BLE配对绑定过程梳理

（一）BLE SM为以下三种procedure提供支持：
1. Pairing;
2. Bondig;
3. Encryption Re-establishment;

区别于传统蓝牙的配对过程，BLE的配对过程发生在连接过程之后；为了弄清BLE的配对绑定过程，首先对BLE的广播连接过程进行了梳理，流程图如下图所示：

Devices that need to form a connection to another device listen for connectable
advertising packets. Such devices are referred to as initiators. If the advertiser
is using a connectable advertising event, an initiator may make a connection
request using the same advertising PHY channel on which it received the
connectable advertising packet. The advertising event is ended and connection
events begin if the advertiser receives and accepts the request for a
connection be initiated. Once a connection is established, the initiator becomes