package com.foxinmy.weixin4j.wxa;
   
   import java.security.AlgorithmParameters;
   import java.security.Key;
   import java.security.Security;
   
   import javax.crypto.Cipher;
   import javax.crypto.spec.IvParameterSpec;
   import javax.crypto.spec.SecretKeySpec;
  
  import org.bouncycastle.jce.provider.BouncyCastleProvider;
  
  /**
   * @since 1.8
   */
  final class AESUtils {
  
  	private static boolean initialized = false;
  
  	private AESUtils() {
  	}
  
  	/**
  	 * AES解密
  	 *
  	 * @param content 密文
  	 * @param keyByte key
  	 * @param ivByte 初始向量
  	 * @return 明文
  	 */
  	static byte[] decrypt(byte[] content, byte[] keyByte, byte[] ivByte) {
  		initialize();
  		try {
  			Cipher cipher = Cipher.getInstance("AES/CBC/PKCS7Padding");
  			Key sKeySpec = new SecretKeySpec(keyByte, "AES");
  
  			cipher.init(Cipher.DECRYPT_MODE, sKeySpec, generateIV(ivByte)); // 初始化
  			byte[] result = cipher.doFinal(content);
  			return result;
  		} catch (Exception e) {
  			throw new RuntimeException(e);
  		}
  	}
  
  	private static synchronized void initialize() {
  		if (initialized) {
  			return;
  		}
  
  		Security.addProvider(new BouncyCastleProvider());
  		initialized = true;
  	}
  
  	private static AlgorithmParameters generateIV(byte[] iv) throws Exception {
  		AlgorithmParameters params = AlgorithmParameters.getInstance("AES");
  		params.init(new IvParameterSpec(iv));
  		return params;
  	}
  
  }