Physical layer security is a method to ensure the confidentiality of a wireless communication from encryption keys exploiting the randomness of the reciprocal propagation channel between a pair of legitimate users, Alice and Bob. This confidentiality is achieved owing to the decorrelation between these channels and that experienced by a third terminal (Eve), acting as an eavesdropper. In this work, we evaluate the secret key capacity of a simple channel model, based on a disc of scatterers. The model allows to consider any distance between Bob and Eve within the disc, thus is not limited to a spatial stationarity, and is suitable to investigate the impact on the security of multiple antennas.