JPS6010888A - Video signal ciphering device - Google Patents

Abstract

PURPOSE:To attain ciphering with high confidentiality and to cipher an input video signal within a signal level range by converting an input video signal into a digital signal and converting the order of a specific bit. CONSTITUTION:A video signal such as a TV video signal give to an input terminal IN is converted into a digital signal by an A/D converting circuit AD. The AD conducts digital conversion in, e.g., 5-bit and its output is led to a ciphering circuit SC. The SC exchanges the order of the 3rd and 4th bits to normal bit orders (1-5) from the AD and the conversion is attained in the bit order of 1, 2, 4, 3, 5 as an output. The output of the SC is converted into an analog signal by a D/A converting circuit DA according to the normal bit order. The analog signal converted by the DA is different from the input video signal since the order of the 3rd and 4th bit is exchanged.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a video signal encryption device used for pay television broadcasting and the like.

[Technical background of the invention and its problems]

Conventionally, encryption methods used in pay television broadcasting involve the synchronization signal part, that is, methods that remove part of the synchronization and convert the polarity, and methods that utilize polarity reversal of the video signal period. Ta.

On the other hand, there is also a demand for a system in which the signal format is similar to that of normal broadcast waves, but the video signal is encrypted, and in response to these demands, methods such as partially reversing the video part while leaving the synchronized part as is are required. has been adopted. However, this method has the disadvantage that as the number of combinations increases, the circuit on the decoder side becomes complex, and as the number of ancestral combinations decreases, decoding becomes relatively easy.

[Purpose of the invention]

The present invention was made to eliminate such drawbacks, and it essentially has a large number of combinations and performs highly confidential encryption. Moreover, only the video signal is encrypted within a normal specified level range. It has the advantage of being able to transmit signals that are broadcast in the same way as regular broadcast waves.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to the drawings.

As shown in Figure 1, the transmitting side (TR,) and the receiving side (RC)
is connected to the transmitter side (TR) by a transmission cable (CA).
The video signal is encrypted at the receiving end (RC), and decrypted at the receiving end (RC).

The transmitting side (T) includes an analog-to-digital conversion circuit (hereinafter referred to as A/D conversion circuit) (CAD) and an encryption circuit (scL).
It consists of a digital-to-analog dual conversion circuit (hereinafter referred to as D/A conversion circuit) (DA), and video signals such as television video signals introduced to the input terminal (IN) are processed by the A/D conversion circuit (AD). is converted into a digital signal by The A/D conversion circuit (AD) performs digital conversion using, for example, 5 bits, and its output is introduced into the encryption circuit (SC). The encryption circuit (SC) uses an A/D conversion circuit (AD
) The order of specific bits among the output bits is exchanged, as shown in FIG. 2(a). In Figure 2 fa), the normal bit order (1 to 1) from the A/D conversion circuit (AD) is shown.
5), the orders of the third and fourth bits are exchanged, and the output is converted into bit orders of 1, 2, 4, and 3.5. The output of the encoder circuit (SC) is converted into an analog signal by the fiD/A conversion circuit (DA) according to the regular bit order, and sent to the receiving side (1'LC) via the transmission cable (CA).
). This analog 'signal converted by this D/A conversion circuit (DA) has the third and fourth bit orders exchanged, so it becomes a signal different from the input video signal.

On the other hand, the receiving side (R, C) includes an analog-to-digital conversion circuit (hereinafter referred to as A/D conversion circuit) (AD), a decoding circuit (DS), and a digital-to-analog conversion circuit (hereinafter referred to as the A/D conversion circuit)
The analog signal from the transmission cable (CA) is transmitted to the A/D converter circuit (DA).
) is converted into a digital signal by a decoding circuit (D
S) is introduced. The output of this A/D conversion circuit (AD) is a digital signal with a bit order in which the orders of the third and fourth pits in the encryption circuit (SC) are exchanged.
The decoding circuit (DS) performs the inverse transformation of this bit exchange to perform decoding. The decoding circuit (DS) is shown in Figure 2 (b).
), the third and fourth bit orders are exchanged to obtain an output converted to the normal bit order. This decoding circuit (D
S) The output is converted into an analog signal by a D/A conversion circuit (DA), and a video signal identical to the input video signal is output to an output terminal (OUT).

The encryption circuit (SC) replaces all the pits of the A/Di conversion circuit (AD) output as shown in FIG. 3(a), and the decryption circuit (DS) ) can be decoded by 0. By exchanging this bit order, there are 120 combinations for 5 bits. Furthermore, if the number of bits in the A/D conversion circuit (AD) is 8 bits, there are even more combinations. Continuing with this, the encryption circuit (SC) selects the most suitable one among these combinations and performs encryption.
In the decoding circuit (DS), packaged circuit components each having a corresponding circuit may be inserted into a socket or the like, or a circuit component selected from circuit components having different circuits may be used. good.

〔Effect of the invention〕

As described above, the present invention has a large number of combinations, can perform highly confidential encryption, and can perform encryption within the level range of input video signals, such as television video signals, etc. can be treated exactly the same as normal broadcast waves.

[Brief explanation of the drawing]

FIG. 1 is a circuit configuration diagram showing an embodiment of a video signal encryption device according to the present invention, FIG. 3(a) and 3(b) are circuit configuration diagrams respectively showing other embodiments of the encryption circuit and decryption circuit in FIG. 1. AD...analog-digital conversion circuit, SC...encryption circuit, DS...decryption circuit, DA...digital-analog conversion circuit. Agent Patent Attorney Noriyuki Chikaten (and 1 other person)

Claims (1)

[Claims] A video signal encryption device that converts an input video signal into a digital signal, converts the order of specific bits, and encrypts the video signal.