Generic Access Profile (GAP)

Bluetooth Low Energy specifies a generic profile that enables BLE devices to communicate with each other. It can be understood as a base profile which is the same throughout the BLE devices. It defines basic requirements of a Bluetooth device. This generic profile is used to tie all the layers together and identifies all the layers from PHY to L2CAP. It helps to universally maintain all the layers of Bluetooth Low Energy.

Generic Access Profile defines security by implementing cryptographic algorithms that enable devices to securely transfer data attributes. This functionality is achieved by Security Manager which is implemented on the protocol stack. As GAP is universally spread over all the layers, it can maintain and dictate the standard to all the layers. The Advanced Encryption Standard (AES) is used for secure key exchange between the peers to start a communication. GAP sets the procedures for security by giving the trust to the peers to carry sensitive data across the Bluetooth connection.

Generic Access Profile (GAP) also defines the roles used in the Bluetooth Low Energy. These roles are Broadcaster, Observer, Peripheral, and Central. These roles are really important to understand as the foundation of BLE is based on it. Based on the implementation, a BLE device can operate under one role at a time. This multi-role scenario is only possible if the underlying controllers support those roles.