阅读说明：本技术 秘密计算装置、秘密计算方法、程序、以及记录介质 (Secret calculation device, secret calculation method, program, and recording medium ) 是由 五十岚大 于 2019-02-26 设计创作，主要内容包括：秘密计算装置利用x<Sub>i</Sub>(这里i＝0,1,2)的秘密分散值{x<Sub>i</Sub>}来计算秘密分散值{s<Sub>i</Sub>}＝{x<Sub>i</Sub>}-1/2,通过利用了秘密分散值{s<Sub>i</Sub>}的秘密计算来计算秘密分散值{y}＝{4s<Sub>0</Sub>s<Sub>1</Sub>s<Sub>2</Sub>}+1/2并进行输出,并通过利用了随机数r的秘密分散值{r}以及秘密分散值{s<Sub>i</Sub>}的秘密计算来计算秘密分散值{y<Sub>r</Sub>}＝{4rs<Sub>0</Sub>s<Sub>1</Sub>s<Sub>2</Sub>}+{r}/2并进行输出。(Secret computing device using x i Secret variance value { x of (where i is 0,1,2) } i Calculating a secret variance value s i }＝{x i -1/2, by using secret scatter values s i Calculating a secret variance value y 4s by secret calculation 0 s 1 s 2 +1/2, and outputs the result by using a secret variance value { r } and a secret variance value { s } of a random number r i Calculating a secret variance value y by secret calculation r }＝{4rs 0 s 1 s 2 And { r }/2 and output.)

1. A secret computing apparatus having:

a subtraction part using x_iSecret scatter value x for e 0,1_iCalculating a secret variance value s_i}＝{x_i}-1/2；

A first exclusive OR operation unit using the secret variance value s_iSecret of }Secret variance value { y } - {4s } is calculated by secret calculation₀s₁s₂} +1/2 and output; and

a second exclusive OR operation unit for calculating a secret variance value { r } and a secret variance value { s } using a random number r_iCalculating a secret variance value y by secret calculation_r}＝{4rs₀s₁s₂} + { r }/2 and output,

wherein i is 0,1, 2.

2. The covert computing device of claim 1,

j is 0,1,2, the secret computing device is three secret computing devices P₀、P₁、P₂The secret calculation device P of any one of_jFor said secret computing means P_jOf { x } is a secret dispersion value_iIs { x }_i}_j，

The secret calculation device further includes a random number acquisition unit configured to acquire a random number w ∈ {0,1} satisfying w ═ w ∈ [, {0,1}, where₀+w₁+w₂mod2 secret scatter value w^B _j＝(w_j,w_{(j+1)mod 3})，

{x_j}_j＝(w_j,0),{x_{(j+1)mod 3}}_j＝(0,w_{(j+1)mod 3}),{x_{(j+2)mod 3}}_j＝(0,0)。

3. The covert computing device of claim 2,

the subtraction part subtracts w_jAnd w_{(j+1)mod 3}Computing the secret dispersion value s as an element of a finite field_i}，

The secret variance value y is a secret variance value obtained in a case where the random number w is secret-spread over the finite field.

4. The secret computing device of any one of claim 1 to claim 3,

the first exclusive OR operation unit passesUsing secret scatter values 4s₀And secret scatter value s₁Secret calculation to obtain a secret variance value {4s }₀s₁And by using said secret variance value {4s }₀s₁And secret scatter value s₂Secret calculation to obtain a secret variance value {4s }₀s₁s₂}，

The second exclusive-or operation unit uses a secret variance value {4r } and a secret variance value { s }₀Secret calculation to obtain a secret variance value {4rs }₀And by using the secret variance value {4rs }₀And secret scatter value s₁Secret calculation to obtain a secret variance value {4rs }₀s₁And by using the secret variance value {4rs }₀s₁And secret scatter value s₂Secret calculation to obtain a secret variance value {4rs }₀s₁s₂}。

5. A secret calculation method of a secret calculation apparatus includes,

a subtraction step in which the subtraction part uses x_iSecret scatter value x for e 0,1_iCalculating a secret variance value s_i}＝{x_i}-1/2；

A first exclusive-or operation step in which the first exclusive-or operation unit uses the secret variance value { s }_iCalculating a secret variance value y 4s by secret calculation₀s₁s₂} +1/2 and output; and

a second exclusive-OR operation step in which the second exclusive-OR operation unit uses a secret variance value { r } using a random number r and the secret variance value { s }_iCalculating a secret variance value y by secret calculation_r}＝{4rs₀s₁s₂} + { r }/2 and output,

wherein i is 0,1, 2.

6. The secret calculation method of claim 5,

j is 0,1,2, the secret computing device is three secret computing devices P₀、P₁、P₂The secret calculation device P of any one of_jFor said secret computing means P_jOf { x } is a secret dispersion value_iIs { x }_i}_j，

The secret calculation method further has: a random number acquisition step in which a random number acquisition unit acquires a random number w ∈ {0,1} satisfying w ═ w ∈₀+w₁+w₂Secret scatter value of mod2 w^B _j＝(w_j,w_{(j+1)mod 3})，

{x_j}_j＝(w_j,0),{x_{(j+1)mod 3}}_j＝(0,w_{(j+1)mod 3}),{x_{(j+2)mod 3}}_j＝(0,0)。

7. A program for causing a computer to function as the secret calculation apparatus according to any one of claim 1 to claim 4.

8. A computer-readable recording medium storing a program for causing a computer to function as the secret calculation apparatus according to any one of claims 1 to 4.

Technical Field

The present invention relates to a secret computing technique, and more particularly to a secret computing technique capable of detecting erroneous computation.

Background

α₀E {0,1} and α₁An exclusive or α ∈ {0,1} of ∈ {0,1} may be obtained by α ═ α₀+α₁-2α₀α₁And (4) calculating.By using this, α₀And alpha₁And alpha₂E {0,1}, exclusive or β ═ α₀(XOR)α₁(XOR)α₂E {0,1} can be calculated by the following equation.

α＝α₀+α₁-2α₀α₁(1)

β＝α+α₂-2αα₂(2)

There is known a secret calculation technique for performing addition, subtraction, and multiplication while concealing a value (see, for example, non-patent document 1). For example, if the respective uses are concealed by₀、α₁、α₂Secret variance value of [ alpha ]₀}、{α₁}、{α₂Where the expressions (1) and (2) are calculated by secret calculation, α can be obtained₀、α₁、α₂Is equal to the secret dispersion value { beta } of xor beta. By performing such secret calculation with a plurality of secret calculation apparatuses and collecting a predetermined number of results obtained with the respective secret calculation apparatuses, it is possible to recover the exclusive or β.

Disclosure of Invention

Problems to be solved by the invention

Since the secret calculation is performed using the secret variance value, it is difficult to detect that an erroneous calculation has been performed. In particular, it is difficult to detect that multiplication by secret calculation is performed erroneously. Therefore, the following method is considered: in addition to secret calculation of an original calculation formula, secret calculation is performed by multiplying the calculation formula by a random number, and an erroneous calculation is detected using the results.

However, except for the case of multiplying by a certain multiple, when multiplication is performed in secret calculation, communication between secret calculation devices is necessary. Thus, it is possible to provideThe smaller the number of multiplications other than the multiplication by a predetermined factor, the smaller the traffic volume. When secret calculation is performed on the values obtained by multiplying each of equations (1) and (2) by a random number r, multiplication other than multiplication by a constant multiple needs to be performed three times (r α) for calculation of equation (1)₀,rα₁,2rα₀α₁) For the calculation of expression (2), multiplication by a constant multiple is required to be performed once (r α)₂). Therefore, communication for four multiplications is required in the secret calculation.

In the present invention, the amount of communication in the case of performing a secret calculation of exclusive-OR of three values is reduced to enable detection of erroneous calculation.

Means for solving the problems

In the present invention, i is 0,1,2, and x is used_iSecret variance value of { x }_iCalculating a secret variance value s_i}＝{x_i-1/2, and by using a secret scatter value s_iCalculating a secret variance value y 4s by secret calculation₀s₁s₂+1/2, and outputs the result by using a secret variance value { r } and a secret variance value { s } of a random number r_iCalculating a secret variance value y by secret calculation_r}＝{4rs₀s₁s₂And { r }/2 and output.

Effects of the invention

This reduces the amount of communication in the case of performing exclusive-or secret calculation of three values, thereby enabling erroneous calculation to be detected.

Drawings

Fig. 1 is a block diagram illustrating the structure of a crypto-computing system of an embodiment.

Fig. 2 is a block diagram illustrating a configuration of a secret calculation apparatus of the embodiment.

Fig. 3 is a flowchart for explaining a secret calculation method according to the embodiment.

Detailed Description

Hereinafter, embodiments of the present invention will be described.

[ summary ]

First, an outline of the embodiment will be describedA preparation method comprises the following steps. In the secret calculation device according to the embodiment, first, the subtraction unit uses x_iSecret scatter value x for e 0,1_iCalculating a secret variance value s_i}＝{x_i-1/2 and output. Here, i is 0,1, 2. For example, the subtraction unit calculates the secret variance value s_i}＝{x_i-1/2mod q. Here, q is a positive integer. For example, q is an integer of 2 or more or 3 or more (e.g., prime number). Then, the first exclusive-OR operation unit uses the secret variance value s_iThe secret calculation of the secret scatter value y is calculated and output.

{y}＝{4s₀s₁s₂}+1/2 (3)

For example, the first exclusive-OR operation unit uses the secret variance value {4s }₀And secret scatter value s₁Secret calculation to obtain a secret variance value {4s }₀s₁And by using a secret scatter value {4s }₀s₁And secret scatter value s₂Secret calculation to obtain a secret variance value {4s }₀s₁s₂}. Then, the second exclusive OR unit passes the secret variance { r } and the secret variance { s } using the random number r_iCalculating a secret variance value y by secret calculation_rAnd output is performed.

{y_r}＝{4rs₀s₁s₂}+{r}/2 (4)

For example, the second exclusive-OR operation unit uses the secret variance {4r } and the secret variance { s }₀Secret calculation to obtain a secret variance value {4rs }₀And by using the secret scatter value {4rs }₀And secret scatter value s₁Secret calculation to obtain a secret variance value {4rs }₀s₁And by using the secret scatter value {4rs }₀s₁And secret scatter value s₂Secret calculation to obtain a secret variance value {4rs }₀s₁s₂}. The secret calculation method is not limited, and can be, for example, the method described in non-patent document 1. As described above, s_i、y、y_rIs an element that defines a set of four arithmetic operations. Only need to decideFour arithmetic operations are defined, and any set is possible. An example of such a set is a finite field F of order p_p. p is an integer of 2 or more. An example of p is an integer of 3 or more, for example, p is a prime number of 3 or more. Will s_i∈F_p，y∈F_p，y_r∈F_pThe respective secret scatter values are denoted as s_i}∈{F_p}，{y}∈{F_p}，{y_r}∈{F_p}。

Here, y is 4s₀s₁s₂+1/2 and s_i＝x_i1/2, this y becomes x₀、x₁And x₂X is exclusive or₀(XOR)x₁(XOR)x₂. The truth table is shown below.

[ TABLE 1 ]

x0	x1	x2	y
				0	0	0	0
0	1	0	1
				0	0	1	1
0	1	1	0
				1	0	0	1
1	1	0	0
				1	0	1	0
1	1	1	1

I.e. by y-4 s₀s₁s₂+1/2, in the above formula (1) or (2), can be obtained by adding α ═ x₀+x₁-2x₀x₁、β＝y、α₀＝x₀、α₁＝x₁、α₂＝x₂The same result. Here, the number of multiplications, other than multiplying by a certain multiple, required to calculate the secret variance value { y } according to equations (1) and (2) is two ({2 ×)₀x₁},{2xx₂} for calculating { y) according to the equations (1) (2)_rMultiplication by a factor other than that required forThe number of multiplications is five ({ rx)₀},{rx₁},{2rx₀x₁},{rx₂},{2rxx₂}). In contrast, the number of multiplications other than the constant factor required for calculating the secret variance value { y } using equation (3) is twice ({4 s)₀s₁},{4s₀s₁s₂}) using equation (4) to calculate { y_rThe number of multiplications required for this time, other than a certain multiple, is three ({4 rs)₀},{4rs₀s₁},{4rs₀s₁s₂}). Therefore, by performing the secret calculation using equations (3) and (4), the number of multiplications other than the multiplication by a certain multiple can be reduced twice as compared with the case of performing the secret calculation using equations (1) and (2). When multiplication by a factor other than a certain number is performed by secret calculation, communication between secret calculation devices is necessary. Therefore, the present embodiment, which reduces the number of multiplications other than the multiplication by a fixed number, can reduce the amount of communication compared to the case of performing secret calculation according to equations (1) and (2).

x₀,x₁,x₂It is unimportant what property e 0,1 is. For example, x₀,x₁,x₂E 0,1 may be a random number, or may be the result of other operations, or may be an input value. Secret scatter value pairs y_rIt is also not important for what purpose. By using x only through secret calculation₀And x₁And x₂X is exclusive or₀(XOR)x₁(XOR)x₂And a secret variance value { y } used to detect that the secret variance value { y } is calculated incorrectly_rThe method of the embodiment can be applied to any application.

For example, j may be 0,1,2, and the secret calculation device may be three secret calculation devices P described above₀、P₁、P₂Any one of the secret calculation devices P_jFor secret computing means P_jSecret variance value of { x }_iIs { x }_i}_jSecret computing device P_jThe random number obtaining unit generates a random number w ═ w for a random number w ∈ {0,1}, where w ═ w is satisfied₀+w₁+w₂Secret scatter value of mod2 w^B _j＝(w_j,w_{(j+1)mod 3}) The subtraction part is used as { x_i{ x } of (here, i ═ 0,1,2)_j}_j＝(w_j,0),{x_{(j+1)mod 3}}_j＝(0,w_{(j+1)mod 3}),{x_{(j+2)mod 3}}_jWhen the secret variance value is equal to (0,0), a secret variance value s is calculated_i}＝{x_i-1/2, the first exclusive-or operation unit uses the secret variance value s_iCalculating a secret variance value (y) of 4s₀s₁s₂+1/2, the second XOR operation unit uses the secret variance value { r } and the secret variance value { s }_iCalculating secret variance value y_r}＝{4rs₀s₁s₂} + { r }/2. In addition, if j is 0,1,2, { x is listed_j}_j,{x_{(j+1)mod 3}}_j,{x_{(j+2)mod 3}}_jThen, the following is shown.

{x₀}₀＝(w₀,0),{x₀}₁＝(0,0),{x₀}₂＝(0,w₀)

{x₁}₀＝(0,w₁),{x₁}₁＝(w₁,0),{x₁}₂＝(0,0)

{x₂}₀＝(0,0),{x₂}₁＝(0,w₂),{x₂}₂＝(w₂,0)

w₀,w₁,w₂E {0,1} is a secret sharing value sub-share (subshare) obtained by secret sharing a random number w at mod (2) according to a secret sharing scheme (for example, see non-patent document 1) which is an addition of a (2,3) threshold secret sharing scheme. The (k, n) threshold secret sharing scheme (also referred to as "k-of-n threshold secret sharing scheme") is a secret sharing scheme in which plaintext can be recovered by using k secret sharing values different from each other among n secret sharing values, but plaintext information cannot be obtained at all from less than k secret sharing values different from each other. Here, k is not more than n, and k and n are integers of 2 or more. RandomNumber w for each secret calculation device P_j(where j is 0,1,2) is concealed, but passed through each secret computing device P_jSelf-generated random number w_jE.g. 0,1, and sent to each secret computing device P_{(j-1)mod 3}Each secret computing device P_jCan obtain the sub-share w_jAnd w_{(j+1) mod 3}. Calculating the devices P from the secrets_jGenerated random number w₀、w₁、w₂Determining a random number w ═ w₀+w₁+w₂mod 2。

At { x_j}_j＝(w_j,0),{x_{(j+1)mod 3}}_j＝(0,w_{(j+1)mod 3}),{x_{(j+2)mod 3}}_j＝(0,0)，s_i∈F_p,y∈F_p,y_r∈F_pIn the case of (1), the subtracting section subtracts w_jE {0,1} and w_{(j+1)mod 3}E {0,1} is regarded as a finite field F_pTo calculate a secret scatter value s_i}. For example, in the finite field F_pIs that of

In the case of (1), 0 is regarded as a finite field F_pOf (2) element(s)Considering 1 as a finite field F_pOf (2) element(s)Thus in the limited domain F_pUpper calculated secret variance value s_i}. Y becomes w₀+w₁+w₂mod2 in finite field F_pThe secret variance value w obtained in the case of the above secret variance is set to be { F } - [_p}. That is, the process of the secret calculation apparatus is as follows: secret distribution method based on addition of (2,3) threshold secret distribution method, secret division method at mod2 for random number wThe secret variance value { w } obtained^B _jA finite field F converted to the random number w_pThe secret dispersion value y e F_pAnd secret scatter value y_r}∈{F_pPair of (secret random number pair).

By combining { r }, { y }, and { y } as described above_rThe checksum is used to verify that y is calculated correctly. For example, the use of r, y, and y is also possible_rSecret calculation of y, generating a secret indicating whether y is satisfied_rSecret variance value of ry information (e.g., { y }_rRy } (see, for example, international publication No. WO2014/112548 (reference 1)), and the verification device may be selected from r, y, and y_rR, y recovery_rAnd then verifies whether y is satisfied_rRy. In the latter case, the authentication device receives the secret variance value { y } ═ 4s₀s₁s₂} +1/2 and a secret scatter value y_r}＝{4rs₀s₁s₂The input of { r }/2 and the secret scatter value { r }, the recovery of the secret scatter value { y } and the secret scatter value { y }_rAnd a secret variance value r, thereby obtaining y-4 s₀s₁s₂+1/2 and y_r＝4rs₀s₁s₂+ r/2 and r, using r and y to obtain y_r' ry at y_r’＝y_rIn the case of (2), the subject matter of successful verification is output, and at y_r’≠y_rIn the case of (2), the content of the verification failure is output.

In general, the secret variance values { y }, and { y }_rAre mutually based on the same secret dispersion (e.g., additive secret dispersion). However, since the secret variance value can be converted by a known method (see references 2 to 6, etc.), the secret variance values { y } and { y } are used_rThe { r } may not all be dispersed according to the same secret as each other. Further, { y } obtained as described above_rBut can also be converted into secret scatter values according to other ways.

Reference 2, Ronald Cramer, Ivan Damgard, and Yuval Ishai, "Share conversion, pseudorandom secret-sharing and applications to secure distributed conversion," Theory of Cryptgoraphy (2005):342-

Reference 3 Japanese laid-open patent publication No. 2016-173533

Reference 4 Japanese patent laid-open publication No. 2016-173532

Reference 5 Japanese patent laid-open publication No. 2016-

Reference 6 Japanese laid-open patent publication No. 2016-156853

[ first embodiment ]

The first embodiment is explained in detail with reference to the drawings.

< Structure >

As shown in fig. 1, the cryptographic secret calculation apparatus 1 according to the embodiment includes N cryptographic secret calculation apparatuses 11-0, …, and 11- (N-1) and a verification apparatus 12, and these apparatuses are configured to be able to communicate with each other via a network. However, N is an integer of 2 or more. For example, N is an integer of 3 or more, and N ═ 3 is an example. As shown in fig. 2, the secret calculation device 11-j (here, j is 0, …, N-1) includes an input unit 111-j, an output unit 112-j, a storage unit 113-j, a control unit 114-j, a subtraction unit 116-j, and exclusive or calculation units 117-j and 118-j. The secret calculation apparatus 11-j executes each process under the control of the control section 114-j. The data obtained by each unit of the secret calculation device 11-j is stored in the storage unit 113-j one by one, and is read as necessary and used in other processes.

< secret calculation processing >

The secret calculation process performed by the secret calculation device 11-j will be described with reference to fig. 3. For details of the secret sharing method and the secret calculation method, for example, refer to non-patent document 1 and the like.

Finite field F_pIs equal to F_pIs given by the secret scatter value r e F_pIs input to the input section 111-j of each secret calculation device 11-j (here, j is 0, …, N-1). In addition, the secret variance values of the respective values γ corresponding to the respective secret calculation devices 11-j are different from each other, but for the sake of simplicity of description, the secret variance value of the value γ is singly labeled as { γ } unless otherwise specified. However, when the secret variance values corresponding to the secret computing devices 11-j are designated, the secret variance values will correspond to the secret computing devicesThe secret scatter value corresponding to the secret computing device 11-j is marked with { gamma }_j. In this embodiment, the secret distribution method based on addition is applied to the finite field F_pThe value of secret distribution of the random number r above is set to { r }, but this is not an important issue in the present invention. The secret variance value { r } in the present embodiment is a value generated outside each secret calculation device 11-j. The value of the random number r is concealed in each secret computing means 11-j. For example, the authentication device 12 may generate and transmit the secret variance value { r } of the random number r to each secret computing device 11-j without notifying each secret computing device 11-j of the value of the random number r. It is not an important matter of the present invention where the secret dispersion value r is generated. The secret variance value { r } is stored in the storage unit 113-j of each secret calculation device 11-j (step S111-j).

x_iSecret scatter value x for e 0,1_iIt is stored in the storage unit 113-j (however, i is 0,1, 2). x is the number of_iBut may be any value. Secret scatter value { x_iThe term "may be a value inputted from the outside of the secret computing device 11-j, a value generated inside the secret computing device 11-j, or a value generated by the secret computing device 11-j in cooperation with a secret computing device 11-j" outside thereof (here, j "∈ {0, …, N-1}, j" ≠ j). The subtraction section 116-j reads the secret variance value { x ] from the storage section 113-j_iBy using the secret variance value x_iSecret calculation of secret, calculating secret variance value s_i}＝{x_i} -1/2 and output (step S116-j).

XOR operation section 117-j (first XOR operation section) uses secret variance value { s ] output from subtraction section 116-j_iCalculating a secret variance value { y } - {4s } by secret calculation₀s₁s₂And +1/2 and output. For example, the exclusive OR operation unit 117-j uses the secret variance value {4s }₀And secret scatter value s₁Secret calculation to obtain a secret variance value {4s }₀s₁By using secret variance value {4s }₀s₁And secret scatter value s₂Secret calculation to obtain a secret variance value {4s }₀s₁s₂}, utilizingSecret scatter value {4s₀s₁s₂And 1/2 to obtain and output the secret variance value y. In these secret calculations, the secret calculation devices 11-0 to 11- (N-1) need to communicate with each other. On the other hand, at secret variance value {4s }₀No communication is required in the calculation of. That is, the exclusive OR operation unit 117-j of the exclusive OR operation unit 117-j can use the secret variance value { s } without performing communication_iTo calculate a secret variance value 4s₀And (step S117-j).

XOR operation unit 118-j (second XOR operation unit) uses secret variance value s output from subtraction unit 116-j_iThe secret variance value y is calculated by secret calculation using the secret variance value r read from the storage unit 113-j and the secret variance value y_r}＝{4rs₀s₁s₂And { r }/2 and output. For example, the XOR operation unit 118-j uses the secret variance {4r } and the secret variance { s }₀Secret calculation to obtain a secret variance value {4rs }₀By using secret variance value {4rs }₀And secret scatter value s₁Secret calculation to obtain a secret variance value {4rs }₀s₁By using secret variance value {4rs }₀s₁And secret scatter value s₂Secret calculation to obtain a secret variance value {4rs }₀s₁s₂Using secret scatter value {4rs }₀s₁s₂And 1/2 to obtain a secret variance value y_rAnd output is performed. In these secret calculations, the secret calculation devices 11-0 to 11- (N-1) need to communicate with each other. On the other hand, no communication is required in the calculation of the secret variance value {4r }. That is, the exclusive-or operation unit 117-j of each exclusive-or operation unit 117-j can calculate the secret variance value {4r } using the secret variance value { r } without performing communication (step S118-j).

Secret variance values y and y_rThe symbols are stored in the storage unit 113-j in association with each other (step S113-j). The output unit 112-j outputs the secret variance value y. The secret variance value y is used for any other secret calculation.

When the secret variance { y } is correctly calculated and verified, the slave storage unit 113-j reads the secret scatter values y, y_rAnd { r }, and verifying the consistency of the images. For example, the secret computing apparatus 11-j uses the secret variance values y and y_rCalculating secret variance value (ry-y) by secret calculation of (r)_rAnd output (refer to reference 1). The secret calculation means 11-j sends the secret variance value ry-y to the verification means 12_r}. The verification device 12 transmits a predetermined number or more of secret variance values { ry-y } transmitted from the secret calculation devices 11-j_rRestore ry-y in_rAt ry-y_rWhen the verification result is 0, the verification result is output to ry-y_rIf not equal to 0, the verification failure is output. Alternatively, the secret calculation apparatus 11-j transmits the secret variance values y and y to the verification apparatus 12_rAnd r. The verification device 12 transmits the secret distribution values { y } and { y } each equal to or greater than a predetermined number, from the secret calculation devices 11-j_rRecovery of y, y in }, { r }_rR, and satisfy ry-y_rWhen the verification result is 0, the verification result is output to satisfy ry-y_rIf not equal to 0, the verification failure is output.

[ second embodiment ]

The second embodiment will be explained. In this embodiment, the following processing is explained: secret distribution method by adding (2,3) threshold secret distribution method, secret distribution is performed at mod2 on random number w, and secret distribution value { w }is obtained^B _jA finite field F converted to the random number w_pThe secret dispersion value y e F_pAnd secret scatter value y_r}∈{F_pPair of (secret random number pair).

< Structure >

As shown in fig. 1, the secret computing apparatus 2 of the embodiment has three secret computing apparatuses 21-0, 21-1, 21-2 and a verification apparatus 12, which are configured to be able to communicate via a network. As shown in fig. 2, the secret calculation device 21-j (here, j is 0,1,2) includes an input unit 111-j, an output unit 112-j, a storage unit 113-j, a control unit 114-j, a random number acquisition unit 215-j, a subtraction unit 216-j, exclusive or calculation units 117-j, 118-j, and a setting unit 219-j. The secret calculation apparatus 21-j executes each process under the control of the control section 114-j. The data obtained by each unit of the secret calculation device 21-j is stored in the storage unit 113-j one by one, and is read as necessary and used in other processes.

< secret calculation processing >

The secret calculation process performed by the secret calculation device 21-j (here, j is 0,1,2) will be described with reference to fig. 3. The following description focuses on differences from the first embodiment, and simplifies the description of common matters.

Finite field F_pIs equal to F_pIs given by the secret scatter value r e F_pIs input to the input section 111-j of each secret calculation device 21-j. The secret variance value { r } in the present embodiment is a secret variance value of a secret variance method based on addition of, for example, (2,3) threshold secret variance methods. The secret variance value { r } is stored in the storage unit 113-j of each secret calculation device 21-j (step S111-j).

The random number acquisition unit 215-j of each secret calculation device 21-j acquires that w ═ w is satisfied for the random number w ∈ {0,1}₀+w₁+w₂Secret scatter value of mod2 w^B _j＝(w_j,w_{(j+1)mod 3}) And output is performed. That is, the random number acquisition unit 215-0 acquires { w }^B ₀＝(w₀,w₁) The random number acquisition unit 215-1 acquires { w }^B ₁＝(w₁,w₂) The random number acquisition unit 215-2 acquires { w }^B ₂＝(w₂,w₀) And output is performed. Here, this processing is performed in a state where the random number w is concealed from each secret computing device 21-j. For example, each random number acquiring unit 215-j generates a random number w_jE {0,1}, and transmits the random number w from the output section 112-j to the secret calculation means 21- ((j-1) mod 3)_j. Random number w transmitted from secret calculation apparatus 21- ((j +1) mod 3)_{(j+1)mod 3}Is inputted to the input section 111-j of the secret calculation apparatus 21-j and is sent to the random number acquisition section 215-j. Through the above processing, the random number acquisition unit 215-j acquires { w }^B _j＝(w_j,w_{(j+1)mod 3}) (step S215-j).

The setting unit 219-j sets the secret variance value { w }^B _j＝(w_j,w_{(j+1)mod 3}) Sub fraction w of_j,w_{(j+1)mod 3}E {0,1} as input, obtaining { x_j}_j＝(w_j,0),{x_{(j+1)mod 3}}_j＝(0,w_{(j+1)mod 3}),{x_{(j+2)mod 3}}_jAnd outputs (0,0) (step S219-j).

{x_j}_j＝(w_j,0),{x_{(j+1)mod 3}}_j＝(0,w_{(j+1)mod 3}),{x_{(j+2)mod 3}}_j(0,0) as { x_iThe symbol (i ═ 0,1,2) is input to the subtraction section 216-j. I.e., { x₀}＝{x₀}₀＝(w₀,0),{x₁}＝{x₁}₀＝(0,w₁),{x₂}＝{x₂}₀The value (0,0) is input to the subtraction section 216-0. { x₀}＝{x₀}₁＝(0,0),{x₁}＝{x₁}₁＝(w₁,0),{x₂}＝{x₂}₁＝(0,w₂) Is input to the subtraction section 216-1. { x₀}＝{x₀}₂＝(0,w₀),{x₁}＝{x₁}₂＝(0,0),{x₂}＝{x₂}₂＝(w₂0) is input to the subtracting section 216-2. The subtraction part 216-j uses the inputted { x_iCalculating a secret variance value s_i}＝{x_i}-1/2∈{F_pAnd output is performed. For example, in { x_iIs such that x_iSecret is dispersed in satisfying x_i＝x_i,0+x_i,1+x_i,2Three secret scatter values (x)_i,0,x_i,1),(x_i,1,x_i,2),(x_i,2,x_i,0) If the value is obtained, the value is related to the secret variance value (x)_i,0,x_i,1),(x_i,1,x_i,2),(x_i,2,x_i,0) Each corresponding secret variance value s_iE.g. to (x)_i,0-1/2,x_i,1),(x_i,1,x_i,2),(x_i,2,x_i,0-1/2). In addition, secret scatter values{s_iFor example, it may be (x)_i,0-1/6,x_i,1-1/6),(x_i,1-1/6,x_i,2-1/6),(x_i,2-1/6,x_i,0-1/6). The former enables high-speed processing. At this time, the subtracting section 216-j subtracts w_jE {0,1} and w_{(j+1)mod 3}E {0,1} is regarded as a finite field F_pThereby computing a secret scatter value s_iAnd (step S219-j).

XOR operation section 117-j (first XOR operation section) uses secret variance value { s ] output from subtraction section 216-j_i}∈{F_pCalculating a secret variance value { y } - {4s } by secret calculation₀s₁s₂}+1/2∈{F_pAnd output (step S117-j).

XOR operation unit 118-j (second XOR operation unit) uses secret variance value s output from subtraction unit 116-j_iThe secret variance value y is calculated by secret calculation using the secret variance value r read from the storage unit 113-j and the secret variance value y_r}＝{4rs₀s₁s₂}+{r}/2∈{F_pAnd output (step S118-j).

Secret variance values y and y_rThe symbols are associated with each other and stored in the storage unit 113-j (step S113-j). The output unit 112-j outputs the secret variance value y. Secret scatter value y e F_pIs a secret scatter value of the random number y over the finite field Fp. { y } may also be converted into a secret sharing value (for example, Shamir secret sharing scheme) according to another secret sharing scheme and output.

When the secret variance { y } is correctly calculated and verified, the secret variance { y } and { y } are read from the storage unit 113-j_rAnd { r }, and verifying the consistency of the images.

[ modifications and the like ]

The present invention is not limited to the above-described embodiments. For example, in the above-described embodiment, the random number r ∈ F_pIs input to each secret calculation apparatus 11-i. However, each secret calculation device 11-i may generate a secret variance value { r }, respectively. Here, the random number r must be concealed for each secret computing device 11-i. Such methods are well known and may be usedTo utilize any method. For example, the secret computing devices 11-0, …, 11- (N-1) can cooperate to generate the secret variance value { r }. As an example, each secret calculation device 11-i' calculates a random number r_i’Secret variance value of { r_i’}_i∈[F_p]And transmitted to the secret calculation devices 11-i (here, i is 0, …, N-1, i 'is 0, …, N-1, and i' ≠ i), each secret calculation device 11-i using the secret variance value { r ≠ i₀}_i,…,{r_N-1}_iTo obtain { r } ═ r { r } by secret calculation of (c) }₀+…+r_N-1}_i。

The various processes described above are not only performed chronologically according to the description, but also may be performed in parallel or individually according to the processing capability or need of the apparatus that performs the processes. In addition, appropriate modifications can be made without departing from the gist of the present invention.

Each of the above-described apparatus devices is configured by executing a prescribed program by, for example, a general-purpose or special-purpose computer including a processor (hardware processor) such as a CPU (central processing unit) and a memory such as a RAM (random-access memory)/ROM (read-only memory). The computer may have one processor and memory, or may have a plurality of processors and memories. The program may be installed in a computer or may be recorded in advance in a ROM or the like. Instead of an electronic circuit (circuit) that realizes a functional configuration by reading a program such as a CPU, a part or all of the processing unit may be configured by using an electronic circuit that realizes a processing function without using a program. The electronic circuit constituting one device may include a plurality of CPUs.

When the above-described configuration is implemented by a computer, the functional contents that each device should have are described by a program. The processing functions described above are realized on a computer by executing the program on the computer. The program describing the contents of the processing can be recorded in advance in a computer-readable recording medium. An example of the computer-readable recording medium is a non-transitory (non-transitory) recording medium. Examples of such recording media are magnetic recording devices, optical discs, magneto-optical recording media, semiconductor memories, and the like.

For example, the distribution of the program is performed by selling, transferring, or lending a portable recording medium such as a DVD or a CD-ROM on which the program is recorded. Further, the program may be stored in a storage device of the server computer in advance, and may be transferred from the server computer to another computer via a network to circulate the program.

The computer that executes such a program first temporarily stores the program recorded on the portable recording medium or the program transferred from the server computer in its own storage device, for example. When executing the processing, the computer reads the program stored in its own storage device and executes the processing according to the read program. As another execution mode of the program, the computer may read the program directly from the portable recording medium and execute the processing according to the program, and may sequentially execute the processing according to the received program each time the program is transferred from the server computer to the computer. The above-described processing may also be performed by a so-called ASP (Application Service Provider) type Service that does not forward a program from a server computer to the computer but implements a processing function only by executing an instruction and result acquisition.

The processing functions of the present apparatus may be realized not by executing a predetermined program on a computer, but at least a part of the processing functions may be realized by hardware.

Description of the symbols

1. 2 secret computing system

11-j, 21-j secret computing device