code: public String decryptEcho(String msgSignature, String timeStamp, String nonce, String echoStr) throws AesException {
          String signature = SHA1.getSHA1(token, timeStamp, nonce, echoStr);
  
          if (!signature.equals(msgSignature)) {
              throw new AesException(AesException.ValidateSignatureError);
          }
  
          return decrypt(echoStr);
      }
docs: 验证URL
  
  @param msgSignature 签名串，对应URL参数的msg_signature
  @param timeStamp    时间戳，对应URL参数的timestamp
  @param nonce        随机串，对应URL参数的nonce
  @param echoStr      随机串，对应URL参数的echostr
  @return 解密之后的echostr
  @throws AesException 执行失败，请查看该异常的错误码和具体的错误信息