def exchange_keys(self, A1: EcPt, A2: EcPt) -> Tuple[EcPt, EcPt]:
curve = EcGroup(713)
g = curve.generator()
b1 = curve.order().random()
B1 = g.pt_mul(b1)
b2 = curve.order().random()
B2 = g.pt_mul(b2)
self._keys = Keys()
self._keys.encryption_key = sha256(A1.pt_mul(b1).export()).digest()
self._keys.hashing_key = sha256(A2.pt_mul(b2).export()).digest()
return B1, B2
