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from public import public
from .coordinates import AffineCoordinateModel
from .curve import EllipticCurve
from .model import ShortWeierstrassModel, MontgomeryModel, TwistedEdwardsModel
from .params import DomainParameters
from .point import InfinityPoint, Point
def __M_map(params, map_parameters, map_point, model):
A = params.curve.parameters["a"]
B = params.curve.parameters["b"]
parameters = map_parameters(A, B)
aff = AffineCoordinateModel(model)
if isinstance(params.curve.neutral, InfinityPoint):
neutral = InfinityPoint(aff)
else:
neutral = map_point(A, B, params.curve.neutral, aff)
curve = EllipticCurve(model, aff, params.curve.prime, neutral, parameters)
return DomainParameters(curve, map_point(A, B, params.generator, aff), params.order,
params.cofactor)
@public
def M2SW(params: DomainParameters) -> DomainParameters:
"""
Convert a Montgomery curve to ShortWeierstrass.
:param params: The domain parameters to convert.
:return: The converted domain parameters.
"""
if not isinstance(params.curve.model, MontgomeryModel) or not isinstance(
params.curve.coordinate_model, AffineCoordinateModel):
raise ValueError
def map_parameters(A, B):
a = (3 - A ** 2) / (3 * B ** 2)
b = (2 * A ** 3 - 9 * A) / (27 * B ** 3)
return {"a": a, "b": b}
def map_point(A, B, pt, aff):
u = pt.x / B + A / (3 * B)
v = pt.y / B
return Point(aff, x=u, y=v)
return __M_map(params, map_parameters, map_point, ShortWeierstrassModel())
@public
def M2TE(params: DomainParameters) -> DomainParameters:
"""
Convert a Montgomery curve to TwistedEdwards.
:param params: The domain parameters to convert.
:return: The converted domain parameters.
"""
if not isinstance(params.curve.model, MontgomeryModel) or not isinstance(
params.curve.coordinate_model, AffineCoordinateModel):
raise ValueError
def map_parameters(A, B):
a = (A + 2) / B
d = (A - 2) / B
return {"a": a, "d": d}
def map_point(A, B, pt, aff):
u = pt.x / pt.y
v = (pt.x - 1) / (pt.x + 1)
return Point(aff, x=u, y=v)
return __M_map(params, map_parameters, map_point, TwistedEdwardsModel())
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