A method comprising: presenting, by a client device, a digital component comprising geofence data that defines one or more physical locations corresponding to the digital component; in response to presenting the digital component, storing, by a trusted program of the client device and in a presentation event data structure, a presentation event data element specifying the geofence data; detecting, by the trusted program and based on location information indicating a current location of the client device and the geofence data, that the client device is within one of the one or more physical locations; and in response to detecting that the client device is within one of the one or more physical locations, transmitting, to a reporting system for the digital component, an event report indicating that a location event for the digital component has occurred, the location event being a visit to the one physical location after the digital component was presented by the client device, wherein the event report comprises an attestation token that comprises: a set of data comprising: a device public key of the client device; an attestation token creation time indicating a time at which the attestation token was created; a device integrity token indicating a level of trustworthiness of the client device; and payload data comprising a location identifier for the one physical location; and a digital signature of the set of data generated using a device private key corresponding to the device public key, wherein the method further comprises at least one of: assigning a visit duration of the visit to a given visit duration quantile of a plurality of visit duration quantiles and including the visit duration quantile in the payload data; assigning a starting time of the visit to a given start time quantile of a plurality of start time quantiles and including the given start time quantile in the payload data; or assigning an end time of the visit to a given end time quantile of a plurality of end time quantiles and including the given end time quantile in the payload data. presenting, by a client device, a digital component comprising geofence data that defines one or more physical locations corresponding to the digital component; in response to presenting the digital component, storing, by a trusted program of the client device and in a presentation event data structure, a presentation event data element specifying the geofence data; detecting, by the trusted program and based on location information indicating a current location of the client device and the geofence data, that the client device is within one of the one or more physical locations; and in response to detecting that the client device is within one of the one or more physical locations, transmitting, to a reporting system for the digital component, an event report indicating that a location event for the digital component has occurred, the location event being a visit to the one physical location after the digital component was presented by the client device, wherein the event report comprises an attestation token that comprises: a set of data comprising: a device public key of the client device; an attestation token creation time indicating a time at which the attestation token was created; a device integrity token indicating a level of trustworthiness of the client device; and payload data comprising a location identifier for the one physical location; and a digital signature of the set of data generated using a device private key corresponding to the device public key, a device public key of the client device; an attestation token creation time indicating a time at which the attestation token was created; a device integrity token indicating a level of trustworthiness of the client device; and payload data comprising a location identifier for the one physical location; and a digital signature of the set of data generated using a device private key corresponding to the device public key, wherein the method further comprises at least one of: assigning a visit duration of the visit to a given visit duration quantile of a plurality of visit duration quantiles and including the visit duration quantile in the payload data; assigning a starting time of the visit to a given start time quantile of a plurality of start time quantiles and including the given start time quantile in the payload data; or assigning an end time of the visit to a given end time quantile of a plurality of end time quantiles and including the given end time quantile in the payload data. assigning a visit duration of the visit to a given visit duration quantile of a plurality of visit duration quantiles and including the visit duration quantile in the payload data; assigning a starting time of the visit to a given start time quantile of a plurality of start time quantiles and including the given start time quantile in the payload data; or assigning an end time of the visit to a given end time quantile of a plurality of end time quantiles and including the given end time quantile in the payload data.