US-20260128886-A1 - TERMINAL DEVICE, MANAGEMENT SERVER DEVICE, CONTROL METHOD, AND RECORDING MEDIUM

US20260128886A1US 20260128886 A1US20260128886 A1US 20260128886A1US-20260128886-A1

Abstract

A secondary device which is a terminal device includes a circuit and a memory connected to the circuit. Using the memory, the circuit: performs device authentication with a primary device which is a video recording device; obtains a content key that is encrypted from the primary device; decrypts the content key using a common key shared between the primary device and the secondary device; reads a content that is encrypted and recorded on a cloud server by the primary device, by accessing the cloud server without passing through the primary device; and decrypts the content read using the content key to play back the content.

Inventors

Tokuo Nakatani
Hideki Fukuda
Takashi Yamaguchi
Yutaka Nishikawa

Assignees

PANASONIC INTELLECTUAL PROPERTY MANAGEMENT CO., LTD.

Dates

Publication Date: 20260507
Application Date: 20230627
Priority Date: 20220831

Claims (13)

1 . A terminal device to be used in a video recording and playback system, the video recording and playback system including: a cloud server device; a video recording device that receives and encrypts a content that is distributed, and records the content encrypted, on the cloud server device via Internet; and the terminal device that plays back the content, the terminal device comprising: a circuit; and a memory connected to the circuit, wherein using the memory, the circuit: performs device authentication with the video recording device; obtains a content key that is encrypted from the video recording device via the Internet; decrypts the content key using a common key shared between the video recording device and the terminal device; reads the content that is encrypted and recorded on the cloud server device, by accessing the cloud server device without passing through the video recording device; and decrypts the content read using the content key to play back the content.
2 . The terminal device according to claim 1 , wherein the circuit performs device authentication with the video recording device via a management server device to obtain the common key to be transmitted from the management server device to the terminal device and the video recording device.
3 - 6 . (canceled)
7 . A management server device to be used in a video recording and playback system, the video recording and playback system including: a cloud server device; a first video recording device that receives and encrypts a content that is distributed, and records the content encrypted, on the cloud server device via Internet; a terminal device that plays back the content; and the management server device that is connected to the first video recording device via Internet, the management server device comprising: a circuit; and a memory connected to the circuit, wherein the memory holds, in association with the cloud server device, first identification information for identifying the first video recording device, and the circuit, when the first video recording device is to be replaced with a second video recording device: replaces the first identification information held by the memory in association with the cloud server device, with second identification information for identifying the second video recording device; and transfers, to the second video recording device, protection information that is used for protecting the content and is held by the first video recording device.
8 . The management server device according to claim 7 , wherein the circuit, when the first video recording device is detachable from the video recording and playback system, executes at least one of: (a) deleting the content recorded on the cloud server device by the first video recording device; (b) deleting cloud account information that is for accessing the cloud server device and is held by the first video recording device or the memory; or (c) deleting the first identification information that is held by the memory in association with the cloud account information.
9 . The management server device according to claim 8 , wherein the protection information is information indicating at least one of a content key for decrypting the content, a checksum for management information of the content, a hash value for the management information of the content, or a dubbing count of the content.
10 . A control method performed by a terminal device to be used in a video recording and playback system, the video recording and playback system including: a cloud server device; a video recording device that receives and encrypts a content that is distributed, and records the content encrypted, on the cloud server device via Internet; and the terminal device that plays back the content, the control method comprising: performing device authentication with the video recording device; obtaining a content key that is encrypted from the video recording device via the Internet; decrypting the content key using a common key shared between the video recording device and the terminal device; reading the content that is encrypted and recorded on the cloud server device, by accessing the cloud server device without passing through the video recording device; and decrypting the content read using the content key to play back the content.
11 . (canceled)
12 . A control method performed by a management server device to be used in a video recording and playback system, the video recording and playback system including: a cloud server device; a first video recording device that receives and encrypts a content that is distributed, and records the content encrypted, on the cloud server device via Internet; a terminal device that plays back the content; and the management server device that is connected to the first video recording device via Internet, the control method comprising: holding, in association with the cloud server device, first identification information for identifying the first video recording device; and when the first video recording device is to be replaced with a second video recording device: replacing the first identification information held by a memory in association with the cloud server device, with second identification information for identifying the second video recording device; and transferring, to the second video recording device, protection information that is used for protecting the content and is held by the first video recording device.
13 . A non-transitory computer-readable recording medium having recorded thereon a program for a terminal device to be used in a video recording and playback system, the video recording and playback system including: a cloud server device; a video recording device that receives and encrypts a content that is distributed, and records the content encrypted, on the cloud server device via Internet; and the terminal device that plays back the content, the program causing a computer of the terminal device to execute: performing device authentication with the video recording device; obtaining a content key that is encrypted from the video recording device via the Internet; decrypting the content key using a common key shared between the video recording device and the terminal device; reading the content that is encrypted and recorded on the cloud server device, by accessing the cloud server device without passing through the video recording device; and decrypting the content read using the content key to play back the content.
14 . (canceled)
15 . A non-transitory computer-readable recording medium having recorded thereon a program for a management server device to be used in a video recording and playback system, the video recording and playback system including: a cloud server device; a first video recording device that receives and encrypts a content that is distributed, and records the content encrypted, on the cloud server device via Internet; a terminal device that plays back the content; and the management server device that is connected to the first video recording device via Internet, the program causing a computer of the management server device to execute: holding, in association with the cloud server device, first identification information for identifying the first video recording device; and when the first video recording device is to be replaced with a second video recording device: replacing the first identification information held by a memory in association with the cloud server device, with second identification information for identifying the second video recording device; and transferring, to the second video recording device, protection information that is used for protecting the content and is held by the first video recording device.
16 . A terminal device to be used in a video recording and playback system, the video recording and playback system including: a cloud server device; a video recording device that receives and encrypts a content that is distributed, and records the content encrypted, on the cloud server device via Internet; and the terminal device that plays back the content, the terminal device comprising: a circuit; and a memory connected to the circuit, wherein using the memory, the circuit: performs device authentication with the video recording device; obtains a content key that is encrypted from a management server device via the Internet; decrypts the content key using a common key shared between the video recording device and the terminal device; reads the content that is encrypted and recorded on the cloud server device, by accessing the cloud server device without passing through the video recording device; and decrypts the content read using the content key to play back the content.

Description

TECHNICAL FIELD The present disclosure relates to a technique used in a system that records and plays back distributed content such as a show. BACKGROUND ART Conventionally, there has been proposed a content transfer system including a content transmitting device and a content receiving device that safely transmit and receive content (see, for example, Patent Literature (PTL) 1). In this content transfer system, the content transmitting device performs mutual authentication and transferring of shared keys with the content receiving device, encrypts the content using an encryption key generated from the shared key, and transmits the content to the content receiving device. At this time, the content transmitting device switches the shared key to be transferred according to the security strength that the content receiving device has. Furthermore, there has been proposed a content transfer system that transmits, within an appropriate range of use, contents accumulated in a household, to a terminal via an external network (see, for example, PTL 2). In this content transfer system, the server permits the transfer of content that is shorter than a playback enabled time in response to the terminal requesting for content by remote access, and decreases the playback enabled time by as much as the playback time of the content transferred by remote access. CITATION LIST Patent Literature [PTL 1] Japanese U.S. Pat. No. 6,390,618[PTL 2] Japanese U.S. Pat. No. 6,187,139 SUMMARY OF INVENTION Technical Problem However, when content is recorded on a generally used cloud server, the content transfer systems in PTL 1 and 2 have a problem in that it is difficult to appropriately suppress unauthorized acts regarding the content. In view of this, the present disclosure provides a terminal device, and the like, capable of appropriately suppressing unauthorized acts regarding content. Solution to Problem A terminal device according to an aspect of the present disclosure is a terminal device to be used in a video recording and playback system, the video recording and playback system including: a cloud server device; a video recording device that receives and encrypts a content that is distributed, and records the content encrypted, on the cloud server device via Internet; and the terminal device that plays back the content, the terminal device including: a circuit; and a memory connected to the circuit, wherein using the memory, the circuit: performs device authentication with the video recording device; obtains a content key that is encrypted from the video recording device; decrypts the content key using a common key shared between the video recording device and the terminal device; reads the content that is encrypted and recorded on the cloud server device, by accessing the cloud server device without passing through the video recording device; and decrypts the content read using the content key to play back the content. It is to be noted that these general or specific aspects may be implemented as a device, a method, an integrated circuit, a computer program, or a computer-readable recording medium such as a CD-ROM, or may be implemented as any combination of a device, a method, an integrated circuit, a computer program, and a computer-readable recording medium. Moreover, the recording medium may be a non-transitory recording medium. Advantageous Effects of Invention A terminal device according to the present disclosure can appropriately suppress unauthorized acts regarding content. It should be noted that further advantages and effects of one aspect of the present disclosure will become apparent from the written description and drawings. These advantages and/or effects are provided by several elements described in the embodiments as well as the written description and drawings, but do not necessarily require all of the elements. BRIEF DESCRIPTION OF DRAWINGS FIG. 1 is a diagram illustrating a configuration example of a video recording and playback system in an embodiment. FIG. 2 is a diagram simply illustrating the configuration of the video recording and playback system in the embodiment. FIG. 3 is a diagram illustrating an example of items of information included in a primary device (PD) and a management server of the video recording and playback system in the embodiment. FIG. 4 is a diagram illustrating an example of the configuration of the management server and information included in the management server in the embodiment. FIG. 5 is a diagram illustrating an example of the configuration of the primary device and information included in the primary device in the embodiment. FIG. 6 information included in the primary device in the embodiment. information included in the primary device in the embodiment. FIG. 7 is a diagram for describing the migration of a primary device privilege in the embodiment. FIG. 8 is a diagram illustrating an example of a data structure that includes a content and management information in the emb