Disclosed are: a mobile device, in particular a mobile Passive Keyless Entry, PKE, key device, and an associated method for providing 3D field values of a magnetic field H; an evaluation device for use in a PKE system having a Mobile device and an associated method for determining the direction of a magnetic field vector H=(x, y, z), which is present locally at a position of a 3D antenna of the mobile device; and a PKE system having a PKE base structure, to which preferably the mobile device is associated and which has at least a first base structure antenna, which is operable to emit the, particularly low frequency, magnetic field, the mobile PKE device and the evaluation unit. The mobile device and the associated method are characterized by providing, in addition to providing a first, second and third value vx, vx, and vx indicative of the local X-component x, Y-component y, and Z-component x of the magnetic field vector H, a sum value vS indicative of the sum |S|=|x+y+z| of the local X-, Y-, and Z-components of the magnetic field vector H. The evaluation device and the associated method are characterized by providing the vector V yielded as a vector, which has the direction of the magnetic field vector H, and may be capable to discriminate, if a one-dimensional Relay Station Attack has occurred or if a regular wireless connection has been established between the PKE base structure and the associated mobile device.