为什么 Java AES/CBC 解密后初始字节不正确，如何修复？

Java AES/CBC 解密后初始字节不正确

问题：

尝试时在Java中解密AES/CBC加密的字符串，解密结果的初始字节是错误的。

示例：

以下代码演示了该问题：

import javax.crypto.Cipher;
import javax.crypto.spec.IvParameterSpec;
import javax.crypto.spec.SecretKeySpec;

public class AESEncryptionExample {

  public static void encryptDecryptString() {
    try {
      String key = "mySecretKey";
      String value = "This is a test message";
      String initVector = "initializationVector"; // 16-byte (128-bit) initialization vector

      IvParameterSpec iv = new IvParameterSpec(initVector.getBytes());
      SecretKeySpec skeySpec = new SecretKeySpec(key.getBytes(), "AES");

      // Create encrypt cipher
      Cipher encryptCipher = Cipher.getInstance("AES/CBC/PKCS5Padding");
      encryptCipher.init(Cipher.ENCRYPT_MODE, skeySpec, iv);
      byte[] encryptedBytes = encryptCipher.doFinal(value.getBytes());

      // Create decrypt cipher
      Cipher decryptCipher = Cipher.getInstance("AES/CBC/PKCS5Padding");
      decryptCipher.init(Cipher.DECRYPT_MODE, skeySpec, iv);
      byte[] decryptedBytes = decryptCipher.doFinal(encryptedBytes);

      System.out.println("Original: " + value);
      System.out.println("Decrypted: " + new String(decryptedBytes));
    } catch (Exception e) {
      e.printStackTrace();
    }
  }

  public static void main(String[] args) {
    encryptDecryptString();
  }
}

运行此代码时，解密的输出可能会出现类似的情况至：

Result: `£eB6O�geS��i are you? Have a nice day.

解决方案：

由于在处理加密/解密数据时缺少 Base64 编码/解码，导致解密字符串中的初始字节不正确。要解决此问题，应在传输加密字节之前对加密字节进行 Base64 编码，并在解密之前对接收到的加密字节进行 Base64 解码。

更新示例：

import javax.crypto.Cipher;
import javax.crypto.spec.IvParameterSpec;
import javax.crypto.spec.SecretKeySpec;

import java.util.Base64;

public class CipherAESBase64 {

  public static void encryptDecryptString() {
    try {
      String key = "mySecretKey";
      String value = "This is a test message";
      String initVector = "initializationVector"; // 16-byte (128-bit) initialization vector

      IvParameterSpec iv = new IvParameterSpec(initVector.getBytes());
      SecretKeySpec skeySpec = new SecretKeySpec(key.getBytes(), "AES");

      // Create encrypt cipher
      Cipher encryptCipher = Cipher.getInstance("AES/CBC/PKCS5Padding");
      encryptCipher.init(Cipher.ENCRYPT_MODE, skeySpec, iv);
      byte[] encryptedBytes = encryptCipher.doFinal(value.getBytes());

      // Encode the encrypted bytes into a Base64 string
      String encryptedString = Base64.getEncoder().encodeToString(encryptedBytes);

      // Create decrypt cipher
      Cipher decryptCipher = Cipher.getInstance("AES/CBC/PKCS5Padding");
      decryptCipher.init(Cipher.DECRYPT_MODE, skeySpec, iv);

      // Decode the encrypted Base64 string into bytes
      byte[] decryptedBytes = Base64.getDecoder().decode(encryptedString);

      // Decrypt the decoded bytes
      byte[] decryptedBytes = decryptCipher.doFinal(decryptedBytes);

      System.out.println("Original: " + value);
      System.out.println("Decrypted: " + new String(decryptedBytes));
    } catch (Exception e) {
      e.printStackTrace();
    }
  }

  public static void main(String[] args) {
    encryptDecryptString();
  }
}

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