A system is provided for improving security during data transfer. A transmitter side transfer controller (12) divides data to be transferred into a plurality of pieces, removes a portion of data from each piece and encrypts the piece, and uploads each encrypted piece to different relay servers (22) on the Internet (20). The transmitter side transfer controller (12) also provides a receiver side transfer controller (12) information indicating which piece is uploaded to which relay server (22) using a secure communication protocol. The data of the fragment removed from each piece is transmitted to the receiver side transfer controller (12) separately from the encrypted pieces. The receiver side transfer controller (12) downloads the encrypted pieces each uploaded to the relay server (22), decodes the encrypted pieces, complements the decoded data with the data of the fragment to restore the state before the removal, and assembles the restored pieces to obtain the original data to be transferred.