The disclosed embodiments relate to electronic devices with optical head-mounted displays (OHMDs). Each electronic device includes an OHMD that provides a heads-up display (HUD) and one or more sensors. The electronic device also includes a pairing apparatus that uses the OHMD to generate a first signal that is detectable by the other electronic device. The pairing apparatus also uses the OHMD to detect a second signal from a second OHMD at the other electronic device. Next, the pairing apparatus generates a shared secret with the second electronic device using data associated with the first and second signals and uses the shared secret to establish a secure connection with the second electronic device.