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https://github.com/elseif/MikroTikPatch.git
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60 lines
1.9 KiB
Python
60 lines
1.9 KiB
Python
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# toyecc - A small Elliptic Curve Cryptography Demonstration.
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# Copyright (C) 2011-2022 Johannes Bauer
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#
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# This file is part of toyecc.
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#
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# toyecc 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 by
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# the Free Software Foundation; this program is ONLY licensed under
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# version 3 of the License, later versions are explicitly excluded.
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#
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# toyecc 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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#
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# You should have received a copy of the GNU General Public License
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# along with toyecc; if not, write to the Free Software
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# Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
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#
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# Johannes Bauer <JohannesBauer@gmx.de>
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#
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from .FieldElement import FieldElement
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class CRT():
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"""Implements the Chinese Remainder Theorem algorithm where a number of
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modular congruences are given that all need to be satisfied."""
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def __init__(self):
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self._moduli = { }
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def add(self, value, modulus):
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"""Adds a value that shall be returned when the result is taken modulo
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the given modulus."""
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assert(modulus not in self._moduli)
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assert(isinstance(value, int))
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assert(isinstance(modulus, int))
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self._moduli[modulus] = value
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return self
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def solve(self):
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"""Solve the Chinese Remainder Theorem for the given values and
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moduli."""
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# Calculate product of all moduli
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product = 1
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for modulus in self._moduli.keys():
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product *= modulus
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# Then determine the solution
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solution = 0
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for modulus in self._moduli.keys():
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if self._moduli[modulus] == 0:
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continue
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rem_product = product // modulus
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one_value = int(FieldElement(rem_product, modulus).inverse())
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solution += rem_product * one_value * self._moduli[modulus]
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return solution % product
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