Rating:

Generic RSA question

n : 126390312099294739294606157407778835887 e : 65537 c : 13612260682947644362892911986815626931

Plugging n into alpertron will immediately return p and q. After getting p and q just the other variables

phi = (p-1) * (q-1)
d = modInverse(e, phi)
pt = pow(ct, d, n)

pt is a bytearray. Deciphering will return us the flag.

Original writeup (https://github.com/darkvoid32/CTF-writeups/tree/master/%C3%A5ngstromCTF%202020/Reasonably%20Strong%20Algorithm).