| 摘要 |
<p>A data transmitter which improves the safety of the transmission using an enciphering key of a decoding key and improves the safety against the leakage of the enciphered transmission data. A large capacity transmission line (152) such as a satellite transmission line through which large capacity data are transmitted and a small capacity transmission line (156) such as a public telephone line which transmits an enciphering key, a decoding key or information for generating these keys are provided. An enciphering session key (107) is generated by using a work key and the address of the receiver on the receiving side. A decoding session key (108) is generated by using the own address and the work key. The work key is, preferably, enciphered and transmitted on the small capacity transmission line (156). In a transmitter (101), not only the data (105) to be transmitted are enciphered by using the enciphering session which is thus converted as described above, but also the transmission control information such as the address data are added to the data (105) and transmitted to a receiver (102) through the large capacity transmission line (152). The enciphered data (110) are decoded by using the decoding session keys (108), which is converted as described above.</p> |
