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- using System;
- namespace SubstitutionBox
- {
- class Program
- {
- static void Main(string[] args)
- {
- byte[] S = new byte[256] { 99, 124, 119, 123, 242, 107, 111, 197, 48, 1, 103, 43, 254, 215, 171, 118,
- 202, 130, 201, 125, 250, 89, 71, 240, 173, 212, 162, 175, 156, 164, 114, 192,
- 183, 253, 147, 38, 54, 63, 247, 204, 52, 165, 229, 241, 113, 216, 49, 21,
- 4, 199, 35, 195, 24, 150, 5, 154, 7, 18, 128, 226, 235, 39, 178, 117,
- 9, 131, 44, 26, 27, 110, 90, 160, 82, 59, 214, 179, 41, 227, 47, 132,
- 83, 209, 0, 237, 32, 252, 177, 91, 106, 203, 190, 57, 74, 76, 88, 207,
- 208, 239, 170, 251, 67, 77, 51, 133, 69, 249, 2, 127, 80, 60, 159, 168,
- 81, 163, 64, 143, 146, 157, 56, 245, 188, 182, 218, 33, 16, 255, 243, 210,
- 205, 12, 19, 236, 95, 151, 68, 23, 196, 167, 126, 61, 100, 93, 25, 115,
- 96, 129, 79, 220, 34, 42, 144, 136, 70, 238, 184, 20, 222, 94, 11, 219,
- 224, 50, 58, 10, 73, 6, 36, 92, 194, 211, 172, 98, 145, 149, 228, 121,
- 231, 200, 55, 109, 141, 213, 78, 169, 108, 86, 244, 234, 101, 122, 174, 8,
- 186, 120, 37, 46, 28, 166, 180, 198, 232, 221, 116, 31, 75, 189, 139, 138,
- 112, 62, 181, 102, 72, 3, 246, 14, 97, 53, 87, 185, 134, 193, 29, 158,
- 225, 248, 152, 17, 105, 217, 142, 148, 155, 30, 135, 233, 206, 85, 40, 223,
- 140, 161, 137, 13, 191, 230, 66, 104, 65, 153, 45, 15, 176, 84, 187, 22
- };
- int[,] linearApproxTable = new int[256, 256];
- for (int inputByte = 0; inputByte < 256; inputByte++)
- {
- for (int outputByte = 0; outputByte < 256; outputByte++)
- {
- int count = 0;
- for (int i = 0; i < 256; i++)
- {
- if ((S[i] & inputByte) == (outputByte & S[i]))
- {
- count++;
- }
- }
- linearApproxTable[inputByte, outputByte] = 2 * count - 256;
- }
- }
- // виведення таблиці лінійних апроксимацій у консоль
- for (int i = 0; i < 256; i++)
- {
- for (int j = 0; j < 256; j++)
- {
- Console.Write("{0,4}", linearApproxTable[i, j]);
- }
- Console.WriteLine();
- }
- // Приклад використання таблиці лінійних апроксимацій для знаходження найкращої лінійної апроксимації
- int maxAbsCount = 0;
- int bestInputByte = 0;
- int bestOutputByte = 0;
- for (int inputByte = 0; inputByte < 256; inputByte++)
- {
- for (int outputByte = 0; outputByte < 256; outputByte++)
- {
- if (inputByte == 0 && outputByte == 0) continue; // пропускаємо [0][0]
- int count = linearApproxTable[inputByte, outputByte];
- int absCount = Math.Abs(count);
- if (absCount > maxAbsCount)
- {
- maxAbsCount = absCount;
- bestInputByte = inputByte;
- bestOutputByte = outputByte;
- }
- }
- }
- Console.WriteLine("Best linear approximation: Pr[X*Y=0] = {0}/{1}", maxAbsCount, 256);
- Console.WriteLine("Input byte: 0x{0:X2}", bestInputByte);
- Console.WriteLine("Output byte: 0x{0:X2}", bestOutputByte);
- Console.ReadKey();
- }
- }
- }
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