Markdium-Introduction to encoding in CKKS

Markdium-python.py

@patch_to(CKKSEncoder)
def compute_basis_coordinates(self, z):
    """Computes the coordinates of a vector with respect to the orthogonal lattice basis."""
    output = np.array([np.real(np.vdot(z, b) / np.vdot(b,b)) for b in self.sigma_R_basis])
    return output

def round_coordinates(coordinates):
    """Gives the integral rest."""
    coordinates = coordinates - np.floor(coordinates)
    return coordinates

def coordinate_wise_random_rounding(coordinates):
    """Rounds coordinates randonmly."""
    r = round_coordinates(coordinates)
    f = np.array([np.random.choice([c, c-1], 1, p=[1-c, c]) for c in r]).reshape(-1)
    
    rounded_coordinates = coordinates - f
    rounded_coordinates = [int(coeff) for coeff in rounded_coordinates]
    return rounded_coordinates

@patch_to(CKKSEncoder)
def sigma_R_discretization(self, z):
    """Projects a vector on the lattice using coordinate wise random rounding."""
    coordinates = self.compute_basis_coordinates(z)
    
    rounded_coordinates = coordinate_wise_random_rounding(coordinates)
    y = np.matmul(self.sigma_R_basis.T, rounded_coordinates)
    return y

encoder = CKKSEncoder(M)