JP2020155935A - Telephone conference system, telephone terminal, and program - Google Patents

Abstract

To improve the confidentiality of conference call.SOLUTION: A telephone conference system (1A) includes: multiple telephone terminals (40) for participating in a conference call; and a conference device (50). Each of the telephone terminals (40) encrypts the voice data of a speaker using homomorphic encryption and transmits the encrypted voice data to the conference device (50). The conference device (50) mixes the encrypted audio data from each telephone terminal (40) and transmits the mixed audio data to each telephone terminal (40). Each telephone terminal (40) decrypts the mixed audio data from the conference device (50).SELECTED DRAWING: Figure 6

Description

The present disclosure relates to conference call systems, telephone terminals, and programs.

In recent years, a conference call system using an IP (Internet Protocol) telephone has become widespread. In a conference call system using an IP telephone, a call is controlled by a SIP (Session Initiation Protocol) signal, and voice is transmitted and received by an RTP (Real time Transport Protocol).

In a conference call system in which a plurality of telephone terminals participate using an IP telephone, the voice data of each telephone terminal is transmitted to the conference device. The conference device mixes the voice data from each telephone terminal and transmits the mixed voice data to each telephone terminal. In this way, the conference call is realized.

Here, when conducting a conference call, the conference device needs to mix the voice data from each telephone terminal as described above, and the voice data from each telephone terminal is naturally encoded so that the conference device can recognize it. Must be method-coded. Therefore, even if a conference call is held with high confidentiality, if each telephone terminal encrypts the voice data, the conference device cannot decrypt the voice data, so that the voice data cannot be mixed and the conference call cannot be realized. ..

Therefore, it is conceivable to implement a process that enables decoding in the conference device itself. For example, in Patent Document 1, an encryption device that encrypts and decrypts voice data is connected to a mixer that mixes voice data, and the voice data is encrypted before the mixer outputs voice data. Is encrypted, and it is disclosed that the encryption device decrypts the voice data after the mixer inputs the voice data.

JP-A-2006-246239

However, in the technique disclosed in Patent Document 1, it is necessary to decrypt the encrypted voice data by an encryption device and treat it as plain text voice data before mixing the voice data from each telephone terminal. Therefore, there is a problem that the confidentiality of the conference call is lowered.

An object of the present disclosure is to provide a conference call system, a telephone terminal, and a program capable of solving the above-mentioned problems and improving the confidentiality of the conference call.

One aspect of the conference call system
With multiple telephone terminals participating in a conference call,
A conference device that mixes audio data from each of the telephone terminals and transmits the mixed audio data to each of the telephone terminals is provided.
Each telephone terminal encrypts the speaker's voice data using homomorphic encryption, and transmits the encrypted voice data to the conference device.
The conference device mixes the voice data from each of the telephone terminals in an encrypted state, and transmits the mixed voice data to each of the telephone terminals.
Each of the telephone terminals decodes the mixed audio data from the conference device.

The telephone terminal according to one aspect is
An encryption unit that encrypts the speaker's voice data using homomorphic encryption,
A communication unit that transmits the encrypted voice data to the conference device and receives the voice data mixed with the voice data from each telephone terminal participating in the conference call from the conference device while being encrypted.
A decoding unit that decodes the mixed audio data from the conference device, and
To be equipped.

The program according to one aspect is
On the computer
Procedures for encrypting speaker voice data using homomorphic encryption,
A procedure for transmitting the encrypted voice data to the conference device and receiving the voice data mixed with the voice data from each telephone terminal participating in the conference call from the conference device while being encrypted.
The procedure for decoding the mixed audio data from the conference device and
It is a program to execute.

According to the above aspect, it is possible to provide a conference call system, a telephone terminal, and a program capable of improving the confidentiality of the conference call.

It is a figure which shows the configuration example of the conference call system which concerns on embodiment. It is a block diagram which shows the structural example of the telephone terminal which concerns on embodiment. It is a block diagram which shows the structural example of the conference apparatus which concerns on embodiment. It is a block diagram which shows the hardware configuration example of the computer which realizes the telephone terminal and the conference device which concerns on embodiment. It is a sequence diagram explaining the operation example of the conference call system which concerns on embodiment. It is a figure which shows the configuration example of the conference call system which conceptually showed the embodiment.

Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. The following descriptions and drawings have been omitted or simplified as appropriate for the purpose of clarifying the explanation. Further, in each of the following drawings, the same elements are designated by the same reference numerals, and duplicate explanations are omitted as necessary. In addition, the specific numerical values and the like shown below are merely examples for facilitating the understanding of the present disclosure, and are not limited thereto.

<Embodiment>
First, the configuration of the conference call system 1 according to the present embodiment will be described with reference to FIG. FIG. 1 is a diagram showing a configuration example of the conference call system 1 according to the present embodiment.
As shown in FIG. 1, the conference call system 1 according to the present embodiment includes a plurality of telephone terminals 10-1 to 10-N (N is a natural number of 2 or more) and a conference device 20. .. In the following drawings, the telephone terminals 10-1 to 10-N may be referred to as telephone terminals #n (n = 1, ..., N). Further, hereinafter, when it is not specified which telephone terminal 10-1 to 10-N, it may be referred to as a telephone terminal 10.

Each telephone terminal 10 is a terminal that participates in a conference call. Each telephone terminal 10 encrypts the speaker's voice data using homomorphic encryption, and transmits the encrypted voice data to the conference device 20.
Here, homomorphic encryption will be briefly described.
Homomorphic encryption has the property of being able to calculate Enc (m1 + m2) and Enc (m1 x m2) without using plaintext or a private key when two ciphertexts Enc (m1) and Enc (m2) are given. It is an encryption method that it has.

Intuitively, if Enc has homomorphism with respect to addition, then Enc (3) and Enc (2) can be calculated as Enc (5), and Enc has homomorphism with respect to multiplication. If it is, Enc (6) can be calculated from Enc (3) and Enc (2).

In the present embodiment, the homomorphic encryption may be any cipher having homomorphism with respect to addition. Therefore, as the homomorphic encryption, either an additive homomorphic encryption capable of only addition and a fully homomorphic encryption capable of both addition and multiplication can be applied. Further, as an example of the additive homomorphic encryption, there is an additive homomorphic encryption using an elliptical ElGamel encryption.

The conference device 20 mixes the voice data from each telephone terminal 10. Here, each telephone terminal 10 encrypts the voice data of the speaker by using homomorphic encryption. Therefore, the conference device 20 can add the voice data from each telephone terminal 10 in the encrypted state, that is, mix by the addition.

The conference device 20 transmits the voice data mixed in the encrypted state to each telephone terminal 10.
Each telephone terminal 10 decodes the voice data mixed in the encrypted state immediately before the voice is output from the speaker or the like.

Therefore, in the present embodiment, all the voice data remains encrypted on the route between the telephone terminal 10 and the conference device 20 and in the conference device 20. Therefore, the confidentiality of the conference call can be improved.

Subsequently, the configuration of the telephone terminal 10 according to the present embodiment will be described with reference to FIG. FIG. 2 is a block diagram showing a configuration example of the telephone terminal 10 according to the present embodiment.
As shown in FIG. 2, the telephone terminal 10 according to the present embodiment includes a microphone 11, an encoding unit 12, an encryption unit 13, a communication unit 14, a decoding unit 15, a voice processing unit 16, and a speaker 17. ing.

The microphone 11 collects the voice of the speaker.
The coding unit 12 encodes the voice data of the speaker collected by the microphone 11 and generates the coded voice data. The coding unit 12 can use, for example, a PCM (Pulse Code Modulation) method as the coding method.

The PCM method is a coding method in which an analog signal is sampled and quantized, the magnitude of the obtained signal is converted into integer data, and the output is output as a set of pulse trains.
When the analog voice data used for the conference call is encoded by the PCM method, for example, it is conceivable to encode the voice data in the following format.
・ Sampling frequency: 8kHz
・ Quantization bit: 8 bits
Therefore, sampling frequency × quantization bit = 8 (kHz) × 8 (bit) = 64 (kbps).

The encryption unit 13 encrypts the speaker-encoded voice data encoded by the coding unit 12 by using homomorphic encryption to generate the encrypted voice data.
The communication unit 14 transmits the encrypted voice data of the speaker encrypted by the encryption unit 13 to the conference device 20.

In addition, the communication unit 14 receives the encrypted voice data mixed in the encrypted state from the conference device 20.
The decryption unit 15 decrypts the encrypted voice data mixed while being encrypted into the coded voice data (that is, decrypts the encryption).

The voice processing unit 16 performs voice processing such as a process of decoding the coded voice data decoded by the decoding unit 15 into voice data (that is, decoding of the coding) and a process of adjusting the volume.
The speaker 17 outputs voice data that has been voice-processed by the voice processing unit 16. In addition, instead of the speaker 17, another device that outputs audio may be provided. Another device may be, for example, a handset, earphones, headphones or the like.

Subsequently, the configuration of the conference device 20 according to the present embodiment will be described with reference to FIG. FIG. 3 is a block diagram showing a configuration example of the conference device 20 according to the present embodiment.
As shown in FIG. 3, the conference device 20 according to the present embodiment includes a communication unit 21, a buffer 22, and a mixing unit 23.

The communication unit 21 receives the encrypted encrypted voice data from each telephone terminal 10.
The buffer 22 temporarily stores the encrypted encrypted voice data from each telephone terminal 10.
The mixing unit 23 mixes the encrypted voice data from each telephone terminal 10 by addition while being encrypted.
The communication unit 21 transmits the encrypted voice data that has been mixed while being encrypted by the mixing unit 23 to each telephone terminal 10.

Subsequently, with reference to FIG. 4, the hardware configuration of the computer 30 that realizes the telephone terminal 10 according to the present embodiment will be described. FIG. 4 is a block diagram showing a hardware configuration example of the computer 30 that realizes the telephone terminal 10 according to the present embodiment.

As shown in FIG. 4, the telephone terminal 10 according to the present embodiment can be realized by the computer 30. The computer 30 includes a processor 31, a memory 32, a storage 33, an input / output interface (input / output I / F) 34, a communication interface (communication I / F) 35, and the like. The processor 31, the memory 32, the storage 33, the input / output interface 34, and the communication interface 35 are connected by a data transmission line for transmitting and receiving data to and from each other.

The processor 31 is, for example, an arithmetic processing unit such as a CPU (Central Processing Unit) or a GPU (Graphics Processing Unit). The memory 32 is, for example, a memory such as a RAM (Random Access Memory) or a ROM (Read Only Memory). The storage 33 is, for example, a storage device such as an HDD (Hard Disk Drive), an SSD (Solid State Drive), or a memory card. Further, the storage 33 may be a memory such as a RAM or a ROM.

The storage 33 stores a program that realizes the functions of each component (encoding unit 12, encryption unit 13, communication unit 14, decoding unit 15, voice processing unit 16, etc.) included in the telephone terminal 10. By executing each of these programs, the processor 31 realizes the functions of the respective components included in the telephone terminal 10. Here, when executing each of the above programs, the processor 31 may read these programs onto the memory 32 and then execute the programs, or may execute the programs without reading them onto the memory 32.

In addition, the above-mentioned programs are stored using various types of non-transitory computer readable media and can be supplied to a computer (including a computer 30). Non-transitory computer-readable media include various types of tangible storage media. Examples of non-temporary computer-readable media include magnetic recording media (eg, flexible disks, magnetic tapes, hard disk drives), magneto-optical recording media (eg, magneto-optical disks), CD-ROMs (Compact Disc-Read Only Memory). , CD-R (CD-Recordable), CD-R / W (CD-ReWritable), semiconductor memory (for example, mask ROM, PROM (Programmable ROM), EPROM (Erasable PROM), flash ROM, RAM (Random Access Memory) )including. The program may also be supplied to the computer by various types of transient computer readable media. Examples of temporary computer-readable media include electrical, optical, and electromagnetic waves. The temporary computer-readable medium can supply the program to the computer via a wired communication path such as an electric wire and an optical fiber, or a wireless communication path.

The input / output interface 34 is connected to a microphone 11 and a speaker 17 included in the telephone terminal 10, as well as a display device, an input device, and the like.

The communication interface 35 transmits / receives data to / from an external device. For example, the communication interface 35 communicates with an external device via a wired network or a wireless network.

The conference device 20 can also be realized by the computer 30 shown in FIG.
For example, when the conference device 20 is realized by the computer 30, the storage 33 stores a program that realizes the functions of each component (communication unit 21, mixing unit 23, etc.) included in the conference device 20. The memory 32 and the storage 33 also serve as a buffer 22.

Hereinafter, the operation of the conference call system 1 according to the present embodiment will be described with reference to FIG. FIG. 5 is a sequence diagram illustrating an operation example of the conference call system 1 according to the present embodiment. Note that FIG. 5 shows an operation example when three telephone terminals 10-1 to 10-3 participate in a conference call.

As shown in FIG. 5, the telephone terminal 10-1 encodes the speaker's voice data by, for example, the PCM method, and the encoded voice data D1 is encrypted by using a quasi-isomorphic encryption and encrypted. The encrypted encrypted voice data Enc (D1) is sequentially transmitted to the conference device 20 (step S101). At this time, in order to prevent digit overflow when the conference device 20 mixes the voice, the telephone terminal 10-1 is less than 8 bits even if the number of quantization bits is set to 8 bits in advance. It is desirable to perform quantization with the number of quantization bits (for example, 6 bits or 7 bits). It is desirable that parameters such as the number of quantization bits at the time of coding be adjusted in advance between the telephone terminals 10 participating in the conference call according to external conditions such as the number of conference participants and noise.

Similarly, the telephone terminal 10-2 sequentially transmits the encrypted voice data Enc (D2) to the conference device 20 (step S102), and the telephone terminal 10-3 confer the encrypted voice data Enc (D3). The data is sequentially transmitted to the device 20 (step S103).

The conference device 20 sequentially receives encrypted voice data Enc (D1) to Enc (D3) from three telephone terminals 10-1 to 10-3 participating in the conference call.
Here, in order to establish a conference call, it is necessary to add the voice data of the voices emitted from the plurality of telephone terminals 10 at the same timing into one voice data. For example, as the voice data for the telephone terminal 10-1, the voice data of the voices emitted from the telephone terminals 10-2 and 10-3 other than the telephone terminal 10-1 at the same timing is added to obtain one voice data. Need to be.

Therefore, the conference device 20 uses the encrypted voice data Enc (D2) and Enc (D3) from the telephone terminals 10-2 and 10-3 other than the telephone terminal 10-1 as the encrypted voice data for the telephone terminal 10-1. ), While still encrypted, is mixed by addition to generate encrypted voice data Enc (D2 + D3).
Similarly, the conference device 20 generates encrypted voice data Enc (D1 + D3) as encrypted voice data for the telephone terminal 10-2, and encrypts as encrypted voice data for the telephone terminal 10-3. The voice data Enc (D1 + D2) is generated (step S104).

Subsequently, the conference device 20 transmits the encrypted voice data Enc (D1 + D2) for the telephone terminal 10-3 to the telephone terminal 10-3 (step S105), and the telephone terminal 10-3 uses the encrypted voice data Enc (step S105). D1 + D2) is decoded (step S106), and the decoded audio data Dec (Enc (D1 + D2)) is obtained. Since this voice data Dec (Enc (D1 + D2)) is encoded voice data, it is subsequently decoded into voice data, and after voice processing such as volume adjustment is performed, voice is output from the speaker 17. To.

Similarly, the conference device 20 transmits the encrypted voice data Enc (D1 + D3) for the telephone terminal 10-2 to the telephone terminal 10-2 (step S107), and the telephone terminal 10-2 uses the encrypted voice data Enc (step S107). D1 + D3) is decoded (step S108), and the decoded audio data Dec (Enc (D1 + D3)) is obtained.

Further, the conference device 20 transmits the encrypted voice data Enc (D2 + D3) for the telephone terminal 10-1 to the telephone terminal 10-1 (step S109), and the telephone terminal 10-1 transmits the encrypted voice data Enc (D2 + D3). ) Is decoded (step S110) to obtain the decoded audio data Dec (Enc (D2 + D3)).
After that, the above operation is repeated until the conference call is completed.

Subsequently, in the following, the operation when the elliptical ElGamel encryption is used as the additive homomorphic encryption as the operation of the conference call system 1 according to the present embodiment will be described more specifically. Here, as in FIG. 5, an operation example when three telephone terminals 10-1 to 10-3 participate in a conference call will be described.

The elliptic curve has a property that it is easy to obtain a value obtained by multiplying the point P by n, but it is difficult to obtain only n from the point n multiplied by n.
That is, the elliptic curve has the following properties.
n, P → Q = nP: Easy Q = nP → n, P: Difficult In this example, the above properties of the elliptic curve are used.

First, the telephone terminal 10-1 encrypts the encoded voice data D1 in which the voice data of the speaker is encoded by using the elliptical ElGamel encryption.
At this time, the telephone terminal 10-1 selects a random number r1 for the coded voice data D1, encrypts the coded voice data D1 using the selected random number r1 and the public key (P, Q). The encrypted voice data Enc (D1) represented by the following formula (1) is generated.
Enc (D1) = (r1P, D1 + r1Q) ... (1)
Here, due to the nature of the elliptic curve, another person cannot obtain r1 from r1P.
The telephone terminal 10-1 sequentially generates encrypted voice data Enc (D1) and sequentially transmits it to the conference device 20.

Similarly, the telephone terminal 10-2 sequentially transmits the encrypted voice data Enc (D2) to the conference device 20, and the telephone terminal 10-3 sequentially transmits the encrypted voice data Enc (D3) to the conference device 20. Send.

The conference device 20 sequentially receives encrypted voice data Enc (D1) to Enc (D3) from three telephone terminals 10-1 to 10-3 participating in the conference call.
Here, in order to establish a conference call, it is necessary to add the voice data of the voices emitted from the plurality of telephone terminals 10 at the same timing into one voice data. For example, as the voice data for the telephone terminal 10-3, one voice data is obtained by adding the voice data of the voices emitted from the telephone terminals 10-1 and 10-2 other than the telephone terminals 10-3 at the same timing. Need to be.

Here, Enc (D1) and Enc (D2) are expressed as mathematical formulas (2) and (3), respectively.
Enc (D1) = (r1P, D1 + r1Q) ... (2)
Enc (D2) = (r2P, D2 + r2Q) ... (3)

Here, when Enc (D1) and Enc (D2) are added for each component, the following mathematical formula (4) is established.
Enc (D1) + Enc (D2) = ((r1 + r2) P, D1 + D2 + (r1 + r2) Q) ... (4)

Here, assuming that r'= r1 + r2, the mathematical formula (4) is expressed as the following mathematical formula (5).
Enc (D1) + Enc (D2) = (r'P, D1 + D2 + r'Q) ... (5)

That is, the mathematical formula (5) has the same form as the encrypted version of (D1 + D2), and the following mathematical formula (6) is established.
Enc (D1) + Enc (D2) = Enc (D1 + D2) ... (6)

The conference device 20 transmits the encrypted voice data Enc (D1 + D2) for the telephone terminal 10-3 generated above to the telephone terminal 10-3.
Similarly, the conference device 20 generates encrypted voice data Enc (D1 + D3) for the telephone terminal 10-2 and transmits it to the telephone terminal 10-2, and also, the encrypted voice data for the telephone terminal 10-1. Enc (D2 + D3) is generated and transmitted to the telephone terminal 10-1.

The telephone terminal 10-3 that has received the encrypted voice data Enc (D1 + D2) decrypts the encrypted voice data Enc (D1 + D2).
For example, when the general ciphertext c = (C1, C2) is decrypted using the private key x, the following mathematical expression (7) is established.
Dec (c) = C2-xC1 ... (7)
The private key x is held by the telephone terminal 10 participating in the conference call, and from the viewpoint of ensuring security, it is desirable to use a different private key for each conference call.
Further, the following mathematical formula (8) is established as the relational expression between the public key (P, Q) and the private key x.
Q = xP ... (8)

Here, if Enc (D1 + D2) = Enc (D), Enc (D) is expressed by the following mathematical formula (9).
Enc (D) = (rP, D + rQ) ... (9)
When Enc (D) is decrypted using the private key x and the public key (P, Q), the following mathematical formula (10) is established.
Dec (Enc (D)) = (D + rQ) -x (rP) = D + r (xP) -xrP = D ... (10)

The telephone terminal 10-3 decodes the coded voice data D (= D1 + D2) obtained above into voice data, performs voice processing such as adjusting the volume, and then outputs voice from the speaker 17.
Similarly, the telephone terminal 10-2 decodes the encrypted voice data Enc (D1 + D3) and outputs the voice, and the telephone terminal 10-1 decodes the encrypted voice data Enc (D2 + D3) and outputs the voice. Output.
After that, the above operation is repeated until the conference call is completed.

As described above, according to the present embodiment, each telephone terminal 10 encrypts the voice data of the speaker by using homomorphic encryption, and transmits the encrypted voice data to the conference device 20. Therefore, the conference device 20 can mix the voice data from each telephone terminal 10 while being encrypted. Therefore, the conference device 20 mixes the voice data from each telephone terminal 10 while being encrypted, and transmits the mixed voice data to each telephone terminal 10. Each telephone terminal 10 decodes the mixed voice data from the conference device 20.

Therefore, the voice data remains encrypted on the route between the telephone terminal 10 and the conference device 20 and on the conference device 20. Therefore, the conference call can be realized without decoding the voice data on the route between the telephone terminal 10 and the conference device 20 or by the conference device 20, and thereby the confidentiality of the conference call can be improved.

<Concept of embodiment>
Subsequently, with reference to FIG. 6, the configuration of the conference call system 1A conceptually showing the above-described embodiment will be described. FIG. 6 is a diagram showing a configuration example of the conference call system 1A that conceptually shows the above-described embodiment.

As shown in FIG. 6, the conference call system 1A includes a plurality of telephone terminals 40-1 to 40-N and a conference device 50. Hereinafter, when it is not specified which telephone terminal 40-1 to 40-N, it may be referred to as a telephone terminal 40.

Each telephone terminal 40 is a terminal that participates in a conference call. The telephone terminal 40 corresponds to the telephone terminal 10 shown in FIG.
The telephone terminal 40-1 includes an encryption unit 41, a communication unit 42, and a decryption unit 43.

The encryption unit 41 encrypts the speaker's voice data by using homomorphic encryption. The encryption unit 41 corresponds to the encryption unit 13 shown in FIG.
The communication unit 42 transmits the voice data encrypted by the encryption unit 41 to the conference device 50, and from the conference device 50, the voice data from each telephone terminal 40 is mixed while being encrypted. Receive. The communication unit 42 corresponds to the communication unit 14 shown in FIG.
The decoding unit 43 decodes the mixed audio data from the conference device 50. The decoding unit 43 corresponds to the decoding unit 15 shown in FIG.
The telephone terminals 40-2 to 40-N have the same configuration as the telephone terminals 40-1.

The conference device 50 corresponds to the conference device 20 shown in FIG.
The conference device 50 includes a communication unit 51 and a mixing unit 52.
The communication unit 51 receives the voice data of the speaker encrypted by using homomorphic encryption from each telephone terminal 40. The communication unit 51 corresponds to the communication unit 21 shown in FIG.
The mixing unit 52 mixes the voice data from each telephone terminal 40 in an encrypted state. The mixing unit 52 corresponds to the mixing unit 23 shown in FIG.
The communication unit 51 transmits the voice data mixed by the mixing unit 52 to each telephone terminal 40.

Although the present disclosure has been described above with reference to the embodiments, the present disclosure is not limited to the above-described embodiments. Various changes that can be understood by those skilled in the art can be made to the structure and details of the present disclosure within the scope of the present disclosure.

For example, some or all of the above embodiments may be described as, but not limited to, the following appendices.
(Appendix 1)
A communication unit that receives voice data of the speaker encrypted using homomorphic encryption from each of the multiple telephone terminals participating in the conference call.
It is provided with a mixing unit that mixes the voice data from each of the telephone terminals while being encrypted.
The communication unit transmits the voice data mixed by the mixing unit to each of the telephone terminals.
Conference device.
(Appendix 2)
The mixing unit mixes the voice data from each of the telephone terminals by addition while being encrypted.
The conference device according to Appendix 1.
(Appendix 3)
The homomorphic encryption is an additive homomorphic encryption or a fully homomorphic encryption.
The conference device according to Appendix 1 or 2.
(Appendix 4)
The homomorphic encryption is an additive homomorphic encryption using an elliptical ElGamel encryption.
The conference device according to Appendix 1 or 2.
(Appendix 5)
It is a control method of a conference call system including a plurality of telephone terminals participating in a conference call and a conference device.
A step in which each telephone terminal encrypts the speaker's voice data using homomorphic encryption and transmits the encrypted voice data to the conference device.
A step in which the conference device mixes the voice data from each of the telephone terminals in an encrypted state and transmits the mixed voice data to each of the telephone terminals.
A step in which each telephone terminal decodes the mixed audio data from the conference device,
Control methods, including.
(Appendix 6)
It is a control method for telephone terminals.
Steps to encrypt speaker voice data using homomorphic encryption,
A step of transmitting the encrypted voice data to the conference device and receiving the voice data mixed from the conference device while the voice data from each telephone terminal participating in the conference call is encrypted.
The step of decoding the mixed audio data from the conference device, and
Control methods, including.
(Appendix 7)
It is a control method of the conference device.
The step of receiving the voice data of the speaker encrypted using homomorphic encryption from each of the multiple telephone terminals participating in the conference call,
A step of mixing the voice data from each of the telephone terminals while being encrypted,
The step of transmitting the mixed voice data to each of the telephone terminals, and
Control methods, including.
(Appendix 8)
On the computer
A procedure for receiving voice data of a speaker encrypted using homomorphic encryption from each of a plurality of telephone terminals participating in a conference call, and
The procedure for mixing the audio data from each of the telephone terminals while being encrypted, and
The procedure for transmitting the mixed voice data to each of the telephone terminals, and
A program to execute.

1,1A Telephone conference system 10-1 to 10-N Telephone terminal 11 Microphone 12 Encoding unit 13 Encryption unit 14 Communication unit 15 Decoding unit 16 Voice processing unit 17 Speaker 20 Conference device 21 Communication unit 22 Buffer 23 Mixing unit 30 Computer 31 Processor 32 Memory 33 Storage 34 I / O interface (I / O I / F)
35 Communication interface (communication I / F)
40-1 to 40-N Telephone terminal 41 Encryption unit 42 Communication unit 43 Decryption unit 50 Conference device 51 Communication unit 52 Mixing unit

Claims (10)

With multiple telephone terminals participating in a conference call,
Equipped with a conference device,
Each telephone terminal encrypts the speaker's voice data using homomorphic encryption, and transmits the encrypted voice data to the conference device.
The conference device mixes the voice data from each of the telephone terminals in an encrypted state, and transmits the mixed voice data to each of the telephone terminals.
Each of the telephone terminals decodes the mixed audio data from the conference device.
Conference call system. The conference device mixes the voice data from each of the telephone terminals by addition while being encrypted.
The conference call system according to claim 1. The homomorphic encryption is an additive homomorphic encryption or a fully homomorphic encryption.
The conference call system according to claim 1 or 2. The homomorphic encryption is an additive homomorphic encryption using an elliptical ElGamel encryption.
The conference call system according to claim 1 or 2. Each of the telephone terminals samples and quantizes the voice data of the speaker and then encrypts it using homomorphic encryption.
When the speaker's voice is quantized, each telephone terminal performs quantization with a quantization bit number smaller than a preset quantization bit number.
The conference call system according to any one of claims 1 to 4. An encryption unit that encrypts the speaker's voice data using homomorphic encryption,
The voice data encrypted by the encryption unit is transmitted to the conference device, and the voice data from each telephone terminal participating in the conference call is received from the conference device while being encrypted. With the communication department
A decoding unit that decodes the mixed audio data from the conference device, and
A telephone terminal equipped with. The homomorphic encryption is an additive homomorphic encryption or a fully homomorphic encryption.
The telephone terminal according to claim 6. The homomorphic encryption is an additive homomorphic encryption using an elliptical ElGamel encryption.
The telephone terminal according to claim 6. It also has a coding unit that samples and quantizes the speaker's voice data.
The encryption unit encrypts the speaker voice data sampled and quantized by the encoding unit using homomorphic encryption.
When the speaker's voice data is quantized, the coding unit performs the quantization with a quantization bit number smaller than the preset quantization bit number.
The telephone terminal according to any one of claims 6 to 8. On the computer
Procedures for encrypting speaker voice data using homomorphic encryption,
A procedure for transmitting the encrypted voice data to the conference device and receiving the voice data mixed with the voice data from each telephone terminal participating in the conference call from the conference device while being encrypted.
The procedure for decoding the mixed audio data from the conference device and
A program to execute.

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