TLDR   - We are given the KeyGen function, notice that one prime is much larger than the other, so factoring n is possible.
   - Recover n by asking for the encryption of -1. Assume e is small and recover it by solving the dlog by enumeration. Factor n.
   - Compute d (as usual) and decrypt using Square and Multiply adapted for the Complex numbers.
Read complete writeup: [https://sectt.github.io/writeups/CryptoCTF19/crypto_complexrsa/README](https://sectt.github.io/writeups/CryptoCTF19/crypto_complexrsa/README)