Abstract: The present invention relates to a method and system for storing information using TCP communication, and the method includes a communication connection request operation of transmitting, by a client, to a server a first TCP packet containing a header with a SYN field set to be active and an SEQ field in which a random number generated by the client is included, to request a TCP communication connection with the server, an encryption operation of encrypting, by the server, at least one piece of information to be stored in the first TCP packet, a communication connection confirmation operation of transmitting, by the server, to the client a second TCP packet containing a header with a SYN field set to be active, a SEQ field in which the encrypted information is stored, and an ACK field in which a value obtained by adding 1 to the random number included in the SEQ field of the first TCP packet is stored, a response operation of transmitting, by the client, to the server a third TCP packet containing a header wi