PicoCTF19 b00tl3gRSA2

Challenge

In RSA d is alot bigger than e, why dont we use d to encrypt instead of e? Connect with nc 2019shell1.picoctf.com 40480

Hints

What is e generally?

Solution

$ nc 2019shell1.picoctf.com 40480
c: 2227211376737039937815591841583322219566252533744426276462773206888045748184290863025760295434296972640543617203018637540296885139307674289872088998737701404390693351315297815971174195313821697937235534517169830898020526018142713263804256799943353034620585446162361316614966452481137685467482096376041045553
n: 122257867992330123694849053069496256961142485055188967457363024625095520165285145992678350145142588928812101783584788345493756672241488097846310440568192896037282979149068599758350070038965853680896117225473022760423760319172301276128334331212378438916320597811225476816307146390872876401243235221507551945427
e: 9040109072597643764976097642168223465121938486312247071095430326887298636205072210820136484785098279582883641961821327223747575166428907672966727115880535670506948628864730176719767934575396842177316167915271868800274457299592123662593058375645834359674722354498324615375871394016309861546258126561404675201

We seem to be given another message which we need to decipher. e is actually quite large this time.

Let's try: RSACTFTool

$ python RsaCtfTool.py -n 122257867992330123694849053069496256961142485055188967457363024625095520165285145992678350145142588928812101783584788345493756672241488097846310440568192896037282979149068599758350070038965853680896117225473022760423760319172301276128334331212378438916320597811225476816307146390872876401243235221507551945427 -e 9040109072597643764976097642168223465121938486312247071095430326887298636205072210820136484785098279582883641961821327223747575166428907672966727115880535670506948628864730176719767934575396842177316167915271868800274457299592123662593058375645834359674722354498324615375871394016309861546258126561404675201 --uncipher 2227211376737039937815591841583322219566252533744426276462773206888045748184290863025760295434296972640543617203018637540296885139307674289872088998737701404390693351315297815971174195313821697937235534517169830898020526018142713263804256799943353034620585446162361316614966452481137685467482096376041045553
[+] Clear text :                                                                                                       picoCTF{bad_1d3a5_9093280}

Flag

picoCTF{bad_1d3a5_9093280}