JPH0370368A - Facsimile signal transmission system - Google Patents

Abstract

PURPOSE:To prevent the scramble key from being brought to inverse operation easily by inserting a prescribed mark into the upper end and the lower end of a screen to be transmitted. CONSTITUTION:Chargeable broadcast marks 11A, 11B are inserted into spaces of the upper end and the lower end of a screen 10 to be transmitted, respectively. In this case, a design and an inserting position of the chargeable broadcast marks 11A, 11B can be varied. Accordingly, it does not occur that the upper end and the lower end thereof become a blank continuously, and in accordance with the upper end and the lower end thereof, random data is generated. In such a way, it does not occur that a scramble key is brought to inverse operation easily from data for showing white of the blank, and the safety of a scramble is enhanced.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention provides a facsimile signal transmission system suitable for application to pay-based facsimile broadcasting in which image data is scrambled and transmitted.

[Prior Art] Facsimile broadcasting has been proposed as one of the data broadcasting service formats. In this facsimile broadcasting, (a) A facsimile channel using a second subcarrier is provided in the audio frequency band of terrestrial television broadcasting waves, and the second subcarrier is subjected to four-phase differential phase modulation (four-phase DPSK) using a digitalized facsimile signal. (b) Facsimile broadcasting that multiplexes digitized facsimile signals onto a data channel of satellite broadcasting and transmits them.

As one aspect of such facsimile broadcasting, a paid system has been proposed in which image data is scrambled and transmitted, and only those who have paid the fee can obtain the key to unscrambling and receive the data correctly.

In this case, the scrambling method is generally to generate a PN signal (pseudo-random signal) using a predetermined polynomial, and to generate transmission data by taking the exclusive OR of this PN signal and image data. It is.

FIG. 2 shows an example of a transmission data generation circuit.

In the figure, I is a PN signal generation circuit consisting of an n-stage shift register 11 and an adder 12. The PN signal SPN outputted from the PN signal generation circuit 1 is supplied to an exclusive OR circuit 2, and is exclusive ORed with the image data Di to generate transmission data Do.

In this case, the polynomial of the PN signal generation circuit 1 and the initial value of the shift register 11 serve as the scrambling key.

On the receiving side, the same PN signal generation circuit as that on the transmitting side is configured by obtaining this scramble key information using a predetermined method, and the above-mentioned transmission data Do is descrambled.

[Invention tries to solve! ! ! ! ] Here, in a normal screen 10 as shown in FIG. 3, the upper and lower ends of the screen 10 are blank spaces, and no characters are written thereon. According to the standards for facsimile broadcasting, the scanning line density is 7.7 lines/
For example, if there is a margin of 100 meters at the top, the image data for 77 lines from the beginning will be data indicating white. In facsimile broadcasting, these image data (dot data) are converted into MH (Modified
) luffman) and MR (M.

divided Reactive Element A
For example, in a margin of 1 cm, the exit data of about 2 bits becomes a fixed pattern. Therefore, the data indicating white is determined in advance, and there is a possibility that the scrambling key can be calculated backwards from this data.

Furthermore, since there is no scrambling in the page end signal at the bottom edge, if there is a blank space at the bottom edge, there is a possibility that the scramble key will be calculated backwards from the data indicating the white space.

Therefore, it is an object of the present invention to prevent the scramble key from being easily calculated backwards.

[! ! Means for Solving the Problem] The present invention is a facsimile signal transmission method in which image data is scrambled and transmitted, and is characterized in that predetermined marks are inserted at the top and bottom edges of the screen to be transmitted. be.

[Operation] In the above configuration, predetermined marks are inserted at the top and bottom edges of the screen 10 to be transmitted, so the top and bottom edges of the screen 10 do not become a continuous blank space as described above, and this margin The possibility that the scramble key is calculated backwards from the data indicating white is reduced.

[Embodiment] An embodiment of the present invention will be described below with reference to FIG.

In this example, as shown in Figure 1, the screen 1 to be transmitted is
Paid broadcast mark 11 is placed in the upper and lower margins of 0, respectively.
A and 11B are inserted.

In this case, if the paid broadcasting marks 11A, 11B have a fixed pattern, it is undesirable because the pattern will always appear at the beginning and end of the data. Therefore, the design and insertion position of the paid broadcasting marks 11A, 11B should be changed as much as possible. be.

In this example, the pay broadcasting marks 11A and 11B are inserted at the top and bottom edges of the screen 10, so these top and bottom edges do not become continuous blank spaces, that is, they correspond to the top and bottom edges. random data is generated. Therefore, it is possible to prevent the scrambling key from being calculated backwards from the data indicating the white space as in the conventional method.

In the above-mentioned embodiment, pay broadcast marks 11A and IIB are inserted into the margins at the top and bottom of the screen 10 to be transmitted to generate random data. Therefore, any marks may be inserted into the margins at the top and bottom of the screen 10 as long as they generate random data.

However, if characters or figures that don't make sense appear, it will make the recipient feel uncomfortable, so it is better to use something that is not unsightly. It is effective to use pay broadcast marks IIA and IIB, which tell the receiver that it is a broadcast.

[Effects of the Invention] As explained above, according to the present invention, marks are inserted at the top and bottom edges of the screen to be transmitted. Random data is generated corresponding to the bottom edge. Therefore, the scrambling key is not easily calculated backwards from the data indicating the white space as in the past, and the security of scrambling can be improved.

[Brief explanation of drawings]

FIG. 1 is a diagram for explaining one embodiment of the present invention, and FIG.
1! 1 and 3 are diagrams for explaining a conventional example. I.A. Ray 2... 10◆- 11B... PN signal generation circuit, exclusive OR circuit, screen, pay broadcasting mark Explanatory diagram of an example of the pay broadcast mark Figure 1 Diagram showing the screen for transmission Figure 3

Claims (1)

[Claims] (1) A facsimile signal transmission system in which image data is scrambled and transmitted, the facsimile signal transmission system being characterized in that predetermined marks are inserted at the top and bottom edges of the screen to be transmitted.