解决RSA加密中BigInteger字节数组可变长度导致的解密失败问题

import java.io.*; import java.math.BigInteger; import java.util.Random;  public class RSACryptographer {      // 假设 ModPow 和 ReadFileToBinary 方法已定义     // public static BigInteger ModPow(BigInteger base, BigInteger exponent, BigInteger modulus) { ... }     // public static int[] ReadFileToBinary(String path) throws IOException { ... }      public static void RSAEncryptDecrypt(String inputFilePath, String encryptedFilePath, String decryptedFilePath) throws Exception {         Random random = new Random();          // 1. 生成RSA密钥对         BigInteger P = BigInteger.probablePrime(16, random); // 示例：16位素数         BigInteger Q = BigInteger.probablePrime(16, random); // 示例：16位素数          BigInteger N = P.multiply(Q); // 模数 N         BigInteger f = (P.subtract(BigInteger.ONE)).multiply(Q.subtract(BigInteger.ONE)); // 欧拉函数 f(N)          BigInteger d; // 私钥指数         BigInteger c; // 公钥指数 (通常是e)          // 寻找与f互质的d         do {             d = new BigInteger(16, random); // 示例：16位随机数         } while (!(d.gcd(f).equals(BigInteger.ONE)) || d.compareTo(f) >= 0 || d.compareTo(BigInteger.ONE) <= 0);          // 计算c (d的模逆元)         c = d.modInverse(f);          System.out.println("RSA Keys Generated:");         System.out.println("P: " + P);         System.out.println("Q: " + Q);         System.out.println("N (Public Modulus): " + N);         System.out.println("f (Phi(N)): " + f);         System.out.println("d (Private Exponent): " + d);         System.out.println("c (Public Exponent): " + c);         System.out.println("------------------------------------");          // 2. 读取原始文件数据         int[] fileData = ReadFileToBinary(inputFilePath);          // 3. 加密过程         try (DataOutputStream encryptFileStream = new DataOutputStream(new FileOutputStream(encryptedFilePath))) {             System.out.println("Starting encryption...");             for (int messInt : fileData) {                 BigInteger message = BigInteger.valueOf(messInt); // 将单个字节转换为BigInteger                  // 确保消息小于N (对于单字节消息，通常总是小于N)                 if (message.compareTo(N) >= 0) {                     throw new IllegalArgumentException("Message value " + message + " is too large for modulus N=" + N);                 }                  // 加密：encrypt = message^d mod N                 BigInteger encryptedBigInt = ModPow(message, d, N);                  // 将加密后的BigInteger转换为字节数组                 byte[] encryptedBytes = encryptedBigInt.toByteArray();                  // 写入字节数组的长度，然后写入字节数组本身                 encryptFileStream.writeInt(encryptedBytes.Length); // 写入长度 (int占4字节)                 encryptFileStream.write(encryptedBytes);           // 写入加密数据             }             System.out.println("Encryption complete. Encrypted file saved to: " + encryptedFilePath);         }          // 4. 解密过程         try (DataInputStream decryptFileStream = new DataInputStream(new FileInputStream(encryptedFilePath));              FileOutputStream decryptedFileOutputStream = new FileOutputStream(decryptedFilePath)) {             System.out.println("Starting decryption...");             while (decryptFileStream.available() > 0) {                 // 读取加密块的长度                 int length = decryptFileStream.readInt();                  // 根据长度读取加密块的字节数组                 byte[] encryptedBytesToRead = new byte[length];                 decryptFileStream.readFully(encryptedBytesToRead); // 确保读取所有字节                  // 将字节数组转换回BigInteger密文                 BigInteger encryptedBigInt = new BigInteger(encryptedBytesToRead);                  // 解密：decrypted = encryptedBigInt^c mod N                 BigInteger decryptedBigInt = ModPow(encryptedBigInt, c, N);                  // 将解密后的BigInteger转换回原始字节                 // 由于原始消息是单个字节 (0-255)，这里取其低8位                 byte decryptedByte = (byte) (decryptedBigInt.intValue() & 0xFF);                 decryptedFileOutputStream.write(decryptedByte);             }             System.out.println("Decryption complete. Decrypted file saved to: " + decryptedFilePath);         }     }      // 辅助方法：ModPow (模幂运算)     // 假设这是您自己的实现，或者使用BigInteger自带的modPow     public static BigInteger ModPow(BigInteger base, BigInteger exponent, BigInteger modulus) {         return base.modPow(exponent, modulus);     }      // 辅助方法：ReadFileToBinary     public static int[] ReadFileToBinary(String path) throws IOException {         File file = new File(path);         byte[] fileData = new byte[(int)file.length()];         try (FileInputStream in = new FileInputStream(file)) {             in.read(fileData);         }         int[] arrayBytes= new int[fileData.length];          for(int i = 0; i < fileData.length; i++) {             arrayBytes[i] = Byte.toUnsignedInt(fileData[i]);         }         return arrayBytes;     }      public static void main(String[] args) {         try {             // 替换为您的实际文件路径             String input = "C:UsersUserIdeaProjectsCryptoLab1srccryptodino.png";             String encrypted = "C:UsersUserIdeaProjectsCryptoLab1srccryptoendino.png";             String decrypted = "C:UsersUserIdeaProjectsCryptoLab1srccryptodedino.png";             RSAEncryptDecrypt(input, encrypted, decrypted);         } catch (Exception e) {             e.printStackTrace();         }     } }