Abstract: There is provided herein circuitry and methods for applications including touch detection and, in embodiments, low rate communication such as for secure device authentication. The method uses a circuit having a first device having a first pair of unconnected plates and an edge source coupled therebetween. The circuit further comprises a second device having a second pair of respective unconnected plates and a charge sensor coupled therebetween. The method for touch detection comprises applying at least one differential edge between the first pair of unconnected plates using the edge source and detecting touch by coherently (i.e. in time) sensing an imbalance in a near field channel formed between the plates and an output signal of the charge sensor. The present method/circuit has various applications including for touch detection in fencing and secure device authentication employing both touch detection and bidirectional cryptographic communication between key and secure devices.