Data transmission method and data relay method

摘要

In a sending device (100), a fragmenting portion (101) fragments a bit stream according to the predicted relationship of the frames, and the output of the fragmenting portion (101) is allocated to either a TCP (Transmission Control Protocol) or a UDP (User Datagram Protocol) port. In an IP (Internet Protocol) layer, an encrypting portion (102) executes an encryption process only on the port to which bit stream corresponding to the I (Intra) frames is transmitted. In a receiving device (110), a decrypting portion (112) decrypts data on the port to which the bit stream corresponding to the I frames is transmitted, and a reassembling portion (111) restores the data to the original bit stream. This restoration is carried out by lining up the packets in increasing order of TR (Temporal Reference) value. Thus, the amount of time required for encryption and decryption is reduced compared to a case in which encryption is performed on all frames.