In an information embedding apparatus, an image selecting unit selects original image data from an original image data group, a decoder detects a code from the selected original image data, and a candidate code determining unit calculates a candidate code. A melt having one or more of bismuth, tin and lead and having a density in the range of 7. A channel matrix is compiled of the transmit antennas versus the receive antennas and a selection is made of a combination of transmit and receive antennas receiving acceptably a first signal and unacceptably a second signal and vice versa. The locking hole includes two opposite first sides and two opposite second sides. The combination of the second plate sliding within the housing and the two hinges accommodates variations in lateral offset between the two surfaces.