JP2001320357A - Method and device for managing data, and recording medium with data management program data recorded thereon - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide data managing method/device for supplying only data in the range of j-th to i-th data, which are selected from among continuous data, to a user and to provide a recording medium. SOLUTION: A computer system generates first and second value strings, by using first and second one-directional functions from first and second values and generate a third value string through association of the first value string with second value string by using an arbitrary function. When j-th to i-th data are supplied to the user, only an i-th value in the first value string and a j-th value in the second value string are transmitted. When k-th (where j<=k<=i) is used, a k-th value in the first value string and a k-th value in the second value string are operated by using the first and second unidirectional functions. Then, k-th data is obtained through calculation by using the arbitrary function from the k-th values in the first and second value strings.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a data management method and apparatus for providing a user with only an arbitrary range of data from a plurality of continuous data by a computer system, and a recording recording the data management program. Regarding the medium.

[0002]

2. Description of the Related Art At present, services for providing contents such as pay broadcasts, breaking news, stock price information, etc. to subscribers only for a fee through broadcasting, the Internet and the like are expanding.

[0003] As means for providing such services, (1) a content provider delivers contents all day as pay broadcasting.

(2) Regularly deliver breaking news and the like to mobile phones, mobile terminals, personal computers, and the like.

(3) When a content provider is accessed, it is determined whether the accessor has the right to receive the content, and then the content is delivered.

And the like.

[0007] In these services, when the contractor cancels the contract, it is necessary to make the contents delivered thereafter unusable. Similarly, content delivered before the contract must be made unusable even after the contract.

That is, in order to prevent only the contractor from receiving and using the contents under the contract and prevent a person other than the contractor from impersonating the contractor and illegally receiving and using the contents, the following [1] The encryption technology shown in [2] is used.

[1] A contractor obtains a key from a content provider at the time of contract, and the content provider encrypts the content with the key and distributes or publishes the content (web or the like).
Other than the contracted user, who does not hold the key, it cannot decrypt the contents being delivered or viewing the published contents because the keys are not held.

As an example of delivery, there is a pay broadcast such as a satellite broadcast. In satellite broadcasting, a broadcasting station encrypts (scrambles) and broadcasts a content, and a subscriber who receives the encrypted content decrypts (descrambles) the content to view the content. Only the contractor can decrypt the content and cannot use the content.

[2] The contractor performs mutual authentication with the content provider using the key obtained at the time of contract. The content provider confirms whether the contractor really has the right to use the content and provides the content to the contractor.

[0012]

SUMMARY OF THE INVENTION
In the case of the encryption techniques shown in [1] and [2], there are the following problems.

[1] When delivering and publishing by encrypting with the key assigned at the time of contract as in [1]: A service in which a publication (content) is issued to the contractor every month and the contract is valid for 2 years from the contract month think of. The service provider prepares encryption keys for several years in advance, and determines which key is used to encrypt the content for each month. At the time of contract, the contractor can use the contents for two years by obtaining keys for two years from the month. However, such means have the following problems.

A. When the contractor's terminal has a limited storage capacity like a portable terminal, it is difficult to hold many encryption keys.

B. As more services are contracted,
The number of keys that must be held increases, and key management becomes cumbersome.

C. In the case of a content provider, the management cost increases significantly as the number of keys handled increases.

[0017] Further, "A recording medium recording a group key method and apparatus and a group key program (Japanese Patent Application No. 11-4)
No. 0319), a method of reducing the number of keys held by a user by a one-way function is used when the method of "a study of group key method for enterprises (1999 IEICE General Conference)" is used. . When this method is used, the content can be decrypted during the contract period only by paying out one key at the time of contract, but there are the following problems.

D. Once a contract is made and a key is obtained, it is possible to decrypt even the contents before the contract.

In the case of authenticating the key assigned at the time of contract as in [2], there are the following problems as in [1].

E. When the contractor's terminal has a limited storage capacity like a portable terminal, it is difficult to hold many encryption keys. The more services you subscribe to, the more keys you have to keep.

F. In the case of a content provider, the management cost increases significantly as the number of keys handled increases.

G. Once a contract is made and a key is obtained, it is possible to decrypt even the contents before the contract.

That is, in any case, the number of keys that must be held by the contractor increases, the number of keys that must be managed by the content provider increases, and once a contract is made to obtain a key, In addition, there is a problem that the content before the contract can be decrypted.

The present invention has been made in view of the above-mentioned problems, and has recorded therein a data management method, a data management method, and a data management program capable of easily managing keys and preventing decryption of contents other than a contract. It is intended to provide a recording medium.

[0025]

First, the concept of the present invention will be described. If the value obtained by applying the one-way function f to the initial value A is B = f (A), it is easy to calculate B from A due to the characteristics of the one-way function. Can not. In addition, as a one-way function,
If the one-way function has the above characteristics, MD4, MD
5, any method such as SHA may be used.

Referring to FIG. 4, among n data (D {1}, D {2},..., D {n}), D {j} to D {1} ( However, it is assumed that (i−j + 1) pieces of data of j ≦ i) are delivered to the user.

First, n data (D {1}, D {2})
,. . . , D {n}) are calculated in the following procedure.

Step 1. Generate arbitrary values S1 and S2.

Step 2. N values (X {1},..., X {n}) from S1 using the one-way function f1 as follows:
Is calculated.

X {1} (= f1 (X {2})), X {2} (= f1 (X {3}))
,. . . , X {n} (= f1 (S1)). From S2, n values (Y {1},..., Y {n}) are calculated using the one-way function f2 as follows.

Y {1} (= f2 (S2)), Y {2} (= f2 (Y {1}))
,. . . , X {n} (= f2 (Y {n-1})). X {1} calculated in steps 2 and 3 above
,. . , X {n} and Y {1},. . . , Y {n} and n data (D {1}) using an arbitrary function f3 as follows:
,. . , D {n}).

D {1} = f3 (X {1}, Y {1}) D {2} = f3 (X {2}, Y {2}). . . D {n} = f3 (X {n}, Y {n}) An example of f3 is a function that outputs a bit string obtained by connecting two input bit strings.

Next, the data D {1} generated by the above procedure
Out of data D {n}, data D {j} to data D
When delivering (i−j + 1) data of {i} (where j ≦ i) to the user, only two values of X {i} and Y {j} are delivered. Thus, there is an effect that it is not necessary to distribute (i−j + 1) pieces of data, and only two pieces of data need to be distributed.

The user who has received X {i} and Y {j} receives data D {i} from data D {j}.
{k} (where j ≦ k ≦ i) can be calculated and obtained according to the following procedure.

Step 1. Apply f1 to X {i} i−k times to calculate X {k} Step2. 2. Apply f2 to Y {j} kj times to calculate Y {k}. f3 is applied to X {k}, Y {k} to calculate D {k}. However, from the characteristics of the one-way function, X {i + 1},. . . , X {n}, Y {1},. . . , Y {j-1}, it is impossible to calculate D {1},. . . , D {j-1), D {i + 1},. . . , D {n} cannot be calculated at all.

Here, a specific description will be given. A certain data (authority information: a ticket, a ticket, for example) is given to a person who has a right to read a certain magazine from January to April. Thus, only the person who has this data can read the magazine. Therefore, how to actually read a magazine from the data is to calculate key data from the data. The data itself may be key data, and a value obtained by applying a function to the data may be key data. Then, the magazine (encrypted) is decrypted with the key data.

In order to achieve the above-mentioned object, the data management method of the present invention uses a computer system to select, from a plurality of continuous data, a selected j-th to i-th (where j ≦ i) range. A data management method for providing only data to a user, wherein a first value
Generating a first sequence of values using a one-way function of, generating a second sequence of values from a second value using a second one-way function,
A third value sequence is generated by associating the first value sequence with the second value sequence by using an arbitrary function, and the (j-j + 1) data from the j-th to the i-th is used by the user. Is provided to the user, only the i-th value of the first value sequence and the j-th value of the second value sequence are transmitted to the user, and the user receives the i-th value from the j-th value
When using any k-th (j ≦ k ≦ i) data in the range up to the first, a first one-way function is used to convert the i-th value of the first value sequence to the first The k-th value of the second value sequence is calculated from the j-th value of the second value sequence using the second one-way function, and the k-th value of the second value sequence is calculated using the second one-way function. The gist is that the k-th data is obtained from the k-th value of the value sequence and the k-th value of the second value sequence by calculation using the arbitrary function.

Further, according to the data management method of the present invention, n data D {1} and D {2} are processed by a computer system.
,..., D {n}, (i−j + 1) pieces of data ranging from the selected j-th data D {j} to the i-th (j ≦ i) data D {i}. This is a data management method when only data is provided to a user, and X {1} (= f1 (X {2})), X {2} (= f1 (X
{3})),..., X {n} (= f1 (S1)), and n values X {1}
,..., X {n}, and from the value S2, the one-way function f
2, Y {1} (= f2 (S2)), Y {2} (= f2 (Y {1}))
,..., Y {n} (= f2 (Y {n-1})), n values Y {1}
, ..., Y {n}, and using an arbitrary function f3,
The values X {1},..., X {n} and the values Y {1},.
{n}, D {1} = f3 (X1}, Y {1}),
D {2} = f3 (X2}, Y {2}),..., D {n} = f3
(X n}, Y {n}), n data D {1},.
{n}, and when providing (i−j + 1) pieces of data of the j-th data D {j} to the i-th data D {i} (where j ≦ i) to the user, Only the value X {i} and the value Y {j} are transmitted to the user, and the user receives the j-th data D {j}.
Data D {k} out of i-th data D {i}
(Where j ≦ k ≦ i), X {k} is calculated from X {i} using the one-way function f1, and Y {j} is used using the one-way function f2. Calculate Y {k} from
Further, the gist is to obtain data D {k} from X {k} and Y {k} by calculation using the arbitrary function f3.

According to the data management method of the present invention, the n pieces of data C {1}, C {2}, C {2}, D {1}, D {2},. , C {n}, the use of the content C {k} (1 ≦ k ≦ n) is limited to users who can calculate specific data D {k}. .

According to the data management method of the present invention, when the content C {k} is encrypted with a key K {k} derived from specific data D {k}, the user can use the content C {k}. , A key K {k} is derived from the specific data D {k}, and the content C {k} is decrypted using the key K {k}. Is the gist.

According to the data management method of the present invention, the content C {k} is encrypted with an arbitrary key Kt and the specific data D
When the key Kt is encrypted with the key K {k} derived from {k} and attached to the ciphertext, the user calculates specific data D {k} for the content C {k}, Data D
A key K {k} is derived from {k}, and a key Kt is obtained from the attached information.
The point is to decrypt the content C {k} using

According to the data management method of the present invention, the index i of the key K {i} used in the encryption is attached to the ciphertext,
The user uses the specific data D {k} from the index i.
The key point is to derive the key K {i} using

The data management method of the present invention includes a server for managing contents, and uses a key K {k} derived from specific data D {k} when a user requests contents C {k}. The gist is that authentication is performed and the content C {k} is delivered only when the content is passed.

The data management apparatus of the present invention provides a computer system which provides a user with only selected j-th to i-th (where j ≦ i) data from a plurality of continuous data. The data management device according to claim 1, wherein a first value sequence is generated from the first value using the first one-way function, and a second value sequence is generated from the second value using the second one-way function. Generating means for generating a value sequence, associating the first value sequence with the second value sequence using an arbitrary function, and generating a third value sequence; −j + 1)
When providing the data to the user, i in the first value sequence
A transmitting means for transmitting only the j-th value and the j-th value of the second value sequence to the user, and the user selecting an arbitrary k-th value in the range from the j-th to the i-th (where j ≦ k ≦ receiving means for receiving the i-th value of the first value sequence and the j-th value of the second value sequence when using the data of i); and a first one-way function using the first one-way function. From the i-th value of the value sequence to the k-th value of the first value sequence, j of the second value sequence is calculated using the second one-way function.
Computing means for computing the k-th value of the second value sequence from the second value sequence, and the arbitrary function based on the k-th value of the first value sequence and the k-th value of the second value sequence And means for obtaining the k-th data by calculation using

A recording medium according to the present invention is a computer system in which j is selected from a plurality of continuous data.
A computer-readable recording medium storing a data management program for providing only data in a range from the i-th data to the i-th data (where j ≦ i), wherein the data management program is provided from a first value to a first one direction A first value sequence using a sex function, a second value sequence using a second one-way function from a second value, and a second value sequence using an arbitrary function. Generating a third value sequence by associating the value sequence of No. 1 with the second value sequence, and (j-j)
When providing +1) data to the user, the data providing causes the computer to execute a procedure of transmitting only the i-th value of the first value sequence and the j-th value of the second value sequence to the user. When a user uses a program and any k-th (j ≦ k ≦ i) data in the range from the j-th to the i-th, the first one-way function is used to perform the first I in the value sequence
The k-th value of the first value sequence is calculated from the second value, and the k-th value of the second value sequence is calculated from the j-th value of the second value sequence using the second one-way function. A user who causes a computer to execute a procedure of calculating the k-th data from the k-th value of the first value sequence and the k-th value of the second value sequence using the arbitrary function. The gist is that at least one of the programs is recorded.

In the present invention, since the data management program is recorded as a recording medium, the distribution of the program can be enhanced by using the recording medium.

[0047]

Embodiments of the present invention will be described below with reference to the drawings.

(First Embodiment) FIGS. 1 and 2 show the configuration of a data management device according to a first embodiment of the present invention. FIG. 1 is a content issuing organization, and FIG. 2 is a configuration of a user terminal. It is a block diagram which shows each.

Here, as the paid content delivery,
a) deliver publications to subscribers every month; b) if you sign up with a one-year contract, you will be valid for one year from the contract month; c) non-subscribers will not be able to read the publication; d) content will be encrypted The following describes an example of a service in which the contents are distributed and delivered.

The hash chain used in the present embodiment indicates that a hash function f, which is one of the one-way functions, is applied to a certain value A0 many times.

For example, A1 = f (A0) A2 = f (A1) = f (f (A0)) A3 = f (A2) = f (f (A1)) = f (f (f (A0))) When An = f (An-1), it is difficult to obtain A0 from A1. Therefore, A1, A2,..., An can be obtained from A0. A2, ..., An
-1 cannot be obtained.

Next, the configuration of the content issuing organization C will be described with reference to FIG. The content issuing organization C is mainly composed of a content management unit 11 and an authority information management unit 19. The content management unit 11 includes a content storage unit 13, a content transmission unit 15, and a content encryption unit 17, and the content encryption unit 17 includes an encryption key derivation unit 17a and an encryption unit 17b. On the other hand, the authority information management unit 19 includes a secret information storage unit 19a and an authority information calculation unit 19b.

Next, the configuration of the user terminal U will be described with reference to FIG. The user terminal U is mainly composed of a content management unit 31 and an authority information management unit 39. The content management unit 31 includes a content reception unit 35 and a content decryption unit 37. The content decryption unit 37 further includes a decryption key derivation unit 37a and a decryption unit 37b.
It consists of. On the other hand, the authority information management unit 39 includes an authority information storage unit 39a and an authority information calculation unit 39b.

Next, referring to FIG. 3, the procedure for encrypting and decrypting contents will be described step by step.

The content issuing organization C, which is an organization that issues contents (publications), generates n using the one-way function f1 from the secret information S1 when S is secret information.
, X {1} (= f1 (X {2})), X {2} (= f1 (X {3})),.
{n} (= f1 (S1)) and n values Y generated from the secret information S2 using the one-way function f2, ie, Y {1} (= f2 (S2)), Y {2 } (= f2 (Y {1})), ..., Y {n} (= f
2 (Y {n-1})) is stored in the secret information storage unit 19a.

Next, data (object) D generated from the pair of X and Y as follows is authority information. Here, "authority information" is data indicating an authority, such as a ticket or a credential. In the real world, train tickets, concert tickets, admission tickets, and the like are equivalent.

D {1} = f3 (X ｛1}, Y {1}) D {2} = f3 (X ｛2}, Y {2}). . . D {n} = f3 (X {n}, Y {n}) f3 is an arbitrary function and is not particularly limited. X {m}, Y
A means such as applying an arbitrary hash function to a bit string obtained by concatenating {m} (where 1 ≦ m ≦ n) can be used.

The authority information and the publication are related as follows.

The January issue is only for users who can calculate the authority information D {1}. The February issue is only for users who can calculate the authority information D {2}. Only users who can calculate next January issue is only users who can calculate authority information D {13} Next February issue is only users who can calculate authority information D {14} Next March issue is authority information D {15} For example, a contractor A who has contracted for one year from January has X {1
2} and Y {1} are delivered to the contractor A only, and the contractor A stores the authority information in the authority information storage unit 39a. At this time, the content publishing organization C that publishes the publication has X {1},. . . , X {15}, Y {1},. . . , Y {15} need not be stored, and X {1},. . . , X {15},
Y {1},. . . , Y {15}, the secret information S1 and the secret information S2 are stored in the secret information storage unit 19a, and each time the authority information is delivered to the new contractor, the secret information S1 and the secret information S2 are stored.
2 can be calculated.

On the other hand, the content issuing organization C is
X {1},. . . , X {15}, Y {1},. . . , Y {15} in the secret information storage unit 19a, the January issue (C {1}) is encrypted by the following procedure and delivered to the contractor.

I) Authority information D in the authority information calculation unit 19b
{1} is calculated from X {1} and Y {1}. Ii) The encryption key deriving unit 17a converts the encryption key K {1} into the authority information D.
Derived from {1} iii) Encrypt the content C {1} in the encryption unit 17b. In the case of the March issue of the following year (C {15}), the following is performed.

I) Authority information D in the authority information calculation unit 19b
{15} is calculated from X {15} and Y {15}. Ii) The encryption key deriving unit 17a converts the encryption key K {15} to the authority information D.
Derived from {15} iii) Encrypt contents C {15} in encryption section 17b As described above, for any k, the authority information D {k} and the key K {k}
There is no limitation on the method of introducing.

Further, the content issuing organization C sets X {1}
, .., X {15}, Y {1}, .., Y {15} need not be stored, and only the secret information S1 and S2 are stored in the secret information storage unit 1.
9a, and the secret information S in the authority information calculation unit 19b.
X {k} and Y {k} may be calculated from 1, S2.

On the other hand, for example, the user A who has received the February issue
Calculates the authority information D {2} in the authority information calculating unit 39b from X {12}, Y {1} of the authority information storage unit 39a.

Next, the decryption key deriving unit 37a outputs the authority information D
The key K {2} is derived from {2}, and the decrypted unit 37b decrypts the encrypted content.

As described above, the user A sets X {12}, Y {1}
, K {12} can be derived only by holding.

Similarly, contractor B who has contracted for one year from March
Then, X {14}, Y {3} are delivered to the contractor B, and the contractor B decrypts the encrypted content by the same means as the contractor A.

At this time, even if the contractor B newly contracts, the contractor A obtains the information (X {12}, Y
{1}) does not need to be changed.

Further, even if a new contractor is added, the content issuing organization C assigns K {1},.
The content may be encrypted with Y {15}.

(Second Embodiment) In the first embodiment, the encrypted content is delivered to the contractor. However, the publication is stored in an archive server or the like, and is published in response to a request from the contractor. Delivery of goods to the contractor is also conceivable.
When the contractor acquires the content C {k}, the key K {k} is derived from the authority information, and the content provider and the contractor can be authenticated using K {k}. As a result, conventionally, the same number of keys for authentication as the contractor had to be managed, but the number of keys managed by the content provider is reduced and the management cost is reduced.

(Third Embodiment) Here, a contract is made for a pay broadcast in a desired time zone for one day.

The broadcast can not be viewed by anyone other than the contractor.

The broadcast contents are encrypted.

The service will be described as an example.

The broadcasting stations S1 and S2 as in the first embodiment.
X and Y are generated from 2.

Next, a pair of X and Y is used as authority information, and the authority information and the publication are associated as follows.

Broadcasting from 1:00 to 2:00 is only for users who can calculate authority information D {1}. Broadcasting from 2:00 to 3:00 is only for users who can calculate authority information D {2}. Broadcast from 22:00 to 23:00 is only for users who can calculate authority information D {22}. Broadcast from 23:00 to 24:00 is only for users who can calculate authority information D {23}. For example, 10: X {12} and Y {10} are delivered only to the contractor A to the contractor A who has contracted from 00 to 12:00.

Such data management by a hash chain is realized by a recording medium recording a data management program by a hash chain, and the program is provided by being recorded on the recording medium. The distribution of the data management program by the hash chain can be improved.

As described above, according to the present embodiment, n data D {1}, D {2},. . . , D {n}, D {j} to D {i} (where j ≦ i) are (i−j +
1) When passing data to the user, only data X {i} and Y {j} are passed, and data from D {j} to D {i} is converted to X {1},
By obtaining a hash chain from two of Y {j},
A significant advantage is that data management costs can be minimized.

By allocating this data to a series of contents, it becomes possible to minimize the cost of access management to the contents.

Further, since the contractor can access the contents only by holding the authority information allocated at the time of contract, the number of keys that the contractor must hold can be reduced.

Similarly, the number of keys that must be managed by the content provider can be reduced because authority information assigned at the time of contract can be calculated each time.

Furthermore, because of the feature of the one-way function, only the authority information within the contracted range can be calculated. Therefore, once the contract is made and the key is obtained, the problem that the contents before the contract can be decrypted can be overcome. are doing.

In the above embodiment, the case where the present invention is applied to a periodic publication such as a monthly magazine has been described as an example. However, the present invention is not limited to this, and may be appropriately applied to, for example, books of a whole collection. be able to. Examples of the data include content data such as music information, image information, news information, and dictionary information, or identification data for identifying these, but are not particularly limited thereto.

[0085]

As described above, according to the present invention, it is easy to manage keys that must be held by a contractor and keys that must be managed by a content provider, and to be out of the contract range such as before the contract. It is possible to prevent various types of data such as the contents from being decrypted beforehand.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a schematic configuration of an embodiment of a content issuing organization according to the present invention.

FIG. 2 is a block diagram showing a schematic configuration of an embodiment of a user terminal according to the present invention.

FIG. 3 is a block diagram showing a procedure for encrypting and decrypting content.

FIG. 4 is a diagram illustrating data management by a hash chain.

[Explanation of symbols]

 C Content issuing institution U User terminal 11 Content management unit 13 Content storage unit 15 Content transmission unit 17 Content encryption unit 17a Encryption key derivation unit 17b Encryption unit 19 Authority information management unit 19a Secret information storage unit 19b Authority information calculation unit 31 Content management unit 35 Content reception unit 37 Content decryption unit 37a Decryption key derivation unit 37b Decryption unit 39 Authority information management unit 39a Authority information storage unit 39b Authority information calculation unit

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Hikaru Morita 2-3-1 Otemachi, Chiyoda-ku, Tokyo Nippon Telegraph and Telephone Corporation F-term (reference) 5B049 AA05 BB25 EE00 GG10 5J104 AA01 AA16 EA02 EA04 JA03 NA02 NA11

Claims (9)

[Claims] 1. A data management method for providing, to a user, only data in a selected j-th to i-th (where j ≦ i) data from a plurality of continuous data by a computer system. Generating a first sequence of values from a first value using a first one-way function, generating a second sequence of values from a second value using a second one-way function, A third value sequence is generated by associating the first value sequence with the second value sequence using an arbitrary function, and the (j-j + 1) data from the j-th to the i-th is used by the user. To the user, only the i-th value of the first value sequence and the j-th value of the second value sequence are transmitted to the user, and the user can send the value within the range from the j-th value to the i-th value. Any k of
When using the (th) data (j ≦ k ≦ i), the first one-way function is used to convert the i-th value of the first value sequence to the k-th value of the first value sequence. , The k-th value of the second value sequence is calculated from the j-th value of the second value sequence by using the second one-way function, and the k-th value of the first value sequence and the k-th value are calculated. 2. A data management method, wherein k-th data is obtained by calculation from the k-th value of the value sequence of 2 using the arbitrary function. 2. The computer system selects i-th data from j-th data D {j} selected from n data D {1}, D {2},..., D {n}. j ≦ i) is a data management method for providing only (i−j + 1) pieces of data up to data D {i} to a user, using a one-way function f1 from a value S1. X {1} (= f1 (X {2})), X {2} (= f1 (X {3})),..., X {n} (= f1 (S1)) X {1},..., X {n} are generated, and Y {1} (= f2 (S2)), Y {2} (= f2 (Y {1})), ..., Y {n} (= f2 (Y {n-1})) to generate n values Y {1}, ..., Y {n} Using the function f3, the values X {1},..., X {n}
And values Y {1},..., Y {n}, D {1} = f3 (X ｛1}, Y {1}), D {2} = f3 (X ｛2} , Y {2}),..., D {n} = f3 (X {n}, Y {n}) to generate n data D {1},. The j-th data D {j} to the i-th data D {i}
When providing (i−j + 1) pieces of data (where j ≦ i) to the user, only the value X {i} and the value Y {j} are transmitted to the user, and the user receives the j-th data. When using arbitrary data D {k} (where j ≦ k ≦ i) among the i-th data D {i} from the data D {j}, X { i}, X {k} is calculated from Y {j} using the one-way function f2, and X {k} is calculated using the arbitrary function f3.
A data management method characterized by obtaining data D {k} from {k}, Y {k} by calculation. 3. The n data D {1}, D {2},.
, D {n}, n contents C {1}, C {2}
, ..., C {n}, the contents C {k} (1
3. The data management method according to claim 2, wherein use of .ltoreq.k.ltoreq.n) is restricted to only users who can calculate specific data D {k}. 4. The content C {k} is a specific data D
When encrypted with a key K {k} derived from {k}, the user calculates specific data D {k} for the content C {k}, and obtains a key from the specific data D {k}. 4. The data management method according to claim 3, wherein K {k} is derived, and the content C {k} is decrypted using the key K {k}. 5. The content K {k} is encrypted with an arbitrary key Kt, and a key K {k} derived from specific data D {k}.
When the key Kt is encrypted and attached to the ciphertext, the user calculates specific data D {k} for the content C {k}, and from this specific data D {k}, the key K {k The data management method according to claim 3, wherein the content C {k} is derived from the attached information using the key Kt. 6. An index i of a key K {i} used for the encryption is attached to a ciphertext, and a user can obtain the specific data D {k} from the index i.
The key K {i} is derived by using the following equation.
Data management method described in. 7. A server for managing contents, wherein when a user requests contents C {k}, specific data D
5. The data management method according to claim 3, wherein authentication is performed using a key K {k} derived from {k}, and the content C {k} is delivered only when the authentication is successful. . 8. A data management apparatus for providing a user with only data in a selected j-th to i-th (where j ≦ i) data from a plurality of continuous data by a computer system. A first sequence of values is generated from a first value using a first one-way function, and a second sequence is generated from a second value using a second one-way function.
Generating means for generating a third value string by associating the first value string with the second value string using an arbitrary function, and generating the third value string from the j-th to the i-th ( When providing (i−j + 1) pieces of data to the user, transmitting means for transmitting only the i-th value of the first value sequence and the j-th value of the second value sequence to the user; The user selects any k in the range from the j-th to the i-th.
Receiving means for receiving the i-th value of the first value sequence and the j-th value of the second value sequence when the j-th (where j ≦ k ≦ i) data is used; A function is used to convert the i-th value of the first value sequence to the k-th value of the first value sequence, and the second one-way function is used to convert the j-th value of the second value sequence to the second value. Calculating means for respectively calculating the k-th value of the value sequence of k, and the k-th value of the k-th value of the first value sequence and the k-th value of the second value sequence using the arbitrary function Means for obtaining data by calculation. 9. A data management program for providing to a user only data in a selected j-th to i-th (where j ≦ i) data from a plurality of continuous data by a computer system. Computer-readable recording medium, comprising: generating a first sequence of values from a first value using a first one-way function; and generating a second one-way function from a second value. Generating a second value sequence by using the first value sequence and a second value sequence by using an arbitrary function to generate a third value sequence; When providing (i-j + 1) pieces of data up to the i-th data to the user, a procedure for transmitting only the i-th value of the first value sequence and the j-th data of the second value sequence to the user A data providing program for causing a computer to execute Any of k in the range of up to Luo i-th
When using the data of the th (j ≦ k ≦ i), the first
The i-th value of the first value sequence is used for the k-th value of the first value sequence using the one-way function, and the j-th value of the second value sequence is used for the j-th value of the second value sequence using the second one-way function. Calculating the k-th value of the second value sequence from the values, and using the arbitrary function from the k-th value of the first value sequence and the k-th value of the second value sequence A computer-readable recording medium that records at least one of a user program that causes a computer to execute a procedure for calculating k-th data.