Tags: coppersmith pattern rsa 

Rating: 4.0

tl;dr:
1. Notice repeating pattern in AES-ECB encrypted private key
2. Notice that one of the primes has to be in a form `k * 0x1000...10000...100001 +S`
3. Use Coppersmith method to find small roots of polynomial `f(x) = N/pattern -x`
4. Recover prime factors

Full writeup: https://github.com/p4-team/ctf/tree/master/2019-11-02-google-ctf/fractorization