JPH04223731A - Privacy communication system - Google Patents
Privacy communication systemInfo
- Publication number
- JPH04223731A JPH04223731A JP2406536A JP40653690A JPH04223731A JP H04223731 A JPH04223731 A JP H04223731A JP 2406536 A JP2406536 A JP 2406536A JP 40653690 A JP40653690 A JP 40653690A JP H04223731 A JPH04223731 A JP H04223731A
- Authority
- JP
- Japan
- Prior art keywords
- central station
- station
- signal
- slave
- slave stations
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Pending
Links
- 230000006854 communication Effects 0.000 title claims abstract description 23
- 238000004891 communication Methods 0.000 title claims abstract description 23
- 230000005540 biological transmission Effects 0.000 claims abstract description 46
- 230000003287 optical effect Effects 0.000 claims description 24
- 238000011144 upstream manufacturing Methods 0.000 claims description 21
- 230000002457 bidirectional effect Effects 0.000 claims description 17
- 238000006243 chemical reaction Methods 0.000 claims description 6
- 238000000034 method Methods 0.000 claims description 6
- 230000007175 bidirectional communication Effects 0.000 claims description 5
- 239000013307 optical fiber Substances 0.000 claims 4
- 238000010079 rubber tapping Methods 0.000 abstract 1
- 238000010586 diagram Methods 0.000 description 11
- 230000006835 compression Effects 0.000 description 2
- 238000007906 compression Methods 0.000 description 2
- 230000008878 coupling Effects 0.000 description 2
- 238000010168 coupling process Methods 0.000 description 2
- 238000005859 coupling reaction Methods 0.000 description 2
- 238000005516 engineering process Methods 0.000 description 1
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Abstract
Description
【０００１】0001
【産業上の利用分野】本発明は中央局から伝送路を介し
て、複数の子局へ双方向通信を行なう、１：ｎの双方向
伝送回路網において、複数の子局間の秘話を効果的に確
保し得る秘話通信方式に関する。[Industrial Application Field] The present invention provides an effective way to communicate secret information between multiple slave stations in a 1:n bidirectional transmission network that performs bidirectional communication from a central station to multiple slave stations via a transmission path. This invention relates to a confidential communication method that can be secured in a secure manner.
【０００２】0002
【従来の技術】中央局と複数の子局間を、波長多重伝送
方式乃至時間軸圧縮一芯双方向多重伝送方式を用いて双
方向通信を行なう、１：ｎの双方向伝送回路網において
、中央局から複数の子局に対して送信される信号は、複
数の子局においては多分にブロードキャストなものであ
り、複数の子局間の秘話を効果的に確保し得る必要性が
あった。2. Description of the Related Art In a 1:n bidirectional transmission network that performs bidirectional communication between a central station and a plurality of slave stations using a wavelength division multiplexing transmission method or a time axis compression single-core bidirectional multiplexing transmission method, The signals transmitted from the central station to the plurality of slave stations are mostly broadcast signals, and there is a need to effectively ensure confidentiality among the plurality of slave stations.
【０００３】従来の技術は、特開昭６３−２３７６３３
号公報に示されるように、複数の子局間の秘話を効果的
に確保し得る為に、複数の子局はそれぞれ暗号化の為の
、呼設定の都度生成され定期的に更新される鍵を中央局
に伝送し、中央局は前記複数の子局から送信される鍵に
より、複数の子局へ送信する信号を暗号化し、複数の子
局は、受信信号を前記鍵により復号化することにより複
数の子局間の秘話を確保する、秘話通信方式があった。[0003] The conventional technology is disclosed in Japanese Patent Application Laid-Open No. 63-237633.
As shown in the publication, in order to effectively ensure confidentiality between multiple slave stations, each slave station uses a key for encryption that is generated each time a call is set up and updated regularly. to a central station, the central station encrypts signals to be transmitted to the plurality of slave stations using the keys transmitted from the plurality of slave stations, and the plurality of slave stations decrypt the received signals using the keys. There was a confidential communication method that ensured confidential communication between multiple slave stations.
【０００４】しかし、前記秘話通信方式においては、前
記鍵を呼設定の都度生成する機能及び定期的に更新する
機能をそれぞれの子局がもたねばならず、子局のもつハ
ード量が増えると言った問題があった。However, in the confidential communication system, each slave station must have the function of generating the key each time a call is set up and the function of periodically updating the key, and as the amount of hardware that the slave stations have increases, There was a problem as mentioned.
【０００５】特に、子局を加入者の端末装置とした場合
には、コスト的に大きな問題となる[0005] In particular, when the slave station is used as a subscriber's terminal device, there is a big problem in terms of cost.
【０００６】。[0006].
【発明が解決しようとする課題】このように中央局から
複数の子局への双方向通信を行なう、双方向伝送回路網
において、中央局から複数の子局へ信号が多分にブロー
ドキャストな場合、複数の子局間の秘話を効果的に確保
し、尚且つハード量が少なく、コスト的に安価である秘
話通信方式が必要である。[Problem to be Solved by the Invention] In a bidirectional transmission network that performs bidirectional communication from a central station to a plurality of slave stations, when signals are often broadcast from the central station to a plurality of slave stations, There is a need for a confidential communication system that effectively secures confidential communication between a plurality of slave stations, requires less hardware, and is inexpensive in terms of cost.
【０００７】本発明は、複数の子局間の秘話を効果的に
確保し、尚且つハード量が少なく、コスト的に安価であ
る秘話通信方式を提唱している。The present invention proposes a confidential communication system that effectively secures confidential communication between a plurality of slave stations, requires less hardware, and is inexpensive in terms of cost.
【０００８】[0008]
【課題を解決するための手段】本発明は、子局から中央
局へ送信する子局の信号により、中央局から子局に対し
て送信する、該当子局に対応した信号のみを暗号化する
ことにより、中央局から各子局に分配される信号の秘話
を行なう。[Means for Solving the Problems] The present invention encrypts only the signal corresponding to the corresponding slave station, which is transmitted from the central station to the slave station, by the signal of the slave station transmitted from the slave station to the central station. By doing so, the signals distributed from the central station to each slave station are kept confidential.
【０００９】[0009]
【作用】本発明は子局から中央局へ送信する頻繁に変化
する上り信号により、中央局から子局へ送信する下り信
号を暗号化し、子局において前記上り信号により中央局
から子局へ送信する下り信号を復号化するため、複数の
子局間での信号の予測は困難である。[Operation] The present invention encrypts the downlink signal transmitted from the central station to the slave station using the frequently changing uplink signal transmitted from the slave station to the central station, and the slave station transmits the uplink signal from the central station to the slave station. Therefore, it is difficult to predict signals between multiple slave stations.
【００１０】又、電話信号の場合、上り信号が無信号に
近く最下位ビットしか変化しない状態においても、前記
上り信号の最上位ビット、最下位ビットのビットの位置
を置換することにより、複数の子局間での盗聴は不可能
となる。In the case of telephone signals, even when the upstream signal is near no signal and only the least significant bit changes, by replacing the positions of the most significant bit and the least significant bit of the upstream signal, multiple Eavesdropping between slave stations becomes impossible.
【００１１】又、完全な無信号状態においても秘話を行
なうため、子局からの前記上り信号にスクランブルをか
け、中央局にて上り信号と、下り信号の排他的論理和を
とる。 本発明は暗号化のための鍵となるランダムパ
ターン生成せずに、子局から中央局へ送信する上り信号
のランダム性を用いることにより、暗号化に要するハー
ド量を減少させている。[0011] Furthermore, in order to carry out confidential communication even in a completely no-signal state, the upstream signal from the slave station is scrambled, and the central station performs an exclusive OR of the upstream signal and the downstream signal. The present invention reduces the amount of hardware required for encryption by using the randomness of the upstream signal transmitted from the slave station to the central station without generating a random pattern that is the key for encryption.
【００１２】0012
【実施例】以下、本発明の一実施例を図をもって説明す
る。DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.
【００１３】本発明は、図３、図４に示すような、中央
局と複数の子局を結ぶ１：ｎの伝送路網構成において、
中央局から子局への下り信号はブロードキャストなもの
であり、子局から中央局への上り信号はタイムスロット
的に１：１に対応している双方向光乃至同軸伝送回路網
構成における複数の子局間の秘話に関するものである。
双方向光乃至同軸伝送回路網を構成するにあたって
は、図９における時間軸圧縮一芯双方向多重伝送方式や
、図１０における光波長多重伝送方式が考えられる。
本発明の特徴とするところは、子局から中央局への
上り信号により、中央局から子局への下り信号を暗号化
し、前記下り信号を子局にて記憶しておいた前記上り信
号により復号化する点にある。The present invention provides a 1:n transmission line network configuration connecting a central station and a plurality of slave stations as shown in FIGS. 3 and 4.
The downlink signal from the central station to the slave station is a broadcast signal, and the uplink signal from the slave station to the central station is a multiple signal in a bidirectional optical or coaxial transmission network configuration with a 1:1 time slot correspondence. It concerns secrets between slave stations. In constructing a bidirectional optical or coaxial transmission network, the time-base compressed single-core bidirectional multiplexing transmission system shown in FIG. 9 and the optical wavelength multiplexing transmission system shown in FIG. 10 can be considered. The characteristics of the present invention are that the downstream signal from the central station to the slave station is encrypted by the upstream signal from the slave station to the central station, and the downlink signal is encrypted by the upstream signal stored in the slave station. At the point of decoding.
【００１４】図１は、本発明を光波長多重伝送方式にて
実施した場合の局内装置構成の概略図であり、図２は子
局の、図３は中央局の局内装置構成を示す。FIG. 1 is a schematic diagram of the internal equipment configuration when the present invention is implemented using an optical wavelength division multiplexing transmission system, FIG. 2 shows the internal equipment configuration of a slave station, and FIG. 3 shows the internal equipment configuration of a central station.
【００１５】子局６において、加入者インターフェース
１７より入力された上り信号は２分岐され、一方はビッ
ト置換部１６で、図７の様に最上位ビットと最下位ビッ
トを置換し、記憶部１４にて記憶される。もう１方は、
信号を多重器１２にて多重され、スクランブラ２７にて
スクランブルされ、Ｅ／Ｏ変換器１０にて光信号に変換
され、光結合分離器８により波長多重されて伝送路２に
送信される。In the slave station 6, the upstream signal inputted from the subscriber interface 17 is branched into two, one of which is sent to the bit replacement section 16, where the most significant bit and the least significant bit are replaced as shown in FIG. It will be stored in The other one is
The signals are multiplexed by the multiplexer 12, scrambled by the scrambler 27, converted into optical signals by the E/O converter 10, wavelength-multiplexed by the optical coupler/demultiplexer 8, and transmitted to the transmission line 2.
【００１６】伝送路２より、光受動分割器７を介して、
伝送路１により中央局５に、送信される上り信号は、光
結合分離器２５により分離されＯ／Ｅ変換器２３にて電
気信号に変換された後、デスクランブラ２０によりデス
クランブルされ、信号分離器２６に入力される。From the transmission line 2, via the optical passive splitter 7,
The upstream signal transmitted to the central station 5 via the transmission line 1 is separated by an optical coupler/separator 25, converted to an electrical signal by an O/E converter 23, and then descrambled by a descrambler 20 to separate the signals. The signal is input to the device 26.
【００１７】信号分離器２６により、各子局単位に分離
された上り信号は、２分岐され一方は変換部を経て中継
系へ、もう一方はそれぞれビット置換器１９へ送信され
る。The upstream signal separated for each slave station by the signal separator 26 is split into two branches, one of which is sent to the relay system via a converter, and the other is sent to the bit replacer 19, respectively.
【００１８】ビット置換器１９に入力された信号は、図
８の様に最上位ビットと最下位ビットを置換し、暗号化
回路２１に入力され、交換部から送信される、下り信号
を暗号化する。暗号化回路２１は図１では、排他的論理
和回路にて示されている。The signal input to the bit replacer 19 replaces the most significant bit and the least significant bit as shown in FIG. do. The encryption circuit 21 is shown in FIG. 1 as an exclusive OR circuit.
【００１９】排他的論理和による変換は図５のようにな
る。また暗号化回路２１は図６に示すように、コード変
換回路でも可能である。The conversion by exclusive OR is as shown in FIG. Further, the encryption circuit 21 can also be a code conversion circuit, as shown in FIG.
【００２０】暗号化回路２１により暗号化された複数の
下り信号は、信号多重器２２により多重され、Ｅ／Ｏ変
換器２４により光信号に変換され、光結合分離器により
光波長多重され、伝送路１に送信される。A plurality of downlink signals encrypted by the encryption circuit 21 are multiplexed by a signal multiplexer 22, converted into optical signals by an E/O converter 24, optically wavelength-multiplexed by an optical coupler/demultiplexer, and transmitted. route 1.
【００２１】伝送路１より、光受動分割器７を介して、
伝送路２により複数の子局６に送信された下り信号は、
光結合分離器８により分離され、Ｏ／Ｅ変換器９により
電気信号に変換され、信号分離器１３により各子局単位
の信号に分離される。From the transmission line 1, via the optical passive splitter 7,
The downlink signals transmitted to the plurality of slave stations 6 via the transmission path 2 are
The signals are separated by the optical coupling/separator 8, converted into electrical signals by the O/E converter 9, and separated into signals for each slave station by the signal separator 13.
【００２２】信号分離器１３より送出された下り信号は
、復号化タイミング制御部１１により復号化のタイミン
グを制御された前記の記憶部１４に記憶された上り信号
により、復号化回路１５にて復号化される。復号化回路
１５は図１では排他的論理和回路にて示されているが、
暗号化の時と同様に図６のコード変換も可能である。The downstream signal sent from the signal separator 13 is decoded by the decoding circuit 15 using the upstream signal stored in the storage unit 14 whose decoding timing is controlled by the decoding timing control unit 11. be converted into The decoding circuit 15 is shown as an exclusive OR circuit in FIG.
The code conversion shown in FIG. 6 is also possible as in the case of encryption.
【００２３】本発明は、秘話の信頼度を高めるため、頻
繁に変化する上り信号にビット置換をし、さらにスクラ
ンブルをかけているので、盗聴は不可能な秘話方式であ
る。[0023] In the present invention, in order to increase the reliability of the secret message, the frequently changing upstream signal is subjected to bit replacement and further scrambled, so that eavesdropping is impossible.
【００２４】又、下り信号の暗号化を行なう際に、特別
なアルゴリズムを用いて暗号化を行なう必要が無く、又
、暗号化、復号化のための、鍵となるデータのやりとり
がないので、ハード量の削減が可能となる。[0024] Furthermore, when encrypting the downlink signal, there is no need to use a special algorithm for encryption, and there is no exchange of key data for encryption and decryption. It is possible to reduce the amount of hardware.
【００２５】本発明は、前述した実施例に限定されるも
のではない。The present invention is not limited to the embodiments described above.
【００２６】本発明は子局から中央局へ送信する頻繁に
変化する上り信号により、中央局から子局へ送信する下
り信号を暗号化し、子局において前記上り信号により中
央局から子局へ送信する下り信号を復号化する秘話方式
であるという要旨を逸脱しない範囲で適宜応用可能であ
る。[0026] The present invention encrypts the downlink signal transmitted from the central station to the slave station using the frequently changing uplink signal transmitted from the slave station to the central station, and the slave station encrypts the downlink signal transmitted from the central station to the slave station using the upstream signal. It can be applied as appropriate without departing from the gist that it is a confidential method for decoding downlink signals.
【００２７】[0027]
【発明の効果】以上の説明により、本発明は装置のハー
ド量削減を実施し、又複数の子局間において、十分な秘
話を確保できる。As described above, the present invention can reduce the amount of hardware in the device and ensure sufficient confidentiality between a plurality of slave stations.
【図１】本発明の一実施例を示す中央局の概略構成図。FIG. 1 is a schematic configuration diagram of a central office showing an embodiment of the present invention.
【図２】本発明の一実施例を示す子局の概略構成図。FIG. 2 is a schematic configuration diagram of a slave station showing an embodiment of the present invention.
【図３】双方向光伝送回路網の概略構成図。FIG. 3 is a schematic configuration diagram of a bidirectional optical transmission network.
【図４】双方向光乃至同軸伝送回路網の概略構成図。FIG. 4 is a schematic configuration diagram of a bidirectional optical or coaxial transmission network.
【図５】排他的論理和を用いた場合の、下り信号の暗号
化、復号化を示す概略図。FIG. 5 is a schematic diagram showing encryption and decryption of a downlink signal when exclusive OR is used.
【図６】コード変換を用いた場合の、下り信号の暗号化
、復号化を示す概略図。FIG. 6 is a schematic diagram showing encryption and decoding of a downlink signal when code conversion is used.
【図７】子局におけるビット置換例を示す図。FIG. 7 is a diagram showing an example of bit replacement in a slave station.
【図８】中央局におけるビット置換例を示す図。FIG. 8 is a diagram showing an example of bit replacement in the central office.
【図９】時間軸圧縮一芯双方向多重伝送方式概略図。FIG. 9 is a schematic diagram of a time-base compression single-core bidirectional multiplex transmission system.
【図１０】光波長多重伝送方式概略図。FIG. 10 is a schematic diagram of an optical wavelength division multiplexing transmission system.
１，２，３，４…伝送路、５…中央局、６…子局、７…
光受動分割器、８，２５…光結合分離器、９，２３…光
／電気変換器、１０，２４…電気／光変換器、１１…復
号化タイミング制御部、１２，２２…信号多重器、１３
，２６…信号分離器、１４…記憶部、１５…復号化回路
、１６，１９…ビット置換器、１７…加入者インターフ
ェース、１８…交換器、２０…デスクランブラ、２１…
暗号化回路、２７…スクランブラ、２８，３１…バース
ト信号制御部、２９，３０，３２，３３…記憶部、３４
…送出タイミング制御部。1, 2, 3, 4...Transmission line, 5...Central station, 6...Slave station, 7...
Passive optical splitter, 8, 25... Optical coupling/separator, 9, 23... Optical/electrical converter, 10, 24... Electrical/optical converter, 11... Decoding timing control section, 12, 22... Signal multiplexer, 13
, 26...Signal separator, 14...Storage unit, 15...Decoding circuit, 16, 19...Bit replacer, 17...Subscriber interface, 18...Switcher, 20...Descrambler, 21...
Encryption circuit, 27... Scrambler, 28, 31... Burst signal control unit, 29, 30, 32, 33... Storage unit, 34
...Sending timing control section.
Claims (10)
網構成において、中央局から複数の子局への下り信号が
ブロードキャストなものであり、複数の子局から中央局
への上り信号が子局と中央局とを１対１に対応している
双方向伝送回路網において、子局から中央局へ送信する
上り信号により、中央局は子局に送信する下り信号を暗
号化し、子局は中央局からの前記下り信号を、あらかじ
め記憶しておいた前記上り信号により復号化することに
より、受信信号の秘話を行う秘話通信方式。Claim 1: In a 1:n transmission line network configuration connecting a central station and multiple slave stations, the downlink signals from the central station to the multiple slave stations are broadcast, and the signals from the multiple slave stations to the central station are In a bidirectional transmission network where the upstream signals of the slave station and the central station correspond one-to-one, the upstream signal sent from the slave station to the central station causes the central station to encrypt the downstream signal sent to the slave station. A confidential communication method in which the slave station performs confidential communication of the received signal by decoding the downlink signal from the central station using the upstream signal stored in advance.
網構成において、中央局と光受動分割器を結ぶ光ファイ
バー伝送路１と、光受動分割器と複数の子局間を結ぶ光
ファイバー伝送路２からなる、双方向光伝送回路網にお
いて、請求項１記載の秘話通信方式。Claim 2: In a 1:n transmission line network configuration connecting a central station and a plurality of slave stations, an optical fiber transmission line 1 connecting the central station and a passive optical splitter and a transmission line between the optical passive divider and a plurality of slave stations are provided. 2. A secret communication system according to claim 1, in a bidirectional optical transmission network comprising optical fiber transmission lines 2 connecting the two.
網構成において、中央局と複数の伝送路の分岐点を結ぶ
光ファイバー伝送路３と複数の伝送路の分岐点と複数の
子局を１：１に結ぶ光ファイバー伝送路４からなる。双
方向光伝送回路網において、請求項１記載の秘話通信方
式。Claim 3: In a 1:n transmission line network configuration connecting a central station and a plurality of slave stations, an optical fiber transmission line 3 connecting a central station and branch points of a plurality of transmission lines, and a plurality of branch points of a plurality of transmission lines and a plurality of It consists of an optical fiber transmission line 4 that connects the slave stations on a 1:1 basis. 2. The confidential communication system according to claim 1 in a bidirectional optical transmission network.
網構成において、中央局と複数の伝送路の分岐点を結ぶ
同軸伝送路３と複数の伝送路の分岐点と複数の子局を１
：１に結ぶ同軸伝送路４からなる、双方向伝送回路網に
おいて、請求項１記載の秘話通信方式。Claim 4: In a 1:n transmission line network configuration connecting a central station and a plurality of slave stations, a coaxial transmission line 3 connecting a central station and branch points of a plurality of transmission lines, and a plurality of branch points of a plurality of transmission lines and a plurality of 1 slave station
2. A secret communication system according to claim 1, in a bidirectional transmission network comprising a coaxial transmission line 4 connected to a PC.
より下り信号を暗号化する際に、排他的論理和を用いて
暗号化を行ない、子局が中央局からの前記下り信号を復
号化する際に、排他的論理和を用いて、復号化を行なう
ことを特徴とする、請求項１記載の秘話通信方式。5. When the central station encrypts the downlink signals from the uplink signals from a plurality of slave stations, the encryption is performed using exclusive OR, and the slave stations encrypt the downlink signals from the central station. 2. The confidential communication system according to claim 1, wherein the decoding is performed using an exclusive OR.
より下り信号を暗号化する際に、コード変換を用いて、
暗号化を行ない、子局が中央局からの前記下り信号によ
り復号化する際に、コード変換を用いて、復号化を行な
うことを特徴とする、請求項１記載の秘話通信方式。6. When the central station encrypts the downstream signals from the upstream signals from the plurality of slave stations, using code conversion,
2. The confidential communication system according to claim 1, wherein when the slave station encrypts and decodes the downlink signal from the central station, code conversion is used to perform the decoding.
り信号を暗号化する際に、前記上り信号の最上位ビット
、最下位ビットのビットの位置を置換して、請求項５ま
たは６いずれか一項の記載内容を用いて暗号化を行ない
、子局が中央局からの前記下り信号により復号化する際
に、前記上り信号の最上位ビット、最下位ビットのビッ
トの位置を置換して、請求項５または６いずれか一項の
記載内容を用いて復号化を行なうことを特徴とする、請
求項１記載の秘話通信方式。7. When the central station encrypts the downstream signal using the upstream signal from the slave station, the central station replaces the positions of the most significant bit and the least significant bit of the upstream signal. Encryption is performed using the content described in any one of the clauses, and when the slave station decrypts the downlink signal from the central station, the bit positions of the most significant bit and the least significant bit of the upstream signal are replaced. 7. The confidential communication system according to claim 1, wherein decoding is performed using the contents described in either claim 5 or 6.
ンブルをかけ、子局から中央局へ送信する機能を有し、
中央局から子局への前記下り信号を暗号化する際に、前
記上り信号により、前記下り信号を暗号化する機能を有
することを特徴とする、請求項１記載の秘話通信方式。8. Having a function of scrambling the upstream signal from the slave station to the central station and transmitting the scrambled signal from the slave station to the central station,
2. The confidential communication system according to claim 1, further comprising a function of encrypting the downlink signal using the uplink signal when encrypting the downlink signal from the central station to the slave station.
式を用いて、双方向通信を行なう双方向伝送回路網にお
いて、請求項１記載の秘話通信方式。9. The confidential communication system according to claim 1, in a bidirectional transmission network that performs bidirectional communication between a central station and a plurality of slave stations using an optical wavelength division multiplexing transmission system.
双方向多重伝送方式を用いて、双方向通信を行なう双方
向伝送回路網において、請求項１記載の秘話通信方式。10. The confidential communication system according to claim 1, in a bidirectional transmission network for performing bidirectional communication between a central station and a plurality of slave stations using a time-base compressed single-core bidirectional multiplex transmission system.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2406536A JPH04223731A (en) | 1990-12-26 | 1990-12-26 | Privacy communication system |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2406536A JPH04223731A (en) | 1990-12-26 | 1990-12-26 | Privacy communication system |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| JPH04223731A true JPH04223731A (en) | 1992-08-13 |
Family
ID=18516158
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP2406536A Pending JPH04223731A (en) | 1990-12-26 | 1990-12-26 | Privacy communication system |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPH04223731A (en) |
-
1990
- 1990-12-26 JP JP2406536A patent/JPH04223731A/en active Pending
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