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"""Provides curve model classes for the supported curve models."""
from ast import parse, Expression, Module
from typing import List, MutableMapping
from importlib_resources import files, as_file
from importlib_resources.abc import Traversable
from public import public
from pyecsca.ec.coordinates import EFDCoordinateModel, CoordinateModel
@public
class CurveModel:
"""Model(form) of an elliptic curve."""
name: str
shortname: str
coordinates: MutableMapping[str, CoordinateModel]
parameter_names: List[str]
coordinate_names: List[str]
equation: Expression
ysquared: Expression
base_addition: List[Module]
base_doubling: List[Module]
base_negation: List[Module]
base_neutral: List[Module]
full_weierstrass: List[Module]
to_weierstrass: List[Module]
from_weierstrass: List[Module]
class EFDCurveModel(CurveModel):
"""A curve model from [EFD]_ data."""
_efd_name: str
_loaded: bool = False
def __init__(self, efd_name: str):
self._efd_name = efd_name
self.shortname = efd_name
if self._loaded:
return
self.__load(efd_name)
def __load(self, efd_name: str):
self.__class__._loaded = True # skipcq: PYL-W0212
self.__class__.coordinates = {}
self.__class__.parameter_names = []
self.__class__.coordinate_names = []
self.__class__.base_addition = []
self.__class__.base_doubling = []
self.__class__.base_negation = []
self.__class__.base_neutral = []
self.__class__.full_weierstrass = []
self.__class__.to_weierstrass = []
self.__class__.from_weierstrass = []
for entry in files("pyecsca.ec").joinpath("efd", efd_name).iterdir():
with as_file(entry) as file_path:
if entry.is_dir():
self.__read_coordinate_dir(
self.__class__, file_path, file_path.stem
)
else:
self.__read_curve_file(self.__class__, file_path)
def __read_curve_file(self, cls, file_path: Traversable):
def format_eq(line, mode="exec"):
return parse(line.replace("^", "**"), mode=mode)
with file_path.open("rb") as f:
for raw in f.readlines():
line = raw.decode("ascii").rstrip()
if line.startswith("name"):
cls.name = line[5:]
elif line.startswith("parameter"):
cls.parameter_names.append(line[10:])
elif line.startswith("coordinate"):
cls.coordinate_names.append(line[11:])
elif line.startswith("satisfying"):
cls.equation = format_eq(line[11:], mode="eval")
elif line.startswith("ysquared"):
cls.ysquared = format_eq(line[9:], mode="eval")
elif line.startswith("addition"):
cls.base_addition.append(format_eq(line[9:]))
elif line.startswith("doubling"):
cls.base_doubling.append(format_eq(line[9:]))
elif line.startswith("negation"):
cls.base_negation.append(format_eq(line[9:]))
elif line.startswith("neutral"):
cls.base_neutral.append(format_eq(line[8:]))
elif line.startswith("toweierstrass"):
cls.to_weierstrass.append(format_eq(line[14:]))
elif line.startswith("fromweierstrass"):
cls.from_weierstrass.append(format_eq(line[16:]))
else:
cls.full_weierstrass.append(format_eq(line))
def __read_coordinate_dir(self, cls, dir_path: Traversable, name: str):
cls.coordinates[name] = EFDCoordinateModel(dir_path, name, self)
def __eq__(self, other):
if not isinstance(other, EFDCurveModel):
return False
return self._efd_name == other._efd_name
def __getstate__(self):
return self.__dict__.copy()
def __setstate__(self, state):
if not self.__class__._loaded:
self.__load(state["_efd_name"])
self.__dict__.update(state)
def __hash__(self):
return hash(self._efd_name)
def __str__(self):
return f"{self.__class__.__name__.replace('Model', '')}"
def __repr__(self):
return f"{self.__class__.__name__}()"
@public
class ShortWeierstrassModel(EFDCurveModel):
"""
Short-Weierstrass curve model.
.. math::
y^2 = x^3 + a x + b
"""
def __init__(self):
super().__init__("shortw")
@public
class MontgomeryModel(EFDCurveModel):
"""
Montgomery curve model.
.. math::
B y^2 = x^3 + A x^2 + x
"""
def __init__(self):
super().__init__("montgom")
@public
class EdwardsModel(EFDCurveModel):
"""
Edwards curve model.
.. math::
x^2 + y^2 = c^2 (1 + d x^2 y^2)
"""
def __init__(self):
super().__init__("edwards")
@public
class TwistedEdwardsModel(EFDCurveModel):
"""
Twisted-Edwards curve model.
.. math::
a x^2 + y^2 = 1 + d x^2 y^2
"""
def __init__(self):
super().__init__("twisted")
_dirs = list(files("pyecsca.ec").joinpath("efd").iterdir())
if not _dirs:
import warnings
warnings.warn(
"EFD not available, pyecsca is mis-installed. "
"Make sure that you check out the git submodules prior to install (when installing from git)."
)
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