0xL4ugh CTF write up

Forenscis

 

3Cd7MMS7GmZMwxmRTfQwoXvxcDkGt8o4cFzwPUrg

then what?

 

 

 

아 base58이었넹

ah it was base58 encoded strings.

---

 

ascii 85 -> pastebin.pl/view

 

use "d02a7960"

 

pastebin.pl/view/d02a7960

 

morse code

 

S0METIM35SH4RK1SFR13ND1Y

 

---

png file.

4F -> 4E

43 -> 44

 

46 -> 4e

 

nothing here :(

 

 

move to 5527125

start and end...?

xor 6

---

Crypto

{ ^),!&),!!$,^$,!^%,!$&,!%),!&#,!!#,^#,!&!,!$@,^),!$!,!^@,!$$,!#&,^!,!^#,!#&,!!),^#,!!$,!@),!)^,!@%,^!,^!,!&% }

 

! -> 1

@ -> 2

# -> 3

...

60 170 114 64 165 147 150 173 113 63 171 142 60 141 162 144 137 61 163 137 110 63 114 120 106 125 61 61 175

hmm..

Isn't it this?

 

아 8진수였네

ah octal..

---

n = 5028492424316659784848610571868499830635784588253436599431884204425304126574506051458282629520844349077718907065343861952658055912723193332988900049704385076586516440137002407618568563003151764276775720948938528351773075093802636408325577864234115127871390168096496816499360494036227508350983216047669122408034583867561383118909895952974973292619495653073541886055538702432092425858482003930575665792421982301721054750712657799039327522613062264704797422340254020326514065801221180376851065029216809710795296030568379075073865984532498070572310229403940699763425130520414160563102491810814915288755251220179858773367510455580835421154668619370583787024315600566549750956030977653030065606416521363336014610142446739352985652335981500656145027999377047563266566792989553932335258615049158885853966867137798471757467768769820421797075336546511982769835420524203920252434351263053140580327108189404503020910499228438500946012560331269890809392427093030932508389051070445428793625564099729529982492671019322403728879286539821165627370580739998221464217677185178817064155665872550466352067822943073454133105879256544996546945106521271564937390984619840428052621074566596529317714264401833493628083147272364024196348602285804117877
e = 65537
c = 4690057718147075505522680135959473215321622692923721213835300886402444910436674094980456964526719786485709929645871497583481786451712108343985733309427211434750949557522557087475715799166136616546091244246093209194216096205011115055709130990240778725741521267153888212132276867942685123502211572949952162376597662509054070693025973089923370015547373862589488928782901235791144433788299046705518327561160954291094820233386528023713184029738780555483600166071578613803010858511582163397706626459433456365568227181855121476317779040965290548179086133039864725660837003894485377993939038122515590380127757353399577646033195886942935498851291625325622687406058565345707842924577200871090281931390828399034387159796711570518912284855782049322766568438776035673997640836043767460584670094065481165095303859142188605921710309909549354356478577687136627040919972987279885429990570784611705563443122226291405511409355924588407638851356402686178076614729462505897314633054448103933929160379080620408454649164684464952565103672481604538187885457480005006907884784443460386864548916037417492123123957243478299871616131317172973941585334012558762947082226744473068190488648000780008598569174088053018903156614111943478152720349210983651343

search n at www.factordb.com/

factordb.com

good.

 

 

---

braille

 

0xL4ugh{I_Th1nk_Br1ll3_W45_$m4rt}

 

---

Web

make money~

 

I found base32 strings in cookie.

 

 

 

---

 

 

Reverse Engineering

 

HxD

---

 

WA! Flag!

---

rand() % 4 값을 반복 생성하여 파일 크기와 동일한 크기의 배열에 저장한다.

파일의 j번째 바이트와 랜덤값이 들어간 배열의 j번째 바이트를 가져와서

mystery함수 호출

 

Repeat generation of values (rand() %4) and push them on an array of the same size as the file size.
Gets the jth byte of the file and the jth byte of the array containing random values.

call mystery function

 

랜덤값이 2또는 0인경우 파일의 값과 1을 xor연산하여 리턴.

 

If the random value is 2 or 0, xor computes the byte and 1 of the file and returns it.

 

 

 

main 함수에서 srand(0)을 사용했으므로 시드가 고정.

랜덤값을 구할 수 있음.

 

 

The seed is fixed because it used sand(0) in main func.
I can get random values.

 

 

 

---

 

Programming

 

 

 

---

Misc

Sonic Visualiser

spectrogram

FLAG : 0xL4ugh{SP3c7ro_1s_Gr347}

 

 

---

 

github.com/jzyra/DecodeAndroidGesture

jzyra/DecodeAndroidGesture

 

 

---

 

github.com/ribt/dtmf-decoder

ribt/dtmf-decoder

 

 

66#666#8#33#888#33#777#999#8#44#444#66#4#666#66#7777#2#6#33#9#2#999#

->
noteverythingonsameway