Abstract: A modulation device including: a modulation unit for modulating a carrier in an audible sound range by an encoded transmission signal to generate a modulated signal; a masker sound generation unit for generating a masker signal outputted as a masker sound for making the modulated signal harder to hear when transmitted with the modulated signal; and an acoustic signal generation unit for inserting the masker signal in the modulated signal to generate an acoustic signal.

Abstract: Cryptographically Protected Prefixes (“CPPs”) are used to create IP addresses, preventing any correlation between a CPP IP address and a host's geographic location. An IP address is subdivided into address prefixes of multiple segments. Each segment is encrypted with a cryptographic key known only to a subset of routers in the access network domain (or Privacy Domain). Therefore, each router obtains the information it needs to forward a packet of information, but not any additional information.

Abstract: A packet communication terminal is provided without delay in packet communication between the packet communication terminal moving between different networks, and a correspondent packet communication terminal. The packet communication terminal comprises network address acquiring part, network address storage, network address notifying part, and packet receiver. When there exist a plurality of networks to which the packet communication terminal can be connected, the network address acquiring part acquires a plurality of network addresses from the respective networks. The network address storage stores the plurality of network addresses. The network address notifying part notifies the correspondent packet communication terminal of the plurality of network addresses. The packet receiver receives packets generated from identical data and sent from the correspondent packet communication terminal to the respective network addresses.