mirror of https://github.com/nucypher/pyUmbral.git
60 lines
1.6 KiB
Python
60 lines
1.6 KiB
Python
"""
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Copyright (C) 2018 NuCypher
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This file is part of pyUmbral.
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pyUmbral is free software: you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published b
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the Free Software Foundation, either version 3 of the License, or
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(at your option) any later version.
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pyUmbral is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with pyUmbral. If not, see <https://www.gnu.org/licenses/>.
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"""
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from typing import List
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from cryptography.hazmat.backends import default_backend
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from cryptography.hazmat.primitives import hashes
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from cryptography.hazmat.primitives.kdf.hkdf import HKDF
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from umbral.curvebn import CurveBN
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def lambda_coeff(id_i: CurveBN, selected_ids: List[CurveBN]) -> CurveBN:
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ids = [x for x in selected_ids if x != id_i]
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if not ids:
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return None
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result = ids[0] / (ids[0] - id_i)
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for id_j in ids[1:]:
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result = result * id_j / (id_j - id_i)
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return result
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def poly_eval(coeff: List[CurveBN], x: CurveBN) -> CurveBN:
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result = coeff[-1]
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for i in range(-2, -len(coeff) - 1, -1):
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result = (result * x) + coeff[i]
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return result
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def kdf(ecpoint: 'Point', key_length: int) -> bytes:
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data = ecpoint.to_bytes(is_compressed=True)
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return HKDF(
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algorithm=hashes.BLAKE2b(64),
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length=key_length,
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salt=None,
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info=None,
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backend=default_backend()
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).derive(data)
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