Software Design

Demystifying the Bluetooth Device Pairing State Machine

State Diagrams · made in Skemio

State diagram showing Bluetooth device flow from Discovering to Authenticating, Paired, and Connected, with transitions for drops and unpairing ending at final.
State diagram showing Bluetooth device flow from Discovering to Authenticating, Paired, and Connected, with transitions for drops and unpairing ending at final.
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What it shows

  • Peripheral advertises while Central listens in discovering state.
  • Passkey exchange and cryptographic keys are bound in authenticating.
  • Paired devices store keys to allow instant auto-reconnects later.

The takeaway

Pairing exchanges long-term crypto keys once; connection uses them repeatedly.

More state diagrams