According to one aspect of the technique of the present disclosure, there is provided a method for securely communicating data. The method includes: (a) establishing a first encryption scheme, a data integrity checking scheme, an encryption key and an authentication key through a communication connection with a receiver; (b) generating a random key; (c) generating secure data including random key information obtained by encrypting the random key using the encryption key and the first encryption scheme; authentication information generated based on the random key, the data integrity checking scheme and the authentication key; and data information obtained by encrypting data using the random key and a second encryption scheme whose operation load is lower than that of the first encryption scheme; and (d) transmitting the secure data to the receiver.