IJCTF 2020 - Vault

Description

We locked our secret box, You can directly ping the bot (@Vault #8895 ) using “start” to get the secret but we don’t know the door code we used random() also we used sleep(10).

shift register…

Author : Harsh and warlock_rootx

Hint

• if pin in user_input():

Solution

We started to talk with the discord bot (start):
Time to test your lock picking skills

I AM   

_ _ _ _ _ _ _

LOCKED  

[ 0 ] [ 1 ]

We guessed that the vault password was seven character long and contained only 0 and 1.

After some random test we realized that some times a password was accepted (and we were prompted with the next phase of the lock picking) and other times it was wrong.
We understood (Hint) that the password had to be a substring of the text we submitted.

Discord limit the length of a message by 2000 character, too little to list all the possibilities of the pin with lenghts of seven in binary.

Luckily we knew the De Brujin sequence.
We generated all the string for the various lock picking test.

Time to test your lock picking skills

    I AM   

_ _ _ _ _ _ _

   LOCKED  

[ 0 ] [ 1 ]

00000001000001100001010000111000100100010110001101000111100100110010101001011100110110011101001111101010110101111011011101111111000000

First lock opened! Hurry up and open the next one before the gaurds show up

       I AM      

   _ _ _ _ _ _   

      LOCKED     

[ 4 ] [ 5 ] [ 6 ]

44444454444464444554444564444654444664445454445464445554445564445654445664446454446464446554446564446654446664454454464454554454564454654454664455454455464455554455564455654455664456454456464456554456564456654456664464464554464564464654464664465454465464465554465564465654465664466454466464466554466564466654466664545454645455545455645456545456645464645465545465645466545466645545545645546545546645554645555545555645556545556645564645565545565645566545566645645646545646645654645655545655645656545656645664645665545665645666545666646464655464656464665464666465465466465555465556465565465566465655465656465665465666466466555466556466565466566466655466656466665466666555555655556655565655566655655656655665655666656565666566566666644444

Second Lock Opened! Dang your a professional. Third lock now…

             I AM            

           _ _ _ _           

            LOCKED           

[ 5 ] [ 6 ] [ 7 ] [ 8 ] [ 9 ]

5555655575558555955665567556855695576557755785579558655875588558955965597559855995656575658565956665667566856695676567756785679568656875688568956965697569856995757585759576657675768576957765777577857795786578757885789579657975798579958585958665867586858695876587758785879588658875888588958965897589858995959665967596859695976597759785979598659875988598959965997599859996666766686669667766786679668766886689669766986699676768676967776778677967876788678967976798679968686968776878687968876888688968976898689969697769786979698769886989699769986999777787779778877897798779978787978887889789878997979887989799879998888988998989999555

Third lock open, now you have to be fast.

          I AM         

       _ _ _ _ _       

         LOCKED        

[ 1 ] [ 2 ] [ 3 ] [ 4 ]

11111211113111141112211123111241113211133111341114211143111441121211213112141122211223112241123211233112341124211243112441131211313113141132211323113241133211333113341134211343113441141211413114141142211423114241143211433114341144211443114441212212123121241213212133121341214212143121441221312214122221222312224122321223312234122421224312244123131231412322123231232412332123331233412342123431234412413124141242212423124241243212433124341244212443124441313213133131341314213143131441321413222132231322413232132331323413242132431324413314133221332313324133321333313334133421334313344134141342213423134241343213433134341344213443134441414214143141441422214223142241423214233142341424214243142441432214323143241433214333143341434214343143441442214423144241443214433144341444214443144442222232222422233222342224322244223232232422333223342234322344224232242422433224342244322444232332323423243232442332423333233342334323344234242343323434234432344424243242442433324334243432434424433244342444324444333334333443343433444343443444441111

Fourth lock open. Come on just two more…

                I AM               

              _ _ _ _              

               LOCKED              

[ 0 ] [ 1 ] [ 2 ] [ 5 ] [ 8 ] [ 9 ]

000010002000500080009001100120015001800190021002200250028002900510052005500580059008100820085008800890091009200950098009901010201050108010901110112011501180119012101220125012801290151015201550158015901810182018501880189019101920195019801990202050208020902110212021502180219022102220225022802290251025202550258025902810282028502880289029102920295029802990505080509051105120515051805190521052205250528052905510552055505580559058105820585058805890591059205950598059908080908110812081508180819082108220825082808290851085208550858085908810882088508880889089108920895089808990909110912091509180919092109220925092809290951095209550958095909810982098509880989099109920995099809991111211151118111911221125112811291152115511581159118211851188118911921195119811991212151218121912221225122812291252125512581259128212851288128912921295129812991515181519152215251528152915521555155815591582158515881589159215951598159918181918221825182818291852185518581859188218851888188918921895189818991919221925192819291952195519581959198219851988198919921995199819992222522282229225522582259228522882289229522982299252528252925552558255925852588258925952598259928282928552858285928852888288928952898289929295529582959298529882989299529982999555585559558855895598559958585958885889589858995959885989599859998888988998989999000

Last one…

    I AM   

_ _ _ _ _ _ _ _ _ _ _

   LOCKED  

[ 0 ] [ 1 ]

The minimum length of the De Bruijn sequence is 2058… We deleted the last 58 character and it still worked.

000000000001000000000110000000010100000000111000000010010000000101100000001101000000011110000001000100000010011000000101010000001011100000011001000000110110000001110100000011111000001000010000010001100000100101000001001110000010100100000101011000001011010000010111100000110001000001100110000011010100000110111000001110010000011101100000111101000001111110000100001100001000101000010001110000100100100001001011000010011010000100111100001010001000010100110000101010100001010111000010110010000101101100001011101000010111110000110001100001100101000011001110000110100100001101011000011011010000110111100001110001000011100110000111010100001110111000011110010000111101100001111101000011111110001000100100010001011000100011010001000111100010010011000100101010001001011100010011001000100110110001001110100010011111000101000110001010010100010100111000101010010001010101100010101101000101011110001011001100010110101000101101110001011100100010111011000101111010001011111100011000111000110010010001100101100011001101000110011110001101001100011010101000110101110001101100100011011011000110111010001101111100011100101000111001110001110100100011101011000111011010001110111100011110011000111101010001111011100011111001000111110110001111110100011111111001001001010010010011100100101011001001011010010010111100100110011001001101010010011011100100111011001001111010010011111100101001011001010011010010100111100101010011001010101010010101011100101011011001010111010010101111100101100111001011010110010110110100101101111001011100110010111010100101110111001011110110010111110100101111111001100110110011001110100110011111001101001110011010101100110101101001101011110011011010100110110111001101110110011011110100110111111001110011110011101010100111010111001110110110011101110100111011111001111010110011110110100111101111001111101010011111011100111111011001111111010011111111101010101011010101011110101011011101010111011010101111110101101011101011011011010110111110101110111101011110111010111110110101111111101101101111011011101110110111111101110111111011110111110111111111110000000000

IJCTF{0p3n3d_d3_bru1jn_v4ul75}