JPH0581095B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a system (for example, The present invention relates to an audio data transmission method that improves the strength of confidential communication and enables the transmission of audio data without synchronization timing shift in a home bus system using a digital multifunction telephone with a built-in controller.

[Prior Art] In a system in which a plurality of digital telephones and a controller are connected via a line, and voice data is encrypted using secret key data and transmitted,
As shown in Figure 7, the audio data transmission format for one call consists of a bit synchronization code (16 bits), a frame synchronization code (15 bits), an ID code (8 bits), and control data (64 bits).
and secret key data (64 bits)
It consisted of a 167-bit control word 1 and audio data 2 following this control word 1.

[Problems to be Solved by the Invention] However, in the transmission method using the conventional transmission format as shown in FIG. Since the control word 1 having the synchronization code and the secret key data for secret speech is added only once, as the amount of audio data 2 increases, the secret speech strength tends to decrease and the synchronization timing shifts. The problem was that it was easy.

The present invention was made in view of the above-mentioned problems.
It is an object of the present invention to provide a voice data transmission system that improves the strength of confidential conversations and that does not cause synchronization timing shifts.

[Means for Solving the Problems] The voice data transmission method according to the present invention is applicable to a system in which a plurality of digital telephones and a controller are connected via a line, and voice data is encrypted with private key data and transmitted. , an audio frame formed by dividing the audio data of one call into m bits, an n-bit synchronization frame having a synchronization code and a secret key code and inserted before each of the divided audio frames, and a synchronization code and a secret key code. The head of the line signal frame having the head of line identification code and the secret key data and added before the first synchronization frame of the synchronization frames is time-division multiplexed and transmitted at a bit rate v, and the m/v and n /v is set at a rate at which the reproduced sound of the audio data does not sound unnatural, and the secret key data in the topic signal frame is a variable data portion that is randomly set from among multiple types of data for each call. and a fixed data part that is set in a fixed manner, and the confidential key code in the synchronization frame converts the variable data part of the confidential key data into one of the plurality of types of data for each voice frame within one call. Consisting of a code for randomly variably setting arbitrary data, audio data is double encrypted and transmitted using secret key data and secret key data whose variable data part is changed based on the secret key code. It is characterized by the fact that it is made to do so.

[Operation] From the transmitting side, following the beginning signal frame having the synchronization code, the beginning of the conversation identification code, and the secret key data, an n-bit synchronization frame having the synchronization code and the secret key code, and the voice data of one call are transmitted. m
Audio frames divided into bits are transmitted alternately in a time-division manner. At this time, the audio data in each audio frame is a key formed by replacing the secret key data in the beginning signal frame and the variable data part of this secret key data with data corresponding to the secret key code in the immediately preceding synchronization frame. The data is doubly encrypted. Therefore, the strength of the secret story is improved.

On the receiving side, the secret key data and the voice frame are synchronized by the synchronization code in the beginning signal frame and the synchronization code in the synchronization frame, and the secret key data in the beginning signal frame and the synchronization code in the synchronization frame are synchronized. The voice data encrypted for each voice frame is decoded into the original voice data using the double key with the secret key data in which the variable data portion is variably set based on the secret key code, and this decrypted Audio data is converted from digital to analog to become an audio signal. At this time, m/v and n/v, which represent the period of non-audio data and the period of audio data that appear alternately, are set at a ratio that does not make the reproduced sound of the audio data unnatural. It doesn't sound unnatural.

[Embodiment] Figures 1 to 6 show an embodiment of the present invention, and Figure 6 shows the configuration of the system. It is a pair cable. The pair cable 11 includes a controller 12, a digital telephone 13, 1 having a built-in encryption circuit, decryption circuit, etc.
4,15, AV (audio visual) equipment 1
6, a facsimile 17, a personal computer 18, a word processor 19, and a security device 20 are coupled, and a transmitting/receiving antenna 22 for transmitting and receiving data to and from a cordless digital telephone 21 is coupled. Note that the controller 12 may be housed in one (for example, 13) of the digital telephones 13, 14, and 15, thereby making this a digital multifunction telephone.

In the system shown in FIG.
As in the case of transmitting a call from the digital telephone 13 to the digital telephone 14 controlled by
A signal transmission format for transmitting a signal including audio data and control data at a bit rate v (for example, v=2400 bps) is configured as shown in FIG. That is, a synchronization frame 30 of n bits (for example, n = 48), a top-of-speech signal frame 40 of m bits (for example, m = 720), and data obtained by doubly encrypting the voice data of one call using secret key data, which will be described later. audio frames 51, 52, 53, etc., which are divided into m bits, and an n-bit synchronization frame having the same configuration as the synchronization frame 30 inserted before each of these audio frames 51, 52, 53, etc. Frames 61, 62, 63...
This is achieved by time-division multiplexing. For example, when n=48, the synchronization frame 30 includes a 16-bit bit synchronization code 31, a 15-bit frame synchronization code 32, a 2-bit type identification code 33,
It consists of 48 bits consisting of an 8-bit ID code 34, a 4-bit control identification code 35, and a 3-bit secret key code 36.

The first speech signal frame 40 has m=720, for example.
In the case of
After a 105-bit head signal block 40a consisting of 64-bit secret key data 45 is repeated five times in sequence, a 195-bit blank data block 40b with no data is added, resulting in a total of 720 bits.

As shown in FIG. 2, the secret key data 45 in the beginning signal frame 40 includes a 16-bit variable data portion 45a and a 48-bit fixed data portion 45b.
The variable data portion 45a is variable and set for each voice data call, and
For example, based on a code table as shown in FIG. 3 stored in the memory of the digital telephone 13 on the transmitting side, the 16-bit data of the 8 types corresponding to the secret key code 36 of the bit in the synchronization frame 30 is determined. One of these types is randomly set and varied for each call, and the fixed data portion 45b is fixedly set until it is decoded by a third party, for example. Further, the secret key code 36 in the synchronization frames 61, 62... is the voice frame 51, 52 of one call.
This is set to be changed for each time, and is used to replace the variable data portion 45a of the secret key data 45 with any data out of eight types of 16-bit data based on the code table shown in FIG. It is.

In the system shown in FIG.
AV by the digital telephone 13 controlled by
When a signal consisting only of control data without an audio signal is transmitted at a bit rate v, such as when controlling only the device 16 on or off, the signal transmission format is configured as shown in FIG. There is. That is, n bits (e.g. n=
48) synchronous frames 30a, 61a, 62a...
and empty data frames 70, 71, 72, . . . with no data of m bits (for example, m=720) are alternately multiplexed in a time division manner.

Next, the operation of the above embodiment will be explained.

(1) First, the case of transmitting audio data and control data will be explained.

(B) In the system shown in FIG. 6, audio data is transmitted from one of the plurality of digital telephones 13, 14, 15, for example 13, to the other digital telephone 14, and control for turning on or off the AV equipment 16 is provided. When data is to be transmitted, the signal transmission format at this time is as shown in FIG. That is, 1
The audio data of the call is converted from analog to digital (A-D) in the digital telephone 13 on the calling side, and then converted into audio frames 51, 52, every m bits (for example, m=720)...
and each audio frame 51, 52... is divided into secret key data 45 in the beginning signal frame 40 and the immediately preceding synchronization frame 6.
Based on the secret key code 36 in 1, 62, . . . , the variable data portion 45a is doubly encrypted with the secret key data replaced with the corresponding data. Therefore, the strength of confidential information is improved. Then, n bits (for example, n=
48) and the m-bit leading signal frame 4 inserted between the first synchronization frame 61 and the earliest synchronization frame 30 of the synchronization frames 61, 62...
0 are time-division multiplexed and transmitted via the pair cable 11 at a bit rate v (for example, v=
2400bps).

(b) The digital telephone 14 on the receiver side synchronizes with the bit synchronization code 41 and frame synchronization code 42 in the head signal frame 40, and reads the head identification code 43 and ID code 4.
When it is confirmed that the voice data is for the self by step 4, the encrypted received voice data is converted into the received secret key data 45 and the secret key data in which the variable data portion 45a is replaced with the secret key code 36. Based on this, each audio frame 51, 52, . . . is decoded, D/A converted, and the audio is received.

Moreover, the audio data is divided into audio frames 51, 52, . . . each having m bits, and is divided into synchronization frames 62, 63, . 720/2400=300 msec) and the division period n/v (for example, n/v=48/2400=20 msec) are set at a ratio that does not produce unnatural sound, so that the reproduced sound does not become unnatural.

Moreover, each of the audio frames 51, 52... is based on the bit synchronization code 31,
Since synchronization is achieved by the frame synchronization codes 31, 32, 32, .

(c) The AV device 16 on the controlled side uses the bit synchronization code 3 in the synchronization frames 30, 61, 62...
1, 31..., and when the ID code 34 confirms that it is the control data for itself, it is created based on the type identification code 33 and the control identification code 35, as shown in FIG. A predetermined control (for example, turning the power on or off) is performed using the control word. In other words, when the type identification code is "00", the control word "00010" is created by doubling the control identification code "0001", and when the type identification code is "01", the control word "0001" is created. Control word "00011" is created by doubling and adding 1.

(2) Next, a case will be explained in which there is no audio data and only control data is transmitted.

(b) Multiple digital telephones 13, 14, 15
If control data for turning on or off is transmitted from one of the devices, for example 13, to the AV device 16, the signal transmission format at this time is as shown in FIG. That is, n
(e.g. n=48) bit synchronization frame 30
a, 61a, 62a, . . . and m-bit empty data frames 70, 71a, 72a, . . . are alternately multiplexed and transmitted in a time-division manner. That is, the beginning signal frame 40 is deleted from the transmission format including the audio data shown in FIG. 1, and each audio frame 51, 52, . . . is left empty. At this time, the type identification code 33, ID code 34, and control identification code 35 in the synchronization frames 30a, 61a, 62a, . . . are set corresponding to the AV equipment 16. In addition, the synchronization frame 30
Secret key code 3 in a, 61a, 62a...
Since 6 is unnecessary, it may be empty data.

(b) Similarly to (c) of (1) above, when the AV equipment 16 confirms that the control data is for itself using the ID code 34, it identifies the control data using the type identification code 33 and the control identification code 35. A predetermined control (for example, turning the power on or off) is performed by the control word created as shown in FIG.

In the embodiment, the digital telephone 13,
AV for controlling electronic devices other than 14 and 15
Although the device 16 is controlled, the same applies to the control of other electronic devices (for example, the security device 20).

In the above embodiment, the bit rate v is
2400bps, the number of bits in the audio frame is 720,
Although the number of bits n of the synchronization frame was set to 48, the present invention is not limited to this, and m/v and n/v may be selected so that the reproduced sound of the audio data does not become unnatural. For example, when the bit rate v is 2400 bps or more and n is about 50, m/n is set to 15 or more.

[Effects of the Invention] As described above, the voice data transmission system according to the present invention includes a voice frame formed by dividing the voice data of one call into m bits, and a voice frame inserted before each of the divided voice frames. The n-bit synchronization frame and the leading signal frame added before the first synchronizing frame among these synchronizing frames are time-division multiplexed and transmitted at a bit rate v, and the secret key in the leading signal frame is Since the audio data is double-encrypted and transmitted using the data and the confidential key data whose variable data portion is changed based on the confidential key code in the synchronization frame, the confidential information strength of the audio data is It can be further improved. Furthermore, since a synchronization frame is inserted before each audio frame, even if the volume of audio data increases, the synchronization timing on the receiver side is unlikely to shift. Moreover, the variable data part of the secret key data, which is the first key, is changed based on the secret key code.
Since the secret key data, which is the second key, is created, the transmission data length can be shortened and transmission efficiency can be improved. Furthermore, since m/v and n/v are set to ratios that do not make the reproduced sound of the audio data unnatural, the reproduced sound does not become unnatural.

[Brief explanation of the drawing]

1 to 6 show an embodiment of the audio data transmission method according to the present invention. FIG. 1 is a diagram for explaining the transmission format of a signal including audio data and control data, and FIG. is a diagram for explaining the contents of the confidential key data in FIG. 1, FIG. 3 is an explanatory diagram of a code table showing the correspondence between the confidential key code and the variable data part, and FIG. 4 is a diagram for explaining the contents of the confidential key data in FIG. Figure 5 is a diagram to explain the creation of a control word, Figure 6 is a block diagram showing the system configuration, and Figure 7 is a diagram to explain the conventional signal transmission format. This is a diagram. 11...Pair cable (2-wire line), 12...
... Controller, 13, 14, 15, 21 ... Digital telephone, 16, 17, 18, 19, 20
...Electronic equipment other than digital telephones, 30,3
0a, 61, 61a, 62, 62a, 63... Synchronization frame, 36... Secret key code, 40...
Top of the line signal frame, 45... Confidential key data, 4
5a...Variable data part of secret key data 45,
45b...fixed data part of secret key data 45, m, n...number of bits, v...bit rate.

Claims (1)

[Claims] 1. In a system in which a plurality of digital telephones and a controller are connected via a line and voice data is encrypted and transmitted using secret key data, the voice data of one call is transmitted every m bits. A voice frame formed by dividing, an n-bit synchronization frame having a synchronization code and a secret key code and inserted before each of the divided voice frames, a synchronization code, a speech head identification code, and secret key data. The first synchronization frame of the synchronization frame and the beginning signal frame added before the first synchronization frame are time-division multiplexed and transmitted at a bit rate v, and the m/v and n/v are transmitted in a manner that the reproduced sound of the audio data is The secret key data in the beginning signal frame is set to a ratio that does not produce a natural sound, and the secret key data in the beginning signal frame consists of a variable data part that is randomly set from among multiple types of data for each call, and a fixed data part that is fixedly set. The secret key code in the synchronization frame is for randomly and variably setting the variable data portion of the secret key data to arbitrary data among the plurality of types of data for each voice frame within one call. Audio data consisting of a code, wherein the audio data is doubly encrypted and transmitted using secret key data and secret key data whose variable data portion is changed based on the secret key code. Transmission method. 2 The bit rate v is set to 2400bps, the number of bits m of the audio frame is set to 720, and the number of bits of the synchronization frame n is set to 48.The secret key data in the beginning signal frame consists of a 48-bit fixed data part and 8 types. It consists of a 16-bit variable data part consisting of arbitrary data in the 16-bit data of
2. The audio data transmission system according to claim 1, wherein the secret key code in the synchronization frame consists of 3 bits for randomly and variably setting any one of eight types of variable data parts in the secret key data.