tl;dr1. Factor polynomial `n` into polynomials `p` and `q`2. Calculate `s = (2^p_deg - 1)*(2^q_deg - 1)`3. Calculate `d = modinv(e,s)`4. Solve `pt = pow(ct, d, n)`
https://github.com/p4-team/ctf/tree/master/2019-03-23-0ctf-quals/crypto_babyrsa