# babyrsa

Author: [roerohan](https://github.com/roerohan)

## Source

```
This is just RSA for babies!
```

## Exploit

The factors can be recovered from factordb.

```py
import math
from Crypto.Util.number import inverse

e = 0x10001

n = 19574201286059123715221634877085223155972629451020572575626246458715199192950082143183900970133840359007922584516900405154928253156404028820410452946729670930374022025730036806358075325420793866358986719444785030579682635785758091517397518826225327945861556948820837789390500920096562699893770094581497500786817915616026940285194220703907757879335069896978124429681515117633335502362832425521219599726902327020044791308869970455616185847823063474157292399830070541968662959133724209945293515201291844650765335146840662879479678554559446535460674863857818111377905454946004143554616401168150446865964806314366426743287
s = 3737620488571314497417090205346622993399153545806108327860889306394326129600175543006901543011761797780057015381834670602598536525041405700999041351402341132165944655025231947620944792759658373970849932332556577226700342906965939940429619291540238435218958655907376220308160747457826709661045146370045811481759205791264522144828795638865497066922857401596416747229446467493237762035398880278951440472613839314827303657990772981353235597563642315346949041540358444800649606802434227470946957679458305736479634459353072326033223392515898946323827442647800803732869832414039987483103532294736136051838693397106408367097
c = 7000985606009752754441861235720582603834733127613290649448336518379922443691108836896703766316713029530466877153379023499681743990770084864966350162010821232666205770785101148479008355351759336287346355856788865821108805833681682634789677829987433936120195058542722765744907964994170091794684838166789470509159170062184723590372521926736663314174035152108646055156814533872908850156061945944033275433799625360972646646526892622394837096683592886825828549172814967424419459087181683325453243145295797505798955661717556202215878246001989162198550055315405304235478244266317677075034414773911739900576226293775140327580

# From factordb

p = 137526660281921131221818797107719332505145627503966517923070280130875449016216283557144366594925577458093232503891037595787957060953687166721367679274343931891139309595758625134752102980837611457006046816552168551932124923087090435785959383128842381406539452056309367997750395905747259198693037451326868517899

q = 142330230705328145595283676471239195558844969347785580004001554538877181973869318257471293219512143354019499347549183531116588694914100319083003689276059546015147159203569933280678564050512749524779927522346194056170602443980796876645843108623490893506040488132906421994550401879219627124260709500352428249413

print(p*q == n)

phi = (p-1)*(q-1)

d = inverse(e, phi)

m = pow(c,d,n)

m = hex(m)[2:]

print(bytes.fromhex(m))
```

The flag is:

```
DUCTF{e4sy_RSA_ch4ll_t0_g3t_st4rt3d}
```

Original writeup (https://github.com/csivitu/CTF-Write-ups/tree/master/DUCTF/crypto/babyrsa).