> For the complete documentation index, see [llms.txt](https://docs.cooku222.kr/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.cooku222.kr/project-remind/contest/undefined/osu-gaming-ctf-2025.md).
# Osu!gaming CTF 2025
RubiyaLab으로 참여했다.
1위하고 있었는데 아쉽다.
3솔했다고 카운트 됐는데 하나는 얻어탄거고 실질적(?) 2솔했다. \
\
Crypto / pls-nominate
```
from math import prod
ns = [250595396282063209494575040924347535718377683482891600245762578107828862102674761114596255712438613333084596184792828788407383247558654559454089469986479081755983932855108019303831103066796233258382489582930536579371270189763162153515702860564938568045151352777820047894231299381399970139347989102071591624967158663442340607621438098266100701196825065519485094630829410736139969891010792546625692049625954656831699035171996469050264653519, 274193894251894220756361545934981580561716587343502325614560502213231097664469582415896327192024233714369720707686115433619798180404789138894067772483823865845960858748702597162370083356345247341014451005796413454404641015516131648586490172413946109076519615677569833823093216546284937656690546486895353267404868698676199564604463636499575466246860736708986174600028222786416474243294353345680209117811499529853520907091701228114817603341, 250799342406461286072464998395337312450245201655027007410237718631499754452822255347456526289099898965321822671514782488741429427305776533799167428860480805487315744950556177330105418061977431001775317350105402223927656557524000999352457757910475375628290615583082601813818635461940350546377443417651889260364946457646723831198413138381669914264256219982213937975414376723125047495586971424241557485231775101178049132539231505246677535311, 424944038623958440933855665649910939213053530859402286143675513220496021786445337272966523453996205752202713497414819150875478398393046433188515528170856189163826639434032436582059667688688880862276540443913407720932133045261989787061306952765245738545030903458101323357019464537917143233906507656465350475977450213990615572573474700619979502153864626401863294100140176446546365233603532530624614938982882757207592863414287369042546971519, 190902360498923981884467164531021372209737709612751157876047387113070619788864781987406983172298076877277648095765822757629049183301893699559004938030166520411955041284763767367633388446007417241478444104664237424445213634253699407015432110027972438018815169650491766550691229860103594060212173628624522421052861949630723039778975476515078589820738377723637869903050748150998629965678848786824733474968760721078438148119740362699143145661]
cs = [123451724931477698812069511077458860459906769716993869507604368750013627155203649026878565706523272034474865506508962044958969096479439140090681403538412644329412752922637248582028201974150208943081418296518937380419465322558643434318990712657710219963788075009287648875763482189708828745866942138140694074154628539909488581608681566648945293332282252866416448399029058170554552880389525160322280616124297247776106117085199571903380300602, 25521272212086093871680233376409740841684880441320606653986457586214228433726846827063346040622596803682405351090250464809787622301562945715858274147064371839443966925136930647541454865892780911461753966896009773200289476756676124794087249400266226027218836477923252144492106017794796924100502787481309583584738175138358520327875032255246435556182629496953900460417813322557030951101538854106453327597012091626682332420269075467900021711, 185794248348100154380171644978622218400518238250460812348815837123659842567285820889770059992960889881347901994420631735102166283167843240900863871790624347481898956733174665116495731603736544724548220276282583347110470600528846477853732162784786525839648496719341390265839130761362980916014963941737879183454424512265005367317359376039242988696224018798645014519276397488302687294083964113652155465518932071360150626192713920598188877877, 253586754830185402755129821208401339617813079433078480306550244166018490731187464131167959996920120199131859308803805312785667542198282217092146066559207637833505962392131719788571007971893923218099583927291388588829681723690416962688366275898952085934742953047229390090702589945168823704791405472122768397486450092804662113840124827388352338015003693741233274505595280978468538153880244070082267537407664878646371738748713917087874183934, 179921278884389482689970386454786826216817164768869732618011304299464646110222440114625532548731013316437178194666578920837571688939194292542951671294588526331670811293769249832666220726222224721812635640949602967313922271367769076173808739323285134139353621782784562334885703861549547716097420971226456620806331145247840335617343331077891979324239020388123429770254863290698575175653976557893390825861821917810477967554648397683909903482]
prefix = b"hello there can you pls nominate my map https://osu.ppy.sh/beatmapsets/2436259 :steamhappy: i can bribe you with a flag if you do: "
def crt(residues, moduli):
N = 1
for m in moduli: N *= m
x = 0
for (a, m) in zip(residues, moduli):
Ni = N // m
inv = pow(Ni, -1, m)
x = (x + a * Ni * inv) % N
return x, N
def int_nth_root(n, k):
lo, hi = 0, 1 << ((n.bit_length() + k - 1)//k)
while hi**k <= n: hi <<= 1
while lo + 1 < hi:
mid = (lo + hi) // 2
p = mid**k
if p == n: return mid, True
if p < n: lo = mid
else: hi = mid
return lo, (lo**k == n)
C, N = crt(cs, ns)
root = None
for k in range(1000000):
r, ok = int_nth_root(C + k*N, 5)
if ok:
root = r
print("k =", k)
break
m = root.to_bytes((root.bit_length()+7)//8, 'big')
flag = m[len(prefix):]
print(flag.decode())
```
CRT에 K를 늘려 계산해준다.\
\
OSINT / weebbolt
```
loner
diary
ongaku
ghost - 34°49'39.1"N 131°59'19.9"E
bench
punchdrunk
cafe - 44250 California 60, Desert Center, CA 92239 미국, https://maps.app.goo.gl/QHyLN3vY5soJPm4QA
roe - 0268 Oslo, 노르웨이(비겔란 조각공원, 확인이 필요)
technology - https://www.google.com/maps/place/나가사키+바이오+파크/@32.9884961,129.7846928,16.31z/data=!4m6!3m5!1s0x356abb0261bec585:0xf1f109703254736c!8m2!3d32.9881189!4d129.7832963!16s%2Fg%2F121q4d06?entry=ttu&g_ep=EgoyMDI1MTAyMi4wIKXMDSoASAFQAw%3D%3D
pumpitup-
```
지오신트 문제다. 구글 이미지 검색 써서 10개 장소 노가다로 찾아 풀어준다.
---
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