JP2015015760A - Content providing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To transmit content in a range of proper use of a user while limiting the number of apparatuses to simultaneously transmit the content.SOLUTION: A content utilization device periodically transmits a key ID corresponding to an exchange key by a command, and a content providing device holds the corresponding exchange key only in a period during which the key ID can be received in every prescribed reception cycle. When the key ID cannot be periodically received anymore, the content providing device discards the corresponding exchange key, and when the command including the key ID is received thereafter, returns a response including information indicating that the exchange key is invalidated.

Description

  The present invention relates to a communication system, a communication apparatus, a communication method, and a computer program for preventing unauthorized use in content transmission. In particular, the present invention relates to a decryption key for encrypted content according to a predetermined mutual authentication and key exchange (AKE) algorithm. The present invention relates to a communication system, a communication device, a communication method, and a computer program for exchanging encrypted content.

  Conventionally, broadcast content and content in packaged media have been used at locations where content usage devices and playback devices are installed, or at devices connected to these devices via a home network (hereinafter referred to as “local access”). (LA) ") was the basic. For example, by connecting to the above-described content utilization device or playback device with a portable device from outside, using the content with transmission via an external network such as a WAN (Wide Area Network) (hereinafter referred to as “Remote Access (RA)”) Is also difficult from a technical point of view, such as communication channels and codecs. However, in the future, data communication technologies such as LTE (Long Term Evolution) and WiMAX (World Interoperability for Microwave Access), High compression codecs such as H.264 are expected to become widespread, and by using these, the feasibility of remote access can be seen. For example, the user can remotely access the home server from the destination and play the content.

  The digitized content is relatively easy to perform illegal operations such as copying and falsification. In particular, in remote access, it is necessary to prevent unauthorized use involved in content transmission and protect the copyright of the content while permitting the use of personal or home content.

  As an industry standard technique regarding transmission protection of digital contents, there is DTCP (Digital Transmission Content Protection) developed by DTLA (Digital Transmission Licensing Administrator). In DTCP, an authentication protocol between devices at the time of content transmission and a transmission protocol for encrypted content are decided. To summarize, the DTCP compliant device does not send out compressed content that is easy to handle in an unencrypted state outside the device, and the key exchange required to decrypt the encrypted content is a predetermined mutual authentication. And the key exchange (Authentication and Key Exchange: AKE) algorithm, and limiting the range of devices that perform key exchange using the AKE command.

  Further, according to the DTCP technology transplanted to the IP network, that is, DTCP-IP (DTCP mapping to IP), digital contents can be distributed through the IP network even at home. The current DTCP-IP (DTCP Volume 1 Specification Supplementation E Revision 1.2) is mainly intended to ensure the use of content only in the home, and a round trip time (RTT: Round Trip Time) for the AKE command. In addition, a limit is set on the hop count (TTL: Time To Live) of the IP router.

  For example, the source continues to monitor each AKE command received from the start of DTCP-IP authentication to immediately before it ends, updates the maximum value of the TTL value, and sets the TTL value immediately before the authentication procedure ends. The maximum value is checked, and if this maximum value is 3 or less, the key exchange is completed to complete the authentication procedure. If the maximum value is exceeded, a proposal has been made for an information communication system that terminates the authentication procedure without performing the final step. (For example, see Patent Document 1).

  In addition, in order to limit unauthorized use of content, the content owner may prohibit one content providing device (Source) from simultaneously transmitting content to a number of content using devices (Sinks).

  On the other hand, a user who uses content may use a plurality of content use devices depending on the situation, or may share one content providing device installed in the home with a family. In such a usage mode, content transmission from one content providing device in a home to a plurality of content using devices is within the range of legitimate use of content, and the number of content owners is limited as described above. Setting content to prohibit content transmission unduly restricts the user's use of content.

JP 2007-36351 A

  An object of the present invention is to provide an excellent communication system, communication apparatus and communication method, and computer capable of suitably transmitting encrypted content by exchanging a decryption key of the encrypted content according to a predetermined mutual authentication and key exchange algorithm.・ To provide a program.

  A further object of the present invention is to allow the transmission of content within the range of legitimate use by the user, while limiting the number of devices that simultaneously transmit content that requires protection for copyright and other purposes. It is an object to provide an excellent communication system, communication apparatus and communication method, and computer program.

The present application has been made in consideration of the above problems, and the invention according to claim 1
A communication system for performing communication for content transmission between a content providing device that provides content and one or more content using devices that use content,
Mutual authentication and key exchange means for exchanging keys for mutual authentication and content encryption between the content providing device and the content using device;
A key recording unit that records a key provided by the content providing device to each content using device in combination with a key ID that identifies the key and a device ID that identifies the content using device;
Key management means for maintaining the information of the key ID in the key recording means only while the content use device periodically transmits a key life management command including the key ID to the content providing device;
A communication system comprising:

  However, “system” here refers to a logical collection of a plurality of devices (or functional modules that realize specific functions), and each device or functional module is in a single housing. It does not matter whether or not.

The invention according to claim 2 of the present application is
Mutual authentication and key exchanging means for exchanging keys for mutual authentication and content encryption with one or more content use devices that are content providing destinations;
A key recording means for recording a key passed to each content use device in combination with a key ID for specifying the key and a device ID for specifying the content use device;
Key management means for maintaining information corresponding to the key ID in the key recording means only while receiving a key life management command including the key ID from the content use device at a predetermined reception cycle;
It is a communication apparatus which comprises.

  According to the invention described in claim 3 of the present application, the key management means of the communication device according to claim 2 stores information corresponding to the key ID for which the key life management command could not be received at a predetermined reception cycle. It is comprised so that it may discard from a recording means.

  According to the invention of claim 4 of the present application, the key management means of the communication device of claim 2 receives the key life management command received in response to receiving the key life management command from the content utilization device. A response indicating that the key is valid is returned when the information corresponding to the key ID included in the key recording means is maintained, and if the corresponding information is discarded from the key recording means, the key is A response indicating invalidity is returned.

  According to the invention described in claim 5 of the present application, the key management means of the communication device according to claim 2 responds to the reception of the key life management command in which information for instructing the key destruction is set. The corresponding key information is discarded from the key management means.

  According to the invention described in claim 6 of the present application, the communication device described in claim 2 further includes registration means for performing pre-registration of the content using device for key exchange. Then, the key management means is configured to send back a response indicating that it has not been registered in response to receiving a key life command from a content utilization apparatus not pre-registered in the registration means.

The invention according to claim 7 of the present application is
Mutual authentication and key exchange means for exchanging a key for mutual authentication and content encryption with a content providing apparatus as a content provider;
A key life management means for transmitting a key life management command including a key ID for identifying a key passed from the content providing device by the mutual authentication and key exchange means;
It is a communication apparatus which comprises.

  According to the invention described in claim 8 of the present application, the key life management means of the communication device according to claim 7 is a key life management in which information for instructing key destruction is set when the key becomes unnecessary. It is configured to send commands.

The invention according to claim 9 of the present application is
A mutual authentication and key exchange step of exchanging keys for mutual authentication and content encryption with one or more content utilization devices that are content providers;
A key recording step for recording a key passed to each content use device in combination with a key ID for specifying the key and a device ID for specifying the content use device;
A key management step of maintaining information corresponding to the key ID in the key recording means only while receiving a key life management command including the key ID from the content use device at a predetermined reception cycle;
Is a communication method.

The invention according to claim 10 of the present application is
A mutual authentication and key exchange step of exchanging keys for mutual authentication and content encryption with a content providing device as a content provider;
A key life management step of transmitting a key life management command including a key ID for identifying the key passed from the content providing device in the mutual authentication and key exchange step;
Is a communication method.

The invention according to claim 11 of the present application is a content providing apparatus in a communication system that performs communication for content transmission between a content providing apparatus that provides content and one or more content using apparatuses that use the content. A computer program written in a computer-readable format to execute a process for operation on a computer,
Mutual authentication and key exchange means for exchanging keys for mutual authentication and content encryption with one or more content use devices which are content providing destinations;
Key recording means for recording a key passed to each content using device in combination with a key ID for specifying the key and a device ID for specifying the content using device;
Key management means for maintaining information corresponding to the key ID in the key recording means only while receiving a key life management command including the key ID from the content utilization device at a predetermined reception cycle;
It is a computer program to function as.

According to a twelfth aspect of the present invention, in a communication system that performs communication for content transmission between a content providing device that provides content and one or more content using devices that use the content, A computer program written in a computer-readable format to execute a process for operation on a computer,
Mutual authentication and key exchange means for exchanging keys for mutual authentication and content encryption with a content providing device as a content provider;
Key life management means for transmitting a key life management command including a key ID for identifying a key passed from the content providing device by the mutual authentication and key exchange means;
It is a computer program to function as.

  Each computer program according to claims 11 and 12 of the present application defines a computer program written in a computer-readable format so as to realize predetermined processing on a computer. In other words, by installing the computer program according to claims 11 and 12 of the present application on a computer, a cooperative action is exhibited on the computer, which is the same as the communication device according to claims 2 and 7 of the present application, respectively. An effect can be obtained.

  According to the present invention, it is possible to transmit content within the range of legitimate use by the user while limiting the number of devices that simultaneously transmit content that requires protection for copyright and other purposes. Communication system, communication apparatus and communication method, and computer program can be provided.

  According to the first, second, third, seventh, and ninth to twelfth aspects of the present application, the content using device transmits a key life management command including a key ID to the content providing device every predetermined transmission cycle. The content providing apparatus maintains the corresponding key only for a period during which the key life management command can be received at a predetermined reception cycle. Therefore, the content providing apparatus can determine the number of content using apparatuses that can simultaneously transmit the content. The following can be limited.

  According to the invention of claim 4 of the present application, in response to receiving the key life management command, the content providing apparatus responds that the key is valid when maintaining the corresponding key. Reply. Further, when a command is received after the corresponding key is discarded because the key life management command cannot be received at a predetermined reception cycle, a response indicating that the key is invalid is returned. Therefore, the content using apparatus can confirm the current status of the key held by the content using apparatus.

  According to the invention described in claims 5 and 8 of the present application, the content use device sets information indicating that it is not necessary in the key life management command corresponding to the unnecessary key, and the content providing device does not require the key. In response to receiving the key life management command in which the information indicating that it is set, the corresponding key is discarded, so that it is possible to newly exchange keys with other content using devices within the upper limit of the number of devices. become.

  According to the invention described in claim 6 of the present application, the content providing apparatus can perform pre-registration of the content using apparatus for key exchange in response to a request from the content owner. The content providing device returns a response indicating that it has not been registered in response to receiving the key life command from the content using device that has not been pre-registered. Can be recognized.

  Other objects, features, and advantages of the present invention will become apparent from more detailed description based on embodiments of the present invention described later and the accompanying drawings.

FIG. 1 is a diagram schematically showing a configuration example of a communication system according to the present invention. FIG. 2 is a diagram schematically showing another configuration example of the communication system according to the present invention. FIG. 3 is a diagram schematically illustrating a functional configuration of the content providing apparatus 10. FIG. 4 is a diagram schematically illustrating a functional configuration of the content use apparatus 20. FIG. 5 is a diagram for explaining a mechanism for performing encrypted content transmission between a source and a sink by DTCP-IP. FIG. 6 is a diagram showing an operation sequence of mutual authentication and key exchange using an AKE command performed between the source and the sink according to the current DTCP-IP. FIG. 7 shows an operation sequence of mutual authentication and key exchange including a restriction on the number of content use devices that can simultaneously perform content transmission between the source corresponding to the content providing device and the sink corresponding to the content use device. FIG. FIG. 8 is a diagram illustrating an example of connection table update processing. FIG. 9 is a diagram showing a format example of the KEEP_ALIVE command. FIG. 10 is a diagram showing an example of an operation sequence for updating the lifetime of the exchange key Kr performed between the source and the sink. FIG. 11 is a diagram showing another example of an operation sequence for updating the lifetime of the exchange key Kr performed between the source and the sink.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  The present invention relates to a communication system for securely transmitting content through remote access (RA) via an external network such as a WAN. The communication system basically includes a server (RA-Source) that provides content by remote access and a client (RA-Sink) that requests content by remote access. In this specification, the AKE procedure performed at the time of remote access is referred to as “RA-AKE”. Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 schematically shows a configuration example of a communication system according to the present invention. In the illustrated communication system, a content providing device 10 corresponding to RA-Source is installed in a home, and a content using device 20 corresponding to RA-Sink is outdoors. Then, the content use device 20 remotely accesses the content providing device 10 by a communication function such as a mobile phone.

  The content providing apparatus 10 is generally connected to an external network such as the WAN 50 via the router 30 and the modem 40. The WAN 50 is, for example, the Internet. An IP address on the WAN 50 side is assigned to the router 30 from an Internet Access Service (IAS) provider 60 to which a user subscribes. Also, the content utilization device 20 basically accesses this IP address. The router 30 assigns a private IP address to the content providing apparatus 10, and relays communication by port forwarding for access from the WAN 50. Note that the IP address assigned to the router 30 may be updated by the IAS provider 60. In such a case, the DDNS service 70 is used, and the DNS 30 (Dynamic DNS (Domain Name System) of the router 30 to the content providing apparatus 10 is used. )) Can be supported by using the function.

  FIG. 2 schematically shows another configuration example of the communication system according to the present invention. In the illustrated communication system, a content utilization device 20 corresponding to RA-Sink is also installed in the home and connected to the WAN 50 via a router 31 and a modem 41. The TCP / IP (Transmission Control Protocol / Internet Protocol) communication transmitted from the content use device 20 is address-converted by the NAT (Network Address Translation) function of the router 31, but the rest is the same as in FIG. .

  FIG. 3 schematically shows a functional configuration of the content providing apparatus 10. The content providing apparatus 10 includes a CPU (Central Processing Unit) 11, a content reception / playback unit 12, a communication unit 13, a storage unit 14, and a timer 15, but functions as an RA-Source for remote access. Send content with.

  The content reception / playback unit 12 has a broadcast reception function and a package media playback function. The CPU 11 appropriately protects the content obtained by the content receiving / reproducing unit 12 that can be remotely accessed, and then performs mutual authentication and key exchange by RA-AKE through the communication unit 13. (Content use device 20).

  The storage unit 14 stores the RA-Sink identification information to be stored by the registration process described later, the remote access exchange key shared with the RA-Sink through RA-AKE and the identification information of the exchange key ( Hereinafter, it is also referred to as “key ID”). In the present embodiment, the number of exchange keys and key IDs that can be registered simultaneously is limited to n (where n is a positive integer). A connection table and a receiving device table described later are also stored in the storage unit 14. The storage unit 14 can also be used for storing contents obtained by the content receiving / reproducing unit 12.

  The timer 15 is used when time management is required when handling remotely accessible content (for example, when managing the reception period of the key ID from the RA-Sink as described later).

  FIG. 4 schematically shows a functional configuration of the content use apparatus 20. The content use device 20 includes a CPU 21, a communication unit 22, a content output unit 23, and a storage unit 24, but functions as an RA-Sink and receives content by remote access.

  The RA-Sink content utilization device 20 performs an exchange key and key ID registration process, which will be described later, on the RA-Source (content providing device 10) through the communication unit 22, and also performs RA-AKE to perform RA-Source. The exchange key is obtained and stored in the storage unit 24, the encrypted content obtained from the RA-Source is decrypted with the encryption key calculated based on the key, and the content is output from the content output unit 23. The storage unit 24 is used for storing an exchange key and content received from the RA-Source.

  The timer 25 is used when time management is required when handling remotely accessible content (for example, when managing the transmission period of the key ID from the RA-Source as will be described later).

  In the following description, the method for calculating the encryption key from the exchange key is based on DTCP-IP (however, the gist of the present invention is not necessarily limited to this method).

  Here, a mechanism for performing encrypted content transmission by DTCP-IP between a source corresponding to a content providing apparatus and a sink corresponding to a content using apparatus will be described with reference to FIG. 5 (RA-Source and RA). -It should be understood that the mechanism between the sinks is the same). There are two types of content transmission: a method of copying content on the source to the sink and a method of moving the content from the source to the sink and leaving no content on the source (well-known). The explanation is based on the method.

The Source and Sink first establish one TCP / IP connection and perform authentication (AKE procedure) between devices. A device certificate issued by DTLA (described above) is embedded in the DTCP-compliant device. In the AKE procedure, it is possible to share the authentication key _auth between the source and the sink after confirming that they are regular DTCP-compliant devices.

When the AKE procedure is successful, Source generates an exchange key K _x as a seed of the content key K _c, and sends it to the Sink encrypted authentication key K _auth. In each Source and Sink, by applying a predetermined arithmetic processing on the exchange key K _x, it is possible to generate a content key K _c which is used to encrypt content when the content transmission.

  Then, after an authentication and key exchange procedure by AKE is completed between DTCP-compliant devices, content transmission is started using a protocol such as HTTP (Hyper Text Transfer Protocol) or RTP (Real Time Protocol). In the illustrated example, content transmission is performed according to the HTTP procedure. At this time, a TCP / IP connection for HTTP is created separately from the TCP / IP connection for the AKE procedure (that is, Source and Sink have separate socket information (for the AKE procedure and content transmission, respectively) IP address and port number combination)).

  There are two ways to perform content transmission according to the HTTP protocol: a download format in which Sink requests content from the source, and an upload format in which content is pushed from the source side to the sink. In the former case, the sink as the HTTP client requests content from the source as the HTTP server by, for example, an HTTP request using the HTTP GET method, and the requested content is transmitted as an HTTP response from the source. The In the latter case, the Source as the HTTP client starts transmission with the Sink as the HTTP server, for example, by an HTTP request using the HTTP POST method.

The data transmitted from the source is data obtained by encrypting the content using a key shared after the source performs AKE authentication. Specifically, the source generates a nonce N _c using a random number, and generates a content key K _c corresponding to the exchange key K _x , the nonce N _c, and the encryption mode. Then, the content requested by the sink is encrypted using the content key K _c, and a packet including a payload including the encrypted content, a nonce N _c and a header including encryption mode information is placed on the TCP stream. Send. In the IP protocol, a TCP stream is divided into packet sizes as a predetermined unit, further converted into an IP packet with a header added, and delivered to a specified IP address.

On the sink side, when each IP packet is received from the source, it is assembled into a TCP stream. When the nonce N _c and E-EMI are extracted from this stream, the content key K _c can be calculated using these and the exchange key K _x , and the encrypted content can be decrypted using the content key K _c . Then, the reproduction processing can be performed on the plaintext content after decryption. Alternatively, the sink stores the content in the storage unit 24 or passes it to another device without decrypting the encrypted content. When content transmission using the HTTP protocol is completed in this way, the TCP connection used for content transmission is appropriately disconnected from the sink side, for example. (In DTCP-IP, transmission of copy control information associated with content is realized by two mechanisms: E-EMI (Extended Encryption Mode Indicator) and Embedded CCI (Copy Control Information) described in the header of the packet. .)

In DTCP-IP, be continuous unused time destroys the exchange key K _x before exceeding a predetermined time period (e.g. 2 hours) are defined. Sink is to be able to get the latest exchange key K _x from the Source, it becomes unavailable the encrypted content. In addition, the method of operation of the exchange key K _x, there is a method to use and how to prepare a one-by-one key for each Sink, one of the key regardless of the Sink. In the present embodiment, the providing a replacement key K _x, one for every Sink, assumed the identification information to each exchange key K _x (key ID) is assigned.

  FIG. 6 shows an operation sequence (RTT-AKE) of mutual authentication and key exchange using an AKE command performed in accordance with the current DTCP-IP between the source corresponding to the content providing device and the sink corresponding to the content using device. Show.

  In the challenge-response portion of AKE procedure, an Rx challenge including an Rx random number and an Rx certificate is first transmitted from a sink requesting content. In response to this, a Tx challenge including a Tx random number and a Tx certificate is returned from the source. Thereafter, the Rx response including the Rx random number, the Tx message, and the Tx signature is transmitted from the source, and the Tx response including the Tx random number, the Rx message, and the Rx signature is transmitted from the sink. The procedure continues. In the command transmitted in the challenge / response portion, each challenge command includes a Device ID that is identification information unique to the device.

  In the above challenge / response response procedure, TTL (IP router hop count) is restricted. That is, in the current DTCP-IP, in the TCP / IP communication in which the sending device sends a command used in AKE, the TTL is set to 3 or less, and when the TTL is larger than 3, the receiving device must invalidate the received data. .

  Thereafter, an EXCHANGE_KEY command is transmitted from the source to the sink through the RTT protection protocol (protected RTT protocol), and a response (not shown) is returned from the sink.

  In RTT-AKE according to the current DTCP-IP shown in FIG. 6, contents can be transmitted via an IP network by setting an upper limit on the round-trip delay time (RTT) and the number of hops (TTL) of the IP router for the AKE command. The range is limited. Depending on the content owner, in order to further restrict unauthorized use of content, an upper limit is set for the number of content usage devices (RA-Sinks) that simultaneously transmit content from one content providing device (RA-Source). There is.

  However, users who use content can use a plurality of content utilization devices (RA-Sinks) according to the situation, or share a single content provision device (RA-Source) installed in the home with their families. It is possible to do. Transmitting content from one content providing device in a home to a plurality of content using devices is within the range of proper use of content, and content owners set the number limit and transmit content as described above. The prohibition unreasonably restricts the user's use of content.

  Therefore, in the communication system according to the present embodiment, the upper limit of the number of content use devices that simultaneously transmit content from one content providing device is set to n (where n is a positive integer), and a special by the user. Introduced a mechanism to ensure the legitimate use of content by users while responding to content protection requests from content owners by appropriately replacing the content usage devices included in the upper limit of n devices without switching Yes.

  In order to limit the number of content using devices that can simultaneously transmit content to the content providing device, the content using device sends a key ID corresponding to the exchange key to the content providing device every predetermined transmission cycle. Send by command. Then, the content providing apparatus holds the corresponding exchange key only during a period in which the key ID can be received every predetermined reception cycle. On the other hand, when the command including the key ID cannot be received at a predetermined reception cycle, the corresponding exchange key is discarded. DTCP-IP stipulates that the exchange key be discarded before the continuous non-use time exceeds a predetermined period (described above). In this embodiment, the key ID is included even within 2 hours. If the command cannot be received periodically, the content providing apparatus discards the corresponding exchange key.

  When receiving the command including the key ID, the content providing apparatus checks whether or not the corresponding exchange key is maintained. When a corresponding command is received while the exchange key is maintained, a response including information indicating that the exchange key is valid is returned to the content use apparatus that is the transmission source. On the other hand, when the command is received after the corresponding exchange key is discarded because the command including the key ID cannot be received at a predetermined reception cycle, a response including information indicating that the exchange key is invalid is received. A reply is sent to the content use device of the transmission source.

  Further, when the content providing apparatus cannot receive the command including the key ID periodically, the content providing apparatus receives the command including the key ID corresponding to the exchange key after discarding the exchange key. Then, a response including information that the exchange key (or the content key generated from the exchange key) is invalid is sent back to the content use apparatus as the transmission source.

  Further, when the exchange key becomes unnecessary due to the end of the communication process with the content providing apparatus, the content using apparatus sets information indicating that in a command to be transmitted periodically. When the content providing apparatus receives this command, it discards the corresponding exchange key.

  In addition, the content providing apparatus may perform key life management only with a content use apparatus registered in advance. The content utilization device includes a device ID that identifies itself in a command that is periodically transmitted. On the other hand, the content providing device that has received the command receives the content utilization device corresponding to the device ID included in the received command. Check if is registered. If the content transmission device that is the source of the command transmission is not registered, the content provision device confirms that the content usage device has not been registered before checking the validity of the exchange key corresponding to the key ID included in the command. Is sent back to the content utilization apparatus as the transmission source.

  FIG. 7 shows an operation sequence of mutual authentication and key exchange including a restriction on the number of content use devices capable of simultaneously transmitting content, performed between a source corresponding to the content providing device and a sink corresponding to the content use device. ing. However, the illustrated sequence is based on DTCP Full Authentication processing. Although it is considered that operations that are not set in remote access are common, as with the operation sequence shown in FIG. 6, there is an upper limit on the round trip time (RTT) and the number of hops (TTL) of the IP router for the AKE command. It may be set. However, illustration is omitted.

  When the sink needs content, it sends a CHALLENGE command to the source. At this time, in order to indicate that the mutual authentication and key exchange procedures are intended to share a key (Kr) for remote access to the source, Sink includes a Kr-bit in the CHALLENGE command. Set. In addition, the device ID which is the specific information of the sink is also transmitted by the CHALLENGE command.

  Thereafter, based on the DTCP Full Authentication protocol, a CHALLENGE command from the source, a RESPONSE command from the sink, a RESPONSE command or a RESPONSE2 command from the source are sequentially transmitted.

  In the challenge / response portion, “RESPONSE2” may be sent as a response from the sink to the source. This is a case where the device ID does not become the specific information of the sink by mounting the common device key and the common device certificate, and the IDu sent by the RESPONSE2 command is used as the specific information of the sink.

  The source determines a device ID for specifying the sink (step S71). When the RESPONSE2 is received, the Source uses IDu, and when the RESPONSE2 command is not received, the Device ID is used as the device ID.

  When the source passes the exchange key Kr for remote access to the sink as a result of the mutual authentication and key exchange procedure with the sink, the source is a key ID for specifying the exchange key Kr, and the sink device. As shown in the table below, an entry consisting of a set of IDs is stored in the connection table. In the connection table, it is assumed that entries corresponding to the limited number of sinks capable of simultaneously transmitting content can be stored. In the table below, the number of entries is two, but the gist of the present invention is not limited to two.

  In addition, the Source manages a receiving device table for remote access as shown in the following table, and simultaneously stores a device ID of a sink that performs content transmission in the table. When the content owner requests pre-registration of a sink for remote access, the device ID of the sink is registered in advance in the receiving device table. Although an upper limit may be set for the number of sinks that can be pre-registered in the receiving device table, the gist of the present invention is not limited to a specific upper limit number. An example of a method for registering a sink device ID in the receiving device table is a method in which a source registers a sink when performing RTT-AKE in DTCP.

  As described above, when the source determines the device ID of the sink in the mutual authentication and key exchange procedure with the sink (step S71), the source confirms whether or not it has been registered in the receiving device table (step S72). This is a process for confirming that the content owner may request that the sink for remote access be registered in advance in the source.

  If the device ID of the sink is not registered in the receiving device table (No in step S72), the source sends an AKE_CANCEL command notifying the interruption of the mutual authentication and key exchange procedure to the sink and ends the processing. Source may describe information indicating that the sink is not registered in the receiving device table in the AKE_CANCEL command. The sink may be registered in the receiving device table before key exchange.

  On the other hand, if the sink device ID is already registered in the receiver table (Yes in step S72), then the source checks whether the sink device ID is recorded in the connection table (step S73).

  If the sink device ID is not recorded in the connection table (No in step S73), the source further checks whether there is room to record a new device ID in the connection table (step S75). In the present embodiment, the source manages the number of key IDs that can be recorded in the connection table using a key counter, and can record if the value of the key counter is less than the upper limit value n. Source manages the value of the key counter to be the same as the number of key IDs recorded in the connection table.

  If the value of the key counter has already reached n (No in Step S75), the Source sends an AKE_CANCEL command notifying the interruption of the mutual authentication and key exchange procedure to the Sink and ends the process. The Source may describe information indicating that the number of entries registered in the connection table has reached the upper limit n in the AKE_CANCEL command.

  If the value of the key counter is less than n (Yes in step S75), the source adds 1 to the key counter (step S76), and then the remote access exchange key Kr and the key ID for specifying Kr. (Step S77), and an entry including the exchange key Kr, the key ID and the device ID of the sink is added to the connection table (step S78).

  If the sink device ID is already recorded in the connection table (Yes in step S73), the entry corresponding to the device ID is deleted from the connection table (step S74), and then the remote access exchange is performed. A key Kr and a key ID for specifying Kr are newly generated (step S77), and an entry made up of the exchange key Kr and the key ID and sink device ID is added to the connection table (step S78). As another pattern, instead of deleting the entry corresponding to the device ID from the connection table, the exchange key Kr and the key ID corresponding to the device ID are extracted from the connection table and the information is not added to the connection table again. Processing is also conceivable. However, this pattern is not shown.

  Then, the source encrypts the remote access exchange key Kr generated in step S77 according to the method defined in the DTCP specification, and transmits it to the sink together with the key ID using the EXCHANGE_KEY command.

  At the same time as the source transmits the exchange key Kr to the sink, the life management of the exchange key Kr is started by a timer (step S79). Specifically, the Source prepares a timer corresponding to the key ID (that is, prepares a timer for each key ID stored in the connection table), and sets a predetermined value (for example, a value corresponding to 1 minute). To start down-counting.

  Thereafter, Source automatically reduces the count to zero with a fixed clock. When the timer reaches zero, the Source starts a connection table update process.

  FIG. 8 shows an example of connection table update processing. By updating the connection table, the entry including the key ID that could not be periodically received by the key life management command (AKE_ALIVE.CMD) is deleted from the connection table.

  The source first checks whether an entry including the key ID corresponding to the timer that has become zero exists in the connection table (step S81). If the corresponding entry does not exist in the connection table (No in step S81), the process ends.

  When the corresponding entry exists in the connection table (Yes in step S81), the source deletes the entry including the key ID corresponding to the timer that has become zero from the connection table (step S82), and subtracts 1 from the key counter. (Step S83). As a result, the Source can exchange a key with another Sink (or the same Sink) anew.

  In consideration of the delay required for command communication, a margin is provided until the exchange key is discarded after the timer reaches zero, or until another sink requests a new exchange key as shown in FIG. An operation that does not execute the indicated processing is also conceivable.

  In this manner, while the source performs the lifetime management of the exchange key Kr, the sink can request the lifetime update of the exchange key Kr in use.

  In the present embodiment, the sink requests the lifetime update of the exchange key Kr by transmitting a KEEP_ALIVE command at a predetermined transmission cycle. Further, the source maintains the corresponding key by receiving the KEEP_ALIVE command at a predetermined reception cycle. FIG. 9 shows a format example of the KEEP_ALIVE command. In the illustrated example, the KEEP_ALIVE command describes, in the payload, a field that describes a device ID that is information for identifying a sink that is a transmission source, and a key ID that is information for identifying an exchange key Kr that requires lifetime update. The last 1 bit including the field is used as a discard flag for instructing discard of the exchange key Kr.

  When the source receives the KEEP_ALIVE command, it performs a lifetime update process and then returns a KEEP_ALIVE response. Although not shown, it is conceivable to use the status field defined in the DTCP AKE Control Command Format for the response information of the KEEP_ALIVE response.

  The source sets a value indicating a predetermined time in a timer corresponding to the key ID included in the KEEP_ALIVE command received from the sink, and updates the lifetime by performing control so that the downcount is performed again from that value. It should be noted that this lifetime update processing is performed even if the corresponding key has not yet been discarded even after the timer becomes zero.

  FIG. 10 shows an example of an operation sequence for updating the lifetime of the exchange key Kr performed between the source and the sink. When the sink receives the exchange key Kr and its key ID from the source, the sink transmits a KEEP_ALIVE command at a predetermined transmission cycle.

  When the source receives the KEEP_ALIVE command from the sink, it checks whether the device ID included in the command has been registered in the receiving device table (step S101).

  If the device ID in the KEEP_ALIVE command is not registered in the receiving device table (No in step S101), the source sets the response information as “device not registered” (step S105), and sends a KEEP_ALIVE response including this response information. The request is sent to the sink of the request source, and the process ends.

  On the other hand, if the device ID in the KEEP_ALIVE command has already been registered in the receiving device table (Yes in step S101), the source subsequently checks whether the key ID in the KEEP_ALIVE command exists in the connection table (step S102). ).

  If the key ID in the KEEP_ALIVE command does not exist in the connection table (No in step S102), the source sets the response information as “key invalid” (step S106), and sends a KEEP_ALIVE response including this response information to the request source. To the sink and finish the process.

  If the key ID in the KEEP_ALIVE command is present in the connection table (Yes in step S102), the source initializes the timer corresponding to this key ID with a value indicating a predetermined time, and then downloads it again. Counting is started (step S103). Then, the source sets the response information to “key is valid” (step S104), transmits a KEEP_ALIVE response including this response information to the requesting sink, and ends the processing.

  When the mutual authentication and key exchange procedures with the source are completed, the sink repeatedly transmits the KEEP_ALIVE command at a transmission period within a predetermined period as long as the acquired exchange key Kr is to be maintained.

  Further, the sink may request the source to discard the exchange key Kr when the exchange (content reception) with the source is completed and the exchange key Kr becomes unnecessary. By deleting the corresponding entry from the connection table, the source can perform communication (content transmission) by connecting another new sink to the source within the upper limit number n.

  For example, the sink can request the source to discard the exchange key Kr by including information for requesting the destruction of the exchange key Kr in the KEEP_ALIVE command transmitted at a predetermined transmission cycle. In the format example of the KEEP_ALIVE command shown in FIG. 9, the payload includes a discard flag, and by setting this discard flag, the exchange key Kr can be instructed to be discarded.

  FIG. 11 shows another example of an operation sequence for updating the lifetime of the exchange key Kr performed between the source and the sink. The operation sequence shown is different from the operation sequence shown in FIG. 10 in that it includes a process of discarding the exchange key Kr that is no longer needed.

  When the source receives the KEEP_ALIVE command from the sink, it checks whether the device ID included in the command has been registered in the receiving device table (step S111).

  If the device ID in the KEEP_ALIVE command is not registered in the receiving device table (No in step S111), the source sets the response information as “device not registered” (step S116), and sends a KEEP_ALIVE response including this response information. The request is sent to the sink of the request source, and the process ends.

  On the other hand, when the device ID in the KEEP_ALIVE command has already been registered in the receiving device table (Yes in step S111), the source subsequently checks whether the key ID in the KEEP_ALIVE command exists in the connection table (step S112). ).

  If the key ID in the KEEP_ALIVE command does not exist in the connection table (No in step S112), the source sets the response information as “key invalid” (step S120), and sends a KEEP_ALIVE response including this response information to the request source. To the sink and finish the process.

  When the key ID in the KEEP_ALIVE command exists in the connection table (Yes in step S112), the source further checks whether the discard flag in the KEEP_ALIVE command is set (step S113).

  When the discard flag in the KEEP_ALIVE command is set (Yes in step S113), the Source discards the key ID in the command and the exchange key corresponding to the key ID (step S117) and the key in the command. The entry of the exchange key and device ID corresponding to the ID is deleted from the connection table (step S118), and the key counter is decremented by 1 (step S119). Then, the source sets the response information as “key invalid” (step S120), transmits a KEEP_ALIVE response including the response information to the sink of the request source, and ends the process.

  On the other hand, when the discard flag in the KEEP_ALIVE command is not set (No in step S113), the source initializes a timer corresponding to this key ID with a value indicating a predetermined time, and starts down-counting again ( Step S114). Then, the source sets the response information to “key is valid” (step S115), transmits a KEEP_ALIVE response including this response information to the requesting sink, and ends the processing.

  According to the operation sequence shown in FIG. 10 and FIG. 11, in the case where the content in the content providing device (Source) installed in the home is used from outside, the content using device (Sink) that simultaneously uses the content. ), The content providing apparatus maintains the content providing apparatus because the content using apparatuses that have performed mutual authentication and key exchange procedures with the content providing apparatus transmit the KEEP_ALIVE command at a predetermined transmission cycle. It is possible to accurately grasp the exchange key to be used, and it is possible to newly communicate with another content using apparatus by discarding the unnecessary exchange key.

  Since the content providing apparatus manages the exchange key to be maintained based on the key ID, even if the address changes during the mobile communication by the content using apparatus, it can be processed without being affected by the change.

  The present invention has been described in detail above with reference to specific embodiments. However, it is obvious that those skilled in the art can make modifications and substitutions of the embodiment without departing from the gist of the present invention.

  As an application example of the present invention, a communication system that remotely accesses a server on a home network to which DTCP-IP is applied from a client outside the home and uses contents can be cited. It is not limited to a communication system using DTCP-IP or a communication system that remotely accesses content. The present invention is similarly applied to a communication system that transmits content within the range of legitimate use by a user while limiting the number of devices that simultaneously transmit content that needs to be protected for copyright and other purposes. be able to.

  In short, the present invention has been disclosed in the form of exemplification, and the description of the present specification should not be interpreted in a limited manner. In order to determine the gist of the present invention, the claims should be taken into consideration.

10. Content providing device (RA-source)
11 ... CPU
DESCRIPTION OF SYMBOLS 12 ... Content receiving / reproducing part 13 ... Communication part 14 ... Memory | storage part 15 ... Timer 20 ... Content utilization apparatus (RA-sink)
21 ... CPU
22 ... Communication unit 23 ... Content output unit 24 ... Storage unit 25 ... Timer 30, 31 ... Router 40, 41 ... Modem 50 ... WAN
60 ... IAS service 70 ... DDNS service

Claims (1)

A content providing device that provides content to a content using device,
Registration means for registering a device ID for identifying the content utilization device;
Determining means for determining whether or not the content use device registered in the registration means is within a predetermined limit number;
A key supply means for supplying a key for content encryption to the content use device in accordance with a determination result of the determination means;
Recording means for recording a key supplied by the key supply means together with a key ID for identifying a key and a device ID of the content use device;
Confirmation means for maintaining the key for a predetermined period when the key ID and the device ID are confirmed based on information received from the content utilization device;
And a content providing device that limits a period during which the content using device can acquire content by remote access.
 

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