamCon CTF 2022 20225 writeupsHerald
Insomni'hack teaser 2022 20225 writeupsRebuilding
Cyber Apocalypse CTF 2022: Intergalactic Chase 20225 writeupsSerial Killer
TAMUctf 2022 20225 writeupsTeleport
Cyber Apocalypse CTF 2022: Intergalactic Chase 20225 writeupsAlienware
Cyber Apocalypse 2021 20215 writeupsbabyrev
corCTF 2021 20215 writeupsHacker Manifesto
Tenable CTF 2021 20215 writeupsInfiltration
Cyber Santa is Coming to Town 20215 writeupsK3RN3L DROID
K3RN3LCTF 20215 writeupsNormal
ImaginaryCTF 2021 20215 writeupsRocca pia
DaVinciCTF 2021 20215 writeupsScraps
DeconstruCT.F 2021 20215 writeupsThat's not crypto
justCTF [*] 2020 20215 writeupsTo Do
H@cktivityCon 2021 CTF 20215 writeups.PNG2
UTCTF 2020 20205 writeups[basics] Reverse Engineering
UTCTF 2020 20205 writeups1000 and 1 night
Aero CTF 2020 20205 writeupsAdvanced Reversing Mechanics 1
rgbCTF 2020 20205 writeupsAdvanced Reversing Mechanics 2
rgbCTF 2020 20205 writeupsArchRide
InCTF 2020 20205 writeupsAutorev, Assemble!
ångstromCTF 2020 20205 writeupsbubbly
redpwnCTF 2020 20205 writeupsCrack the heart
UTCTF 2020 20205 writeupsCrossw0rd
SarCTF by Saratov State University 20205 writeupseasy strcmp
zer0pts CTF 2020 20205 writeupsExcellent Crackme
VolgaCTF 2020 Qualifier 20205 writeupsLEMON
Houseplant CTF 2020 20205 writeupsprehistoric mario
ALLES! CTF 2020 20205 writeupsRTCP trivia
Houseplant CTF 2020 20205 writeupssimple
SharkyCTF 20205 writeupsTenet
HITCON CTF 2020 20205 writeupsYOU wa SHOCKWAVE
PlaidCTF 2020 20205 writeups042
TAMUctf 19 20195 writeupsbeleaf
CSAW CTF Qualification Round 2019 20195 writeupsBlink
BSidesSF 2019 CTF 20195 writeupsCr4ckZ33C0d3
TAMUctf 19 20195 writeupsDaHeck
HSCTF 6 20195 writeupsFriendSpaceBookPlusAllAccessRedPremium.com
Google Capture The Flag 2019 (Quals) 20195 writeupshfs-mbr
Midnight Sun CTF 2019 Quals 20195 writeupsHow2decompyle
BambooFox CTF 20195 writeupsKernel Crackme
X-MAS CTF 2019 20195 writeupsNoCCBytes
TAMUctf 19 20195 writeupsxHell
INS'hAck 2019 20195 writeupsxmas_future
hxp 36C3 CTF 20195 writeupsAssemble your way to the flag
Pragyan CTF 2018 20185 writeupsBack to the BASICs
Google Capture The Flag 2018 (Quals) 20185 writeupsBeginner's Quest - Admin UI
Google Capture The Flag 2018 (Quals) 20185 writeupsdec dec dec
TokyoWesterns CTF 4th 2018 20185 writeupsRev1
ångstromCTF 2018 20185 writeupsRev2
ångstromCTF 2018 20185 writeupsShoop
TUCTF 2018 20185 writeupsSlammer
Xiomara CTF 2018 20185 writeupsangrybird
Codegate 2017 prequals 20175 writeupscrackme1
DEF CON CTF Qualifier 2017 20175 writeupseasy
BSides San Francisco CTF 20175 writeupsfloppy
Block CTF 2017 20175 writeupsFood
Google Capture The Flag 2017 (Quals) 20175 writeupsno_mo_flo
PlaidCTF 2017 20175 writeupspinlock
BSides San Francisco CTF 20175 writeupsThe Turing Agent
Block CTF 2017 20175 writeupsA Strong Feeling
IceCTF 2016 20165 writeupsdMd
Sharif University CTF 2016 20165 writeupsJVM
EKOPARTY CTF 2016 20165 writeupsReverse 100_2
Qiwi-Infosec CTF-2016 20165 writeupsSRM
Sharif University CTF 2016 20165 writeupsCrack Me If You Can
PoliCTF 2015 20155 writeupsEntry language - (Reverse 100)
Defcamp CTF Qualification 2015 20155 writeupsfake
ASIS CTF Finals 2015 20155 writeupsLicense
ASIS CTF Finals 2015 20155 writeupsreversemeplz
PoliCTF 2015 20155 writeupsg++
PlaidCTF 2014 20145 writeupsReversing 200
CSAW CTF Qualification Round 2013 20135 writeupsReversing 400
CSAW CTF Qualification Round 2013 20135 writeupsCoverup
Nullcon Goa HackIM 2026 CTF 20264 writeupsHashinator
Nullcon Goa HackIM 2026 CTF 20264 writeupsOpalist
Nullcon Goa HackIM 2026 CTF 20264 writeupsstack strings 1
Nullcon Goa HackIM 2026 CTF 20264 writeupsstack strings 2
Nullcon Goa HackIM 2026 CTF 20264 writeupsjust TV
justCTF 2024 teaser 20244 writeupsshattered-memories
LA CTF 2024 20244 writeupsctfd-plus
LA CTF 2023 20234 writeupsGalactic Federation
Space Heroes 2023 20234 writeupsbabyree
SEETF 2022 20224 writeupsBreakout
HTB Business CTF 2022: Dirty Money 20224 writeupsDweeno
NahamCon CTF 2022 20224 writeupsKnight Vault
KnightCTF 2022 20224 writeupsMobilize
NahamCon CTF 2022 20224 writeupsOTP Vault
NahamCon CTF 2022 20224 writeupsWithout a Trace
Cyber Apocalypse CTF 2022: Intergalactic Chase 20224 writeupsBackdoor
Cyber Apocalypse 2021 20214 writeupsBell
DCTF 2021 20214 writeupsbread-making
redpwnCTF 2021 20214 writeupsCPP
Google Capture The Flag 2021 20214 writeupsCrackme
DaVinciCTF 2021 20214 writeupsCSRunner
CyberSecurityRumble CTF 20214 writeupsDummyper
Aero CTF 2021 20214 writeupsEasyAssembly
HeroCTF v3 20214 writeupsFunction Pointer Fun
HackPack CTF 2021 20214 writeupshvhpgs{synt}
UIUCTF 2021 20214 writeupsJailbreak
ångstromCTF 2021 20214 writeupsJust In Time
DCTF 2021 20214 writeupskeygen
S.H.E.L.L. CTF 20214 writeupsLost In Your Eyes
DiceCTF 2021 20214 writeupsParallel-The-M0le
m0leCon CTF 2021 Teaser 20214 writeupsPasscode
eHaCON CTF 2K21 20214 writeupspickled-onions
redpwnCTF 2021 20214 writeupsRead/Reverse
darkCON CTF 20214 writeupsScadomware
Intent CTF 2021 20214 writeupsSeeking the flag
eHaCON CTF 2K21 20214 writeupssneks
HSCTF 8 20214 writeupsThe Vault
HTB Uni CTF 2021 - Quals 20214 writeupsTime
Digital Overdose 2021 Autumn CTF 20214 writeupsToo Much
darkCON CTF 20214 writeups
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