Leashing is performed by the Reader. The Reader scans the local environment for devices and receives their relative 802.15.x signal strength. The reader has a configured RSSI threshold which indicates approximately how far away a phone or device is.
When the devices signal strength reaches above the leashing threshold, the reader will attempt a connection with the device to determine if it has a wallet and a valid credential.
If the reader determines that a valid credential is not present on the phone, the reader will blacklist the device from subsequent scans until either the device changes it MAC address, is presented to the reader as a “touch” (very strong signal strength <-32db) or the blacklist timer has expired, approximately 2 minutes.