In some aspects of what is described here, a first wireless device detects proximity of a second wireless device (e.g., by a Near Field Communication (NFC) interface or another type of interface). Based on detecting proximity of the second wireless device, the first wireless device generates a recommendation request from information received from the second wireless device. The first wireless device sends the recommendation request to a trusted authority and receives a response. The response includes the trusted authority's recommendation whether to trust the second wireless device. The first wireless device can determine whether to trust the second wireless device based on the recommendation.