An apparatus is provided for charging a Universal Serial Bus device according to an optimal charging mode. The dot patterns are slash-like markings or glyphs tilted to the right and left with respect to the longitudinal axis of the recording medium. The contacts of each of the contact modules are aligned in a first direction, and corresponding contacts of the contact modules are aligned in a second direction perpendicular to the first direction, so that the contacts are disposed in a matrix arrangement. A hash value generation unit generates a hash value corresponding to the group key.