JP6228903B2 - Information sharing system and method, information sharing apparatus and program - Google Patents

Description

  The present invention relates to an application technology of information security technology, and particularly to a technology for sharing information such as a session key between two parties.

  The following FG method of ID authentication key exchange method is known (for example, see Non-Patent Document 1). Fig. 6 shows the protocol diagram of the FG method.

[Public parameter] Π is a protocol ID, and a unique ID corresponding to the protocol specification. Let κ be the security parameter. Let p be a κ-bit prime and G be a multiplicative cyclic group of order p with g as a generator. Let H ₁ : {0,1} → Z _p and H ₂ : {0,1} → {0,1} be hash functions.

[Key generation] As a key generation algorithm, a master secret key MSK ^ID : = x∈Z _p is selected at random. Further, the key generation algorithm calculates y = g ^x and discloses the master public key MPK ^ID : = (G, g, p, y = g ^x , H ₁ , H ₂ ).

[Key Extraction] With ID _P as input, the key extraction algorithm selects k _P ∈ _R Z _p , and the long-term secret key SSK _P ^ID : = (r _P = g ^kP , s _P = k _P + xH ₁ (ID _P , r _P )) is generated.

[Key Exchange] In the following, it is assumed that user U _A is the initiator of the key exchange session and user U _B is the responder. User U _A has a long-term secret key corresponding to ID _A (r _A = g ^kA , s _A = k _A + xH ₁ (ID _A , r _A )), and user U _B is a long-term secret key corresponding to ID _B (r _B = g ^kB , s _B = k _B + xH ₁ (ID _B , r _B )).

1. User U _A chooses an ad hoc secret key ESK _A ^ID = t _A ∈ _R Z _p uniformly at random. At this time, the user U _A calculates u _A : = ^gt _A and sends a message Mes ₁ ^ID = (ID _A , r _A , u _A ) to the user U _B.
2. User U _B chooses an ad hoc secret key ESK _B ^ID = t _B ∈ _R Z _p uniformly at random. At this time, the user U _B calculates u _B : = ^gtB and sends a message Mes ₂ ID = (ID _A , r _B , u _B ) to the user U _A.

3. User U _A calculates the shared secret information as follows.

z ₁ = (u _B r _B y ^ (H ₁ (ID _B , r _B ))) ^{tA + sA} , z ₂ = u _B ^tA
And obtain a session key K ^ID = H ₂ (z ₁ , z ₂ ). User U _A outputs the session key K ^ID and ends the session.

  User UB calculates the shared secret information as follows:

z ₁ = (u _A r _A y ^ (H ₁ (ID _A , r _A ))) ^{tB + sB} ; z ₂ = u _A ^tB
And obtain a session key K ^ID = H ₂ (z ₁ , z ₂ ). User U _B outputs the session key K ^ID and ends the session.

Dario Fiore, Rosario Gennaro, “Identity-Based Key Exchange Protocols without Pairings”, Transactions on Computational Science 10, P.42-77, 2010

  However, the technique described in the background art has a problem that the hash function must be ideally secure (random oracle) in order to guarantee safety. It is known that a random oracle cannot be realized using an actual hash function. Therefore, it is desirable to have a system that provides security proof without assuming a random oracle.

  The present invention has been made in view of these points, and an object thereof is to provide an information sharing system and method, an information sharing apparatus, and a program that do not necessarily depend on a random oracle.

An information sharing system according to an aspect of the present invention provides an ad hoc secret key generation algorithm in a predetermined PKI authentication key exchange method in an information sharing system that shares information between a first information sharing device and a second information sharing device. The initial message generation algorithm in the PKI authentication key exchange method is Message ^post , the message generation algorithm in the PKI authentication key exchange method is Message, the session key generation algorithm in the PKI authentication key exchange method is SesKey, and the PKI authentication The public parameter in the key exchange method is PP ^PKI , the long-term secret key of the first information sharing device in the PKI authentication key exchange method is SSK _A ^PKI, and the long-term disclosure of the first information sharing device in the PKI authentication key exchange method The key is SPK _A ^PKI, and the second information sharing device in the PKI authentication key exchange method The private key is SSK _B ^PKI , the long-term public key of the second information sharing apparatus in the PKI authentication key exchange method is SPK _B ^PKI , the signature verification algorithm in the predetermined electronic signature method is Ver, and the signature in the electronic signature method is The generation algorithm is Sign, the bit string representing the first information sharing apparatus is U _A , the bit string representing the information related to the first information sharing apparatus is ID _A, and the signature of the first information sharing apparatus is cert _A = Sign (sk, (ID _A , SPK _A ^PKI )), a bit string representing the second information sharing apparatus as U _B , a bit string representing information related to the second information sharing apparatus as ID _B, and the second The signature of the information sharing apparatus is cert _B = Sign (sk, (ID _B , SPK _B ^PKI )), and the first information sharing apparatus generates an ad hoc secret key ESK _A ^PKI = EpheGen (PP ^PKI ) Generator and initial message Mes ₁ ^PKI = Message ^post (PP ^PKI , U _A , SSK _A ^PKI , ESK _A ^PKI ) and SPK _A ^PKI , cert _A together with the initial message generator and Ver (vk, (ID _B , SPK _B ^PKI ), cert _B ) ID _B , SPK _B ^PKI ), cert _B , and if n is 3 or more, i is an odd number from 3 to n and the message Mes _i ^PKI = Message (PP ^PKI , U _A , U _B , SSK _A ^PKI , ESK _A ^PKI , SPK _B ^PKI , Mes ₁ ^PKI ,..., Mes _i-1 ^PKI ) and sent to the second information sharing device, and the information K ^PKI = SesKey (PP ^PKI , U _A , U _B , SSK _A ^PKI , ESK _A ^PKI , SPK _B ^PKI , Mes ₁ ^PKI , ..., Mes _n ^PKI ), and the second information sharing apparatus includes , Ad hoc secret key ESK _B ^PKI = EpheGen (PP ^PKI ) and ad hoc secret key generation unit and Ver (vk, (ID _A , SPK _A ^PKI ), cert _A ) based on (ID _A , SPK _A ^PKI ) , cert _A verifier and initial message Mes ₂ ^PKI = Message (PP ^PKI , U _B , U _A , SSK _B ^PKI , ESK _B ^PKI , SPK _B ^PKI , Mes ₁ ^PKI ) and send it to the first information sharing apparatus together with SPK _B ^PKI , cert _B , and when n is 4 or more, i is an even number between 4 and n, Generate a message Mes _i ^PKI = Message (PP ^PKI , U _B , U _A , SSK _B ^PKI , ESK _B ^PKI , SPK _A ^PKI , Mes ₁ ^PKI , ..., Mes _i-1 ^PKI ) to the first information sharing device A message generator for transmitting and an information generator for generating information K ^PKI = SesKey (PP ^PKI , U _B , U _A , SSK _B ^PKI , ESK _B ^PKI , SPK _A ^PKI , Mes ₁ ^PKI , ..., Mes _n ^PKI ) And including.

An information sharing system according to an aspect of the present invention provides an ad hoc secret key generation algorithm in a predetermined PKI authentication key exchange method in an information sharing system that shares information between a first information sharing device and a second information sharing device. The initial message generation algorithm in the PKI authentication key exchange method is Message ^post , the message generation algorithm in the PKI authentication key exchange method is Message, the session key generation algorithm in the PKI authentication key exchange method is SesKey, and the PKI authentication The public parameter in the key exchange method is PP ^PKI , the long-term secret key of the first information sharing device in the PKI authentication key exchange method is SSK _A ^PKI, and the long-term disclosure of the first information sharing device in the PKI authentication key exchange method The key is SPK _A ^PKI, and the second information sharing device in the PKI authentication key exchange method The private key is SSK _B ^PKI , the long-term public key of the second information sharing apparatus in the PKI authentication key exchange method is SPK _B ^PKI , the signature verification algorithm in the predetermined electronic signature method is Ver, and the signature in the electronic signature method is The generation algorithm is Sign, the bit string representing the first information sharing apparatus is U _A , the bit string representing the information related to the first information sharing apparatus is ID _A, and the signature of the first information sharing apparatus is cert _A = Sign (sk, (ID _A , SPK _A ^PKI )), a bit string representing the second information sharing apparatus as U _B , a bit string representing information related to the second information sharing apparatus as ID _B, and the second The signature of the information sharing apparatus is cert _B = Sign (sk, (ID _B , SPK _B ^PKI )), and the first information sharing apparatus generates an ad hoc secret key ESK _A ^PKI = EpheGen (PP ^PKI ) a generating unit, and transmits (SPK _a ^PKI, cert _a) to the second information sharing device A signal _{unit, Ver (vk, (ID B} , SPK B PKI), cert B) based on ^{_{(ID B, SPK B PKI)}} , and a verification unit for verifying cert _B, initial message Mes ₂ ^PKI = Message ( PP ^PKI , U _A , U _B , SSK _A ^PKI , ESK _A ^PKI , SPK _B ^PKI , Mes ₁ ^PKI ) and an initial message generator for transmitting to the second information sharing device, and when n is 4 or more Is a message Mes _i ^PKI = Message (PP ^PKI , U _A , U _B , SSK _A ^PKI , ESK _A ^PKI , SPK _B ^PKI , Mes ₁ ^PKI , ..., Mes _{i- 1} ^PKI ) and send it to the second information sharing device, and the information K ^PKI = SesKey (PP ^PKI , U _A , U _B , SSK _A ^PKI , ESK _A ^PKI , SPK _B ^PKI , Mes ₁ ^PKI ,..., Mes _n ^PKI ), and the second information sharing device includes an ad hoc secret key generation unit that generates an ad hoc secret key ESK _B ^PKI = EpheGen (PP ^PKI ), and Ver ( vk, (ID _A , SPK _A ^PKI ), cert _A ) based on (ID _A , SPK _A ^PKI ), cert _A and the initial message Sage Mes ₁ ^PKI = Message ^pre (PP ^PKI , U _B , U _A , SSK _B ^PKI , ESK _B ^PKI , SPK _A ^PKI ) is generated and sent to the first information sharing device together with SPK _B ^PKI and cert _B When the generation unit and n is 3 or more, the message Mes _i ^PKI = Message (PP ^PKI , U _B , U _A , SSK _B ^PKI , ESK _B ^PKI , SPK _A ^PKI , Mes ₁ ^PKI ,..., Mes _i-1 ^PKI ) and sending it to the first information sharing device, and information K ^PKI = SesKey (PP ^PKI , U _B , U _A , SSK _B ^PKI , ESK _B ^PKI , SPK _A ^PKI , Mes ₁ ^PKI ,..., Mes _n ^PKI ).

An information sharing method according to an aspect of the present invention is an information sharing method in which information is shared between a first information sharing device and a second information sharing device, and an ad hoc secret key generation algorithm in a predetermined PKI authentication key exchange scheme is defined as EpheGen. The initial message generation algorithm in the PKI authentication key exchange method is Message ^post , the message generation algorithm in the PKI authentication key exchange method is Message, the session key generation algorithm in the PKI authentication key exchange method is SesKey, and the PKI authentication The public parameter in the key exchange method is PP ^PKI , the long-term secret key of the first information sharing device in the PKI authentication key exchange method is SSK _A ^PKI, and the long-term disclosure of the first information sharing device in the PKI authentication key exchange method The key is SPK _A ^PKI, and the long-term secret key of the second information sharing device in the PKI authentication key exchange method is SSK _B ^PKI , the long-term public key of the second information sharing device in the PKI authentication key exchange method is SPK _B ^PKI , the signature verification algorithm in a predetermined electronic signature method is Ver, and the signature generation algorithm in the electronic signature method is Sign, the bit string representing the first information sharing apparatus is U _A , the bit string representing the information related to the first information sharing apparatus is ID _A, and the signature of the first information sharing apparatus is cert _A = Sign (sk , (ID _A , SPK _A ^PKI )), the bit string representing the second information sharing apparatus is U _B , the bit string representing the information related to the second information sharing apparatus is ID _B, and the second information sharing apparatus Cert _B = Sign (sk, (ID _B , SPK _B ^PKI )) and the ad hoc secret key generation unit of the first information sharing device generates an ad hoc secret key ESK _A ^PKI = EpheGen (PP ^PKI ) Ad hoc secret key generation step and first of the first information sharing device Period message generator is the initial message to be sent the initial message _{^{Mes 1 PKI = Message post (PP}} PKI, U A, SSK A PKI, ESK A PKI) generated SPK _A ^PKI and to the second information sharing device with cert _A a generation step, the verification unit of the second information sharing _{apparatus, Ver (vk, (ID a} , SPK a PKI), cert a) based on ^{_{(ID a, SPK a PKI)}} , verified to verify the cert _a Steps,
The initial message generator of the second information sharing device generates an initial message Mes ₂ ^PKI = Message (PP ^PKI , U _B , U _A , SSK _B ^PKI , ESK _B ^PKI , SPK _B ^PKI , Mes ₁ ^PKI ) _The initial message generation step to be transmitted to the first information sharing device together with _B ^PKI and cert _B , and the verification unit of the first information sharing device is based on Ver (vk, (ID _B , SPK _B ^PKI ), cert _B ) (ID _B , SPK _B ^PKI ), the verification step for verifying cert _B , and the message generation unit of the first information sharing apparatus, when n is 3 or more, i is an odd number from 3 to n Message Mes _i ^PKI = Message (PP ^PKI , U _A , U _B , SSK _A ^PKI , ESK _A ^PKI , SPK _B ^PKI , Mes ₁ ^PKI ,…, Mes _i-1 ^PKI ) and a message generation step of transmitting apparatus, the information generating unit of the first information sharing apparatus, information ^{K PKI = SesKey (PP PKI,} U a, U B, SSK a PKI, ESK a PKI, SPK B PKI, Mes 1 ^PKI, ..., information generated to produce a Mes _n ^PKI) step When an ad hoc private key generation unit of the second information sharing apparatus, an ad hoc secret key generating step of generating an ad hoc secret key _{^{ESK B PKI = EpheGen (PP PKI}} ), the message generation unit of the second information sharing apparatus, when n of 4 or more, as each even 4 to n of the i, message _{^{Mes i PKI = message (PP PKI}} , U B, U a, SSK B PKI, ESK B PKI, SPK a PKI, Mes 1 ^PKI ,..., Mes _i-1 ^PKI ) and transmitting the message to the first information sharing apparatus, and the information generation unit of the second information sharing apparatus include information K ^PKI = SesKey (PP ^PKI , U _B , U _A , SSK _B ^PKI , ESK _B ^PKI , SPK _A ^PKI , Mes ₁ ^PKI ,..., Mes _n ^PKI ).

An information sharing method according to an aspect of the present invention is an information sharing method in which information is shared between a first information sharing device and a second information sharing device, and an ad hoc secret key generation algorithm in a predetermined PKI authentication key exchange scheme is defined as EpheGen. The initial message generation algorithm in the PKI authentication key exchange method is Message ^post , the message generation algorithm in the PKI authentication key exchange method is Message, the session key generation algorithm in the PKI authentication key exchange method is SesKey, and the PKI authentication The public parameter in the key exchange method is PP ^PKI , the long-term secret key of the first information sharing device in the PKI authentication key exchange method is SSK _A ^PKI, and the long-term disclosure of the first information sharing device in the PKI authentication key exchange method The key is SPK _A ^PKI, and the long-term secret key of the second information sharing device in the PKI authentication key exchange method is SSK _B ^PKI , the long-term public key of the second information sharing device in the PKI authentication key exchange method is SPK _B ^PKI , the signature verification algorithm in a predetermined electronic signature method is Ver, and the signature generation algorithm in the electronic signature method is Sign, the bit string representing the first information sharing apparatus is U _A , the bit string representing the information related to the first information sharing apparatus is ID _A, and the signature of the first information sharing apparatus is cert _A = Sign (sk , (ID _A , SPK _A ^PKI )), the bit string representing the second information sharing apparatus is U _B , the bit string representing the information related to the second information sharing apparatus is ID _B, and the second information sharing apparatus Cert _B = Sign (sk, (ID _B , SPK _B ^PKI )) and the ad hoc secret key generation unit of the first information sharing device generates an ad hoc secret key ESK _A ^PKI = EpheGen (PP ^PKI ) An ad hoc secret key generation step and the transmission of the first information sharing device The transmission unit transmits (SPK _A ^PKI , cert _A ) to the second information sharing device, and the ad hoc secret key generation unit of the second information sharing device includes the ad hoc secret key ESK _B ^PKI = EpheGen (PP ^The ad hoc secret key generation step for generating ( ^PKI ) and the verification unit of the second information sharing device are based on Ver (vk, (ID _A , SPK _A ^PKI ), cert _A ) (ID _A , SPK _A ^PKI ) , cert _A verification step, the initial message generator of the second information sharing device, the initial message Mes ₁ ^PKI = Message ^pre (PP ^PKI , U _B , U _A , SSK _B ^PKI , ESK _B ^PKI , SPK _A ^PKI ) is generated and transmitted together with SPK _B ^PKI , cert _B to the first information sharing device, and the verification unit of the first information sharing device is configured to verify Ver (vk, (ID _B , SPK _B ^PID ), cert _B ) based on (ID _B , SPK _B ^PKI ), cert _B , and an initial message generator of the first information sharing device An initial message generation step for generating a message Mes ₂ ^PKI = Message (PP ^PKI , U _A , U _B , SSK _A ^PKI , ESK _A ^PKI , SPK _B ^PKI , Mes ₁ ^PKI ) and transmitting it to the second information sharing device; When the message generation unit of the second information sharing apparatus is n is 3 or more, the message Mes _i ^PKI = Message (PP ^PKI , U _B , U _A , SSK _B ^PKI , ESK _B ^PKI , SPK _A ^PKI , Mes ₁ ^PKI ,..., Mesi _-1 ^PKI ) and sending to the first information sharing device, and a message generating unit of the first information sharing device , N is 4 or more, the message Mes _i ^PKI = Message (PP ^PKI , U _A , U _B , SSK _A ^PKI , ESK _A ^PKI , SPK _B ^PKI , Mes ₁ ^PKI ,..., Mes _i-1 ^PKI ) and transmitting it to the second information sharing device, and the information generating unit of the first information sharing device include information K ^PKI = SesKey (PP ^PKI , U _A , U _B , SSK _A ^PKI , ESK _A ^PKI , S PK _B ^PKI , Mes ₁ ^PKI ,..., Mes _n ^PKI ) and the information generation unit of the second information sharing device include information K ^PKI = SesKey (PP ^PKI , U _B , U _A , SSK _B ^PKI , ESK _B ^PKI , SPK _A ^PKI , Mes ₁ ^PKI ,..., Mes _n ^PKI ).

  An information sharing device according to an aspect of the present invention is the first information sharing device and the second information sharing device of the information sharing system.

  Information sharing that does not necessarily depend on a random oracle can be realized.

The functional block diagram of the example of an information sharing system. The functional block diagram of the example of the 1st information sharing apparatus and 2nd information sharing apparatus of 1st embodiment. The figure which illustrates the outline | summary of the process of 1st embodiment. The functional block diagram of the example of the 1st information sharing apparatus and 2nd information sharing apparatus of 2nd embodiment. The figure which illustrates the outline | summary of the process of 2nd embodiment. The figure which illustrates the outline | summary of a process of background art.

  Hereinafter, each embodiment of the present invention will be described.

[First embodiment]
In the information sharing system of the first embodiment, the initiator can calculate the first message without knowing the exchange partner in advance (it can be specified afterwards) Information sharing by combining the PKI authentication key exchange method with the electronic signature method ( For example, an authentication key is shared by an ID authentication key exchange method). First, the PKI authentication key exchange method and electronic signature method, which are parts, will be described. These PKI authentication key exchange method and electronic signature method are not dependent on, for example, a random oracle.

  Subsequent PKI authentication key exchange consists of the following algorithms.

・ PP ^PKI ← Setup (1 ^κ ): Setup algorithm Generates public parameters. κ is a security parameter and is an arbitrary positive integer. 1 ^κ is a bit string of κ bits.

^{_{· (SPK P PKI, SSK P}} PKI) ← StaticGen (PP PKI): to generate the key registration algorithm long-term secret key SSK _P ^PKI and the corresponding long-term public key SPK _P ^PKI, to register the long-term public key SPK _P ^PKI to PKI Publish. The party U _P, is a collection of sharable two or more information sharing device information. Each information sharing device belonging to the party U _P generates a long-term private key and long public key based on the algorithm of StaticGen.

-ESK _P ^PKI ← EpheGen (PP ^PKI ): Ad hoc secret key generation algorithm An ad hoc secret key ESK _P ^PKI is generated.

-Mes ₁ ^PKI <-Message ^post (PP ^PKI , U _A , SSK _A ^PKI , ESK _A ^PKI ): Initial message generation algorithm Initiator U _A uses the long-term secret key SSK _A ^PKI and the ad hoc secret key ESK _A ^PKI. Generate the message Mes ₁ ^PKI . The initial message generation algorithm Message ^{post of} the first embodiment does not require the long-term public key SPK _B ^PKI of the exchange partner U _B.

^{_{· Mes i PKI ← Message (PP}} PKI, U P, U P -, SSK P PKI, ESK P PKI, SPK P- PKI, Mes 1 PKI, ..., Mes i-1 PKI): i-th message generation
The _i- th message Mes _i ^PKI is generated using SSK _P ^PKI , ESK _P ^PKI , SPK _P ^PKI , Mes ₁ ^PKI ,..., Mes _i-1 ^PKI . U _P -is the exchange partner. For example, there is time to perform the information shared between the U _A and U _B, in the case of _{U P = U A U P -} = A U _B, in the case of U _P = U _B is U _P -= U _A. U _P is a bit string representing the initiator U _P. For example, U _A is a bit string representing the first information sharing apparatus U _A is the initiator, U _B is the bit string representing the second information sharing apparatus U _B is the responder.

However, if the responder U _B can generate the second message before receiving the first message Mes ₁ ^PKI (can be executed simultaneously), the second message Mes ₂ ^PKI is generated using only SSK _B ^PKI and ESK _B ^PKI. can do. That is, Mes ₂ ^PKI ← Message ^post (PP ^PKI , U _B , SSK _B ^PKI , ESK _B ^PKI ). This will be described in a modification of the first embodiment.

^{· K PKI ← SesKey (PP PKI} , U P, U P -, SSK P PKI, ESK P PKI, SPK P PKI, Mes 1 PKI, ..., Mes n PKI): session key generation algorithm
_{^{SSK P PKI, ESK P PKI,}} SPK P PKI, Mes 1 PKI, ..., by using the Mes _i ^PKI, generates a session key K ^PKI.

  The electronic signature method is composed of the following algorithm.

· (Vk, sk) ← SigGen (1 κ): to generate a key generation algorithm verification key vk and the signature key sk.

Σ ← Sign (sk, m): Signature generation A signature σ is generated using the plaintext m and the signature key sk.

・ 1 or 0 ← Ver (vk, m, σ): signature verification Using the verification key vk, the plaintext m and the signature σ are verified, and 1 is output if it passes, and 0 is output if it fails.

  FIG. 3 illustrates an outline of an information sharing algorithm using these PKI authentication key exchange method and electronic signature method.

  An information sharing system that executes this information sharing algorithm will be described below. As illustrated in FIG. 1, the information sharing system includes, for example, an administrator device 1 and two or more information sharing devices 2.

The administrator device 1 performs the process of PP ^PKI <-Setup (1 ^κ ) (step S1). That is, the administrator device 1 uses the security parameter κ to generate the public parameter PPP ^PKI based on the setup algorithm of the PKI authentication key exchange method.

The administrator device 1 performs a process of (vk, sk) ← SigGen (1 ^κ ) (step S2). That is, the administrator device 1 generates the verification key vk and the signature key sk using the security parameter κ based on the key generation algorithm SigGen of the electronic signature method. The generated signature key sk is secretly held in the administrator device 1 as a master secret key MSK ^ID . The generated verification key vk and public parameter PP ^PKI are disclosed as a master public key MPK ^ID .

Each information sharing device 2 performs a process of (SPK _P ^PKI , SSK _P ^PKI ) ← StaticGen (PP ^PKI ) (step S 3). That is, each information sharing device 2 generates a long-term secret key SSK _P ^PKI and a long-term public key SPK _P ^PKI based on the key registration algorithm StaticGen of the PKI authentication key exchange method using the public parameter PP ^PKI . The generated long-term secret key SSK _P ^PKI is secretly held in each information sharing device 2. The generated long-term public key SPK _P ^PKI is made public.

Each information sharing apparatus 2 performs a process of cert _P <-Sign (sk, (ID _P , SPK _P ^PKI )) (step S31). That is, each information sharing apparatus 2 generates a signature cert _P based on a signature generation algorithm Sign of the electronic signature method using sk, (ID _P , SPK _P ^PKI ). ID _P is a bit string representing information related to each information sharing device 2. The information related to each information sharing device 2 is, for example, a mail address of each information sharing device 2.

The processing of step S3 and step S31 is performed for each information sharing device 2. The information sharing system a set of information sharing apparatus which actually performs the information sharing in the 2 and the first information sharing apparatus U _A and the second information sharing device U _B. In this case, the first information sharing device U _A generates a long-term secret key SSK _A ^PKI , a long-term public key SPK _A ^PKI and a signature cert _A , and the long-term secret key SSK _A ^ID = (SSK _A ^PKI , SPK _A ^PKI , cert _a) it is kept secret to the second information sharing device U in _B. Further, the second information sharing device U _B generates a long-term secret key SSK _B ^PKI , a long-term public key SPK _B ^PKI, and a signature cert _B , and the long-term secret key SSK _B ^ID = (SSK _B ^PKI , SPK _B ^PKI , cert _B ) is kept secret to the second information sharing device U in _B.

  The processes from step S1 to step S31 are performed in advance as preparations for the information sharing process described below.

Hereinafter, the first information sharing apparatus U _A in the two or more information sharing apparatus 2 information shared between the second information sharing device U _B is a will be described as an example to be performed. A first information sharing apparatus U _A and the second information sharing device U _B, is any set of information sharing devices in the information sharing apparatus 2. First information sharing device U _A is the initiator, the second information sharing apparatus U _B described as responder.

As illustrated in FIG. 2, the first information sharing device U _A includes an ad hoc key generation unit U _A 1, an initial message generation unit U _A 2, a verification unit U _A 3, a message generation unit U _A 4, and an information generation unit U. _A 5 is provided. As illustrated in FIG. 2, the second information sharing device U _B includes an ad hoc key generation unit U _B 1, an initial message generation unit U _B 2, a verification unit U _B 3, a message generation unit U _B 4, and an information generation unit U. _B 5 is provided.

The ad hoc key generation unit U _A 1 of the first information sharing apparatus U _A performs processing of ESK _A ^PKI ← EpheGen (PP ^PKI ) (step S4). That is, the ad hoc key generation unit U _A 1 of the first information sharing device U _A generates the ad hoc key ESK _A ^PKI based on the ad hoc secret key generation algorithm of the PKI authentication key exchange method using the public parameter PP ^PKI . Generated adhoc key ESK _A ^PKI is kept secret to the first information sharing apparatus U _A.

The initial message generating unit U _A 2 of the first information sharing device U _A performs the process of Mes ₁ ^PKI ← Message ^post (PP ^PKI , U _A , SSK _A ^PKI , ESK _A ^PKI ) (step S5). That is, the initial message generation unit U _A 2 of the first information sharing device U _A uses PP ^PKI , U _A , SSK _A ^PKI , ESK _A ^PKI , based on the initial message generation algorithm Message ^post of the PKI authentication key exchange method. To generate the initial message Mes ₁ ^PKI . The generated initial message Mes ₁ ^PKI is, SPK _A ^PKI, it is transmitted together with the cert _A to the second information sharing device U _{B. ^{That, Mes 1 ID = (Mes 1}} PK, SPK A PKI, cert A) is transmitted to the second information sharing device U _B.

The ad hoc key generation unit U _B 1 of the second information sharing apparatus U _B performs the process of ESK _B ^PKI <-EpheGen (PP ^PKI ) (step S6). That is, the ad hoc key generation unit U _B 1 of the second information sharing device U _B generates an ad hoc key ESK _B ^PKI based on the ad hoc secret key generation algorithm EpheGen of the PKI authentication key exchange method using the public parameter PP ^PKI. . The generated ad hoc key ESK _B ^PKI is kept secret to the second information sharing device U in _B.

In this example, the second information sharing apparatus U _B and it is impossible to Mes ₂ ^PKI generation before receiving ^{_{Mes 1 ID = (Mes 1 PKI}} , SPK A PKI, cert A) a. That is, generation of Mes ₂ ^PKI by the second information sharing device U _B is assumed to be possible after receiving ^{_{Mes 1 ID = (Mes 1 PKI}} , SPK A PKI, cert A) from the first information sharing device U _A . Whether or not Mes ₂ ^PKI can be generated before the second information sharing device U _B receives Mes ₁ ^ID = (Mes ₁ ^PKI , SPK _A ^PKI , cert _A ) depends on the base PKI authentication key exchange method To do.

In this case, after receiving Mes ₁ ^ID = (Mes ₁ ^PKI , SPK _A ^PKI , cert _A ), the verification unit U _B 3 of the second information sharing device U _B receives 1 ← ^? Ver (vk, (ID _A , SPK _A ^PKI ), cert _A ) are performed (step S7). That is, the verification unit U _B 3 of the second information sharing apparatus U _B uses vk, (ID _A , SPK _A ^PKI ), cert _A based on the verification algorithm Ver of the electronic signature scheme (ID _A , SPK _A ^PKI ), cert _A is verified.

If the verification in step S7 is passed, the initial message generation unit U _B 2 of the second information sharing device U _B will have Mes ₂ ^PKI ← Message (PP ^PKI , U _B , U _A , SSK _B ^PKI , ESK _B ^PKI , SPK _B ^PKI , Mes ₁ ^PKI ) (step S8). That is, the initial message generation unit U _B 2 of the second information sharing apparatus U _B uses the PKI authentication key using PP ^PKI , U _B , U _A , SSK _B ^PKI , ESK _B ^PKI , SPK _B ^PKI , Mes ₁ ^PKI. An initial message Mes ₂ ^PKI = Message (PP ^PKI , U _B , U _A , SSK _B ^PKI , ESK _B ^PKI , SPK _B ^PKI , Mes ₁ ^PKI ) is generated based on the message generation algorithm Message of the exchange method, and SPK _B ^PKI , It is transmitted to the first information sharing device U _A together with cert _{B. ^{That, Mes 2 ID = (Mes 2}} PKI, SPK B PKI, cert B) is transmitted to the first information sharing apparatus U _A.

  If the verification of step S7 is not passed, the subsequent processing is not performed.

After receiving Mes ₂ ^ID = (Mes ₂ ^PKI , SPK _B ^PKI , cert _B ), the verification unit U _A 3 of the first information sharing device U _A receives 1 ← ^? Ver (vk, (ID _B , SPK _B ^PKI ), cert _B ) (step S9). That is, the verification unit U _A 3 of the first information sharing device U _A uses vk, (ID _B , SPK _B ^PKI ), cert _B and (ID _B , SPK _B ^PKI ), cert _B is verified.

When that pass the verification of step S9, the first information sharing apparatus U _A and the second information sharing apparatus U _B is mutually send each other messages Mes _i ^PKI as described below from i = 3 to i = n . Note that the message generation unit U _A 4 of the first information sharing device U _A performs processing only when n is 3 or more, and does not perform processing when n is less than 3. The message generating unit U _B 4 of the second information sharing apparatus U _B is, n performs processing only if 4 or more, n is not processed in the case of less than 4.

That is, when n is 3 or more, the message generation unit U _A 4 of the first information sharing device U _A sets i as an odd number of 3 or more and n or less and sets Mes _i ^PKI ← Message (PP ^PKI , U _A , U _B , SSK _A ^PKI , ESK _A ^PKI , SPK _B ^PKI , Mes ₁ ^PKI ,..., Mesi _-1 ^PKI ) are performed (step S 10). In other words, when n is 3 or more, the message generation unit U _A 4 of the first information sharing device U _A sets i as an odd number of 3 or more and n or less, and ^PPPKI , U _A , U _B , SSK _A ^PKI , ESK _A ^PKI , SPK _B ^PKI , Mes ₁ ^PKI , ..., Mes _i-1 ^PKI is used to create a message Mes _i ^PKI = Message (PP ^PKI , U _A , U _B , SSK _A ^PKI , ESK _A ^PKI , SPK _B ^PKI , Mes ₁ ^PKI ,..., Mes _i-1 ^PKI ) are generated and transmitted to the second information sharing apparatus U _B as Mes _i ^IDs .

In addition, when n is 4 or more, the message generation unit U _B 4 of the second information sharing device U _B sets i as an even number of 4 or more and n or less, and sets Mes _i ^PKI ← Message (PP ^PKI , U _B , U _A , SSK _B ^PKI , ESK _B ^PKI , SPK _A ^PKI , Mes ₁ ^PKI ,..., Mesi _-1 ^PKI ) are performed (step S11). In other words, the message generation unit U _B 4 of the second information sharing apparatus U _B, when n of 4 or more, as each even 4 to n of the _{^{i, PP PKI, U B,}} U A, SSK B ^PKI , ESK _B ^PKI , SPK _A ^PKI , Mes ₁ ^PKI , ..., Mes _i-1 ^PKI is used to create a message Mes _i ^PKI = Message (PP ^PKI , U _B , U _A , SSK _B ^PKI , ESK _B ^PKI , SPK _A ^PKI , Mes ₁ ^PKI ,..., Mes _i-1 ^PKI ) are generated and transmitted to the first information sharing apparatus U _A as Mes _i ^IDs .

  If the verification in step S9 is not passed, the subsequent processing is not performed.

After that, the information generation unit U _A 5 of the first information sharing device U _A uses K ^PKI ← SesKey (PP ^PKI , U _A , U _B , SSK _A ^PKI , ESK _A ^PKI , SPK _B ^PKI , Mes ₁ ^PKI , ..., Mes _n ^PKI ) is performed (step S12). That is, the information generation unit U _A 5 of the first information sharing device U _A uses PP ^PKI , U _A , U _B , SSK _A ^PKI , ESK _A ^PKI , SPK _B ^PKI , Mes ₁ ^PKI , ..., Mes _n ^PKI Based on the session key generation algorithm of the PKI authentication key exchange method, information K ^PKI = SesKey (PP ^PKI , U _A , U _B , SSK _A ^PKI , ESK _A ^PKI , SPK _B ^PKI , Mes ₁ ^PKI ,…, Mes _n ^PKI )). When the information sharing target is an ID authentication key, the ID authentication key K ^ID = K ^PKI .

In addition, the information generation unit U _B 5 of the second information sharing device U _B has K ^PKI ← SesKey (PP ^PKI , U _B , U _A , SSK _B ^PKI , ESK _B ^PKI , SPK _A ^PKI , Mes ₁ ^PKI , ..., Mes _n ^PKI ) is performed (step S13). That is, the information generating unit U _B 5 of the second information sharing apparatus U _B uses ^{_{PP PKI, U B, U A}} , SSK B PKI, ESK B PKI, SPK A PKI, Mes 1 PKI, ..., the Mes _n ^PKI Based on the session key generation algorithm of the PKI authentication key exchange method, information K ^PKI = SesKey (PP ^PKI , U _B , U _A , SSK _B ^PKI , ESK _B ^PKI , SPK _A ^PKI , Mes ₁ ^PKI ,…, Mes _n ^PKI )). When the information sharing target is an ID authentication key, the ID authentication key K ^ID = K ^PKI .

  In the existing method, ID authentication is realized by the inability to forge the signature by sending the ID with the Schnorr signature along with the classic DH key exchange. In the present invention, an information sharing system (for example, an ID authentication key exchange system) is converted by combining an arbitrary PKI authentication key exchange method and an arbitrary electronic signature method instead of using such a specific method as a base. Configured. If the base PKI authentication key exchange method and electronic signature method are independent of random oracle, the converted information sharing system is also independent of random oracle.

In addition, since the PKI authentication key exchange method and the electronic signature method are known to be based on various problems other than the Diffie-Hellman (DH) problem, the information sharing system that is an ID authentication key exchange method after conversion is also DH. Safety can be guaranteed based on problems other than problems. The DH problem is a problem for ^obtaining g ^ab when (g, g ^a , g ^b ) is given. For example, there is no known algorithm that efficiently solves the lattice problem even if it is realized by a quantum computer. An information sharing system converted from the PKI authentication key exchange method and the electronic signature method based on the lattice problem is also applicable to the quantum computer. It will be safe. The PKI authentication key exchange method based on the lattice problem is described in the following document, for example.

[Reference 1] Atsushi Fujioka, Koutarou Suzuki, Keita Xagawa, Kazuki Yoneyama, “Strongly Secure Authenticated Key Exchange from Factoring, Codes and Lattices”, Public Key Cryptography, 2012, P.467-484
An electronic signature based on the lattice problem is described in the following document, for example.
[Reference 2] Vadim Lyubashevsky, “Lattice Signatures without Trapdoors”, EURO-CRYPT 2012, P.738-755

<Modification of First Embodiment>
In this example, the second information sharing apparatus U _B and is capable of generating a Mes ₂ ^PKI before receiving ^{_{Mes 1 ID = (Mes 1 PK}} , SPK A PKI, cert A) a. Whether the Mes ₂ ^PKI can be generated before the second information sharing device U _B receives Mes ₁ ^ID = (Mes ₁ ^PK , SPK _A ^PKI , cert _A ) depends on the base PKI authentication key exchange method. .

In this case, the second information sharing device U _B, instead of the processing in step S7, the process of step S7 'to be described below.

After the processing in step S6, the initial message generator U _B 2 of the second information sharing apparatus U _{B ^{is, Mes 2 PKI ← Message post (}} PP PKI, U B, SSK B PKI, ESK B PKI) processes of performing ( Step S7 '). That is, the initial message generator U _B 2 of the second information sharing apparatus U _B, using PP ^PKI, U _B, SSK _B ^PKI, the ESK _B ^PKI, based on the initial message generation algorithm Message ^post of PKI authentication key exchange method The initial message Mes ₂ ^PKI is generated. The generated initial message Mes ₂ ^PKI is transmitted to the first information sharing apparatus U _A together with SPK _B ^PKI and cert _{B. ^{That, Mes 2 ID = (Mes 2}} PK, SPK B PKI, cert B) is transmitted to the first information sharing apparatus U _A.

  Thereafter, the process of step S8 is performed.

  Effects similar to those of the first embodiment described above can be obtained also by the modification of the first embodiment.

[Second Embodiment]
In the second embodiment, it is necessary for the initiator to calculate the first message using the information of the exchange partner (post-designation is impossible) Information sharing (for example, ID authentication key exchange) by combining the PKI authentication key exchange method with the electronic signature method Authentication key sharing). First, the PKI authentication key exchange method and electronic signature method, which are parts, will be described. These PKI authentication key exchange method and electronic signature method are not dependent on, for example, a random oracle.

  Post-designation PKI authentication key exchange consists of the following algorithm.

・ PP ^PKI ← Setup (1 ^κ ): Setup algorithm Generates public parameters. κ is a security parameter and is an arbitrary positive integer. 1 ^κ is a bit string of κ bits.

^{_{· (SPK P PKI, SSK P}} PKI) ← StaticGen (PP PKI): to generate the key registration algorithm long-term secret key SSK _P ^PKI and the corresponding long-term public key SPK _P ^PKI, to register the long-term public key SPK _P ^PKI to PKI Publish. The party U _P, is a collection of sharable two or more information sharing device information. Each information sharing device belonging to the party U _P generates a long-term private key and long public key based on the algorithm of StaticGen.

-ESK _P ^PKI ← EpheGen (PP ^PKI ): Ad hoc secret key generation algorithm An ad hoc secret key ESK _P ^PKI is generated.

・ Mes ₁ ^PKI ← Message ^pre (PP ^PKI , U _A , U _B , SSK _A ^PKI , ESK _A ^PKI , SPK _B ^PKI ): Initial message generation algorithm In the base PKI authentication key exchange, initiator U _A is SSK _A ^An initial message Mes ₁ ^PKI is generated using ^PKI , ESK _A ^PKI , and SPK _B ^PKI . Unlike initial message generation algorithm Message ^post of the first embodiment, the initial message generation algorithm Message ^pre of the second embodiment, which require long-term public key SPK _B ^PKI of exchange partner U _B.

The information sharing algorithm described below, the first information sharing device rather than U _A is the initiator, the second information sharing apparatus U _B is the responder, using an initial message generation algorithm Message ^pre, initial message Mes ₁ ^PKI = Message ^pre (PP ^PKI , U _B , U _A , SSK _B ^PKI , ESK _B ^PKI , SPK _A ^PKI ) is generated.

^{_{· Mes i PKI ← Message (PP}} PKI, U P, U P -, SSK P PKI, ESK P PKI, SPK P- PKI, Mes 1 PKI, ..., Mes i-1 PKI): i-th message generation
The _i- th message Mes _i ^PKI is generated using SSK _P ^PKI , ESK _P ^PKI , SPK _P- ^PKI , Mes ₁ ^PKI ,..., Mes _i-1 ^PKI . U _P -is the exchange partner. For example, there is time to perform the information shared between the U _A and U _B, in the case of _{U P = U A U P -} = A U _B, in the case of U _P = U _B is U _P -= U _A. U _P is a bit string representing the initiator U _P. For example, U _A is a bit string representing the first information sharing apparatus U _A is the initiator, U _B is the bit string representing the second information sharing apparatus U _B is the responder.

^{· K PKI ← SesKey (PP PKI} , U P, U P -, SSK P PKI, ESK P PKI, SPK P- PKI, Mes 1 PKI, ..., Mes n PKI): session key generation algorithm
_{^{SSK P PKI, ESK P PKI,}} SPK P PKI, Mes 1 PKI, ..., by using the Mes _i ^PKI, generates a session key K ^PKI.

  The electronic signature method is composed of the following algorithm.

· (Vk, sk) ← SigGen (1 κ): to generate a key generation algorithm verification key vk and the signature key sk.

Σ ← Sign (sk, m): Signature generation A signature σ is generated using the plaintext m and the signature key sk.

・ 1 or 0 ← Ver (vk, m, σ): signature verification Using the verification key vk, the plaintext m and the signature σ are verified, and 1 is output if it passes, and 0 is output if it fails.

  FIG. 5 illustrates an outline of an information sharing algorithm using these PKI authentication key exchange method and electronic signature method.

  An information sharing system that executes this information sharing algorithm will be described below. As illustrated in FIG. 1, the information sharing system includes, for example, an administrator device 1 and two or more information sharing devices 2.

The administrator device 1 performs the process of PP ^PKI <-Setup (1 ^κ ) (step S1). That is, the administrator device 1 uses the security parameter κ to generate the public parameter PPP ^PKI based on the setup algorithm of the PKI authentication key exchange method.

The administrator device 1 performs a process of (vk, sk) ← SigGen (1 ^κ ) (step S2). That is, the administrator device 1 generates the verification key vk and the signature key sk using the security parameter κ based on the key generation algorithm SigGen of the electronic signature method. The generated signature key sk is secretly held in the administrator device 1 as a master secret key MSK ^ID . The generated verification key vk and public parameter PP ^PKI are disclosed as a master public key MPK ^ID .

Each information sharing device 2 performs a process of (SPK _P ^PKI , SSK _P ^PKI ) ← StaticGen (PP ^PKI ) (step S 3). That is, each information sharing device 2 generates a long-term secret key SSK _P ^PKI and a long-term public key SPK _P ^PKI based on the key registration algorithm StaticGen of the PKI authentication key exchange method using the public parameter PP ^PKI . The generated long-term secret key SSK _P ^PKI is secretly held in each information sharing device 2. The generated long-term public key SPK _P ^PKI is made public.

Each information sharing apparatus 2 performs a process of cert _P <-Sign (sk, (ID _P , SPK _P ^PKI )) (step S31). That is, each information sharing apparatus 2 generates a signature cert _P based on a signature generation algorithm Sign of the electronic signature method using sk, (ID _P , SPK _P ^PKI ). ID _P is a bit string representing information related to each information sharing device 2. The information related to each information sharing device 2 is, for example, a mail address of each information sharing device 2.

The processing of step S3 and step S31 is performed for each information sharing device 2. The information sharing system a set of information sharing apparatus which actually performs the information sharing in the 2 and the first information sharing apparatus U _A and the second information sharing device U _B. In this case, the first information sharing device U _A generates a long-term secret key SSK _A ^PKI , a long-term public key SPK _A ^PKI and a signature cert _A , and the long-term secret key SSK _A ^ID = (SSK _A ^PKI , SPK _A ^PKI , cert _a) it is kept secret to the second information sharing device U in _B. Further, the second information sharing device U _B generates a long-term secret key SSK _B ^PKI , a long-term public key SPK _B ^PKI, and a signature cert _B , and the long-term secret key SSK _B ^ID = (SSK _B ^PKI , SPK _B ^PKI , cert _B ) is kept secret to the second information sharing device U in _B.

  The processes from step S1 to step S31 are performed in advance as preparations for the information sharing process described below.

Hereinafter, the first information sharing apparatus U _A in the two or more information sharing apparatus 2 information shared between the second information sharing device U _B is a will be described as an example to be performed. A first information sharing apparatus U _A and the second information sharing device U _B, is any set of information sharing devices in the information sharing apparatus 2. First information sharing device U _A is the initiator, the second information sharing apparatus U _B described as responder.

As illustrated in FIG. 4, the first information sharing device U _A includes an ad hoc key generation unit U _A 1, an initial message generation unit U _A 2, a verification unit U _A 3, a message generation unit U _A 4, and an information generation unit U. _A 5 and a transmitter U _A 6 are provided. As illustrated in FIG. 4, the second information sharing device U _B includes an ad hoc key generation unit U _B 1, an initial message generation unit U _B 2, a verification unit U _B 3, a message generation unit U _B 4, and an information generation unit U. _B 5 is provided.

The ad hoc key generation unit U _A 1 of the first information sharing apparatus U _A performs processing of ESK _A ^PKI ← EpheGen (PP ^PKI ) (step S4). That is, the ad hoc key generation unit U _A 1 of the first information sharing device U _A generates the ad hoc key ESK _A ^PKI based on the ad hoc secret key generation algorithm of the PKI authentication key exchange method using the public parameter PP ^PKI . Generated adhoc key ESK _A ^PKI is kept secret to the first information sharing apparatus U _A.

The transmission unit U _A 6 of the first information sharing device U _A transmits Mes ₁ ^ID = (SPK _A ^PKI , cert _A ) to the second information sharing device U _B.

The ad hoc key generation unit U _B 1 of the second information sharing apparatus U _B performs the process of ESK _B ^PKI <-EpheGen (PP ^PKI ) (step S6). That is, the ad hoc key generation unit U _B 1 of the second information sharing device U _B generates an ad hoc key ESK _B ^PKI based on the ad hoc secret key generation algorithm EpheGen of the PKI authentication key exchange method using the public parameter PP ^PKI. . The generated ad hoc key ESK _B ^PKI is kept secret to the second information sharing device U in _B.

_{^{Mes 1 ID = (SPK A PKI}} , cert A) from the second information sharing apparatus U _A after receiving the verification unit U _B 3 of the second information sharing apparatus U _B ^{is, 1 ←? Ver (vk,} (ID A , SPK _A ^PKI ), cert _A ) (step S7). That is, the verification unit U _B 3 of the second information sharing apparatus U _B uses vk, (ID _A , SPK _A ^PKI ), cert _A based on the verification algorithm Ver of the electronic signature scheme (ID _A , SPK _A ^PKI ), cert _A is verified.

If the verification in step S7 is passed, the initial message generation unit U _B 2 of the second information sharing apparatus U _B uses Mes ₁ ^PKI ← Message ^pre (PP ^PKI , U _B , U _A , SSK _B ^PKI , ESK _B ^PKI , SPK _A ^PKI ) is performed (step S14). That is, the initial message generation unit U _B 2 of the second information sharing device U _B uses ^PPPKI , U _B , U _A , SSK _B ^PKI , ESK _B ^PKI , SPK _A ^PKI, and uses the PKI authentication key exchange method message. Generates the initial message Mes ₁ ^PKI = Message ^pre (PP ^PKI , U _B , U _A , SSK _B ^PKI , ESK _B ^PKI , SPK _A ^PKI ) based on the generation algorithm Message ^pre and first information together with SPK _B ^PKI , cert _B Transmit to shared device U _A. That is, Mes ₂ ^ID = (Mes ₁ ^PKI , SPK _B ^PKI , cert _B ) is transmitted to the first information sharing apparatus U _A.

  If the verification of step S7 is not passed, the subsequent processing is not performed.

After receiving Mes ₁ ^ID = (Mes ₁ ^PKI , SPK _B ^PKI , cert _B ), the verification unit U _B 3 of the first information sharing device U _A receives 1 ← ^? Ver (vk, (ID _B , SPK _B ^PKI ), cert _B ) (step S9). That is, the verification unit U _B 3 of the first information sharing device U _A uses vk, (ID _B , SPK _B ^PKI ), cert _B based on the verification algorithm Ver of the electronic signature scheme (ID _B , SPK _B ^PKI ), cert _B is verified.

  If the verification in step S9 is passed, the following processing is performed. If the verification of step S9 is not passed, the following processing is not performed.

In this example, it is assumed that Mes ₂ ^PKI cannot be generated before the first information sharing apparatus U _A receives Mes ₁ ^ID = (Mes ₁ ^PKI , SPK _B ^PKI , cert _B ). That is, the first information sharing device U _A can generate Mes ₂ ^PKI after receiving Mes ₁ ^ID = (Mes ₁ ^PKI , SPK _B ^PKI , cert _B ) from the second information sharing device U _B. . Whether the generation of Mes ₂ ^PKI is impossible before the first information sharing device U _A receives Mes ₁ ^ID = (Mes ₁ ^PKI , SPK _B ^PKI , cert _B ) depends on the base PKI authentication key exchange method To do.

In this case, the initial message generating unit U _B 2 of the first information sharing device U _A has Mes ₂ ^PKI ← Message (PP ^PKI , U _A , U _B , SSK _A ^PKI , ESK _A ^PKI , SPK _B ^PKI , Mes ₁ ^PKI ) Is performed (step S15). In other words, the initial message generation unit U _A 2 of the first information sharing device U _A uses _P ^PKI , U _A , U _B , SSK _A ^PKI , ESK _A ^PKI , SPK _B ^PKI , Mes ₁ ^PKI , Generate an initial message Mes ₂ ^PKI = Message (PP ^PKI , U _A , U _B , SSK _A ^PKI , ESK _A ^PKI , SPK _B ^PKI , Mes ₁ ^PKI ) based on the message generation algorithm Message of the key exchange method and Mes ₃ ^ID transmitting as the second information sharing apparatus U _B.

Thereafter, the first information sharing apparatus U _A and the second information sharing apparatus U _B transmit each other a message Mes _i ^PKI from i = 3 to i = n as described below. Note that the message generation unit U _B 4 of the second information sharing device U _B performs processing only when n is 3 or more, and does not perform processing when n is less than 3. Further, the message generation unit U _A 4 of the first information sharing device U _A performs processing only when n is 4 or more, and does not perform processing when n is less than 4.

That is, when n is 3 or more, the message generating unit U _A 4 of the second information sharing device U _B sets i as an odd number of 3 or more and n or less and sets Mes _i ^PKI ← Message (PP ^PKI , U _B , ^{_{U a, SSK B PKI, ESK}} B PKI, SPK a PKI, Mes 1 PKI, ..., the processing of Mes _i-1 ^PKI) (step S17). In other words, when n is 3 or more, the message generation unit U _B 4 of the second information sharing device U _B sets i as an odd number of 3 or more and n or less, and ^PPPKI , U _B , U _A , SSK _B ^PKI , ESK _B ^PKI , SPK _A ^PKI , Mes ₁ ^PKI , ..., Mes _i-1 ^PKI is used to create a message Mes _i ^PKI = Message (PP ^PKI , U _B , U _A , SSK _B ^PKI , ESK _B ^PKI , SPK _A ^PKI , Mes ₁ ^PKI ,..., Mes _i-1 ^PKI ) are generated and transmitted to the first information sharing apparatus U _A as Mes _{i + 1} ^ID .

In addition, when n is 4 or more, the message generator U _A 4 of the first information sharing device U _A sets i to be an even number of 4 or more and n or less, and sets Mes _i ^PKI ← Message (PP ^PKI , U _A , U _B , SSK _A ^PKI , ESK _A ^PKI , SPK _B ^PKI , Mes ₁ ^PKI ,..., Mesi _-1 ^PKI ) are performed (step S16). In other words, when n is 4 or more, the message generator U _A 4 of the first information sharing device U _A sets i to an even number of 4 or more and n or less, and ^PPPKI , U _A , U _B , SSK _A ^PKI , ESK _A ^PKI , SPK _B ^PKI , Mes ₁ ^PKI , ..., Mes _i-1 ^PKI is used to create a message Mes _i ^PKI = Message (PP ^PKI , U _A , U _B , SSK _A ^PKI , ESK _A ^PKI , SPK _B ^PKI , Mes ₁ ^PKI ,..., Mes _i-1 ^PKI ) are generated and transmitted as Mes _{i + 1} ^ID to the second information sharing apparatus U _B.

After that, the information generation unit U _A 5 of the first information sharing device U _A uses K ^PKI ← SesKey (PP ^PKI , U _A , U _B , SSK _A ^PKI , ESK _A ^PKI , SPK _B ^PKI , Mes ₁ ^PKI , ..., Mes _n ^PKI ) is performed (step S12). That is, the information generation unit U _A 5 of the first information sharing device U _A uses PP ^PKI , U _A , U _B , SSK _A ^PKI , ESK _A ^PKI , SPK _B ^PKI , Mes ₁ ^PKI , ..., Mes _n ^PKI Based on the session key generation algorithm of the PKI authentication key exchange method, information K ^PKI = SesKey (PP ^PKI , U _A , U _B , SSK _A ^PKI , ESK _A ^PKI , SPK _B ^PKI , Mes ₁ ^PKI ,…, Mes _n ^PKI )). When the information sharing target is an ID authentication key, the ID authentication key K ^ID = K ^PKI .

In addition, the information generation unit U _B 5 of the second information sharing device U _B has K ^PKI ← SesKey (PP ^PKI , U _B , U _A , SSK _B ^PKI , ESK _B ^PKI , SPK _A ^PKI , Mes ₁ ^PKI , ..., Mes _n ^PKI ) is performed (step S13). That is, the information generating unit U _B 5 of the second information sharing apparatus U _B uses ^{_{PP PKI, U B, U A}} , SSK B PKI, ESK B PKI, SPK A PKI, Mes 1 PKI, ..., the Mes _n ^PKI Based on the session key generation algorithm of the PKI authentication key exchange method, information K ^PKI = SesKey (PP ^PKI , U _B , U _A , SSK _B ^PKI , ESK _B ^PKI , SPK _A ^PKI , Mes ₁ ^PKI ,…, Mes _n ^PKI )). When the information sharing target is an ID authentication key, the ID authentication key K ^ID = K ^PKI .

  According to the second embodiment, the same effects as those of the first embodiment described above can be obtained.

<Modification of Second Embodiment>
In this example, it is assumed that Mes ₂ ^PKI can be generated before the first information sharing apparatus U _A receives Mes ₁ ^ID = (Mes ₁ ^PKI , SPK _B ^PKI , cert _B ). Whether the Mes ₂ ^PKI can be generated before the first information sharing device U _A receives Mes ₁ ^ID = (Mes ₁ ^PKI , SPK _B ^PKI , cert _B ) depends on the base PKI authentication key exchange method .

In this case, the first information sharing apparatus U _A performs the process of step S15 ′ described below instead of the process of step S15.

After passing the verification in step S9, the initial message generating unit U _B 2 of the first information sharing device U _A uses Mes ₂ ^PKI <-Message ^pre (PP ^PKI , U _A , U _B , SSK _A ^PKI , ESK _A ^PKI , SPK _B ^PKI ) is performed (step S15 '). In other words, the initial message generator U _A 2 of the first information sharing device U _A uses ^PPPKI , U _A , U _B , SSK _A ^PKI , ESK _A ^PKI , SPK _B ^PKI, and uses the PKI authentication key exchange method. initial message generation algorithm message ^pre an initial message Mes ₂ ^PKI = message ^pre based second information sharing as _{^{(PP PKI, U a, U}} B, SSK a PKI, ESK a PKI, SPK B PKI) generated Mes ₃ ^ID of Transmit to device U _B.

  Thereafter, the process of step S16 is performed.

  Effects similar to those of the first embodiment described above can also be obtained by the modification of the second embodiment.

[Modifications, etc.]
The processes described in the above apparatus and method are not only executed in time series according to the description order, but may also be executed in parallel or individually as required by the processing capability of the apparatus that executes the process.

  In addition, various processing functions in each device described in the above embodiments and modifications may be realized by a computer. In that case, the processing contents of the functions that each device should have are described by a program. Then, by executing this program on a computer, various processing functions in each of the above devices are realized on the computer.

  The program describing the processing contents can be recorded on a computer-readable recording medium. As the computer-readable recording medium, for example, any recording medium such as a magnetic recording device, an optical disk, a magneto-optical recording medium, and a semiconductor memory may be used.

  The program is distributed by selling, transferring, or lending a portable recording medium such as a DVD or CD-ROM in which the program is recorded. Further, the program may be distributed by storing the program in a storage device of the server computer and transferring the program from the server computer to another computer via a network.

  A computer that executes such a program first stores, for example, a program recorded on a portable recording medium or a program transferred from a server computer in its storage unit. When executing the process, this computer reads the program stored in its own storage unit and executes the process according to the read program. As another embodiment of this program, a computer may read a program directly from a portable recording medium and execute processing according to the program. Further, each time a program is transferred from the server computer to the computer, processing according to the received program may be executed sequentially. Also, the program is not transferred from the server computer to the computer, and the above-described processing is executed by a so-called ASP (Application Service Provider) type service that realizes the processing function only by the execution instruction and result acquisition. It is good. Note that the program includes information provided for processing by the electronic computer and equivalent to the program (data that is not a direct command to the computer but has a property that defines the processing of the computer).

  In addition, although each device is configured by executing a predetermined program on a computer, at least a part of these processing contents may be realized by hardware.

Claims (8)

In the information sharing system for sharing information between the first information sharing device and the second information sharing device,
The ad hoc secret key generation algorithm in a given PKI authentication key exchange method is EpheGen, the initial message generation algorithm in the PKI authentication key exchange method is Message ^post , the message generation algorithm in the PKI authentication key exchange method is Message, and the PKI authentication The session key generation algorithm in the key exchange method is SesKey, the public parameter in the PKI authentication key exchange method is PP ^PKI , the long-term secret key of the first information sharing device in the PKI authentication key exchange method is SSK _A ^PKI , and the above The long-term public key of the first information sharing device in the PKI authentication key exchange method is SPK _A ^PKI , the long-term secret key of the second information sharing device in the PKI authentication key exchange method is SSK _B ^PKI , and the PKI authentication key exchange SPK _B ^PKI is the long-term public key of the second information sharing device in the system,
The signature verification algorithm in a predetermined digital signature scheme is Ver, the signature generation algorithm in the digital signature scheme is Sign,
The bit string representing the first information sharing apparatus is U _A , the bit string representing the information related to the first information sharing apparatus is ID _A, and the signature of the first information sharing apparatus is cert _A = Sign (sk, (ID _A , SPK _A ^PKI )), the bit string representing the second information sharing apparatus as U _B , the bit string representing the information related to the second information sharing apparatus as ID _B, and the signature of the second information sharing apparatus as cert _B = Sign (sk, (ID _B , SPK _B ^PKI ))
The first information sharing device includes an ad hoc secret key generation unit that generates an ad hoc secret key ESK _A ^PKI = EpheGen (PP ^PKI ), and an initial message Mes ₁ ^PKI = Message ^post (PP ^PKI , U _A , SSK _A ^PKI , ESK an initial message generator for transmitting SPK _a ^PKI generates _a ^PKI), with cert _a to the second information sharing apparatus, Ver based on _{(vk, (ID B, SPK} B PKI), cert B) (ID B , SPK _B ^PKI ), cert _B , and when n is 3 or more, i is an odd number from 3 to n, and the message Mes _i ^PKI = Message (PP ^PKI , U _A , U _B , SSK _A ^PKI , ESK _A ^PKI , SPK _B ^PKI , Mes ₁ ^PKI ,..., Mes _i-1 ^PKI ) and send it to the second information sharing device, and information K ^PKI = SesKey (PP ^PKI , U _A , U _B , SSK _A ^PKI , ESK _A ^PKI , SPK _B ^PKI , Mes ₁ ^PKI , ..., Mes _n ^PKI ),
The second information sharing apparatus is based on an ad hoc secret key generation unit that generates an ad hoc secret key ESK _B ^PKI = EpheGen (PP ^PKI ), and Ver (vk, (ID _A , SPK _A ^PKI ), cert _A ) ( ID _A , SPK _A ^PKI ), cert _A verifier and initial message Mes ₂ ^PKI = Message (PP ^PKI , U _B , U _A , SSK _B ^PKI , ESK _B ^PKI , SPK _B ^PKI , Mes ₁ ^PKI ) And sends it to the first information sharing apparatus together with SPK _B ^PKI and cert _B , and when n is 4 or more, i is an even number from 4 to n, and the message Mes _i ^{PKI _{= message (PP PKI, U B}} , U a, SSK B PKI, ESK B PKI, SPK a PKI, Mes 1 PKI, ..., Mes i-1 PKI) message generation generating and transmitting to the first information sharing device And an information generation unit that generates information K ^PKI = SesKey (PP ^PKI , U _B , U _A , SSK _B ^PKI , ESK _B ^PKI , SPK _A ^PKI , Mes ₁ ^PKI , ..., Mes _n ^PKI ) ,
Information sharing system. The information sharing system according to claim 1,
The initial message generator of the second information sharing device generates an initial message Mes ₂ ^PKI = Message ^post (PP ^PKI , U _B , SSK _B ^PKI , ESK _B ^PKI ) and transmits it to the first information sharing device,
Information sharing system. In the information sharing system for sharing information between the first information sharing device and the second information sharing device,
The ad hoc secret key generation algorithm in a given PKI authentication key exchange method is EpheGen, the initial message generation algorithm in the PKI authentication key exchange method is Message ^post , the message generation algorithm in the PKI authentication key exchange method is Message, and the PKI authentication The session key generation algorithm in the key exchange method is SesKey, the public parameter in the PKI authentication key exchange method is PP ^PKI , the long-term secret key of the first information sharing device in the PKI authentication key exchange method is SSK _A ^PKI , and the above The long-term public key of the first information sharing device in the PKI authentication key exchange method is SPK _A ^PKI , the long-term secret key of the second information sharing device in the PKI authentication key exchange method is SSK _B ^PKI , and the PKI authentication key exchange SPK _B ^PKI is the long-term public key of the second information sharing device in the system,
The signature verification algorithm in a predetermined digital signature scheme is Ver, the signature generation algorithm in the digital signature scheme is Sign,
The bit string representing the first information sharing apparatus is U _A , the bit string representing the information related to the first information sharing apparatus is ID _A, and the signature of the first information sharing apparatus is cert _A = Sign (sk, (ID _A , SPK _A ^PKI )), the bit string representing the second information sharing apparatus as U _B , the bit string representing the information related to the second information sharing apparatus as ID _B, and the signature of the second information sharing apparatus as cert _B = Sign (sk, (ID _B , SPK _B ^PKI ))
The first information sharing device includes an ad hoc secret key generation unit that generates an ad hoc secret key ESK _A ^PKI = EpheGen (PP ^PKI ), and a transmission unit that transmits (SPK _A ^PKI , cert _A ) to the second information sharing device. _{If, Ver (vk, (ID B} , SPK B PKI), cert B) based on ^{_{(ID B, SPK B PKI)}} , and a verification unit for verifying cert _B, initial message Mes ₂ ^PKI = message (PP ^PKI , U _A , U _B , SSK _A ^PKI , ESK _A ^PKI , SPK _B ^PKI , Mes ₁ ^PKI ) and send it to the second information sharing device, and when n is 4 or more, i is an even number between 4 and n, and the message Mes _i ^PKI = Message (PP ^PKI , U _A , U _B , SSK _A ^PKI , ESK _A ^PKI , SPK _B ^PKI , Mes ₁ ^PKI ,…, Mes _i-1 ^PKI ) And sends it to the second information sharing device, and information K ^PKI = SesKey (PP ^PKI , U _A , U _B , SSK _A ^PKI , ESK _A ^PKI , SPK _B ^PKI , Mes ₁ ^PKI ,... , Mes _n ^PKI ), and an information generation unit,
The second information sharing apparatus is based on an ad hoc secret key generation unit that generates an ad hoc secret key ESK _B ^PKI = EpheGen (PP ^PKI ), and Ver (vk, (ID _A , SPK _A ^PKI ), cert _A ) ( ID _A , SPK _A ^PKI ), cert _A verifier and initial message Mes ₁ ^PKI = Message ^pre (PP ^PKI , U _B , U _A , SSK _B ^PKI , ESK _B ^PKI , SPK _A ^PKI ) are generated SPK _B ^PKI , cert _B together with the initial message generator to be transmitted to the first information sharing device, and when n is 3 or more, i is an odd number of 3 to n and the message Mes _i ^PKI = Message ( PP ^PKI , U _B , U _A , SSK _B ^PKI , ESK _B ^PKI , SPK _A ^PKI , Mes ₁ ^PKI , ..., Mes _i-1 ^PKI ) and a message generator for transmitting to the first information sharing device, An information generator that generates information K ^PKI = SesKey (PP ^PKI , U _B , U _A , SSK _B ^PKI , ESK _B ^PKI , SPK _A ^PKI , Mes ₁ ^PKI , ..., Mes _n ^PKI ),
Information sharing system. The information sharing system according to claim 3,
The initial message generator of the first information sharing device generates an initial message Mes ₂ ^PKI = Message ^pre (PP ^PKI , U _A , U _B , SSK _A ^PKI , ESK _A ^PKI , SPK _B ^PKI ) and generates the second information Send to shared device,
Information sharing system. In the information sharing method for sharing information between the first information sharing device and the second information sharing device,
The ad hoc secret key generation algorithm in a given PKI authentication key exchange method is EpheGen, the initial message generation algorithm in the PKI authentication key exchange method is Message ^post , the message generation algorithm in the PKI authentication key exchange method is Message, and the PKI authentication The session key generation algorithm in the key exchange method is SesKey, the public parameter in the PKI authentication key exchange method is PP ^PKI , the long-term secret key of the first information sharing device in the PKI authentication key exchange method is SSK _A ^PKI , and the above The long-term public key of the first information sharing device in the PKI authentication key exchange method is SPK _A ^PKI , the long-term secret key of the second information sharing device in the PKI authentication key exchange method is SSK _B ^PKI , and the PKI authentication key exchange SPK _B ^PKI is the long-term public key of the second information sharing device in the system,
The signature verification algorithm in a predetermined digital signature scheme is Ver, the signature generation algorithm in the digital signature scheme is Sign,
The bit string representing the first information sharing apparatus is U _A , the bit string representing the information related to the first information sharing apparatus is ID _A, and the signature of the first information sharing apparatus is cert _A = Sign (sk, (ID _A , SPK _A ^PKI )), the bit string representing the second information sharing apparatus as U _B , the bit string representing the information related to the second information sharing apparatus as ID _B, and the signature of the second information sharing apparatus as cert _B = Sign (sk, (ID _B , SPK _B ^PKI ))
The ad hoc secret key generation unit of the first information sharing apparatus generates an ad hoc secret key ESK _A ^PKI = EpheGen (PP ^PKI );
The initial message generator of the first information sharing device generates an initial message Mes ₁ ^PKI = Message ^post (PP ^PKI , U _A , SSK _A ^PKI , ESK _A ^PKI ) and the second information together with SPK _A ^PKI , cert _A An initial message generation step to be sent to the shared device;
Verification unit of the second information sharing apparatus, Ver a verification step of verifying the _{(vk, (ID A, SPK} A PKI), cert A) based on ^{_{(ID A, SPK A PKI)}} , cert A,
The initial message generator of the second information sharing device generates an initial message Mes ₂ ^PKI = Message (PP ^PKI , U _B , U _A , SSK _B ^PKI , ESK _B ^PKI , SPK _B ^PKI , Mes ₁ ^PKI ) An initial message generation step to be sent to the first information sharing device together with _B ^PKI and cert _B ;
Verification unit of the first information sharing apparatus, Ver a verification step of verifying the _{(vk, (ID B, SPK} B PKI), cert B) based on ^{_{(ID B, SPK B PKI)}} , cert B,
When the message generating unit of the first information sharing apparatus is n is 3 or more, the message Mes _i ^PKI = Message (PP ^PKI , U _A , U _B , SSK _A ^PKI , ESK _A ^PKI , SPK _B ^PKI , Mes ₁ ^PKI ,..., Mes _i-1 ^PKI ) and sending it to the second information sharing device;
Information generating unit of the first information sharing apparatus, information ^{K PKI = SesKey (PP PKI,} U A, U B, SSK A PKI, ESK A PKI, SPK B PKI, Mes 1 PKI, ..., Mes n PKI) to An information generation step to generate;
The ad hoc secret key generation unit of the second information sharing apparatus generates an ad hoc secret key ESK _B ^PKI = EpheGen (PP ^PKI );
When the message generating unit of the second information sharing apparatus is n is 4 or more, the message Mes _i ^PKI = Message (PP ^PKI , U _B , U _A , SSK _B ^PKI , ESK _B ^PKI , SPK _A ^PKI , Mes ₁ ^PKI , ..., Mes _i-1 ^PKI ) and sending it to the first information sharing device,
The information generation unit of the second information sharing apparatus sets information K ^PKI = SesKey (PP ^PKI , U _B , U _A , SSK _B ^PKI , ESK _B ^PKI , SPK _A ^PKI , Mes ₁ ^PKI , ..., Mes _n ^PKI ) An information generation step to generate;
Information sharing method. In the information sharing method for sharing information between the first information sharing device and the second information sharing device,
The ad hoc secret key generation algorithm in a given PKI authentication key exchange method is EpheGen, the initial message generation algorithm in the PKI authentication key exchange method is Message ^post , the message generation algorithm in the PKI authentication key exchange method is Message, and the PKI authentication The session key generation algorithm in the key exchange method is SesKey, the public parameter in the PKI authentication key exchange method is PP ^PKI , the long-term secret key of the first information sharing device in the PKI authentication key exchange method is SSK _A ^PKI , and the above The long-term public key of the first information sharing device in the PKI authentication key exchange method is SPK _A ^PKI , the long-term secret key of the second information sharing device in the PKI authentication key exchange method is SSK _B ^PKI , and the PKI authentication key exchange SPK _B ^PKI is the long-term public key of the second information sharing device in the system,
The signature verification algorithm in a predetermined digital signature scheme is Ver, the signature generation algorithm in the digital signature scheme is Sign,
The bit string representing the first information sharing apparatus is U _A , the bit string representing the information related to the first information sharing apparatus is ID _A, and the signature of the first information sharing apparatus is cert _A = Sign (sk, (ID _A , SPK _A ^PKI )), the bit string representing the second information sharing apparatus as U _B , the bit string representing the information related to the second information sharing apparatus as ID _B, and the signature of the second information sharing apparatus as cert _B = Sign (sk, (ID _B , SPK _B ^PKI ))
The ad hoc secret key generation unit of the first information sharing apparatus generates an ad hoc secret key ESK _A ^PKI = EpheGen (PP ^PKI );
_A transmitting step in which the transmitting unit of the first information sharing device transmits (SPK _A ^PKI , cert _A ) to the second information sharing device;
The ad hoc secret key generation unit of the second information sharing apparatus generates an ad hoc secret key ESK _B ^PKI = EpheGen (PP ^PKI );
Verification unit of the second information sharing apparatus, Ver a verification step of verifying the _{(vk, (ID A, SPK} A PKI), cert A) based on ^{_{(ID A, SPK A PKI)}} , cert A,
The initial message generator of the second information sharing device generates an initial message Mes ₁ ^PKI = Message ^pre (PP ^PKI , U _B , U _A , SSK _B ^PKI , ESK _B ^PKI , SPK _A ^PKI ), and SPK _B ^PKI , an initial message generation step to be sent to the first information sharing device together with cert _B ;
Verification unit of the first information sharing apparatus, Ver a verification step of verifying the _{(vk, (ID B, SPK} B PKI), cert B) based on ^{_{(ID B, SPK B PKI)}} , cert B,
The initial message generator of the first information sharing device generates an initial message Mes ₂ ^PKI = Message (PP ^PKI , U _A , U _B , SSK _A ^PKI , ESK _A ^PKI , SPK _B ^PKI , Mes ₁ ^PKI ) An initial message generation step to be transmitted to the second information sharing device;
When the message generation unit of the second information sharing apparatus is n is 3 or more, the message Mes _i ^PKI = Message (PP ^PKI , U _B , U _A , SSK _B ^PKI , ESK _B ^PKI , SPK _A ^PKI , Mes ₁ ^PKI , ..., Mes _i-1 ^PKI ) and sending it to the first information sharing device,
When the message generation unit of the first information sharing apparatus is n is 4 or more, the message Mes _i ^PKI = Message (PP ^PKI , U _A , U _B , SSK _A ^PKI , ESK _A ^PKI , SPK _B ^PKI , Mes ₁ ^PKI ,..., Mes _i-1 ^PKI ) and sending it to the second information sharing device;
Information generating unit of the first information sharing apparatus, information ^{K PKI = SesKey (PP PKI,} U A, U B, SSK A PKI, ESK A PKI, SPK B PKI, Mes 1 PKI, ..., Mes n PKI) to An information generation step to generate;
The information generation unit of the second information sharing apparatus sets information K ^PKI = SesKey (PP ^PKI , U _B , U _A , SSK _B ^PKI , ESK _B ^PKI , SPK _A ^PKI , Mes ₁ ^PKI , ..., Mes _n ^PKI ) An information generation step to generate;
Information sharing method.   The information sharing apparatus which is said 1st information sharing apparatus or said 2nd information sharing apparatus of the information sharing system of Claim 1 or 3.   The program for functioning a computer as each part of the information sharing apparatus of Claim 7.

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