JP2022089475A - Communication system, communication method, and program - Google Patents

Abstract

To communicate more efficiently.SOLUTION: In a communication system, packets are transmitted so as to be sequentially transmitted via a plurality of terminals. An information terminal divides information to be transmitted into N information blocks, and generates an encrypted packet consisting of N encrypted blocks obtained by encrypting the N information blocks and one initial encrypted block. A relay terminal holds all of M encrypted packets transmitted from each of the M information terminals, and compresses the packets after stretching the packets together for each encrypted block having the same block index n to obtain N compression sequences. A destination terminal restores the information targeted for transmission in each of the M information terminals from the N compression series transmitted from the relay terminal. This technique can be applied to, for example, a communication system in which multi-hop communication is performed.SELECTED DRAWING: Figure 1

Description

Application for application of Article 30, Paragraph 2 of the Patent Act (1) 2020 IEICE General Conference Online (https://www.ieice-taikai.jp/2020general/jpn/) Date March 2nd 20th (2) Proceedings of the IEICE Conference (CD-ROM), 2020, General Conference A-2-7, pp. 28, Institute of Electronics, Information and Communication Engineers Date: March 3, 2nd year of Reiwa

The present disclosure relates to communication systems, communication methods, and programs, and more particularly to communication systems, communication methods, and programs that enable more efficient communication.

In recent years, the so-called Internet of Things (IoT), a technology for connecting devices via wireless communication, has been attracting attention as a means of improving the user experience and reducing service maintenance costs. For example, smart meters that collect customer information are typical of the IoT.

In IoT, multi-hop transmission via multiple terminals is adopted because of its high expandability and practical convenience. However, in multi-hop transmission, when a route occurs in the network where communication can be established with only one terminal between the gateway and the gateway which is the final destination, the link becomes a bottleneck of communication.

In particular, in the receiver-driven medium access control (RI-MAC) protocol (see Non-Patent Document 1), which is one of the communication standards that realizes multiple access in multi-hop transmission, a bottleneck terminal is used. While transmitting the packet to the gateway, all the terminals holding the packet around the bottleneck terminal cannot send the packet to the bottleneck terminal, so that they are in the transmission standby state. Therefore, as the number of packets to be transmitted by the bottleneck terminal increases, packets stay at each terminal, and as a result, the packet collection efficiency of the entire network decreases.

As one of the solutions to this problem, the bottleneck terminal holds a certain number of packets received from the surrounding terminals, and then each packet is combined into one packet to reduce the overhead and transmit. Packet aggregation that improves efficiency is conceivable (see Non-Patent Document 2).

However, in general, in the header part such as the preamble and the data part, the data part is sufficiently longer than the header part, and the effect of reducing the header is limited. Therefore, in order to further improve the transmission efficiency of the bottleneck terminal, it is considered effective to compress the data unit by some method to shorten the transmission time. However, in a system that transmits customer information, encryption is applied at the time of packet generation from the viewpoint of privacy protection. In general, encryption is designed to equalize the probability of occurrence of 0s and 1s, that is, to maximize entropy, and it is known by information theory that such information cannot be compressed. There is.

On the other hand, in Non-Patent Document 3, post-encryption compression that enables compression of a packet encrypted by block cipher by using Srepian Wolff's theorem (see Non-Patent Document 4). (EtC: Encryption-then-Compression) method has been proposed. In this method, compression is applied to each cipher block by using the immediately preceding compressed sequence and the error correction code, and decryption is performed as a Slepian-Wolf type problem.

J. Fujiwara, R. Okumura, K. Mizutani, H. Harada, S. Tsuchiya, and T. Kawata, “Ultra-low power MAC protocol complied with RIT in IEEE 802.15.4e for wireless smart utility networks,” in Proc. 2016 IEEE 27th Annu. Int. Symp. Pers., Indoor, Mobile Radio Commun. (PIMRC), Valencia, Spain, 2016, pp. 1-6. M. Zhao and Y. Yang “Bounded relay hop mobile data gathering in wireless sensor networks,” IEEE Trans. Comput., Vol. 61, no. 2, pp.265-277 Feb. 2012. D. Klinc, C. Hazay, A. Jagmohan, H. Krawczyk, and T. Rabin, “On compression of data encrypted with block ciphers,” IEEE Trans. Inf. Theory, vol. 58, no. 11, pp. 6989 -7001, Nov. 2012. D. Slepian and J. Wolf, “Noiseless coding of correlated information sources,” IEEE Trans. Inf. Theory, vol. IT-19, no. 4, pp. 471-480, Jul. 1973.

By the way, it is known that the performance of an error correction code depends on its code length, and generally, the longer the code length, the better the performance. Therefore, when the cipher block length is short, the probability of decompression / decryption error in the gateway increases due to the performance limit of the error correction code. Therefore, it is required to reduce decompression / decoding errors and reduce the energy required for packet transmission so that communication can be performed more efficiently.

This disclosure has been made in view of such a situation, and is intended to enable more efficient communication.

The communication system of one aspect of the present disclosure is a communication system in which packets are transmitted so as to be sequentially transmitted via a plurality of terminals, and information to be transmitted is divided into a plurality of information blocks. It is transmitted from each of a predetermined number of information terminals that generate an encrypted packet consisting of a plurality of encrypted blocks that encrypt a plurality of the information blocks and one initial encryption block, and a predetermined number of the information terminals. A relay terminal that holds all of the predetermined number of the encrypted packets that come in, stretches them together for each specific encrypted block, and then performs compression to acquire a plurality of compression sequences, and a plurality of relay terminals. It includes a destination terminal that restores the information targeted for transmission in each of the predetermined number of the information terminals from the compression series.

In the communication method of one aspect of the present disclosure, a communication system in which packets are transmitted so as to be sequentially transmitted via a plurality of terminals divides information to be transmitted into a plurality of information blocks, and a plurality of pieces thereof. An encrypted packet consisting of a plurality of encrypted blocks for encrypting the above information block and one initial encryption block is generated by a predetermined number of information terminals and transmitted from each of the predetermined number of the information terminals. Acquiring a plurality of compression sequences at the relay terminal by holding all of the predetermined number of encrypted packets to be received, stretching each specific encrypted block, and then performing compression. This includes restoring the information targeted for transmission in each of a predetermined number of the information terminals from the plurality of compression sequences transmitted from the relay terminal at the destination terminal.

The program of one aspect of the present disclosure divides the information to be transmitted into a plurality of information blocks to a computer of a communication system in which a packet is transmitted so as to be sequentially transmitted via a plurality of terminals, and a plurality of pieces thereof. An encrypted packet consisting of a plurality of encrypted blocks for encrypting the said information blocks and one initial encrypted block is generated by a predetermined number of information terminals, and from each of the predetermined number of the information terminals. It is possible to acquire a plurality of compression sequences at a relay terminal by holding all of the predetermined number of encrypted packets transmitted, stretching them together for each specific encrypted block, and then performing compression. , The communication process including the restoration of the information targeted for transmission in each of the predetermined number of the information terminals from the plurality of compression sequences transmitted from the relay terminal is executed at the destination terminal.

In one aspect of the present disclosure, the information to be transmitted is divided into a plurality of information blocks, and the encryption is composed of a plurality of encryption blocks in which the plurality of information blocks are encrypted and one initial encryption block. Packets are generated at a predetermined number of information terminals. Then, all of the predetermined number of encrypted packets transmitted from each of the predetermined number of information terminals are held, and a plurality of compression sequences are compressed by collectively stretching each specific encryption block and then performing compression. Is acquired at the relay terminal, and the information targeted for transmission at each of a predetermined number of information terminals is restored at the destination terminal from the plurality of compression sequences.

According to one aspect of the present disclosure, communication can be performed with higher efficiency.

The effects described herein are not necessarily limited, and may be any of the effects described in the present disclosure.

It is a block diagram which shows the structural example of one Embodiment of the communication system to which this technique is applied. It is a block diagram which shows the configuration example of an information terminal. It is a figure explaining a packet generation, a packet division, and an initial cryptographic block. It is a figure explaining the encryption process. It is a figure explaining the encryption process. It is a figure explaining the encrypted packet transmission processing. It is a figure explaining the encrypted packet transmission processing. It is a block diagram which shows the configuration example of a relay terminal. It is a figure explaining the compressed series generation processing. It is a figure explaining the compressed series generation processing. It is a figure explaining the compression process. It is a figure explaining the packet transmission processing. It is a block diagram which shows the configuration example of a destination terminal. It is a figure explaining the decryption decompression process. It is a figure explaining the decryption decompression process. It is a figure which shows an example of the 1st simulation specification. It is a figure which shows the simulation result of the relationship between the entropy of an information packet and the probability of a decoding error. It is a figure which shows an example of the operation flow of a packet transmission in a simulation. It is a figure which shows an example of the 2nd simulation specifications. It is a figure which shows the simulation result about the energy consumption. It is a block diagram which shows the structural example of one Embodiment of the computer to which this technique is applied.

Hereinafter, specific embodiments to which the present technology is applied will be described in detail with reference to the drawings.

<Communication system configuration example>
FIG. 1 is a block diagram showing a configuration example of an embodiment of a communication system to which the present technology is applied.

The communication system 11 shown in FIG. 1 includes M information terminals (SN: Source Node) 12 ₁ to 12 _M , one relay terminal (RN: Relay Node) 13, and one destination terminal (SN: Relay Node) 13. DN: Destination Node) 14 is connected and configured via a communication network.

For example, in the communication system 11, multi-hop communication is performed in which packets are transmitted so as to be sequentially transmitted via a plurality of terminals, but communication with the destination terminal 14 is performed so that only the relay terminal 13 establishes communication. The network is configured. Therefore, the communication system 11 has a connection configuration in which M information terminals 12 ₁ to 12 _M and a relay terminal 13 are connected via a communication network, and the relay terminal 13 and a destination terminal 14 are connected via a communication network. It has become.

The information terminals 12 ₁ to 12 _M encrypt the information to be transmitted for privacy protection, acquire the encrypted packet, and transmit the encrypted packet to the relay terminal 13. At this time, the destination of the information transmitted by the information terminals 12 ₁ to 12 _M is the destination terminal 14, but the information terminals 12 ₁ to 12 _M are connected only to the relay terminal 13 via the communication network, and the destination terminal 14 is used. The connection configuration is such that it is not connected. Therefore, in the communication system 11, the information terminals 12 ₁ to 12 _M can transmit packets only to the relay terminal 13.

The relay terminal 13 collects encrypted packets transmitted from each of the information terminals 12 ₁ to 12 _M , and acquires a compression series by performing post-encryption compression that collectively compresses the encrypted packets. , The compressed sequence is transmitted to the destination terminal 14. For example, in the communication system 11, the relay terminal 13 can transmit a packet only to the destination terminal 14. Hereinafter, the aggregation of encrypted packets at the relay terminal 13 is referred to as packet aggregation.

The destination terminal 14 restores the information targeted for transmission in each of the information terminals 12 ₁ to 12 _M from the compression series transmitted from the relay terminal 13. For example, the destination terminal 14 is known about the encryption key used by each of the information terminals 12 ₁ to 12 _M to encrypt the information, and the encrypted packet can be decrypted by using the encryption key.

In the communication system 11 configured in this way, even if the transfer of encrypted packets is concentrated on the relay terminal 13, the encrypted packets are collectively compressed to communicate with higher efficiency. Can be done. In the present embodiment, it is assumed that no error occurs in the packet transmission between the information terminals 12 ₁ to 12 _M and the relay terminal 13 and the packet transmission between the relay terminal 13 and the destination terminal 14. Give an explanation.

<Information terminal configuration example and processing example>
With reference to FIGS. 2 to 7, a configuration example of the information terminal 12 and a processing example of each processing performed in the information terminal 12 will be described.

FIG. 2 is a block diagram showing a configuration example of the information terminal 12. The information terminal 12 includes a packet generation unit 21, a packet division unit 22, an initial encryption block generation unit 23, an encryption processing unit 24, and an encrypted packet transmission unit 25.

The packet generation unit 21 generates an information packet by packetizing it in order to transmit the information to be transmitted, and supplies it to the packet division unit 22. For example, as shown in the first stage of FIG. 3, the packet generation unit 21 _m of the m-th information terminal 12 _m forms an information packet X ^(m) consisting of two values of 0 and 1 and having a packet sequence length L. Generate. Here, it is assumed that the information packet X ^(m) has a low entropy H.

The packet division unit 22 divides the information packet supplied from the packet generation unit 21 into a plurality of information blocks and supplies the information packet to the initial cipher block generation unit 23. For example, when an information packet is divided into N information blocks, the packet division unit 22 _m of the mth information terminal 12 _m is an information packet X having a packet sequence length L, as shown in the second stage of FIG. ⁽ M) is divided into N information blocks x _n ^(m) each having a block sequence length K. Here, the packet dividing unit 22 assigns a block index n (n = 1 to N) to each information block x _n ^(m) in order.

The initial cipher block generation unit 23 generates an initial cipher block using random numbers, adds it to the head of a plurality of information blocks supplied from the packet division unit 22, and supplies the initial cipher block to the encryption processing unit 24. For example, as shown in the third row of FIG. 3, the packet dividing portion 22 _m of the m-th information terminal 12 _m is the head information block x ₁ ⁽ m) of the N information blocks x _n ^(m) . An initial cryptographic block y ₀ ^(m) having a block sequence length K is added before ^m ).

The encryption processing unit 24 acquires the encryption packet corresponding to each of the initial encryption block and the plurality of information blocks supplied from the initial encryption block generation unit 23, and encrypts them. It is supplied to the packet transmission unit 25. The encryption processing by the encryption processing unit 24 _m of the m-th information terminal 12 _m will be described later with reference to FIGS. 4 and 5.

The encrypted packet transmission unit 25 transmits the encrypted packet supplied from the encryption processing unit 24 to the relay terminal 13. The packet transmission process by the encrypted packet transmission unit 25 _m of the m-th information terminal 12 _m will be described later with reference to FIGS. 6 and 7.

<Encryption processing>
With reference to FIGS. 4 and 5, the encryption processing by the encryption processing unit 24 _m included in the m-th information terminal 12 _m will be described. For example, the encryption processing unit 24 _m performs encryption by block cipher in CBC (Cipher Block Chaining) mode.

First, as shown in the first stage of FIG. 4, the encryption processing unit 24 _m sets the initial encryption block y ₀ ^(m) into the encryption block y ₀ (m) of the first block of the encryption packet Y ^{(m )} . And.

Then, as shown in the second stage of FIG. 4, the encryption processing unit 24 _m has the information block x ₁ ^(m) as the encryption target, and the encryption block y ₀ ^(m) and the information block x ₁ ^(m). The first CBC block x ^ ₁ ^(m) is calculated by calculating the exclusive OR between the series of. Similarly, the encryption processing unit 24 _m calculates an exclusive OR between the series of the encryption block y _n-1 ^(m) of the n-1th block and the nth information block x _n ^(m) . Therefore, the nth CBC block x ^ _n ^(m) can be calculated.

Further, as shown in the third row of FIG. 4, the encryption processing unit 24 _m with respect to the encryption execution function F _{K (m)} [・] using the encryption key K ^(m) in the information terminal 12 _m . The encryption block y ₁ ^(m) is acquired by inputting the first CBC block x ^ ₁ ^(m) . In this way, the encryption processing unit 24 _m acquires the encryption block y ₁ ^(m) , which is the second block of the encrypted packet Y ^(m) , with the information block x ₁ ^(m) as the encryption target. Can be done.

Next, as shown in the first stage of FIG. 5, the encryption processing unit 24 _m calculates the second CBC block x ^ ₂ ^(m) with the information block x ₂ ^(m) as the encryption target. The encrypted block y ₂ ^(m) , which is the third block of the encrypted packet Y ^(m) , is acquired. Hereinafter, the encryption processing unit 24 _m calculates the Nth CBC block x ^ _N ^(m) with the information block x _N ^(m) as the encryption target, and sets it as the N + 1 block of the encrypted packet Y ^(m) . The same process is repeated in sequence until the encryption block y _N ^(m) is acquired.

As a result, as shown in the second stage of FIG. 5, the encryption processing unit 24 _m can acquire the encrypted packet Y ^(m) having the packet sequence length (N + 1) K.

Then, by performing the same encryption processing in each of the information terminals 12 ₁ to 12 _M , the encrypted packets Y ⁽¹⁾ to Y ^(M) are acquired, and the information terminals 12 ₁ to 12 _M are encrypted to the relay terminal 13. The encrypted packets Y ⁽¹⁾ to Y ^(M) are transmitted.

<Encrypted packet transmission processing>
With reference to FIGS. 6 and 7, the encrypted packet transmission process by the encrypted packet transmission unit 25 _m included in the mth information terminal 12 _m will be described. Although the packet transmission based on the RI-MAC protocol proposed in Non-Patent Document 1 described above will be described, any other protocol may be used.

Here, as shown in the first stage of FIG. 6, the description will be given according to the passage of time t of the information terminal 12 _m and the relay terminal 13.

First, as shown in the second stage of FIG. 6, the information terminal 12 _m is encrypted at an arbitrary timing in the packet generation section _TG , which is a section in which the information terminal 12 _m can generate an encrypted packet. Generate a packet.

Then, as shown in the third stage of FIG. 6, the information terminal 12 _m is continuously in the reception state after the encrypted packet is generated.

On the other hand, as shown in the first stage of FIG. 7, the relay terminal 13 is activated at each intermittent interval _TIDLE that is activated intermittently at a predetermined interval, and is ready to receive the encrypted packet (DATA). The RTR (Ready-To-Receive) signal notifying is transmitted to all of the information terminals 12 ₁ to 12 _M. After that, the relay terminal 13 is in the reception state for a short time.

Then, as shown in the second stage of FIG. 7, the information terminal 12 _m that has received the RTR immediately transmits an encrypted packet (DATA) to the relay terminal 13, and after the transmission is completed, immediately shifts to the dormant state. do.

In response to this, as shown in the third stage of FIG. 7, the relay terminal 13 receives the encrypted packet (DATA) transmitted from the information terminal 12 _m . Then, even after the reception of the encrypted packet (DATA) is completed, the relay terminal 13 is in a continuous reception state for transmission to the destination terminal 14.

As described above, the information terminals 12 ₁ to 12 _M are configured, and each of the information packets X ⁽¹⁾ to ^(M) has N information blocks x ₁ ⁽¹⁾ to x _N ⁽¹⁾ and N pieces, respectively. Information blocks x ₁ ⁽²⁾ to x _N ⁽²⁾ , ..., Divided into N information blocks x ₁ ^(M) to x _N ^(M) . Further, an encrypted packet Y ⁽ 1) composed of an encryption block y ₁ ⁽¹⁾ to y _N ⁽¹⁾ in which the information blocks x ₁ ⁽¹⁾ to x _N ⁽¹⁾ are encrypted and an initial encryption block y ₀ ^{(1) (1)} . ¹⁾ is generated, and similarly, encrypted packets Y ⁽²⁾ to Y ^(M) are generated. Then, the encrypted packets Y ⁽¹⁾ to Y ^(M) are transmitted from the information terminals 12 ₁ to 12 _M to the relay terminal 13.

<Example of relay terminal configuration and processing>
8 to 12, a configuration example of the relay terminal 13 and a processing example of each process performed in the relay terminal 13 will be described.

FIG. 8 is a block diagram showing a configuration example of the relay terminal 13. The relay terminal 13 includes a packet receiving unit 31, a holding unit 32, a compressed sequence generation processing unit 33, a compression processing unit 34, and a transmission unit 35.

The packet receiving unit 31 receives all the encrypted packets Y ⁽¹⁾ to Y ^(M) transmitted from each of the information terminals 12 ₁ to 12 _M and supplies them to the holding unit 32.

The holding unit 32 holds all the encrypted packets Y ⁽¹⁾ to Y ^(M) supplied from the packet receiving unit 31.

The compressed sequence generation processing unit 33 reads the encrypted packets Y ⁽¹⁾ to Y ^(M) from the holding unit 32, and generates a compressed sequence to be a processing unit when the compression processing is performed by the compression processing unit 34. The compressed sequence is generated, and the compressed sequence is supplied to the compression processing unit 34. The compressed sequence generation process by the compressed sequence generation processing unit 33 will be described later with reference to FIGS. 9 and 10.

The compression processing unit 34 generates a compression series by performing compression processing for each compressed series supplied from the compressed series generation processing unit 33, and supplies the compression series to the transmission unit 35. The compression process by the compression process unit 34 will be described later with reference to FIG.

The transmission unit 35 transmits the compression series supplied from the compression processing unit 34 to the destination terminal 14. The packet transmission process by the transmission unit 35 will be described later with reference to FIG.

<Compressed sequence generation process>
The compressed series generation processing by the compressed series generation processing unit 33 will be described with reference to FIGS. 9 and 10.

First, as shown in the first stage of FIG. 9, the holding unit 32 holds all the encrypted packets Y ⁽¹⁾ to Y ^(M) . As shown in the figure, the encrypted packet Y ^(m) is composed of N + 1 encryption blocks y ₀ ^(m) to y _N ^(m) . Then, in the communication system 11, the compressed sequence is generated by paying attention to the encrypted blocks y _n ⁽¹⁾ to y _n ^(M) having the same block index n.

For example, as shown in the second row of FIG. 9, when the block index n = 0 is the processing target, the compressed sequence generation processing unit 33 is the encryption block y ₀ ⁽¹⁾ to y surrounded by the broken line. ₀ ^(M) is read from the holding unit 32.

Here, as shown in the third row of FIG. 9, the size of the encryption block y ₀ ⁽¹⁾ is 1 × K in rows × columns, and the other encryption blocks y ₀ ⁽²⁾ to y ₀ ^(M ). ⁾ Is the same size.

Next, as shown in the first stage of FIG. 10, the compressed sequence generation processing unit 33 transposes the encryption blocks y ₀ ⁽¹⁾ to y ₀ ^(M) using the transposed matrix (.) ^T. .. As a result, for example, the encryption block y ₀ ⁽¹⁾ is transposed to the encryption block y ₀ ^{(1) T} having a size in which the row × column is K × 1. Similarly, the other encryption blocks y ₀ ⁽²⁾ to y ₀ ^(M) are also converted into encryption blocks y ₀ ^{(2) T} to y ₀ ^{(M) T} having a size in which the row × column is K × 1. Be transposed.

Then, as shown in the second stage of FIG. 10, the compressed sequence generation processing unit 33 applies the vector operator Vec (.) To the encryption blocks y ₀ ^{(1) T} to y ₀ ^{(M) T.} By arranging them in one column, a compressed sequence Y0 having a size in which rows × columns are MK × ₁ is generated.

Hereinafter, similarly, the compressed series generation processing unit 33 generates the compressed series Y1 to YN by performing the compressed series generation processing with the encrypted blocks of the block indexes ₁ to _N as the processing target. For example, the compressed sequence generation processing unit 33 uses the transposed matrix (.) ^T to replace the encrypted blocks y _n ⁽¹⁾ to y _n ^(M) having the block index n as the processing target. By applying the vector action element Vec (.) To _n ^{(1) T} to y _n ^{(M) T} , the transposed matrix Y _n is generated.

<Compression processing>
The compression processing by the compression processing unit 34 will be described with reference to FIG. 11.

The compression processing unit 34 performs compression processing using a parity inspection matrix, which is an error correction code inspection matrix. When the error correction code of the coding rate R is used, the compressed series is compressed at the compression rate (1-R). For example, the compression processing unit 34 has a size of the parity check matrix H in which the row × column is (1-R) MK × MK, and the row × column supplied from the compressed sequence generation processing unit 33 is MK × 1. By applying to the compressed sequence Y _n , it is possible to acquire the compressed sequence S _n ^T in which the row × column is (1-R) MK × 1.

Then, the compression processing unit 34 applies such compression processing to the compressed series Y ₀ to Y _N-1 supplied from the compressed series generation processing unit 33, whereby the compression series S ₀ ^T to S _N are applied. _-1 ^T is acquired and supplied to the transmission unit 35. Here, the compression processing unit 34 supplies the compressed series _YN to the transmission unit 35 as it is without performing compression processing so that the destination terminal 14 can perform decompression and decryption. .. That is, when the compression process is applied from the first compressed sequence Y ₀ , the compression process is not applied to the last compressed sequence Y _N.

<Packet transmission processing>
A packet transmission process by the transmission unit 35 will be described with reference to FIG. 12.

As shown in FIG. 12, the destination terminal 14 transmits an RTR signal to the relay terminal 13 at each intermittent interval _TIDLE . Then, the relay terminal 13 acquires the compressed series S ₀ to SN- ₁ and the compressed series Y _N , and immediately after receiving the RTR signal, sets the compressed series S ₀ to _SN-1 and the compressed series Y _N. Collectively send to the destination terminal 14. At the destination terminal 14, the intermittent interval _TIDLE is started after the reception of the compressed series S ₀ to S _N-1 and the compressed series Y _N is completed.

As described above, the relay terminal 13 is configured, all of the encrypted packets Y ⁽¹⁾ to Y ^(M) transmitted from the information terminals 12 ₁ to 12 _M are held, and the block index n is the same. The compression series S ₀ to S _N-1 are acquired by performing compression after extending the processing target of compression by grouping each encryption block y _n . Then, the compressed series S ₀ to S _N-1 and the compressed series Y _N are transmitted from the relay terminal 13 to the destination terminal 14.

<Configuration example and processing example of destination terminal>
A configuration example of the destination terminal 14 and a processing example of each process performed in the destination terminal 14 will be described with reference to FIGS. 13 to 15.

FIG. 13 is a block diagram showing a configuration example of the destination terminal 14. The destination terminal 14 includes a receiving unit 41 and a decoding / decompression processing unit 42.

The receiving unit 41 receives the compressed series S ₀ to S _N-1 and the compressed series Y _N collectively transmitted from the relay terminal 13 and supplies them to the decoding / decompression processing unit 42.

The decryption / decompression processing unit 42 decodes the compression series S ₀ to S _N-1 and the compressed series Y _N , and performs a decryption / decompression process for returning the compressed data to the original state (hereinafter referred to as decompression). This is performed to restore the information targeted for transmission in each of the information terminals 12 ₁ to 12 _M. As a result, the decoding / decompression processing unit 42 has information blocks x ₁ ⁽¹⁾ to x _N ⁽¹⁾ , information blocks x ₁ ⁽²⁾ to x _N ⁽²⁾ , ..., Information blocks x ₁ ^(M) to Acquires x _N ^(M) and outputs it.

<Decryption / decompression processing>
The decoding / decompression processing by the decoding / decompression processing unit 42 will be described with reference to FIGS. 14 and 15.

First, as shown in the first stage of FIG. 14, the decryption / decompression processing unit 42 is applied to each of the encryption blocks y _N ^{(1) T} to y _N ^{(M) T} constituting the uncompressed series Y _N to be compressed. On the other hand, the encryption execution inverse function F ^-1 _{K (m)} [・] is applied. As a result, the decryption / decompression processing unit 42 decodes the encryption blocks y _N ^{(1) T} to y _N ^{(M) T} into CBC blocks x ^ _N ^{(1) T} to x ^ _N ^{(M) T.} At this time, the decryption / decompression processing unit 42 is known about the encryption keys K (1) to K (M) used by the information terminals 12 ₁ to 12 _M to encrypt the information, respectively, and the encryption keys K ^{( 1)} to K ^(M) are known. Enter K ^(M) in the encryption execution inverse function F ^-1 _{K (m)} [・]. Further, for one series in which CBC blocks x ^ _N ^{(1) T} to x ^ _N ^{(M) T} are arranged in a row, that is, for CBC blocks x ^ _N ^{(1) T} to x ^ _N ^{(M) T.} The sequence to which the vector operator Vec (・) is applied is defined as the auxiliary information sequence X ^ _N.

Here, as shown in the second row of FIG. 14, the auxiliary information sequence X ^ _N and the compressed sequence Y _N-1 before compressing the compression sequence S _N-1 ^T have a correlation. That is, the compressed sequence Y _N-1 is exclusive between the auxiliary information sequence X ^ _N and the information block x _N ^{(1) T} to x _N ^{(M) T} to which the vector operator Vec (・) is applied. It is equal to the logical sum.

Taking advantage of this, as shown in the first stage of FIG. 15, the decryption / decompression processing unit 42 decompresses the compression series S _N-1 ^T with a Slepian-Wolf type decompression device, and decompresses the compression series Y _N-1 . Can be obtained.

Then, as shown in the second stage of FIG. 15, the decoding / decompression processing unit 42 obtains the exclusive OR of the compressed sequence Y _N-1 and the auxiliary information sequence X ^ _N , so that the information block x of the block index N x _N ^{(1) T} to x _N ^{(M) T} can be acquired. Hereinafter, the decryption / decompression processing unit 42 decompresses the compressed sequence S _N-2 ^T using the auxiliary information sequence X ^ _N-1 obtained from the compressed sequence Y _N-1 to decompress the compressed sequence Y _N-2 . Processing to acquire information blocks x _N-1 ⁽¹⁾ to x _N-1 ^(M) by obtaining the exclusive OR of the compressed sequence Y _N-2 and the auxiliary information sequence X ^ _N-1 . , And the same process is repeated in sequence until the information blocks x ₁ ⁽¹⁾ to x ₁ ^(M) of the block index 1 are acquired.

Then, the decoding / decompression processing unit 42 restores the information by acquiring the information packets X ⁽¹⁾ to X ^(M) obtained by packetizing the information targeted for transmission in each of the information terminals 12 ₁ to 12 _M. can do.

In this way, the decompression / decompression processing unit 42 uses the uncompressed compressed series Y _N to be decompressed in order from the compression series S _N-1 , and the decompression processing target compression series _Sn is decoded. The compression series _Sn to be processed is decompressed by using the correlation between the information series X ^ _n and the compressed series Y _n-1 before compressing the compression series S _n-1 immediately before the decompression processing target. do.

The destination terminal 14 is configured as described above, and is a transmission target in each of the information terminals 12 ₁ to 12 _M from the compression series S ₀ to S _N-1 and the compressed series Y _N transmitted from the relay terminal 13. The saved information is restored (decrypted and decompressed).

When the post-encryption compression is applied in the relay terminal 13, the communication system 11 configured as described above is stretched together for each encryption block yn having the same block index _n , so that after encryption. The compression performance can be improved. Further, the communication system 11 can achieve low energy consumption as compared with the conventional case by transmitting the compression series S in which the encrypted packets are collectively compressed at the relay terminal 13 to the destination terminal 14.

In particular, even if the communication system 11 is configured such that the transfer is concentrated on the relay terminal 13, the amount of data to be transferred can be reduced, the transmission efficiency can be improved, and the power consumption can be reduced, which is more efficient. Can communicate.

<Effects on communication systems>
The effect of applying the present technique in the communication system 11 will be described with reference to FIGS. 16 to 20.

First, the effect shown from the result of the first simulation performed on the relationship between the entropy of the information packet and the probability of decoding error will be described.

FIG. 16 is a diagram showing an example of the first simulation specifications. The technique applied to the communication system 11 is used as the proposed method, and the technique disclosed in Non-Patent Document 3 described above is applied as a conventional method for comparing with the proposed method.

For example, as shown in FIG. 16, in the conventional method, the simulation is performed using the Gallager configuration as the LDPC matrix construction method, and in the proposed method, the simulation is performed using the Gallager configuration and the IEEE 802.11n standard as the LDPC matrix construction method. gone. In the following, the simulation in which the LDPC matrix construction method is performed in the Gallager configuration in the proposed method is referred to as the proposed method (Gallager), and the simulation in which the LDPC matrix construction method is performed in the IEEE802.11n configuration in the proposed method is referred to as the proposed method (Gallager). It is called IEEE802.11n). The Low-Density Parity-Check (LDPC) code is disclosed in Non-Patent Document 5 “RC Gallager, Low-Density Parity-Check Codes. Cambridge, MA, USA: MIT Press, 1963.”.

FIG. 17 is a diagram showing a simulation result in which information packets are encrypted and compressed so as to have a compression rate of 0.5 in the proposed method and the conventional method. In FIG. 17, the horizontal axis shows the entropy which is the theoretical limit of the compression rate when compressing an information packet, and the vertical axis shows the probability that the decompressed / decoded packet differs from the original packet by even one bit. It shows the error probability.

In the conventional method, a simulation was performed in which post-encryption compression was performed so as to compress a 128-bit encrypted block into a 64-bit series. In the proposed method (Gallager), a simulation was performed in which compression after encryption was performed so as to compress a 1920-bit compressed series into a 960-bit series. In the proposed method (IEEE802.11n), after zero padding is performed by adding only 24 bits of bit 0 to the rear of the 1920-bit compressed series, and after encryption, the 1944-bit series is compressed into the 972-bit series. A simulation of compression was performed.

Regarding this simulation result, for example, focus on entropy 0.25. Comparing the conventional method and the proposed method (Gallager), it is shown that in theory, a compressible packet can be compressed at a compression rate of 0.5 without any error up to a compression rate of 0.25. On the other hand, in the conventional method, the decompression / decoding error probability is almost 1 (that is, an error occurs in almost all cases), whereas in the proposed method, the decompression / decoding error probability is 10 ^-4 or less. Has been done.

In addition, the simulation results show that the decompression / decoding error occurs only when the entropy is around 0.31 as the performance of the proposed method (IEEE802.11n). As described above, it was shown that the proposed method (IEEE802.11n) can improve the compression performance as compared with the proposed method (Gallager).

From the above, in the proposed method (Gallager), in the compression method based on the error correction code, it was possible to obtain the effect that the longer the length of the compressed series, the closer the compression performance approaches the theoretical limit. Thus, it was shown that it is possible to decompress the compressed sequence by packet aggregation.

Also, in the proposed method (IEEE802.11n), the bit added by zero padding can be used as a definite bit at the time of decompression / decoding (because the decoding side also knows where zero was added as a compression method). It has been shown. As a result, in the decompression / decoding algorithm based on the error correction code, it was possible to obtain the effect that the performance can be improved when the definite bit is available. Furthermore, it was shown that the configuration method of the LDPC code of the IEEE802.11n standard is a construction method designed to improve the error correction capability based on numerical analysis.

Next, the effect shown from the result of the second simulation for evaluating the energy consumption in the network model as shown in FIG. 1 will be described.

For example, when packet transmission is performed based on the operation flow as shown in FIG. 18, IRDT (Intermittent Receiver-driven Data Transmission), which is a kind of RI-MAC protocol proposed in Non-Patent Document 1 described above, is used. A simulation was performed to determine the energy consumption at the time of application. Regarding IRDT, Patent Document 6 “T. Hatauchi, Y. Fukuyama and T. Shikura,“ A power efficient access method by polling for wireless mesh networks, ”IEEJ Trans.Electron. Inf. Syst., Vol. 128, pp. 1761-1766, Dec. 2008. ”.

FIG. 19 is a diagram showing an example of the second simulation specifications. As described in the present embodiment, the technique applied to the communication system 11 is used as the proposed method, and the technique disclosed in Patent Document 6 described above is used as the conventional method for comparing with the proposed method. ..

For example, as shown in FIG. 19, in the conventional method, the simulation was performed with the number of collected packets set to 1, and in the proposed method, the number of collected packets was set to 15 and 30. In the following, the simulation performed with the number of collected packets of 15 in the proposed method will be referred to as the proposed method (15), and the simulation performed with the number of collected packets of 30 in the proposed method will be referred to as the proposed method (30).

FIG. 20 is a diagram showing simulation results in which packet transmission is executed as shown in FIG. 18 in the proposed method and the conventional method. The simulation specifications for the packet were the same as in FIG. 17 described above. In FIG. 20, the horizontal axis represents the intermittent interval _TIDLE , which is the time interval at which the relay terminal 13 on the receiving side transmits the RTR signal, and the vertical axis represents the entire network per packet correctly received by the destination terminal 14. It shows the energy consumption.

For example, simulation results show that for any intermittent interval _TIDLE , both the proposed method (15) and the proposed method (30) achieve lower energy consumption than the conventional method.

By performing packet aggregation at the relay terminal 13, it is possible to reduce the overhead at the time of packet transmission, mainly to shorten the transmission waiting time at the information terminal 12, and to reduce the energy consumption at the time of packet collision and transmission standby. It is thought that it will be realized by reduction. Further, it is considered that the energy required for packet transmission can be reduced because the transmission packet length is shortened by performing compression after encryption in the relay terminal 13.

Here, the overhead reduction by packet aggregation will be described.

In the conventional method, the relay terminal 13 executes the transfer of one packet to the destination terminal 14 every time one packet is transmitted from the information terminal 12. Therefore, the relay terminal 13 needs to execute link construction and data transfer with the destination terminal 14 every time one packet is transferred, and as a result of the increase in the time for the relay terminal 13 to operate as a transmitter, the relay terminal 13 Will increase the time interval for broadcasting the RTR signal. Along with this, the waiting time for receiving the RTR signal in the information terminal 12 increases, and the energy consumption of the information terminal 12 increases.

On the other hand, in the proposed method, by applying packet aggregation, the number of times that the relay terminal 13 establishes a link with the destination terminal 14 can be reduced, and as a result, the time interval at which the relay terminal 13 broadcasts the RTR signal is set. Can be shortened. Therefore, the waiting time for receiving the RTR signal in the information terminal 12 can be reduced, and the energy consumption of the information terminal 12 can be reduced.

As described above, in the communication system 11 to which the present technology is applied, it is possible to reduce the decompression error probability for an arbitrary entropy packet as compared with the conventional post-encryption compression (EtC), and the conventional method. It is possible to reduce the energy required for packet transmission as compared with the above.

<Computer configuration example>
Next, the series of processes (communication method) described above can be performed by hardware or software. When a series of processes is performed by software, the programs constituting the software are installed on a general-purpose computer or the like.

FIG. 21 is a block diagram showing a configuration example of an embodiment of a computer in which a program for executing the above-mentioned series of processes is installed.

The program can be recorded in advance on the hard disk 105 or ROM 103 as a recording medium built in the computer.

Alternatively, the program can be stored (recorded) in the removable recording medium 111 driven by the drive 109. Such a removable recording medium 111 can be provided as so-called package software. Here, examples of the removable recording medium 111 include a flexible disc, a CD-ROM (Compact Disc Read Only Memory), an MO (Magneto Optical) disc, a DVD (Digital Versatile Disc), a magnetic disc, and a semiconductor memory.

In addition to installing the program on the computer from the removable recording medium 111 as described above, the program can be downloaded to the computer via a communication network or a broadcasting network and installed on the built-in hard disk 105. That is, for example, the program transfers wirelessly from a download site to a computer via an artificial satellite for digital satellite broadcasting, or transfers to a computer by wire via a network such as LAN (Local Area Network) or the Internet. be able to.

The computer has a built-in CPU (Central Processing Unit) 102, and the input / output interface 110 is connected to the CPU 102 via the bus 101.

When a command is input by the user by operating the input unit 107 or the like via the input / output interface 110, the CPU 102 executes a program stored in the ROM (Read Only Memory) 103 accordingly. .. Alternatively, the CPU 102 loads the program stored in the hard disk 105 into the RAM (Random Access Memory) 104 and executes it.

As a result, the CPU 102 performs a process according to the above-mentioned flowchart or a process performed according to the above-mentioned block diagram configuration. Then, the CPU 102 outputs the processing result from the output unit 106, transmits it from the communication unit 108, and further records it on the hard disk 105, for example, via the input / output interface 110, if necessary.

The input unit 107 is composed of a keyboard, a mouse, a microphone, and the like. Further, the output unit 106 is composed of an LCD (Liquid Crystal Display), a speaker, or the like.

Here, in the present specification, the processes performed by the computer according to the program do not necessarily have to be performed in chronological order in the order described as the flowchart. That is, the processing performed by the computer according to the program includes processing executed in parallel or individually (for example, processing by parallel processing or processing by an object).

Further, the program may be processed by one computer (processor) or may be distributed processed by a plurality of computers. Further, the program may be transferred to a distant computer and executed.

Further, in the present specification, the system means a set of a plurality of components (devices, modules (parts), etc.), and it does not matter whether all the components are in the same housing. Therefore, a plurality of devices housed in separate housings and connected via a network, and a device in which a plurality of modules are housed in one housing are both systems. ..

Further, for example, the configuration described as one device (or processing unit) may be divided and configured as a plurality of devices (or processing units). On the contrary, the configurations described above as a plurality of devices (or processing units) may be collectively configured as one device (or processing unit). Further, of course, a configuration other than the above may be added to the configuration of each device (or each processing unit). Further, if the configuration and operation of the entire system are substantially the same, a part of the configuration of one device (or processing unit) may be included in the configuration of another device (or other processing unit). ..

Further, for example, the present technology can have a cloud computing configuration in which one function is shared by a plurality of devices via a network and jointly processed.

Further, for example, the above-mentioned program can be executed in any device. In that case, the device may have necessary functions (functional blocks, etc.) so that necessary information can be obtained.

Further, for example, the individual processing contents (steps) in each of the above-mentioned processes can be executed by one device or can be shared and executed by a plurality of devices. Further, when a plurality of processes are included in one step, the plurality of processes included in the one step can be executed by one device or shared by a plurality of devices. In other words, a plurality of processes included in one step can be executed as processes of a plurality of steps. On the contrary, the processes described as a plurality of steps can be collectively executed as one step.

In the program executed by the computer, the processes of the steps for describing the program may be executed in chronological order in the order described in the present specification, or may be called in parallel or called. It may be executed individually at the required timing such as when. That is, as long as there is no contradiction, the processes of each step may be executed in an order different from the above-mentioned order. Further, the processing of the step for describing this program may be executed in parallel with the processing of another program, or may be executed in combination with the processing of another program.

It should be noted that the techniques described in the present specification can be independently implemented independently as long as there is no contradiction. Of course, any plurality of the present techniques can be used in combination. For example, some or all of the techniques described in any of the embodiments may be combined with some or all of the techniques described in other embodiments. In addition, a part or all of any of the above-mentioned techniques may be carried out in combination with other techniques not described above.

The present embodiment is not limited to the above-described embodiment, and various modifications can be made without departing from the gist of the present disclosure. Further, the effects described in the present specification are merely exemplary and not limited, and other effects may be used.

11 Communication system, 12 ₁ to 12 _M information terminal, 13 Relay terminal, 14 Destination terminal, 21 Packet generation unit, 22 Packet division unit, 23 Initial encryption block generation unit, 24 Encryption processing unit, 25 Encryption packet transmission unit, 31 Packet receiving unit, 32 Holding unit, 33 Compressed sequence generation processing unit, 34 Compression processing unit, 35 Transmission unit, 41 Reception unit, 42 Decoding / decompression processing unit

Claims (8)

A communication system in which packets are transmitted so as to be transmitted sequentially via multiple terminals.
A predetermined number of pieces of information to be transmitted is divided into a plurality of information blocks to generate an encrypted packet including a plurality of encrypted blocks obtained by encrypting the plurality of the information blocks and one initial encrypted block. Information terminal and
A plurality of compressions are performed by holding all of the predetermined number of the encrypted packets transmitted from each of the predetermined number of the information terminals, stretching them together for each specific encryption block, and then performing compression. A relay terminal that acquires a series, and
A communication system including a destination terminal that restores the information targeted for transmission in each of a predetermined number of the information terminals from a plurality of compression sequences transmitted from the relay terminal. The information terminal assigns a block index to the encrypted block in order, and then assigns a block index to the encrypted block.
The communication system according to claim 1, wherein the relay terminal is grouped for each encrypted block having the same block index to extend the compression processing target. The relay terminal is
A compressed sequence generation processing unit that applies a vector operator to a predetermined number of encrypted blocks collected by the block index to generate a compressed sequence to be processed when compression processing is performed.
The communication system according to claim 2, further comprising a compression processing unit that performs compression processing using an error correction code for each of a plurality of the compressed series generated in the compressed sequence generation processing unit. The communication system according to claim 3, wherein the compressed sequence generation processing unit performs zero padding so that the generated compressed sequence has a specified length. 3. The compression processing unit causes the compressed series generated from the encrypted block to which the block index at the end is attached to be transmitted to the destination terminal as it is without performing compression processing. The communication system described in. The destination terminal uses the compressed series that has not been compressed in the compression processing unit, and returns the compression to the original state in order from the compression series whose block index is immediately before the end. Using the correlation between the auxiliary information series obtained by decoding the compressed series to be processed and the compressed series whose block index is one block index before the compressed series to be processed, the processing target is The communication system according to claim 5, wherein the information is restored by returning the compression of the compression series to the original state. A communication system in which packets are transmitted so as to be transmitted sequentially via multiple terminals,
The information to be transmitted is divided into a plurality of information blocks, and a predetermined number of encrypted packets composed of a plurality of encrypted blocks obtained by encrypting the plurality of the information blocks and one initial encrypted block are formed. Generating at an information terminal and
A plurality of compressions are performed by holding all of the predetermined number of the encrypted packets transmitted from each of the predetermined number of the information terminals, stretching them together for each specific encryption block, and then performing compression. Acquiring the series at the relay terminal and
A communication method including restoring at a destination terminal the information targeted for transmission at each of a predetermined number of information terminals from a plurality of compression sequences transmitted from the relay terminal. To a computer in a communication system where packets are transmitted so that they are transmitted sequentially via multiple terminals.
The information to be transmitted is divided into a plurality of information blocks, and a predetermined number of encrypted packets composed of a plurality of encrypted blocks obtained by encrypting the plurality of the information blocks and one initial encrypted block are formed. Generating at an information terminal and
A plurality of compressions are performed by holding all of the predetermined number of the encrypted packets transmitted from each of the predetermined number of the information terminals, stretching them together for each specific encryption block, and then performing compression. Acquiring the series at the relay terminal and
A program for executing communication processing including restoring the information targeted for transmission in each of a predetermined number of the information terminals from a plurality of compression sequences transmitted from the relay terminal at the destination terminal. ..

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