c#纯代码实现byte数组的xxtea加密和解密，不适用库

XXTEA是一种开源的对称密码算法，其核心思想是位级操作。以下是C#纯代码实现XXTEA加密和解密的过程： **加密部分（使用纯字节操作）**: ```csharp using System; using System.Text; public class Xxtea { private const int SBOX_SIZE = 256; private static readonly byte[] sbox = new byte[256]; static Xxtea() { for (int i = 0; i < SBOX_SIZE; i++) { sbox[i] = (byte)(i + ((i * i) % 256)); } } public byte[] Encrypt(byte[] data, byte key) { if (data == null || data.Length == 0 || key == null || key.Length != 16) throw new ArgumentException("Invalid input"); int len = data.Length; int n = len >> 1; byte[] state = new byte[4]; Array.Copy(data, 0, state, 0, n); byte[] keyX = new byte[16]; Array.Copy(key, 0, keyX, 0, 16); for (int round = 0; round < 32; round++) { for (int i = 0; i < n - 1; i += 2) { int t = RotateLeft(state[i + 1], 13) ^ state[i + 1]; int xoredKey = KeySchedule(keyX, round, t); state[i] ^= xoredKey; state[i + 1] ^= RotateLeft(xoredKey, 8); } if (len % 2 == 1) { int t = RotateLeft(state[n - 1], 13) ^ state[n - 1]; int xoredKey = KeySchedule(keyX, round, t); state[n - 1] ^= xoredKey; } } byte[] result = new byte[len]; Array.Copy(state, 0, result, 0, n); Array.Copy(state, n, result, n, len - n); return result; } // 密钥扩展函数 private static byte[] KeySchedule(byte[] key, int rounds, int v) { byte[] keyX = new byte[16]; Array.Copy(key, 0, keyX, 0, 16); for (int i = 0; i < rounds; ++i) { v = MixColumn(keyX, v); } return keyX; } // MixColumn操作 private static byte[] MixColumn(byte[] data, int index) { for (int i = 0; i < 4; i++) { int col = data[index + i]; col = ShiftRows(col); col = AddRoundKey(col, sbox); data[index + i] = col; } return data; } // ShiftRows操作 private static byte ShiftRows(byte value) { value = (byte)((value << 1) | (value >> 7)); value = (byte)((value << 2) | (value >> 5)); value = (byte)((value << 3) | (value >> 3)); return value; } // AddRoundKey操作 private static byte AddRoundKey(byte value, byte keyByte) { return (byte)((value + keyByte) & 0xFF); } private static byte RotateLeft(byte value, int shift) { return (byte)(((value << shift) | (value >> (8 - shift))) & 0xFF); } } ``` **解密部分**: ```csharp public byte[] Decrypt(byte[] encryptedData, byte key) { if (encryptedData == null || encryptedData.Length == 0 || key == null || key.Length != 16) throw new ArgumentException("Invalid input"); int len = encryptedData.Length; int n = len >> 1; byte[] state = new byte[4]; Array.Copy(encryptedData, 0, state, 0, n); byte[] keyX = new byte[16]; Array.Copy(key, 0, keyX, 0, 16); for (int round = 0; round < 32; round++) { for (int i = 0; i < n - 1; i += 2) { int t = RotateRight(state[i + 1], 13) ^ state[i + 1]; int xoredKey = KeySchedule(keyX, round, t); state[i] ^= xoredKey; state[i + 1] ^= RotateRight(xoredKey, 8); } if (len % 2 == 1) { int t = RotateRight(state[n - 1], 13) ^ state[n - 1]; int xoredKey = KeySchedule(keyX, round, t); state[n - 1] ^= xoredKey; } } byte[] result = new byte[len]; Array.Copy(state, 0, result, 0, n); Array.Copy(state, n, result, n, len - n); return result; } // 简化版的RotateRight操作 private static byte RotateRight(byte value, int shift) { return (byte)(((value >> shift) | (value << (8 - shift))) & 0xFF); } ```