微信硬件平台的接收微信消息能力，接收图片的时候，download_url下载的文件无法打开，是经过加密的文件，还有个enckey应该是解密的密钥。

https://iot.weixin.qq.com/wiki/new/index.html?page=1-2

文档里没有提到如何解密图片文件。

以下是收到的推送消息：

{"device_id":"gh_c20b0ca4a15a_3c517fde897fd6df","device_type":"gh_c20b0ca4a15a","msg_id":801277587,"msg_type":"set","services":{"wxmsg_file":{"type":"jpg","name":"4422dfcdf954483204a42120418d5cfe.jpg","size":8124,"md5":"5bbe8adefd93f7c6af26076790ef4fdb","download_url":"http://wxapp.tc.qq.com/202/20303/stodownload?filekey=30340201010420301e020200ca04025348041035c0faf79c83c0af9018e3efce6f8d1302022000040d00000004627466730000000131&hy=SH&storeid=32303230303232363134323031303030303632363731303032366231326464376536346630393030303030306361&bizid=1023"},"wxmsg_image":{"type":"jpg","name":"4422dfcdf954483204a42120418d5cfe.jpg","size":8124,"md5":"5bbe8adefd93f7c6af26076790ef4fdb","download_url":"http://wxapp.tc.qq.com/202/20303/stodownload?filekey=30340201010420301e020200ca04025348041035c0faf79c83c0af9018e3efce6f8d1302022000040d00000004627466730000000131&hy=SH&storeid=32303230303232363134323031303030303632363731303032366231326464376536346630393030303030306361&bizid=1023","enckey":"-3368858470621432036"}},"user":"xxx"}