Cryptography – Key management – Key distribution
Reexamination Certificate
1998-05-29
2002-04-16
Peeso, Thomas R. (Department: 2132)
Cryptography
Key management
Key distribution
C380S033000
Reexamination Certificate
active
06373952
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a data transmission apparatus for transmitting data and a method of the same, more particularly relates to a data transmission apparatus which suitably manages an encoding key and a decoding key used where a large amount of data is encoded and transferred and a method of the same.
BACKGROUND ART
Conventionally, in a TV broadcast or other data distribution service using a communications satellite, the flow of data was made in only one direction, that is, from the data distributor to the user. In recent years, since the transmission of digital data using communications satellite has becomes possible, transmission using the communications satellites has started for not only analog video and audio data such as TVS and movies, but also the text utilized in computers and digital video and audio data.
Here, conventional data distribution services using communications satellites such as TV broadcasting has been of the form with data distributed by a data distributor being simultaneously received and used by a large number of users. Contrary to this, where the digital data used in computers is distributed via a communications satellite, a function for distributing the data from the data distributor to a single or a plurality of users is required.
In the conventional transmission system using a communications satellite, however, there is a problem in that since the distribution is performed for analog data and since the data distribution is performed in only one direction from the data distributor to the user. Since no function for checking the errors in transmission is provided, the reliability of the data transmission is low. In the distribution of digital data, if even one bit of error is caused in the data due by the transmission, the received data no longer has any meaning.
In order to distribute such digital computer data by a wireless system with a high quality, it is necessary to secure a communication path for not only the distribution of data in one direction from the data distributor to the user, but also a communication path from the user to the data distributor. The conventional transmission system is not provided with such a function.
Also, in the conventional simultaneous communication or broadcast system from a data distributor to many users, all users always receive, use, or view the same information. There is no personal identification information of the system users, therefore it is not possible to distribute data from the data distributor to only specific users.
Further, where data is transmitted or a conversation is conducted by using a public telephone line, dedicated line, etc., in order to prevent the leakage of the transmitted information or maintain the reliability of the information against attack (interference) with respect to the transmitted information, plain text data is encoded (scrambled) and then transmitted, and the encoded data is decoded (descrambled) at the destination of reception. As a typical encoding system, a common key encoding system and a public key system have been known.
The common key encoding system is also referred to as the symmetrical encoding system. An algorithm private type and an algorithm public type have been known. As a typical algorithm public type, the DES (data encryption standard) has been known.
In the public key system, since an enormous amount of calculation is necessary for deriving the generated key from an inspection key, the generated key is not substantially decoded, therefore it is an encoding system wherein the encoding key can be made public and is referred to also as the asymmetrical key encoding system.
The encoding system is determined in accordance with the type of the line system through which the transmission data is transmitted, the degree of secrecy (secret) of the transmitted data, the amount of transmitted data, etc.
In data transmission using a dedicated line, the degree of leakage of the information and the attack of the transmitted data is low. But when data is transmitted by using a public telephone line, the degree of the leakage of information and the degree of attack becomes high. Further, the transmission of data using a satellite broadcasting line can be received by many unspecified apparatuses, therefore the degree of leakage of information becomes even higher.
FIG. 1
is a schematic structural view of an example of an encoded data transmitting apparatus for encoding the data on the transmission line by a common key encoding system.
In the encoded data transmitting apparatus of FIG.
1
, reference numeral
101
denotes a transmitting apparatus (transmitter), reference numeral
102
denotes a receiving apparatus (receiver),
103
denotes a tapping apparatus (tapper), reference numeral
104
denotes a data transmission line, reference numeral
105
denotes data which should be transmitted, reference numeral
106
denotes an encoding unit provided in the transmitting apparatus
101
, reference numeral
107
denotes an encoding key (encoding session key) used for the encoding in the encoding unit
106
, reference numeral
108
denotes a decoding key (decoding session key), reference numeral
109
denotes a decoder for decoding the encoded data received from the data transmission line
104
using the decoding key, and reference numeral
110
denotes the data after decoding.
The transmitting apparatus
101
, when transmitting the data
105
onto the transmission line
104
, has the encoding unit
106
encode the data
105
by using the encoding key
107
and transmits the encoded data to the receiving apparatus
102
via the transmission line
104
.
The receiving apparatus
102
, when receiving the encoded data from the transmission line
104
(encoded data), has the decoder
109
decode the received encoded data by using the decoding key
108
corresponding to the encoding key
107
so as to obtain an intended decoded (deciphered) data
110
.
In this example, even if the tapping apparatus
103
receives the encoded data from the transmission line
104
in the same way as the receiving apparatus
102
, there is no decoding key
108
, so it is difficult to correctly decode this. Namely, the tapping apparatus
108
ends up handling encoded (scrambled) data as is, therefore, in actuality, the information is prevented from being leaked to the tapping apparatus
103
side.
In a principal encoding system of the common key encoding system in this example, generally the encoding key
107
and the decoding key
108
have the same bit train.
Recently, broadcasters have been making satellite broadcasts for providing TV programs to only specific contractors. The transmission system used for the satellite broadcast can transmit a large amount of data (information) such as a video and audio in a short time. Further, a transmission system using a satellite can transmit a large amount of information in a short time and therefore is not limited to broadcasts—it has been widely utilized for the transmission of data such as computer data.
In transmission using a satellite, however, unlike a one-to-one communication system such as a telephone line and dedicated line, many unspecified receivers can easily receive the data (by receiving apparatuses), so it is easy to be tapped by nature. As a result, there is a high possibility that for example a pay satellite broadcast will be tapped. Therefore, it has been proposed too to also encode the video data and audio data of a TV broadcast for transmission.
In actual transmission, the encoding is not carried out for all data, but the data which should be encoded is encoded and transmitted onto the transmission line in accordance with the content of the data to be transmitted in the transmitting apparatus (for example, whether it is pay data or not). The receiver decodes all or part of the encoded data to determine whether or not the all or partially decoded data is necessary for it at the present by the information obtained as a result of this.
In the encoded data transmitting apparatus for transmitting encoded data in this way,
Asano Tomoyuki
Ishii Makoto
Kubota Ichiro
Bell Boyd & Lloyd LLC
Peeso Thomas R.
Sony Corporation
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