JPH0224058B2 - - Google Patents

Description

[Detailed Description of the Invention] (Field of the Invention) The present invention relates to a signal synchronization method for data transmission.
In particular, the present invention relates to a signal synchronization method for concealing data transmission.

(Explanation of prior art) In today's information society, important data and confidential information of companies etc. are often communicated, and therefore there is an increasing demand for data confidentiality in data transmission, regardless of whether it is wired or wireless. It is increasing.
In particular, unlike wired data transmission, wireless data transmission uses the same space as a medium, and due to its characteristics, it can be easily intercepted by a third party. It is difficult. For example, in conventional data transmission, when data must be kept confidential, the main focus is to first synchronize (bit synchronization, frame synchronization) on the line using conventional synchronization methods, and then encrypt the data to be transmitted. It was placed there. Therefore, those trying to decipher the data could easily know the beginning of the data, providing a major clue for cryptanalysis.

FIG. 1 shows an example of the configuration of a conventional synchronization signal. The synchronization signal consists of a bit synchronization signal (hereinafter referred to as bit sync) BS followed by a frame synchronization signal (hereinafter referred to as frame sync) FS. In order to keep data secret in such a synchronization method, it is necessary to encrypt the data itself. However, even when the data is encrypted, as mentioned above, there is a clear separation between the synchronization signal part and the data part.
Particularly in the case of data transmission in the form of packets, it is relatively easy to decipher (since it is a short text).

Furthermore, in wireless data transmission, it may be difficult to establish normal synchronization depending on the radio wave environment and operating conditions (due to the presence of noise, interference, and standing waves). In the synchronization method shown in FIG. 1, for example, if the frame sync FS is destroyed in a burst, there is a risk that synchronization will not be achieved or that data frames will be synchronized. Therefore, if the line is a wireless system, measures must be taken to prevent synchronization failure or erroneous synchronization due to disturbance noise or the like.

(Summary of the Invention) The present invention has been made in view of the above points, and its purpose is to further enhance the confidentiality of data during data transmission.

According to the present invention, in data transmission in which a data signal is transmitted following a synchronization signal, the synchronization signal includes a bit synchronization signal and a plurality of frame synchronization signals following the bit synchronization signal, and each of the plurality of frame synchronization signals has a different signal pattern. The frame synchronization signal is mixed into a random pattern at different intervals, and frame synchronization in data transmission is established based on the detection of the frame synchronization signal and its position within the random pattern. According to the present invention, a signal synchronization method for data transmission with higher data confidentiality and extremely resistant to disturbance noise and the like is achieved.

(Explanation of Examples) Figure 2 is a patent application filed in 1983 by the same applicant as the present application.
162748 is a schematic configuration diagram showing a signal synchronization method for data transmission, which is the background of the present invention. FIG. In this method, focusing on the fact that synchronization is established if the first bit position of the data frame can be detected, three types of bit syncs SP ₀ , SP ₁ ,
SP ₂ and three types of frame syncs F ₀ , F ₁ , and F ₂ are arranged as shown in the diagram, and frame syncs F ₀ and F ₁ are placed at positions d ₁ bit and d ₂ bits from the end of frame sync F ₂ , respectively. It has been done. The optimal frame sync pattern is determined from coding theory.

In the synchronization algorithm of the synchronization signal shown in FIG. 2, some reception conditions are defined as follows, for example.

C ₁ : Detects F ₀ C ₂ : Detects F ₁ C ₃ : Detects F ₂ C ₄ : C ₁ and C ₃ and d ₁ is correct C ₅ : C ₂ and C ₃ and d ₂ is correct Correct C ₆ : C ₁ and C ₂ and C ₃ C ₇ : C ₁ and C ₂ , and d ₁ and d ₂ are correct Synchronization is established when any of C ₄ , C ₅ , C ₆ , and C ₇ is established. shall be. For example, to explain the case where synchronization is established due to the establishment of reception condition C ₄ , first a pattern identical to frame sync F ₀ is detected in the data string captured in synchronization with the reception clock, and its d ₁ After the clock, a pattern identical to frame sync _F2 is detected and synchronization is established (that is, the next bit is recognized as the first bit of the data frame). If _C7 holds true, it is detected that the _d1 clock point after _F0 detection and the _d2 clock point after _F1 detection correspond to the same bit position, and synchronization is established. In this way, even if a certain frame sync is destroyed in a burst, the data position can be predicted using the remaining frame sync, making it easy to establish accurate synchronization even on transmission lines with a lot of external interference, such as wireless transmission lines. Become.

FIG. 3 is a schematic configuration diagram showing a signal synchronization method for data transmission, which is a preferred embodiment of the present invention, and is an application of the synchronization method shown in FIG. The figure includes a synchronization signal bit sync BS and a plurality of frame syncs F ₀ , F ₁ ..., F _o that follow it, and the frame syncs F ₀ , F ₁ ,..., F _o are arranged in a random pattern (random number) RN as shown in the figure. It is mixed. Each frame sync F ₀ , F ₁ , ..., F _o has a different signal pattern, and the interval at which they are mixed into the random pattern RN (that is, the interval at which the frame sync pattern occurs) is D ₁ .D. ₂ ,...D _o bits. At this time, each frame sync F ₀ ,
It is assumed that the intervals from F ₁ , ..., F _o to the first bit position of the data are d ₁ , d ₂ , ..., d _o bits, respectively.

In the synchronization system shown in FIG. 3, the data other than the bit sync BS for bit synchronization is a random number string (random pattern) including the data, and it is not possible to visually distinguish between the synchronization signal part and the data part. Now, the frame sync patterns F ₀ to _{F o} and the frame sync pattern generation intervals D ₁ to _{D o} are made variable (therefore, d ₁ to dn also change), and these are changed appropriately according to the encryption standard to generate a synchronization signal. If the data is transmitted as part, the receiving side cannot determine the position of the first bit of the data (that is, cannot synchronize) unless it knows this cryptographic protocol.
The received data becomes nothing more than a meaningless random number sequence. If we try to decipher this signal,
This requires a complicated analysis in which the next bit of the bit sync BS is shifted one bit at a time, and the amount of time required to decrypt the code is greater than in the past.

The reason for providing n frame syncs, F ₀ , F ₁ , ..., F _o , is to provide cryptographic strength and to prevent burst errors when using a wireless line. If some of these frame sync patterns can be recognized, synchronization can be established. An appropriate value for the number of frame syncs is selected depending on the required encryption strength and the status of the data transmission path. The above D ₁ , D ₂ ,...,
The same applies to D _o and d ₁ , d ₂ , ..., d _o .

When realizing this invention, it can be realized in hardware by providing a random pattern generator on the transmitting side and changing the generation interval of the frame sync pattern according to the cryptographic protocol, or it can be realized by hardware. It is also easy to implement this in software using a CPU. On the receiving side, for example, if the bit-synchronized received signal is stored in memory and this stored data is used in hardware or CPU-based software using various pattern recognition techniques based on cryptographic regulations, the position of the first bit of the data can be determined. can be easily determined. In this case, even if not all frame syncs can be recognized as described above with respect to FIG. 2, some of them can be recognized and the above-mentioned d ₁ to d _o related to this can be recognized.
If some of (and D ₁ to _{D o} ) are found to be correct, it is possible to determine the position of the first bit of the data according to the majority theory, and therefore synchronization is established.
The majority logic here refers to a logic that establishes synchronization when a certain number or more of the set reception conditions are satisfied.

Note that it is also possible to use a random pattern instead of the bit sync BS in FIG. 3, as long as you are prepared for the hardware or software to become slightly more complicated, and in this case, the encryption strength will be further improved. Of course, encryption of the data part can also be used, and it goes without saying that the encryption strength will be improved in this case.

(Effects of the Invention) As described above, according to the present invention, since the synchronization signal is encrypted during data transmission in which the data signal is transmitted following the synchronization signal, the position of the first bit of the data frame becomes difficult to identify at a glance. , it becomes possible to further enhance data confidentiality during data transmission.

Further, according to the present invention, in addition to improving data confidentiality, it is also possible to improve signal strength against disturbance noise, etc., and is particularly effective for data transmission by wireless system.

[Brief explanation of drawings]

FIG. 1 is a diagram showing an example of the configuration of a conventional synchronization signal, FIG. 2 is a schematic configuration diagram showing a signal synchronization method for data transmission, which is the background of the present invention, and FIG. 3 is a preferred embodiment of the present invention. 1 is a schematic configuration diagram showing a signal synchronization method for data transmission. In the figure, BS, SP ₀ to SP ₂ are bit sync,
FS, F ₀ to _{F o} indicate frame sync, and RN indicates random pattern, respectively.

Claims (1)

[Claims] 1. In data transmission in which a data signal is transmitted following a synchronization signal, the synchronization signal includes a bit synchronization signal and a plurality of frame synchronization signals following the bit synchronization signal, and each of the plurality of frame synchronization signals is different. The frame synchronization signal has a signal pattern and is mixed into the random pattern at different intervals, and frame synchronization establishment in the data transmission is performed based on the detection of the frame synchronization signal and its position in the random pattern, thereby making the synchronization signal A signal synchronization method for data transmission characterized by encryption.