Described herein is an information transmission apparatus for encrypting and transmitting first data and second data, the information transmission apparatus including: encryption element for deriving a second key from a first key by using an irreversible function, encrypting the first data by using the first key to generate encrypted first data and encrypting the second data by using the second key to generate encrypted second data; and transmission element for transmitting the encrypted first data, the encrypted second data and the first key.