common.py

"""This file contains methods and objects which are reused through multiple files."""


"""q is the integer modulus which is used in Falcon."""
q = 12 * 1024 + 1


def split(f):
    """Split a polynomial f in two polynomials.

    Args:
        f: a polynomial

    Format: coefficient
    """
    n = len(f)
    f0 = [f[2 * i + 0] for i in range(n // 2)]
    f1 = [f[2 * i + 1] for i in range(n // 2)]
    return [f0, f1]


def merge(f_list):
    """Merge two polynomials into a single polynomial f.

    Args:
        f_list: a list of polynomials

    Format: coefficient
    """
    f0, f1 = f_list
    n = 2 * len(f0)
    f = [0] * n
    for i in range(n // 2):
        f[2 * i + 0] = f0[i]
        f[2 * i + 1] = f1[i]
    return f


def sqnorm(v):
    """Compute the square euclidean norm of the vector v."""
    res = 0
    for elt in v:
        for coef in elt:
            res += coef ** 2
    return res