JP2008113203A5

JP2008113203A5 -

Info

Publication number: JP2008113203A5
Application number: JP2006294647A
Authority: JP
Filing date: 2006-10-30
Publication date: 2009-10-22

Claims

A key generation device comprising a first processing unit and a second processing unit for generating different encryption keys,
The first processing unit includes:
n receivers are assigned to a leaf, and a Y-ary tree structure whose height is represented by (log _Y n) is hierarchically configured and exists below an intermediate node existing between the leaf and the root. A tree structure constituting a sub-group comprising a plurality of the leaves,
To the leaves and the intermediate node, respectively, a first leaf assigning unit that assigns leaf keys g _y,
Different parameters ν _{x, y} (x: hierarchy, y: 1, 2,..., Y ^x ) and node parameters γ _{x, y} (x: hierarchy, y: 1, 2) ,..., Y ^x ), respectively,
Identify the path to the leaf from the root, the assigned to the intermediate nodes or the leaves existing on the path leaf keys g _y and the parameters assigned to the parent node of the intermediate node or the leaf ν _{x, y} and the node parameters gamma _x, on the basis of _y, the first key calculation unit for calculating a key,
With
The second processing unit, said n receiving apparatus, the grouping based on the Y or an integer B, you calculate the encryption key of the receiving device, the key generation apparatus.

The key generation device randomly selects a prime number p, determines a bilinear group G having the prime number p as an order, and randomly selects g as a generation source of the G Further comprising
The parameter assignment unit are each all nodes except the leaf node parameters _{_{γ x, y (γ x,}} y is an integer) is selected randomly, the generator g and the node parameters gamma _x, the _y based, following the said intermediate node and the route by using the formula a parameter [nu _x, assign a _y, a key generating apparatus according to claim 1.

The first processing unit includes:
A first random number determination unit that randomly selects a secret random number α (α is an integer);
The first leaf key assignment unit includes:
Based on the following formula B, it calculates the leaf keys g _y,
The first key calculation unit includes:
The intermediate node or the leaf key g _y assigned to the leaf, the intermediate nodes or the leaves said parameter gamma _x assigned to the parent _node, the value obtained by _y squared, shall be the private key, claim 3. The key generation device according to 2.
(Y = 1, 2,..., Y, Y + 2,..., 2Y)

The second processing unit includes:
A second random number determination unit that randomly selects a secret random number α ′ (α ′ is an integer);
A second leaf key assigning unit for assigning leaf keys g _b ^′ (b = 1, 2,..., B) to the leaves;
A second key calculating unit that calculates an encryption key of each receiving device based on the leaf key g _b ^′ ;
With
Said second leaf key allocation unit, the 'based on, leaf key g _b satisfying the equation C ^below' second said determined by the random number determination section random α you calculated, the key generation device according to claim 3 .
(B = 1, 2,..., B, B + 2,..., 2B)

The key generation device further includes a distribution unit that distributes the key set calculated by the first processing unit or the second processing unit to each receiving device,
The distribution unit, a transmission unit that transmits both said first second secret key obtained in private key and the second processing unit obtained in the first processing unit to the respective receiving devices, Ru comprising, The key generation apparatus according to claim 1.

Identify the reception device to exclude from among n receiving apparatus, Ru with exclusion receiver device specifying unit for determining a set S of receiving not excluding device, the encryption device.

The encryption device is:
It is determined whether or not the number r of receivers to be excluded satisfies the following formula D.
When the number r of receivers to be excluded satisfies the formula D, a second session key determination unit that generates a session key using the key generated by the second processing unit is selected,
When the number r of receivers to be excluded does not satisfy the formula D, a first session key determination unit that generates a session key using the key generated by the first processing unit is selected. further Ru comprising a session key selection unit, the encryption device according to claim 6.

The first session key determining unit randomly selects t (t is an integer) to determine a session key s = e (g _Y , g ₁ ) ^t ,
The second session key determination unit, t (t is an integer) by selecting at random, to determine the session key _{_{s = e (g B, g}} 1) t,
The encryption device further includes an encryption unit that encrypts the content to be distributed using either the session key s by the first session key determination unit or the session key s by the second session key determination unit. comprising encryption apparatus according to claim 7.
Here, e (g _Y , g ₁ ) indicates a bilinear mapping for two elements g _Y and g ₁ on the bilinear group , and e (g _B , g ₁ ) is on the bilinear group. A bilinear map for two elements g _B and g ₁ is shown .

The first session key determination unit
In the hierarchical tree structure, each node existing on the path from the leaf of the excluded receiver to the root is marked, and the parameters ν _{x, y} assigned to the marked node , the marked nodes using said leaf key g _y assigned to the intermediate nodes to a parent node, calculating a first header element represented by the following formula E, the first header element calculation unit,
A first header information generation unit that uses the first header elements c _{x, y} and g ^t obtained in the first header element calculation unit as header information;
Further Ru comprising a encryption device according to claim 8.
Here, S _{x, y} will belong to the marked nodes each subgroup to a parent node, shows a set of child nodes that are not marked.

The second session key determination unit
Using the parameter ν _{x, y} assigned to the intermediate node having the parent node of the leaf as a child node, and the leaf key g _b ^′ assigned to the leaf, a second expression expressed by the following formula F is given. A second header element calculation unit for calculating a header element;
A second header information generation unit that uses the second header element c _b obtained in the second header element calculation unit and the g ^t as header information;
Further Ru comprising a encryption device according to claim 8.

A receiving device capable of communicating with a key generation device and an encryption device,
In the key generation device, n receiving devices are assigned to the leaf, and a Y-ary tree structure whose height is expressed by (log _Y n) is hierarchically configured and exists between the leaf and the root. configure the subgroup comprising a plurality of said leaf that is present in the lower intermediate node, to said leaf and said intermediate node, respectively, assigned the leaf keys g _y, the the intermediate node and the root, different parameters [nu _{x, y} (x: hierarchy, y: 1, 2,..., Y ^x ) and node parameters γ _{x, y} (x: hierarchy, y: 1, 2,..., Y ^x ) are assigned respectively. identify the path from the root to the leaf, the intermediate nodes or with the leaf key g _y assigned to the leaf, the intermediate nodes or the leaves of the parent node to assign existing on the path Was the parameter [nu _x, and encryption key calculated based _y and the node parameters gamma _x, a _y, the n receiving apparatus, which is calculated by grouping based on the Y or an integer B encryption Ru comprising a receiving unit for receiving key and, respectively, the receiving apparatus.

The receiving unit further receives information on the set S of receiving devices that are not excluded, which is information identifying receiving devices to be excluded,
The receiving device is:
A decoding scheme selection unit that calculates the number r of receivers to be excluded from the set S of receivers that are not excluded, and determines whether or not the number r of receivers to be excluded satisfies the following expression G Further comprising
The decoding method selection unit includes:
When the number r of receivers to be excluded satisfies the equation G, the second decoding processing unit is selected,
If the number r of the receiving device wherein is excluded it does not satisfy the formula G is you select a first decoding processing unit, the receiving apparatus according to claim 11.

The first decoding processing unit
A determination unit that determines whether or not a receiving device is included in the set S;
A first session key calculation unit for calculating a session key s based on the secret key;
With
When the determination unit determines that the receiving device is included in the set S, the first session key calculation unit calculates the session key s based on the following equation H, that turn into decrypting the encrypted content, the receiving apparatus according to claim 12.

The second decoding processing unit
A determination unit that determines whether or not a receiving device is included in the set S;
A second session key calculation unit for calculating a session key s based on the secret key;
With
When the determination unit determines that the reception device is included in the set S, the second session key calculation unit calculates the session key s based on the following formula I, that turn into decrypting the encrypted content, the receiving apparatus according to claim 13.

n receiving devices are assigned to leaves, and a Y-ary tree structure having a height of (log _Y n) is hierarchically configured, and exists below intermediate nodes existing between the leaves and the root. A tree structure forming step for forming a subgroup consisting of a plurality of the leaves;
To the leaves and the intermediate node, respectively, a first leaf assignment step of assigning leaf keys g _y,
Different parameters ν _{x, y} (x: hierarchy, y: 1, 2,..., Y ^x ) and node parameters γ _{x, y} (x: hierarchy, y: 1, 2) ,..., Y ^x ), respectively,
Identify the path to the leaf from the root, the assigned to the intermediate nodes or the leaves existing on the path leaf keys g _y and the parameters assigned to the parent node of the intermediate node or the leaf ν a first key calculating step of calculating an encryption key of each receiving device based on _{x, y} and the node parameter γ _{x, y} ;
A second key calculating step of grouping the n receiving devices based on the integer B greater than or equal to Y and calculating an encryption key of the receiving device;
Ru equipped with, key creation method.

Identify the reception device to exclude from among n receiving apparatus, Ru with exclusion receiver device specifying step of determining the set S of the reception is not excluded device, encryption method.

n receiving devices are assigned to leaves, and a Y-ary tree structure having a height of (log _Y n) is hierarchically configured, and exists below intermediate nodes existing between the leaves and the root. configure the subgroup comprising a plurality of said leaf, with respect to the leaf and the intermediate node, respectively, assigned the leaf keys g _y, the the intermediate node and the root, different parameters ν _{x, y (x:} hierarchical, y : 1, 2,..., Y ^x ) and node parameters γ _{x, y} (x: hierarchy, y: 1, 2,..., Y ^x ) are assigned, and the path from the root to the leaf is assigned. identify the assigned to the intermediate nodes or the leaves existing on the path leaf keys g _y and the parameters [nu _x assigned to parent nodes of the intermediate nodes or the _leaves, And said node parameter gamma _x, encryption key calculated based on the _y, receiving said n number of the receiving device, for receiving the encryption key calculated by grouping based on the Y or an integer B, and respectively Ru comprising the step, key processing method.

On the computer,
n receivers are assigned to a leaf, and a Y-ary tree structure whose height is represented by (log _Y n) is hierarchically configured and exists below an intermediate node existing between the leaf and the root. A tree structure function that constitutes a subgroup consisting of a plurality of the leaves,
To the leaves and the intermediate node, respectively, a first leaf assignment function of assigning leaf keys g _y,
Different parameters ν _{x, y} (x: hierarchy, y: 1, 2,..., Y ^x ) and node parameters γ _{x, y} (x: hierarchy, y: 1, 2) ,..., Y ^x )
Identify the path to the leaf from the root, the assigned to the intermediate nodes or the leaves existing on the path leaf keys g _y and the parameters assigned to the parent node of the intermediate node or the leaf ν a first key calculation function for calculating an encryption key of each receiving device based on _{x, y} and the node parameter γ _{x, y} ;
A second key calculating function for grouping the n receiving devices based on the integer B equal to or greater than Y and calculating an encryption key of the receiving device;
A program to realize

A program for causing a computer to specify a receiving device to be excluded from n receiving devices and to realize an exclusion receiving device specifying function for determining a set S of receiving devices that are not excluded.

A computer is assigned n receiving devices to a leaf, and a Y-ary tree structure whose height is represented by (log _Y n) is hierarchically configured, and is a subordinate of an intermediate node existing between the leaf and the root. A leaf group g _y is assigned to each of the leaf and the intermediate node, and different parameters ν _{x, y} (x: ^{hierarchical, y: 1,2, ···, Y} x) and node parameters γ _x, y _(x: hierarchy, y: 1, 2, · · ·, allocation ^{Y x)} and each said leaf from said root identify the path to, assigned to the intermediate nodes or with the leaf key g _y assigned to the leaf, the parent node of the intermediate node or the leaf is present on the path the Parameter [nu _x, and encryption key calculated based _y and the node parameters gamma _x, a _y, the n receiving apparatus, and encryption key calculated by grouping based on the Y or an integer B, For realizing the receiving function to receive each.