65 lines
2.2 KiB
C#
65 lines
2.2 KiB
C#
using NUnit.Framework;
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using System;
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using System.Collections.Generic;
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namespace Obfuz.EncryptionVM.Instructions
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{
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public class MultipleInstruction : EncryptionInstructionBase
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{
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private readonly int _multiValue;
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private readonly int _revertMultiValue;
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private readonly int _opKeyIndex;
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public MultipleInstruction(int addValue, int opKeyIndex)
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{
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_multiValue = addValue;
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_opKeyIndex = opKeyIndex;
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_revertMultiValue = (int)ModInverseOdd((uint)addValue);
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Verify();
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}
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private void Verify()
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{
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int a = 1122334;
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Assert.AreEqual(a, a * _multiValue * _revertMultiValue);
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}
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public static uint ModInverseOdd(uint a)
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{
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if (a % 2 == 0)
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throw new ArgumentException("Input must be an odd number.", nameof(a));
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uint x = 1; // 初始解：x₀ = 1 (mod 2)
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for (int i = 0; i < 5; i++) // 迭代5次（2^1 → 2^32）
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{
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int shift = 2 << i; // 当前模数为 2^(2^(i+1))
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ulong mod = 1UL << shift; // 使用 ulong 避免溢出
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ulong ax = (ulong)a * x; // 计算 a*x（64位避免截断）
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ulong term = (2 - ax) % mod;
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x = (uint)((x * term) % mod); // 更新 x，结果截断为 uint
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}
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return x; // 最终解为 x₅ mod 2^32
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}
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public override int Encrypt(int value, int[] secretKey, int salt)
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{
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return value * _multiValue + secretKey[_opKeyIndex] + salt;
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}
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public override int Decrypt(int value, int[] secretKey, int salt)
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{
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return (value - secretKey[_opKeyIndex] - salt) * _revertMultiValue;
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}
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public override void GenerateEncryptCode(List<string> lines, string indent)
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{
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lines.Add(indent + $"value = value * {_multiValue} + _secretKey[{_opKeyIndex}] + salt;");
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}
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public override void GenerateDecryptCode(List<string> lines, string indent)
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{
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lines.Add(indent + $"value = (value - _secretKey[{_opKeyIndex}] - salt) * {_revertMultiValue};");
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}
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}
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}
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