Function recover_secret2 

pub fn recover_secret2(
    e0: &Curve2,
    basis_a: (&Point2, &Point2),
    ell: u64,
    a: u32,
    basis_b: (&Point2, &Point2),
    images: (&Point2, &Point2),
) -> Option<(BigInt, Point2, Vec<IsogenyStep2>)>

Images → generator reconstruction (flat oracle). The secret isogeny φ: E₀ → E of degree ℓᵃ has kernel ⟨P_A + [s]Q_A⟩; the published torsion images φ(P_B), φ(Q_B) pin s down. Enumerate the whole keyspace and return the scalar whose unfolded chain reproduces both images — a genuine images → generator inversion at SIDH scale. O(ℓᵃ); the correctness oracle for the structured recovery below.