Given information

They've gotten into your mind, but haven't managed to dive that deep yet. Root them out before it becomes an issue.

 cat ciphertext-bb416c708f242b0c70d6f2c07d646d9f.txt
Modulus: 98570307780590287344989641660271563150943084591122129236101184963953890610515286342182643236514124325672053304374355281945455993001454145469449640602102808287018619896494144221889411960418829067000944408910977857246549239617540588105788633268030690222998939690024329717050066864773464183557939988832150357227
One factor of N:  9695477612097814143634685975895486365012211256067236988184151482923787800058653259439240377630508988251817608592320391742708529901158658812320088090921919
Public key: 65537
Ciphertext: 75665489286663825011389014693118717144564492910496517817351278852753259053052732535663285501814281678158913989615919776491777945945627147232073116295758400365665526264438202825171012874266519752207522580833300789271016065464767771248100896706714555420620455039240658817899104768781122292162714745754316687483

First steps

The challenge is distributed as a file containing some information that may be used to decipher the given ciphertext

One Shot Solve

As this is an introductory challenge, we can solve it in a fairly strait-foward way, in this case using the RsaCtfTool:

 ./RsaCtfTool.py -n 102346477809188164149666237875831487276093753138581452189150581288274762371458335130208782251999067431416740623801548745068435494069196452555130488551392351521104832433338347876647247145940791496418976816678614449219476252610877509106424219285651012126290668046420434492850711642394317803367090778362049205437 --uncipher 4458558515804625757984145622008292910146092770232527464448604606202639682157127059968851563875246010604577447368616002300477986613082254856311395681221546841526780960776842385163089662821 -e 3

...

Results for /tmp/tmpxi7twzzn:

Unciphered data :
HEX : 0x666c61677b77335f6e6565645f376f5f67305f6433657033727d
INT (big endian) : 164587995846552213349276905669580061809447554828318448024777341
INT (little endian) : 201584106411901694616549114265403818352500570162482437244939366
STR : b'flag{w3_need_7o_g0_d3ep3r}'

...

As you can see, the ciphertext could be unciphered pretty much the same way as in the Dream Stealing challenge.

Flag

flag{w3_need_7o_g0_d3ep3r}