According to an embodiment, a communication device is connected to a key generating device which generates an encryption key. The communication device includes a querying unit, an encryption processor, and a selecting unit. The querying unit is configured to send a query to the key generating device about capability information which indicates capability of the key generating device to generate the encryption key. The encryption processor is configured to implement a plurality of encryption functions. The selecting unit is configured to select, from among the plurality of encryption functions, an encryption function according to the capability information. The encryption processor implements the encryption function thus selected.