In one embodiment, a security logic of first portable device is configured to receive first motion sample information from at least one motion sensor of the first portable device and second motion sample information from at least one motion sensor of a second portable device, the first and second motion sample information obtained responsive to training movement of the first and second portable devices by a first user. Based on the motion sample information, the security logic is configured to generate a device pairing value, generate a first confidence value based on the first motion sample information and first reference motion sample information stored in the first portable device corresponding to reference movement of the first portable device by the first user, generate a relationship key pair for a relationship, and communicate the first confidence value and a public key of the relationship key pair to the second portable device using the device pairing value. Other embodiments are described and claimed.