A communication system including a plurality of communication apparatuses (10a, 10b), wherein a first communication apparatus includes: short-range active communication means for transmitting an inquiry signal to a short-range external communication apparatus by electromagnetic waves and waiting for a response to the inquiry signal; first long-range communication means capable of communication by the electromagnetic waves in a range wider than the communication area of the short-range active communication means; first switching means for switching to either the short-range active communication means or the long-range communication means; and asymmetric key generating means for generating a pair of an encryption key and a decryption key corresponding to the encryption key, the encryption key and the decryption key in the pair being asymmetric to each other, wherein a second communication apparatus includes: short-range passive communication means for receiving the inquiry signal from a short-range external communication apparatus and transmitting a response signal in response to the inquiry signal; second long-range communication means capable of communication by the electromagnetic waves in a range wider than the communication area of the short-range passive communication means; second switching means for switching to either the short-range passive communication means or the long-range communication means; session key generating means for generating a random number and using the generated random number to generate a session key; and encrypting means for encrypting the session key, wherein the second communication apparatus is configured to use the encryption key transmitted from the first communication apparatus by the short-range active communication means to encrypt the session key into an encrypted session key and to transmit the encrypted session key to the first communication apparatus by the short-range passive communication means, and wherein the first communication apparatus is configured to use the decryption key to decrypt the encrypted session key into the session key and to transmit to the second communication apparatus by the short-range active communication means a communication switching request signal to request the switching from a short-range communication to a long-range communication with the session key by using the first and second long-range communication means (104, 109). short-range active communication means for transmitting an inquiry signal to a short-range external communication apparatus by electromagnetic waves and waiting for a response to the inquiry signal; first long-range communication means capable of communication by the electromagnetic waves in a range wider than the communication area of the short-range active communication means; first switching means for switching to either the short-range active communication means or the long-range communication means; and asymmetric key generating means for generating a pair of an encryption key and a decryption key corresponding to the encryption key, the encryption key and the decryption key in the pair being asymmetric to each other, short-range passive communication means for receiving the inquiry signal from a short-range external communication apparatus and transmitting a response signal in response to the inquiry signal; second long-range communication means capable of communication by the electromagnetic waves in a range wider than the communication area of the short-range passive communication means; second switching means for switching to either the short-range passive communication means or the long-range communication means; session key generating means for generating a random number and using the generated random number to generate a session key; and encrypting means for encrypting the session key,