JP2003174441A - Contents encrypting method and device and contents decoding method and device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To realize encryption corresponding to multi-cast for changing a cryptographic key in every second order, and for facilitating countermeasures to terminal equipment whose processing capability is low in distributing the contents of an IP stream or the like. <P>SOLUTION: An encrypting server 2 encrypts and transmits a cryptographic key (key array) Kcn for encrypting the IP stream to a terminal 3 in each transmission interval of a prescribed cryptographic key, and encrypts and transmits the packet of the IP stream by using one cryptographic key Kcn in each prescribed encryption interval. Also, the encrypting server 2 encrypts and transmits the updated new cryptographic key (key array) Kcn to the terminal 3 in each update interval of the prescribed cryptographic key. When the received packet are data, the terminal 3 decodes the packet by one cryptographic key (key array) Kcn, and when the packet are associated with the cryptographic key, the terminal 3 decodes and stores the packet. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to an IP (Internet Pr
The present invention relates to content encryption in a network using a communication protocol such as otocol), and more particularly to a content encryption method, a decryption method and devices for realizing multicast-compatible encryption and decryption.

[0002]

2. Description of the Related Art In content distribution by IP, an on-demand service in which a service is first started when a user requests it, and an IP stream is already flowing on the network, and when the user requests it, the service is on the network. A live service, such as receiving an IP stream flowing through, can be considered.

When considering the above two services, unicast is used for on-demand service and multicast is used for live service.

[0004] In addition, copyright protection technology is important in order to provide a service with billing in content distribution. Copyright protection technologies include digital watermark technology and encryption technology for preventing unauthorized viewing of content.

Now, consider the encryption technique used in IP communication. As encryption technology in IP communication, SSL (Secure Socket Layer) and TLS (Tra
Mainly HTTP (Hyperte) such as nsport Layer Securty)
xt Transfer Protocol (IP-Virtual Private), which is a technology used in communication and Internet (IPsec (IP Securty Protocol)).
There are technologies used for encryption of point-to-point communication when constructing (Network).

SSL and TLS exchange encryption keys,
The handshake protocol is RFC (Reqest For Comm).
ent), and it is almost a prerequisite that cryptographic key exchange is performed using this protocol. IP
In the case of sec, IKE (Internet Key
Exchange) is often used, but not necessarily IKE
Need not be used and can be said to be a protocol separate from key exchange.

It is possible to apply these encryption techniques to content distribution. But to apply 3
There are two challenges.

The first problem is SSL, TLS, and IPse.
c is a protocol mainly for unicast communication and does not support multicast communication.

The second problem is that there is an insufficient point as a technique for encrypting contents whose copyright management is strict. In digital broadcasting of video, when encrypting a compressed video, a mechanism for increasing the strength is provided with a mechanism for changing an encryption key at regular time intervals of the order of seconds.

Although there is a mechanism for changing the key in IKE used in SSL, TLS, and IPsec, the change is performed by exchanging the key between the server and the client which are performing encryption. , It is difficult to change keys at short time intervals such as seconds.

The third problem is SSL, TLS, and IPse.
c is that it is the method used when encrypting all of the data. For some contents, it is considered that it is not necessary to encrypt all the packets. It may be difficult for a terminal device (client device) having low processing capability to decode all of the packets in such content.

As described above, the conventional techniques have the problems that they do not support multicast, that there is no mechanism for changing the encryption key in a short time, and that there is only a mechanism that encrypts all data. .

[0013]

SUMMARY OF THE INVENTION Therefore, the problem to be solved by the present invention is that, with regard to the encryption of contents used to prevent unauthorized viewing of contents, it is compatible with multicast and is encrypted at a short time interval such as second order. It is an object of the present invention to provide a content encryption method and a decryption method having a mechanism for changing a key and a mechanism for encrypting a part of data.

[0014]

According to the present invention, it is possible to solve the problems of the prior art by using a device having a mechanism for identifying a multicast address for each packet and encrypting the contents of an IP stream. And
In the following description of the present invention, an example in which IP is used as the communication protocol will be described, but the communication protocol used in the present invention is not limited to IP.

First, the IP address of the IP stream input to the encryption device for encrypting the content is discriminated, and if the multicast address is set as the object to be encrypted, the encryption process is started. To do.
Here, in order to simplify the explanation, it is assumed that a common key method is used as an IP stream encryption method.

In the encryption device, the content is encrypted in packet units at preset time intervals or packet intervals. Also, in this case, the encryption key for encryption is updated at preset time intervals or packet intervals. Furthermore, this also applies encryption to an encryption key that encrypts the content at preset time intervals or packet intervals, and sends it out as a multicast stream together with the encrypted content (hereinafter referred to as encrypted content).

The terminal device that has received the encrypted IP stream first waits for the reception of the encryption key that encrypted the encrypted content. The encryption key obtained by some means is used as the encryption key obtained by encrypting the received encrypted content, and the encryption key obtained by encrypting the content is extracted. Next, the encrypted content is received, and the content is decrypted by using the encryption key that encrypted the content extracted earlier.

As described above, in the encryption of the IP stream, the multicast key is supported, and the encryption key used for the encryption is transmitted together with the encrypted content, so that the encryption key can be changed on the order of seconds and at every hour or By having a mechanism for selecting an IP packet to be encrypted on a packet-by-packet basis, a part of the IP stream can be encrypted.

By applying the present invention, it is possible to encrypt stream contents compatible with multicast. Also, as with digital broadcasting, it is possible to change the encryption key on the order of seconds to enhance security. Further, since it has a mechanism for encrypting a part of the content, it is easy to equip a client device having a low CPU processing capacity with this mechanism.

[0020]

1 and 2 are an IP network configuration diagram and a hierarchical configuration diagram of encryption keys common to all the embodiments described below. In the following description of the embodiments of the present invention, an example in which encryption is performed by the common key method will be described, but the present invention can be similarly implemented even when an encryption method other than the common key method is used. It is possible.

The network system shown in FIG.
A stream server 1 for distributing an IP stream such as a video, an encryption server 2 for encrypting and transmitting an input IP stream, a terminal 3 for decrypting the encrypted IP stream, and content encryption. An encryption key management server 4 that manages the encryption key to be performed and distributes the encryption key used by the encryption server 2 and the terminal 3, and an IP network 5 including a router compatible with multicast.

In the figure, 6 is an encryption key Kej different for each encryption server 2, 7 is an encryption key Kui different for each terminal 3, 8 is an encryption key Kej, and an encryption key Kph different for each IP stream is encrypted. Data, 9 is data obtained by encrypting a different encryption key Kph for each IP stream with the encryption key Kui, 10 is a transmission direction of the IP stream output from the stream server 1,
11 is the transmission direction of the IP stream encrypted by the encryption server 2, 12 is the communication path between the stream server 1 and the encryption server 2, 13 is the communication path between the encryption key management server 4 and the encryption server 2, and 14 Represents a communication path between the encryption key management server 4 and the terminal 3.

In the hierarchical structure diagram of the encryption key shown in FIG. 2, the same reference numerals as those in FIG. 1 correspond to those shown in FIG. The configuration of the encryption key used in this system is the encryption key Kcn2 used to encrypt the IP stream itself.
0, an encryption key Kph21 used to encrypt the encryption key Kcn20, and a unique encryption server 2 used to encrypt the encryption key Kph21 when the encryption key Kph21 is distributed through a network. The encryption key Kej6 and the encryption key Kui7 unique to each terminal 3 have three layers.

In FIG. 2, 22 is an IP stream, 23 is an encrypted IP stream, 24 is a decrypted IP stream, 25 is an IP stream of an encryption key Kcn20 encrypted with an encryption key Kph21, and 26 is an encryption. The distribution of the encryption key Kph21 encrypted by the key Kej6 and the distribution 27 of the encryption key Kph21 encrypted by the encryption key Kui7.

For example, the encryption server 2 uses the encryption key Kph21.
Encryption key Kph21 from the encryption key management server 4 that manages
When receiving the distribution, the encryption server 2 makes an authentication request to the encryption key management server 4 using the public key encryption method. When the authentication is successful, the encryption key management server 4 distributes to the encryption server 2 the encryption encryption key Kph21 encrypted using the encryption key Kej6 unique to each encryption server 2.

Further, when the terminal 3 receives the distribution of the encryption key Kph21 from the encryption key management server 4 which manages the encryption key Kph21, the terminal 3 makes an authentication request to the encryption key management server 4. When the authentication is successful, the encryption key management server 4 distributes to the terminals 3 the encrypted encryption key Kph21 encrypted using the encryption key Kui7 unique to each terminal 3. The public key cryptosystem can also be used for the authentication at this time.

The details are as follows. When the encryption server 2 makes an authentication request to the encryption key management server 4, the encryption key Kej6, which is a common key different for each encryption server 2, is previously stored in the encryption server 2 and the encryption key management server 4.
Encryption key Kph2 for encrypting the encryption key Kcn20 from the encryption server 2 to the encryption key management server 4
1 is requested, and the encryption key management server 4 uses the common key encryption key Kej corresponding to the encryption server 2 for which the acquisition request is made.
The encryption key Kej encrypted by encrypting the encryption key Kph21 for encrypting the encryption key Kcn20 using 6
(Kph) is generated and the encryption key Kej (Kph) is distributed to the encryption server 2.

The encryption server 2 that has received the encryption key Kej (Kph) encrypts the encryption key Kcn20 by decrypting the received encryption key Kej (Kph) using the encryption key Kej6 of the common key. To obtain the encryption key Kph21.

The terminal 3 receives the encryption key K from the encryption key management server 4.
Similarly, when the encryption key Kph21 for decrypting the cn20 is obtained, the same authentication request is made to obtain it.

[First Embodiment] FIG. 3 is a diagram for explaining the first embodiment of the present invention.
The outline of a ther packet is shown. Content I
As shown in FIG. 3, the P-packet 30 includes an Ether header, an IP header, a UDP header, and an encryption information header 31 in which information regarding encryption is described.

The encrypted information header 31 includes a version information section 31a that holds the version number of this encryption method, a length information section 31b that indicates the size of the encrypted information header 31,
Message type information section 31c, encryption type information section 31
d, a flag section 31e, and a key ID section 31f. The key ID portion 31f is mainly used in the second and fourth embodiments described later, and may be omitted depending on the mode of implementation.

If the data part of the IP packet is stream data, "1" is stored in the message type part 31c, and the data part of the IP packet is the encryption key K.
In the case of the array of the content encryption key Kcn encrypted by ph, "2" is stored. In the encryption type information section 31d, for example, "1" is stored when the encryption type is Camellia, and "2" is stored when the encryption type is DES.

When the flag part 31e is "0", this packet is an unencrypted packet and the data of the data part is not encrypted. When it is "1" or "2", this packet is Is an encrypted packet and indicates that the data in the data part is encrypted. Also, especially "1"
The case indicates that the encryption key for encrypting the data of the data part has not been changed from the previous time, and the case of “2” indicates that the encryption key for encrypting the data of the data part has been changed. The key ID part 31f indicates which array element of the encryption key array the encryption key obtained by encrypting the data of the data part is.

FIG. 4 is a block diagram of the encryption server 2 and the terminal 3 for explaining the first embodiment of the present invention.

The encryption server 2 includes a stream encryption interval determination means 40, a key array update interval determination means 41, a key array transmission interval determination means 42, a stream encryption means 43, a key array update means 44, and a key array encryption means. 45, a key array storage means 46, an encrypted information header adding means 47, and a packet transfer means 48.

Further, the terminal 3 for receiving the content has a packet receiving means 50, an encrypted information header discriminating means 51,
The key array decoding means 52, the key array updating means 53, the key array storing means 54, and the stream decoding means 55 are provided.

In the present system, in content distribution using IP, the IP stream is encrypted in real time by the common key method and transmitted to the terminal 3. Some time t
Kcn [i] is a key for encrypting the IP stream input in [i], and an array including a plurality of Kcn [i] is defined as a key array Kcn [] and a key array Kcn []. Let Kph be an encryption key for encrypting the encryption key, and the encryption server 2 encrypts the IP stream using these.

In this system, in order to encrypt a part of data, a parameter α for defining the packet encryption interval (or frequency) and a key indicating how often the encryption key used for encryption is changed. Parameter β that determines the update interval (or frequency) of array Kcn and key array Kcn of the encryption key
Parameter γ that determines the transmission interval (or frequency) of the key array Kcn that indicates how often the key sequence is transmitted to the terminal 3.
Is given as a parameter for encryption control in the encryption server 2. These intervals may be determined by time or may be determined by the number of packets.

First, the encryption server 2 uses the input IP
It is determined whether or not the stream is subject to encryption. If the stream is not subject to encryption, the packet transfer means 48 is used as it is.
To the network.

The stream encryption interval discriminating means 40, when the input IP stream is an object of encryption,
Whether or not the IP stream should be encrypted is determined by the encryption interval. That is, whether or not to encrypt the IP stream is determined according to a predetermined packet encryption interval α.

When the IP stream is encrypted,
The key array update interval determination means 41 determines the update interval of the encryption key Kcn [i] for encrypting the IP stream. When it is determined that the encryption key Kcn [i] needs to be updated, the key array updating means 44 sets the encryption key Kcn [i + 1] and the subsequent updates when the size of the key array Kcn [] is n. The key array Kcn [] stored in the key array storage means 46 is updated with the new encryption key Kcn [] up to the encryption key Kcn [i + 1 + n] used at each interval.

The stream encryption means 43 encrypts the IP stream using the first encryption key Kcn [i] of the key array Kcn [] stored in the key array storage means 46, and the encrypted information header adding means. Appropriate encrypted information header is added by 47 and sent out from the packet transfer means 48.

Further, the key array transmission interval discriminating means 42 discriminates whether or not it is the transmission interval of the key array Kcn [] by referring to the parameter γ, and when it is necessary to transmit the key array Kcn []. When the size of the key array Kcn [] is n, the encryption key Kcn [i + n] used at each subsequent update interval from the encryption key Kcn [i] stored in the key array storage means 46.
The above key array Kcn [] is encrypted using the encryption key Kph different for each IP stream, an appropriate encryption information header is added by the encryption information header adding unit 47, and the packet transfer unit 48 sends it.

When it is determined that the input IP stream is an encryption target and the IP stream is not encrypted by the determination based on the encryption interval α for encrypting the IP stream, the input IP stream Is encrypted without being encrypted, and an appropriate encrypted information header is added by the encrypted information header adding means 47 and sent from the packet transfer means 48. Also in this case, the key array transmission interval determination means 42 determines whether or not it is the transmission interval of the key array Kcn [], and if transmission is necessary, the encryption key Kcn [i stored in the key array storage means 46. ] To the encryption key Kcn [i + n] used at each subsequent update interval Kcn
[] Is encrypted using an encryption key Kph different for each IP stream, an appropriate encryption information header is added by the encryption information header adding means 47, and the packet transfer means 48 is added.
Sent from.

In the terminal 3, when the packet receiving means 50 receives the packet from the encryption server 2, the encryption information header determining means 51 determines the encryption information header of the packet.

As a result of determining the encryption information header, when the input IP stream is the stream to be encrypted, the IP stream is data or a key encrypted with the encryption key Kph. It is determined whether the array is Kcn []. If the IP stream is data, it is further determined whether or not the IP stream is encrypted. If the IP stream is encrypted, the key array Kcn [] held in advance is determined. It is determined whether or not is required to be updated.

When the key array Kcn [] needs to be updated,
The key array updating means 53 stores the value of the array value Kcn [i + 1] of the number i + 1 in the array value Kcn [i] of the number i of the key array Kcn [] held in the key array storage means 54, and sequentially, The storage position is advanced to the array value Kcn [n of number n-1.
The key array storage means 54 is updated repeatedly until the array value Kcn [n] of number n is stored in [-1].

After that, the stream decryption means 55 decrypts the encryption of the input IP stream using the updated key Kcn [i], and passes it to the upper layer which performs the output process for viewing the content.

When it is not necessary to update the key array Kcn [], the stream decrypting means 55 has the key array storing means 54.
Key Kcn [i] of number i in the key array Kcn [] stored in
Is used to decrypt the encryption of the input IP stream and pass it to the upper layer.

When the IP stream is not encrypted, the input IP stream is passed as it is to the upper layer without decrypting the encryption.

As a result of discriminating the encrypted information header, its I
If the P stream is not the data but the key array Kcn [] encrypted with the encryption key Kph, the key array decryption means 52 decrypts the input IP stream using the encryption key Kph, The key array Kcn [] obtained in the above step is overwritten on the key array Kcn [] stored in the key array storage means 54 to update it.

FIG. 5 is a processing flowchart of the encryption server 2 for explaining the first embodiment of the present invention, FIG.
Is a processing flowchart of the terminal 3.

First, a multicast IP stream is input from the stream server 1 shown in FIG. 1 to the encryption server 2 (step S1). The encryption server 2 first determines whether or not the target is a multicast IP stream that is set as an encryption target (step S2). If it is not the multicast IP stream to be encrypted, it is sent to the network without any modification (step S3).

In the case of the multicast IP stream to be encrypted, the current time has passed from the time t1 of the previous encryption and the time interval α or more which is set in advance in the encryption server 2 for performing the encryption has passed. It is determined whether or not (step S4).

When the time interval α for performing encryption has passed, the current time is the time t2 at which the key array Kcn was previously updated.
It is then determined whether or not the update time interval β of the encryption key Kcn has passed (step S5).

When the update time interval β of the key array Kcn or more has elapsed, the encryption key array Kcn [i] (i = 0 to n) is updated (step S6). Here, the encryption key array Kcn
[I] (i = 0 to n) is an array including a plurality of encryption keys Kcn, and in the present embodiment, the content encryption at the present time is the encryption key having the smallest number in this array. Will be used. Further, the update operation here means that when the size of the encryption key array is n and the array starts from 0, the encryption key Kcn whose array number is 1
Put [1] in the array number 0, the encryption key Kcn [2] whose array number was 2 in the array number 1, and so on. Repeatedly until -1 is entered, and new encryption key Kcn of array number n
The operation is to generate [n].

Next, the input data is encrypted using the encryption key Kcn [0] having the smallest number in the encryption key array (step S7). Then, an appropriate encrypted information header (31 in FIG. 3) is added to the data and the data is output (step S8).

After outputting the data, the updated encryption key array Kcn [i] (i = 0 to n) is encrypted by using the encryption key Kph set for each multicast stream type, and the encrypted Kph A packet having (Kcn [i] (i = 0 to n)) as data is generated (step S9). An appropriate encryption information header is added to the generated key data of Kph (Kcn [i] (i = 0 to n)) and output (step S1).
0).

When the update time interval β of the key array Kcn has not elapsed, the encryption key K with the lowest number in the encryption key array K
The input data is encrypted using cn [0] (step S11). Then, an appropriate encryption information header is added to the data and the data is output (step S
12).

After outputting the data, it is determined whether or not the present time has passed the sending time interval γ of the key array Kcn from the time t3 at which the key array Kcn was sent before (step S).
13). If it has not elapsed, the process returns to step S1 to wait for the next input from the stream server 1.

If the transmission time interval γ of the key array Kcn has passed, the encryption key array Kcn [i] (i = 0 to n) is set to the encryption key Kph set for each multicast stream type.
Encrypted by using the encrypted Kph (Kcn [i]
A packet having (i = 0 to n)) as data is generated (step S14). Generated Kph (Kcn [i] (i = 0 to
An appropriate encryption information header is added to the key data of (n)) and output (step S15).

If it is determined in step S4 that the time interval α for encryption has not elapsed, the input data is not encrypted, an appropriate encryption information header is added, and the data is output as it is. Yes (step S1
6). Then, the processing from step S13 onward is performed.

By the above operation, encrypted data, non-encrypted data, and encrypted encryption key array are generated and sent to the network.

Next, the operation of the terminal 3 shown in FIG. 1 which receives the packet sent from the encryption server 2 by some means will be described with reference to the flowchart of FIG.

First, it is judged whether or not it is an encrypted multicast stream which is the object of decryption (step S20). If it is not an encrypted multicast stream, the process is passed to the upper layer that processes the received data as it is.

If the packet is an encrypted multicast stream, the encryption information header is checked to identify whether the packet is data or an encryption key array (step S2).
1).

If it is an encryption key array, the encryption key array Kph (Kcn [i] (i = 0 to n)) encrypted by using the encryption key Kph previously obtained by some means is decrypted. To obtain Kcn [i] (i = 0 to n) (step S2)
2). In this update operation, the key array 61 newly obtained as shown in FIG. 7 is replaced by the key array held by the terminal 3 side until then (step S).
23). The array 60 of Kcn before updating is updated like the array 61 of Kcn after updating.

If it is data, the encrypted information header is checked to identify whether it is encrypted (step S24). If it is not encrypted, the process is passed to the upper layer as it is.

If the data is encrypted, the encrypted information header is checked to identify whether the encryption key array has been updated (step S25).

If the encryption key array has been updated, the encryption key array update operation is performed (step S26). In this update operation, as shown in FIG. 8, the encryption key array is updated by carrying it up one by one. Array 70 of Kcn before update
Will be updated as in the updated Kcn array 71.

Next, the encryption key array Kcn [i] (i = 0 to n)
The data is decrypted by using the encryption key Kcn [0] having the youngest array element number (step S27), and the process is passed to the upper layer.

If the encryption key array has not been updated,
The data is decrypted using the encryption key Kcn [0] having the smallest array number of the encryption key array Kcn [i] (i = 0 to n) (step S27), and the process is passed to the upper layer.

By the above operation, the encrypted data can be decrypted by the terminal 3.

[Second Embodiment] FIG. 9 is a processing flowchart of the encryption server 2 for explaining the second embodiment of the present invention, and FIG. 10 is a processing flowchart of the terminal 3.

Encryption server 2 in the second embodiment
4 is similar to that shown in FIG. 4, except that the encryption key used in the stream encryption means 43 in the encryption server 2 and the decryption key used in the stream decryption means 55 in the terminal 3 are The management method is different.

First, a multicast IP stream is input from the stream server 1 shown in FIG. 1 to the encryption server 2 (step S30). The encryption server 2 first determines whether or not the target is a multicast IP stream set as an encryption target (step S31). If it is not the multicast IP stream to be encrypted, it is sent to the network without modification (step S32).

In the case of the multicast IP stream to be encrypted, the current time has passed from the time t1 of the previous encryption and the time interval α for performing the encryption previously set in the encryption server 2 has elapsed. It is determined whether or not (step S33).

When the time interval α for performing encryption has passed, the current time is the time t2 at which the key array Kcn was previously updated.
It is then determined whether or not the update time interval β of the encryption key Kcn has elapsed (step S34).

When the update time interval β of the key array Kcn or more has elapsed, the encryption key array Kcn [i] (i = 0 to n) is updated (step S35). Here, the encryption key array K
cn [i] (i = 0 to n) is an array including a plurality of encryption keys Kcn, and the update operation is that the size of the encryption key array is n and the array starts from 0. In this case, the encryption key Kcn [1] having the array element number 1 is placed in the array element number 0, the encryption key Kcn [2] having the array element number 2 is placed in the array element number 1, ... Encryption key K with number n
The operation is repeated until cn [n] is placed in the array element number n-1, and a new encryption key Kcn [n] of the array element number n is generated.

Next, 1 is added to the key ID (used key number) which is the index number used for data encryption and incremented (step S36). Next, the key ID (= k)
The input data is encrypted using the encryption key Kcn [k] pointed to by (step S37). Then, an appropriate encryption information header is added to the data and the data is output (step S38).

After outputting the data, the updated encryption key array Kcn [i] (i = 0 to n) is encrypted using the encryption key Kph set for each multicast stream type, and the encrypted Kph A packet having (Kcn [i] (i = 0 to n)) as data is generated (step S39). An appropriate encryption information header is added to the generated key data of Kph (Kcn [i] (i = 0 to n)) and output (step S
40).

When the update time interval β of the key array Kcn has not elapsed, the encryption key Kcn of the current key ID (= k)
The input data is encrypted using [k] (step S41). Then, an appropriate encryption information header is added to the data and the data is output (step S4).
2).

After outputting the data, it is judged whether or not the present time has passed the sending time interval γ of the key array Kcn from the time t3 when the key array Kcn was sent before (step S).
43). If it has not elapsed, the process returns to step S30 and waits for the next input from the stream server 1.

When the transmission time interval γ of the key array Kcn or more has elapsed, the encryption key array Kcn [i] (i = 0 to n) is set to the encryption key Kph set for each multicast stream type.
Encrypted by using the encrypted Kph (Kcn [i]
A packet having (i = 0 to n) as data is generated (step S44). Generated Kph (Kcn [i] (i = 0 to
An appropriate encrypted information header is added to the key data of (n)) and output (step S45).

If it is determined in step S33 that the time interval α for encryption has not elapsed, the input data is not encrypted, an appropriate encryption information header is added, and the data is output as it is. Yes (Step S
46). After that, the processing from step S43 is performed.

By the above operation, encrypted data, non-encrypted data, and encrypted encryption key array are generated and sent to the network.

Next, the operation of the terminal 3 shown in FIG. 1 which receives the packet sent from the encryption server 2 by some means will be described with reference to the flowchart of FIG.

First, it is determined whether or not it is an encrypted multicast stream which is the object of decryption (step S50). If it is not an encrypted multicast stream, the process is passed to the upper layer as it is.

If the packet is an encrypted multicast stream, the encryption information header is checked to identify whether the packet is data or an encryption key array (step S5).
1).

If it is the encryption key array, the encryption key array Kph (Kcn [i] (i = 0 to n)) encrypted by using the encryption key Kph obtained by some means is decrypted. ，
Kcn [i] (i = 0 to n) is obtained (step S52).
In this update operation, the encryption key array 80 as shown in FIG.
Is newly obtained, and the key array held by the terminal 3 side up to that point is replaced by the newly obtained key array as it is to be updated (step S53).

If it is data, the encrypted information header is checked to identify whether it is encrypted (step S54). If it is not encrypted, the process is passed to the upper layer as it is.

When encrypted, the encryption key array Kcn [i] (i
Key ID (= 0 to n) indicating which encryption key to use (=
k) is read (step S55), the data is decrypted using the encryption key Kcn [k] indicated by the key ID (step S56), and the process is passed to the upper layer.

By the above operation, the encrypted data can be decrypted by the terminal 3.

[Third Embodiment] FIG. 12 is a processing flowchart of the encryption server 2 for explaining the second embodiment of the present invention, and FIG. 13 is a processing flowchart of the terminal 3.

Encryption server 2 in the third embodiment
Although the block diagram of the terminal 3 and the terminal 3 is not shown, it is almost the same as that in FIG. 4. The difference from the third embodiment in FIG. 4 is the encrypted information header adding means 4 of the encryption server 2.
7, a UDP (User Datagram Protocol) port number changing means is used, and a UDP port number determining means is used instead of the encrypted information header determining means 51 of the terminal 3.

First, a multicast IP stream is input from the stream server 1 shown in FIG. 1 to the encryption server 2 (step S60). The encryption server 2 first determines whether or not the target is a multicast IP stream set as an encryption target (step S61). If it is not the multicast IP stream to be encrypted, it is sent to the network without any modification (step S62).

In the case of the multicast IP stream to be encrypted, the current time has passed the time t1 previously encrypted, and the time interval α or more previously set in the encryption server 2 for performing the encryption has passed. It is determined whether or not (step S63).

If the time interval α for performing encryption has passed, the current time is the time t2 at which the key array Kcn was previously updated.
It is then determined whether or not the update time interval β of the encryption key Kcn has elapsed (step S64).

When the update time interval β of the key array Kcn or more has elapsed, the encryption key array Kcn [i] (i = 0 to n) is updated (step S65). Here, the encryption key array K
cn [i] (i = 0 to n) is an array including a plurality of encryption keys Kcn, and in the present embodiment, the current content encryption is the encryption with the lowest number in this array. We will use the key. Further, the update operation here means that when the size of the encryption key array is n and the array starts from 0, the encryption key Kcn whose array number is 1
Put [1] in the array number 0, the encryption key Kcn [2] whose array number was 2 in the array number 1, and so on. Repeatedly until -1 is entered, and a new encryption key Kcn of array element number n
The operation is to generate [n].

Next, the input data is encrypted using the encryption key Kcn [0] having the smallest number in the encryption key array (step S66). Then, the UDP (Use
The data number is output after changing the port number of r Datagram Protocol) to an appropriate value (step S67).

After outputting the data, the updated encryption key array Kcn [i] (i = 0 to n) is encrypted using the encryption key Kph set for each multicast stream type, and the encrypted Kph A packet having (Kcn [i] (i = 0 to n)) as data is generated (step S68). After that, a UDP port number having an appropriate value is added to the generated Kph (Kcn [i] (i = 0 to n)) and transmitted as a UDP packet (step S69).

When the update time interval β of the key array Kcn has not elapsed, the encryption key K having the lowest number in the encryption key array K
The input data is encrypted using cn [0] (step S70). Then, the UDP (Use
The data number is output after changing the port number of r Datagram Protocol) to an appropriate value (step S71).

After outputting the data, it is determined whether or not the present time has passed the sending time interval γ of the key array Kcn from the time t3 at which the key array Kcn was sent before (step S).
72). If it has not elapsed, the process returns to step S60 and waits for the next input from the stream server 1.

When the transmission time interval γ of the key array Kcn or more has elapsed, the encryption key array Kcn [i] (i = 0 to n) is set to the encryption key Kph set for each multicast stream type.
Encrypted by using the encrypted Kph (Kcn [i]
A packet having (i = 0 to n) as data is generated (step S73), and the generated Kph (Kcn [i] (i = 0 to 0) is generated.
The port number of UDP having an appropriate value is added to (n)) and the packet is transmitted as a UDP packet (step S74).

If it is determined in step S63 that the time interval α for performing encryption has not elapsed, the input data is not encrypted and the UDP of the data is not encrypted.
The port number is changed to an appropriate value and output (step S75). After that, the processing from step S72 is performed.

By the above operation, the encrypted data, the unencrypted data, and the encrypted encryption key array are generated and sent to the network.

Next, the operation of the terminal 3 shown in FIG. 1 which receives the packet sent from the encryption server 2 by some means will be described with reference to the flowchart of FIG.

First, it is judged whether or not the encrypted multicast stream is the object of decryption (step S80). If it is not an encrypted multicast stream, the process is passed to the upper layer that processes the received data as it is.

If the packet is an encrypted multicast stream, the UDP port number is checked to see if the packet is encrypted data with the encryption key changed.
Whether the data is encrypted without changing the encryption key,
Whether it is the encryption key array or the non-encrypted data is identified (step S81).

If the data is non-encrypted data, the process is passed to the upper layer as it is.

If it is the encryption key array, the encryption key array Kph (Kcn [i] (i = 0 to n)) encrypted by using the encryption key Kph obtained by some means is decrypted. (Step S82), Kcn [i] (i = 0 to n) is obtained. In this update operation, the key array newly obtained as shown in FIG. 7 is replaced by the key array that the terminal 3 had until then to update (step S8).
3).

When the encryption key array is changed and the data is encrypted, the encryption key array update operation is performed. In this update operation, the encryption key array is updated one by one as shown in FIG. 8 (step S84). Next, the data is decrypted using the encryption key Kcn [0] having the smallest array number of the encryption key array Kcn [i] (i = 0 to n) (step S85), and the process is passed to the upper layer.

When the data is encrypted without changing the encryption key, the encryption key array Kcn [i] (i = 0 to 0).
Data is decrypted using the encryption key Kcn [0] having the smallest array element number n) (step S85), and the process is passed to the upper layer.

By the above operation, the encrypted data can be decrypted by the terminal 3.

[Fourth Embodiment] FIG. 14 is a process flowchart of the encryption server 2 for explaining the second embodiment of the present invention, and FIG. 15 is a process flowchart of the terminal 3.

Encryption server 2 in the fourth embodiment
Although a block diagram of the terminal 3 and the terminal 3 is omitted, a UDP (User Datagram) is used instead of the encrypted information header adding means 47 of the encryption server 2 shown in FIG. 4 as in the third embodiment.
Protocol) port number changing means is used, and the terminal 3
Instead of the encrypted information header discriminating means 51, the UDP port number discriminating means is used.

First, a multicast IP stream is input from the stream server 1 shown in FIG. 1 to the encryption server 2 (step S90). In the encryption server 2, first, it is determined whether or not the multicast IP stream is the target of the encryption set (step S91). If it is not the multicast IP stream to be encrypted, it is sent to the network without any modification (step S92).

In the case of the multicast IP stream to be encrypted, the current time has passed the time t1 previously encrypted and the time interval α or more which is set in advance in the encryption server 2 for performing the encryption has passed. It is determined whether or not (step S93).

When the time interval α for performing encryption has passed, the current time is the time t2 at which the key array Kcn was updated before.
It is then determined whether or not the update time interval β of the encryption key Kcn has elapsed (step S94).

When the update time interval β of the key array Kcn or more has elapsed, the encryption key array Kcn [i] (i = 0 to n) is updated (step S95). Here, the encryption key array K
cn [i] (i = 0 to n) is an array including a plurality of encryption keys Kcn, and the update operation is that the size of the encryption key array is n and the array starts from 0. In this case, the encryption key Kcn [1] having the array element number 1 is placed in the array element number 0, the encryption key Kcn [2] having the array element number 2 is placed in the array element number 1, ... Encryption key K with number n
The operation is repeated until cn [n] is placed in the array element number n-1, and a new encryption key Kcn [n] of the array element number n is generated.

Next, 1 is added to the key ID (used key number) which is the index number used for data encryption and incremented (step S96). Next, the key ID (= k)
The input data is encrypted by using the encryption key Kcn [k] pointed to by (step S97). Then, the UDP port number of the data is changed to an appropriate value and the data is output (step S98).

After outputting the data, the updated encryption key array Kcn [i] (i = 0 to n) is encrypted using the encryption key Kph set for each multicast stream type, and the encrypted Kph A packet having (Kcn [i] (i = 0 to n)) as data is generated (step S99). After that, a UDP port number having an appropriate value is added to the generated Kph (Kcn [i] (i = 0 to n)) and the packet is transmitted as a UDP packet (step S100).

If the update time interval β of the key array Kcn has not elapsed, the encryption key Kcn of the current key ID (= k)
The input data is encrypted using [k] (step S101). Then, a UDP port number having an appropriate value is added to the data and the data is transmitted as a UDP packet (step S102).

After outputting the data, it is determined whether or not the current time has passed the sending time interval γ of the key array Kcn from the time t3 at which the key array Kcn was sent before (step S).
103). If it has not elapsed, the process returns to step S90 to wait for the next input from the stream server 1.

When the transmission time interval γ of the key array Kcn has passed, the encryption key array Kcn [i] (i = 0 to n) is set to the encryption key Kph set for each multicast stream type.
Encrypted by using the encrypted Kph (Kcn [i]
A packet having (i = 0 to n)) as data is generated (step S104). Generated Kph (Kcn [i] (i
= 0 to n)) and a UDP port number having an appropriate value is added and transmitted as a UDP packet (step S1).
05).

If it is determined in step S93 that the time interval α for performing encryption has not elapsed, the input data is not encrypted and the UDP of the data is not encrypted.
The port number is changed to an appropriate value and output (step S106). After that, the processing from step S103 is performed.

By the above operation, encrypted data, non-encrypted data, and encrypted encryption key array are generated and sent to the network.

Next, the operation of the terminal 3 shown in FIG. 1 which receives the packet sent from the encryption server 2 by some means will be described with reference to the flowchart of FIG.

First, it is judged whether or not it is an encrypted multicast stream which is the object of decryption (step S110). If it is not an encrypted multicast stream, the process is passed to the upper layer as it is.

If it is an encrypted multicast stream, the UDP port number is checked to identify whether it is encrypted data, an encryption key array, or non-encrypted data (step S111). ).

If the data is non-encrypted data, the process is passed to the upper layer as it is.

If it is an encryption key array, the encryption key array Kph (Kcn [i] (i = 0 to n)) encrypted by using the encryption key Kph obtained by some means is decrypted. (Step S112), Kcn [i] (i = 0 to n) is obtained. In this update operation, the key array newly obtained as shown in FIG. 7 is replaced with the key array that the terminal 3 side had until then (step S11).
3).

When the data is encrypted, the ID (= UD) of the encryption key array Kcn [i] (i = 0 to n)
The data is decrypted using the encryption key Kcn [i] which is the P port number) (step S114), and the process is passed to the upper layer.

By the above operation, the encrypted data can be decrypted by the terminal 3.

In the above four embodiments, the number of the terminals 3, the encryption server 2, the encryption key management server 4, and the stream server 1 is one, but the number is of course not limited. Also, the encryption key Kej unique to the encryption server 2 and the terminal 3
The distribution method of the unique encryption key Kui is not limited. Further, the method of distributing the encryption key Kph for encrypting the encryption key Kcn to the encryption server 2 and the terminal 3 is not limited.

When distributing the encrypted data from the encryption server 2 side or distributing the key array used for decryption, each packet is sent to another multicast address and the multicast is sent to the terminal 3 side. By identifying the address, it is possible to distinguish whether the packet is a content data packet or a key array packet.

In the above description of the embodiment of the present invention, an example of the case of performing encryption by the common key method has been described. However, when an encryption method other than the common key method is used, the encryption server 2 can The key array to be sent to the encryption server 2
It goes without saying that the key array is a decryption key array corresponding to the encryption key used by.

[0138]

As described above, according to the present invention,
When delivering contents such as IP streams, by implementing encryption that supports multicast that changes the encryption key on the order of seconds, it is possible to ensure security and provide inexpensive services, and further encrypt only part of the data. By adopting this technology, it is possible to support terminal devices (client devices) with low processing capacity.

[Brief description of drawings]

FIG. 1 is an IP network configuration diagram to which the present invention is applied.

FIG. 2 is a diagram showing an example of a hierarchical structure of encryption keys when the present invention is applied.

FIG. 3 is a diagram showing an example of a transmission packet in the embodiment of the present invention.

FIG. 4 is a block configuration diagram of an encryption server and a terminal for explaining an embodiment of the present invention.

FIG. 5 is a processing flowchart of the encryption server according to the first embodiment.

FIG. 6 is a processing flowchart of the terminal according to the first embodiment.

FIG. 7 is a diagram showing an example of updating an encryption key array in the first and third embodiments.

FIG. 8 is a diagram showing an example of updating an encryption key array in the first and third embodiments.

FIG. 9 is a processing flowchart of an encryption server according to the second embodiment.

FIG. 10 is a processing flowchart of the terminal according to the second embodiment.

FIG. 11 is a diagram showing an example of an encryption key array used in the second and fourth embodiments.

FIG. 12 is a processing flowchart of an encryption server according to the third embodiment.

FIG. 13 is a processing flowchart of the terminal according to the third embodiment.

FIG. 14 is a processing flowchart of an encryption server according to the fourth embodiment.

FIG. 15 is a processing flowchart of the terminal according to the fourth embodiment.

[Explanation of symbols]

1 stream server 2 encryption server 3 terminal 4 encryption key management server 5 IP network 6 encryption key Kej different for each encryption server Kej 7 encryption key Kui 8 Kej different for each terminal encrypted encryption key Kph different for each IP stream Data 9 Kui encrypted with different encryption key Kph for each IP stream 10 Transmission direction of IP stream output from stream server 11 Transmission direction of IP stream encrypted by encryption server 12 Stream server and encryption server Communication path between 13 Communication path between encryption key management server and encryption server 14 Communication path between encryption key management server and terminal 20 Encryption key Kcn used for encrypting IP stream 21 Encryption key Kcn is encrypted Cryptographic key used to do Kph 22 IP stream 23 Encrypted IP stream 2 4 Decrypted IP stream 25 IP of encryption key Kcn encrypted with encryption key Kph
Stream 26 Delivery of encryption key Kph encrypted by encryption key Kej 27 Delivery of encryption key Kph encrypted by encryption key Kui 30 Packet 31 Encryption information header 40 Stream encryption interval determination means 41 Key array update interval determination means 42 Key Array Transmission Interval Discrimination Means 43 Stream Encryption Means 44 Key Array Update Means 45 Key Array Encryption Means 46 Key Array Storage Means 47 Encryption Information Header Addition Means 48 Packet Transfer Means 50 Packet Reception Means 51 Encryption Information Header Discrimination Means 52 Key Array Decoding Means 53 Key Array Updating Means 54 Key Array Storage Means 55 Stream Decoding Means

Continued front page    (72) Inventor Takako Sato             2-3-1, Otemachi, Chiyoda-ku, Tokyo             Inside Telegraph and Telephone Corporation F term (reference) 5J104 AA16 AA33 AA34 BA03 EA01                       EA18 JA03 JA21 JA31 MA01                       NA02 PA07

Claims (13)

[Claims] 1. A method for encrypting content distributed to a terminal via a network, the method comprising storing a key array including a plurality of encryption keys for encrypting data of content distributed in packets. , If the input stream is the content to be encrypted, the process of determining whether the packet needs to be encrypted based on the predetermined packet encryption interval or frequency information, and the encryption of the packet. If the encryption is required, the data is encrypted by using one encryption key in the key array and distributed, and if the encryption is not required, the process of distributing the data as it is and the update of the key array Is determined based on predetermined key array update interval or frequency information, and if the key array needs to be updated, at least one A process of updating the currently stored key array with a key array including an encryption key and whether or not it is necessary to send the key array, predetermined sending interval or frequency information of the key array, or the key array And the key array of the currently stored encryption key or the decryption key array corresponding to the encryption key, if it is necessary to transmit the key array, A method for encrypting content, which comprises a step of encrypting with a cryptographic key given in advance and distributing data of the encrypted key array. 2. The content encryption method according to claim 1, which is a packet of content data or a packet of key array when distributing a key array used for distribution and decryption of encrypted data. Information that distinguishes
A content encryption method characterized in that the content is added to the header of the packet for distribution. 3. The content encryption method according to claim 1, wherein each packet is transmitted to another multicast address when distributing the encrypted data and the key array used for decryption. A content encryption method characterized in that a packet is a packet of content data or a packet of a key arrangement by identifying the multicast address on the receiving side. 4. The content encryption method according to claim 1, wherein when the encrypted data or a packet of a key array used for decryption on the receiving side is transmitted as a TCP or UDP packet, the data packet and the encryption are transmitted. Content encryption characterized by changing the port number of each key packet and allowing the receiving side to identify the port number to distinguish whether the packet is a content data packet or a key array packet. Method. 5. Any one of claims 1 to 4
In the content encryption method according to the item, when the encryption key for encrypting the key array is distributed to the encryption device that encrypts the content, the encryption device manages the encryption key. Make an authentication request to the key management device,
A content encryption method, wherein an encryption key is distributed from the encryption key management device to the encryption device when authentication is successful. 6. The content encryption method according to claim 5, wherein when the encryption device makes an authentication request to the encryption key management device, a different common key for each encryption device is previously stored in the encryption device. Stored in the encryption device and the encryption key management device, the encryption device requests the encryption key management device to obtain an encryption key for encrypting the key array,
The encryption key management device generates an encrypted encryption key by encrypting an encryption key for encrypting the key array using a common key corresponding to the encryption device for which an acquisition request is made, The encryption device, which has distributed the encryption key to the encryption device and has received the encrypted encryption key, decrypts the received encryption key using the common key to obtain a key array. A content encryption method, characterized in that an encryption key for encrypting is acquired. 7. The content encryption method according to claim 5 or 6, wherein when the encryption device makes an authentication request to the encryption key management device, a public key cryptosystem is used for authentication. Content encryption method characterized by. 8. A method of decrypting content delivered over a network, comprising: receiving an encrypted key array including a plurality of keys for decrypting a packet of delivered content, The process of decrypting using a key sequence for decrypting the key sequence given in advance and storing it as the key sequence used for decrypting the data, and when the input stream is the content to be encrypted, the data is encrypted. If the data is encrypted, it is determined whether the stored key array needs to be updated. If the key array needs to be updated, After updating the key array, if it is not necessary to update the key array, the key array is not updated, and the data is decrypted using one key for decryption in the key array. Conte characterized by Decryption method. 9. The content decryption method according to claim 8, wherein when a decryption key for decrypting the key array is distributed to a terminal that decrypts the content, the terminal manages an encryption key. A content decryption method characterized in that an authentication request is issued to an encryption key management device, and when the authentication is successful, the encryption key management device distributes the decryption key to the terminal. 10. The content decryption method according to claim 9, wherein when the terminal makes an authentication request to the encryption key management device, a common key different for each terminal is preliminarily provided to the terminal and the encryption key. It is held in the key management device, and the terminal requests the encryption key management device to obtain a decryption key for decrypting the key array, and the encryption key management device corresponds to the terminal that has made the acquisition request. An encrypted decryption key is generated by encrypting the decryption key for decrypting the key array using a common key, the decryption key is distributed to the terminal, and the encrypted decryption key is encrypted. A content decryption method, characterized in that a terminal that receives a decryption key obtains a decryption key for decrypting a key array by decrypting the received decryption key using the common key. 11. The content decryption method according to claim 9 or 10, wherein when the terminal makes an authentication request to the encryption key management device, a public key cryptosystem is used for authentication. Content decryption method. 12. An encryption device for encrypting content to be delivered to a terminal via a network, which stores a key array including a plurality of encryption keys for encrypting data of content to be delivered in packets. And a means for determining whether or not the packet needs to be encrypted when the input stream is content to be encrypted, based on a predetermined packet encryption interval or frequency information, and the packet. If the encryption is required, the data is encrypted by using one encryption key in the key array and delivered, and if the encryption is not required, means for delivering the data as it is, and the key array Means for determining whether or not the key array needs to be updated based on a predetermined key array update interval or frequency information, and when the key array needs to be updated,
A means for updating the currently stored key array with a key array including at least one encryption key to be used in the future, and whether or not it is necessary to send out the key array, and a predetermined key array sending interval or A means for discriminating based on the frequency information or the update interval of the key array or the frequency information, and if the key array needs to be transmitted, it corresponds to the key array of the currently stored encryption key or the encryption key thereof. The key array of the decryption key is
A content encryption device, comprising: a means for encrypting with a cryptographic key given in advance and delivering the encrypted data of the key array. 13. A device for decrypting content distributed via a network, which receives an encrypted key array including a plurality of keys for decrypting a packet of distributed content, A means for decrypting using a key for decrypting a key array given in advance and storing it as a key array used for decrypting the data, and when the input stream is the content to be encrypted, the data is encrypted. And if the data is encrypted, it is determined whether or not the stored key array needs to be updated, and if the key array needs to be updated, After updating the key array, if it is not necessary to update the key array,
A content decryption apparatus, comprising means for decrypting data using one key for decryption in the key array without updating the key array.