History Main / PasswordSlotMachine

In RealLife, a ''good'' password system will not reveal anything about an incorrect guess other than "that was wrong," will take the same amount of time to process any input, will be slow enough that you ''can't'' try thousands of passwords a second, and will respond to some number of consecutive wrong tries (usually three to five) by locking the account and alerting the sysadmins. However, many real systems fall short of this ideal; it's easy to make a design or implementation mistake. And a common mistake is to take slightly less time to process an incorrect password if an earlier character is wrong, which allows "locking in" early characters exactly as in this trope.

* ''VideoGame/MissionImpossibleKonami'': There are electronically locked doors that are unlocked by Grant (The only agent with the required expertise in electronics) playing a minigame which involves decoding a 4-digit code, with the correct digit marked by a chime when scrolling through each digit individually.

** Also happens within the ''Last of the Daleks'', where the titular Dalek breaches a door with "a billion combinations", with the eight code numbers cycling through digits until they turn to hashes in rapid succession, opening the door.

More ridiculous is when it cycles through dozens of numbers on the readout when it should, at most, only have to cycle through ten if each digit can be "locked in." If a password is ''n'' symbols long and there are ''m'' possibilities for each symbol, then the complexity of brute force is usually ''m''^''n'', but the password slot machine reduces it to ''m''×''n''.[[note]]This is similar to looking for a particular grain of sand in a small bottle (''m''×''n''), versus the same grain of sand on an entire beach (''m''^''n'').[[/note]] For example, a six-digit password of only numbers takes up to 10^6 = 1,000,000 tries to brute force, but if correct digits "lock in" then it takes at most 10×6 = 60 tries instead (the best strategy would be to cycle through an ordered string e.g. 12345, then 23451, 34512, etc., which would cut guesses down to ''m'').

* Also happens within the ''Last of the Daleks'', where the titular Dalek breaches a door with "a billion combinations", with the eight code numbers cycling through digits until they turn to hashes in rapid succession, opening the door.

In fiction, the way passwords get [[http://en.wikipedia.org/wiki/Brute_force_attack brute forced]] tends to make very little sense. What you normally see in a movie or TV show is all the possible codes flashing on the screen, and then the computer locks in correct digits ''one at a time''. It seems that computer password systems are similar to tumbler locks: You can pick it one at a time. But real passwords either work or don't. It's not a game of ''TabletopGame/{{Mastermind}}''.

Occasionally, the locked in digits aren't even starting at the first digit. No explanation on how a computer would know that this random choice for the seventh digit is correct, and no explanation about how it suddenly knows that 3 is correct when chances are it would have tried a 3 in that space dozens of times by now.

* Parodied in ''Anime/LupinIIICrisisInTokyo'': on encountering a door secured with a password this way, Goemon concentrates, lets out a yell and brings his hand down on the readout. The password falls into place, and an impressed Jigen notes they should try their luck at Vegas. The end credits show them doing just that.

* ''Manga/CaseClosed'': Ran has Conan's phone, thinking he's Shinichi and her sent SMS being on it would prove the connection, and decides to crack the password. [[ThePasswordIsAlwaysSwordfish Birthdates]] aren't correct, so she decides to start with 0000 and proceeding one digit at a time. After a few hours of trying, she wonders if the password is "Sherlock" in number-format (4869 in Japanese pronounciation being Shi-Ha-Ro-Ku) and it turns out to be right.

* The first ''Film/MissionImpossible'' movie adaptation used a similar method back in the 90s, when this trope might conceivably have been TruthInTelevision.

* ''Film/WarGames'' may be the TropeCodifier. Near the end of the movie, WOPR tries to figure out the launch codes to the nuclear weapons, randomly locking in on digits as they scroll by the screen.

* The ''Franchise/JamesBond'' game ''VideoGame/{{Nightfire}}'' featured a handheld gadget that did this so you could get through locked doors in the level. For some reason you push buttons on it as it's working at random intervals.

** A giant binary version of this is used by Megabyte, twice. The first time he used it to hack into stolen files from Dot's organizer; files which happened to contain hundreds of binome [=PIDs.=] The second time he used it to extract a portal command from Phong's mind.

** Another related example was an early UNIX attack where you could tell how many characters in your attempt were correct by measuring how long it took, since the password check would only compare digits until it hit an incorrect one.

** A [[http://en.wikipedia.org/wiki/Padding_oracle_attack Padding Oracle Attack]] is where a poorly configured web service will return a bad padding error when the attacker's guess of the last byte of the plaintext string is incorrect. The one value of the 256 available that does not return the error is the correct byte. On a CBC mode encryption scheme, the attacker than can then roll forward one byte and repeat the attack until the entire message is decrypted Slot Machine style.
* The Nintendo Wii's code signing system which prevents unlicensed programs from running on a non-debug console had a bug similar to the last one. The "key" (sort of like a password) was checked until a "NULL" byte was reached. A hacking group found that ''VideoGame/TheLegendOfZeldaTwilightPrincess'''s key had a NULL byte fairly early, so they could bruteforce out to the null byte and didn't have to figure out the rest of the key. This exploit (called the "strncmp bug" because of the way the Wii used strncmp instead of memcmp [memcmp doesn't stop at null bytes]) paved the way for dozens of others, and nowadays you can run anything on the Wii.

* The [=LanManager=] hash, used to store user passwords in all versions of Windows up to and including XP, is a form of this. It can't be broken one character at a time, but it is split into two seven-character chunks -- which makes it vulnerable to simple lookup tables or plain brute force. For exactly this reason it was partially phased out in XP (maintained only for backwards compatability with [=NT4=] servers) and completely removed in Vista. [[note]]If you are still using XP, Lanman is enabled by default and it is advised to disable it, if there are no [=Win98=] machines in your local network.[[/note]]

The way passwords get [[http://en.wikipedia.org/wiki/Brute_force_attack brute forced]] tends to make very little sense. What you normally see in a movie or TV show is all the possible codes flashing on the screen, and then the computer locks in correct digits ''one at a time''. It seems that computer password systems are similar to tumbler locks: You can pick it one at a time. But real passwords either work or don't. It's not a game of ''TabletopGame/{{Mastermind}}''.

* In the ''Series/DoctorWho'' episode "School Reunion," the ''code to take control of the universe'' is partly cracked like this. [[spoiler: Micky prevents this from happening... [[CutTheJuice by pulling out the plug]]]].

* ''Series/VengeanceUnlimited'' episode "Critical" -- The Bad Guy of the Week and his unwitting genius accomplice play the slots to hack into a police mainframe.

* The [=LanManager=] hash, used to store user passwords in all versions of Windows up to and including XP, is a form of this. It can't be broken one character at a time, but it is split into two 7-character chunks - which makes it vulnerable to simple lookup tables or plain brute force. For exactly this reason it was partially phased out in XP (maintained only for backwards compatability with [=NT4=] servers) and completely removed in Vista. [[note]]If you are still using XP, Lanman is enabled by default and it is advised to disable it, if there are no [=Win98=] machines in your local network.[[/note]]

More ridiculous is when it cycles through dozens of numbers on the readout when it should, at most, only have to cycle through ten if each digit can be "locked in." If a password is ''n'' symbols long and there are ''m'' possibilities for each symbol, then the complexity of brute force is usually ''m''^''n'', but the password slot machine reduces it to ''m''*''n''.[[note]]This is similar to looking for a particular grain of sand in a small bottle (''m''*''n''), versus the same grain of sand on an entire beach (''m''^''n'').[[/note]] For example, a six-digit password of only numbers takes up to 10^6 = 1,000,000 tries to brute force, but if correct digits "lock in" then it takes at most 10*6 = 60 tries instead (the best strategy would be to cycle through an ordered string e.g. 12345, then 23451, 34512, etc., which would cut guesses down to ''m'').

* The [[https://en.wikipedia.org/wiki/Wi-Fi_Protected_Setup Wi-Fi Protected Setup]] PIN feature was found to have a major security flaw in which the registrar reports the first and second halves of the eight-digit PIN separately, making it very vulnerable to brute-force attacks by reducing the amount of [=PINs=] that need to be tested by three orders of magnitude.

* In ''VideoGame/VampireTheMasqueradeBloodlines'', this is the visual effect associated with using the "Hacking" skill on a computer terminal. Given the wide variety of systems represented by that single simple login prompt, this was probably the easiest option.

* Ash uses a gadget that does this to crack the four-digit security code to the employee entrance at a bank in the ''Series/{{Hustle}}'' episode "The Hush Heist,"
* One of Artie's gizmos in ''Series/{{Warehouse 13}}'' is a steampunkish variant with a USB connector.
* ''Series/{{CSINY}}'': Used by a pair of car thieves to crack the security code on a Ferrari in "Cavallino Rampante."
* ''Series/{{Leverage}}'': Hardison uses one of these to crack the ten-digit code on the electronic lock to the server room in "The Nigerian Job."
* ''Series/PersonOfInterest'': [[ArtificialIntelligence The Machine]] uses one in the [[Recap/PersonOfInterestS04E22 Season 4 finale]] to determine the security code of an electrical substation.
* ''Series/LawAndOrderCriminalIntent'': A burglar uses one to crack a hotel safe in "Folie à Deux."

* The old [=NES=] game ''Videogame/ClashAtDemonhead'' featured this after beating the final boss, where you had to crack the code for a [[DoomsdayDevice bomb that would destroy the world]]. You (the player) had a number of chances of guessing the code. Each correctly-guessed digit locks, and you had to guess the remaining.

%%* Sally and her hand-held widget hack into something of Robotnik's this way in ''WesternAnimation/SonicTheHedgehogSatAM''. A train and some acrobatics were involved in this scene as well.

* In ''Film/Terminator2JudgmentDay'', John Connor has a [[ChekhovsGun program on his laptop computer that determines]] ATM [=PINs=] this way.

[[quoteright:350:[[Film/ResidentEvil https://static.tvtropes.org/pmwiki/pub/images/passcode_search_4.jpg]]]]

* ''Film/ResidentEvil''. When Kaplan is trying to get the Red Queen's passcode to open the door to her chamber, the passcode appears one digit at a time.

* ''Manga/DetectiveConan'': Ran has Conan's phone, thinking he's Shinichi and her sent SMS being on it would prove the connection, and decides to crack the password. [[ThePasswordIsAlwaysSwordfish Birthdates]] aren't correct, so she decides to start with 0000 and proceeding one digit at a time. After a few hours of trying, she wonders if the password is "Sherlock" in number-format (4869 in Japanese pronounciation being Shi-Ha-Ro-Ku) and it turns out to be right.

* The [=LanManager=] hash, used to store user passwords in all versions of Windows up to and including XP, is a form of this. It can't be broken one character at a time, but it is split into two 7-character chunks - which makes it vulnerable to simple lookup tables or plain brute force. For exactly this reason it was partially phased out in XP (maintained only for backwards compatability with NT4 servers) and completely removed in Vista. [[note]]If you are still using XP, Lanman is enabled by default and it is advised to disable it, if there are no [=Win98=] machines in your local network.[[/note]]