An apparatus for effecting commercial transactions with a server using a transaction card via a communication device is provided. The method includes intercepting an input command message intended for the router, where the router partitioned into a plurality of logical router partitions, and the input command message expressed in terms of logical router partitions. This makes it possible to maintain a high volume ratio of the ink tank and to achieve stableness of the negative pressure by adequately regulating the deformation of the sheet when the sheet is displaced in the direction of retracting toward the interior of the tank as a result of a reduction of the amount of ink in the tank. The multiplier module includes a Montgomery multiplier configured to perform Montgomery multiplication operation for both the RSA operation and the ECC operation.