Established user habits in carrying multiple wirelessly detectable devices are used to provide or substantiate authentication. In some embodiments, simply detecting that expected devices are co-located within a limited spatial region is sufficient to establish that the devices are being carried by a single individual. In other embodiments, particularly where the potential for spoofing by multiple individuals is a concern, single-user possession of the devices may be confirmed by various corroborative techniques. This approach affords convenience to users, who may be working at a device that lacks the necessary modality (e.g., a fingerprint or vein reader) for strong authentication.