Using properties of elliptic curve pairings, and considering `PiH = G1`, we can compute `PiC = [t^4 - 10 t^3 + ... + 24]G1` and `PiCa = [a t^4 - 10 a t^3 + 35 a t^2 - 50 a t + 24 a]G1` which can be computed from `PKC` and `PKCa` respectively.
More details in the [full writeup](https://github.com/pwning/public-writeup/tree/master/rwctf2023/crypto_0KPR00F)