Secure authenticated distance measurement

The present invention relates to a method for a first communication device that performs an authenticated distance measurement between a first communication device and a second communication device. The present invention also relates to a method of determining whether the data stored in the first communication device should be accessed by the second communication device. Furthermore, the present invention relates to a communication device for performing an authentication type distance measurement to a second communication device. The present invention also relates to a device for playing multimedia content, which has a communication device.

Digital media has become a popular carrier for various types of data information. For example, computer software and audio information are widely available on optical compact discs (CDs), and DVDs are also increasing their distribution share these days. CDs and DVDs utilize a common standard for digital recording of data, software, images and audio. Other media such as recordable discs and solid-state memory have increased significantly in the software and data distribution markets.

The quality, which is significantly superior to the analog format of the digital format, makes the former much more susceptible to fraudulent duplication and pirated production, and the digital format is easier and faster to duplicate. Reproduction of digital data streams, whether compressed, uncompressed, encrypted or unencrypted, generally does not cause any apparent loss of quality in the data. Therefore, digital replication is virtually unlimited with respect to multi-generational replication. On the other hand, analog data with signal-to-noise ratio loss per successive replication is necessarily limited for multi-generational and mass replication.

The advent of digital formats in recent years has resulted in a number of copy protection and DRM systems and methods. These systems and methods use techniques such as encryption, watermarking and rights description (eg, rules for accessing and copying data).

One way to protect content in the form of digital data is -When the receiving device is certified as a compliant device and -When the user of the content has the right to transfer (move, copy) this content to another device, and It is to guarantee that it will only be transferred to.

If content transfer is permitted, this transfer is commonly performed by cryptographic means that ensure that the content cannot be illegally captured in a useful form.

Techniques for performing device authentication and encrypted content transfer are available and are referred to as Secure Authenticated Channels (SACs). Although it may be possible to duplicate content over the SAC, the content industry is stubborn about content distribution over the Internet. This creates a disagreement within the content industry regarding the transfer of content over the Internet, an interface that is well aligned with Ethernet®.

It should also be possible for a user visiting a neighbor to watch a movie he owns on his neighbor's large television screen. Content owners will generally not allow this, but if the license holder of this movie (or the equipment owned by this license holder) can be proven to be near this television screen. , Can be tolerated.

Therefore, it is interesting to be able to include authenticated distance measurements when determining whether content should be accessed or duplicated by other devices.

An article by Stefan Brands and David Chaum, "Distance-Bounding protocols", Eurocrypt '93 (1993), Pages 344-359, describes the integration of the distance-bounding protocol with the public key identification scheme. .. There, distance measurements are described based on time measurements using challenge / response bits and using the commitment protocol. This does not allow certification device compliance testing and is not valid if the two devices must also certify each other.

<p num="0011"> An object of the present invention is to obtain a solution to the problem of performing secure transfer of content over a finite distance.</p>

<p num="0012"> This is achieved by a method in which the first communication device performs an authenticated distance measurement between the first communication device and the second communication device, and the first communication device and the second communication device have a common secret. The common secret is used to perform distance measurements between the first and second communication devices.</p><p num="0013"> Since the common secret is used to perform the distance measurement, when measuring the distance from the first communication device to the second communication device, it is guaranteed that the distance between the correct devices is measured. Can be done.</p><p num="0014"> The method combines a distance measurement protocol with an authentication protocol. This enables and is valid for certification device compliance testing. This is because secure channels are required in any case to allow secure communication between devices, and devices can be tested for compliance first before distance measurements are performed.</p><p num="0015"> In a particular embodiment, the certified distance measurement is as follows: -In the step of transmitting the first signal from the first communication device to the second communication device at the first time t1, the second communication device receives the first signal and the received first first signal. A step configured to generate a second signal by modifying the signal according to the common secret and transmit the second signal to the first apparatus. -The step of receiving the second signal at the second time t2, and -A step to confirm whether the second signal has been modified according to the common secret, and -A step of determining the distance between the first and the second communication device according to the time difference between t1 and t2, and It is executed according to.</p><p num="0016"> Use the secret shared between the first and second communication devices to measure the time difference between the transmission and reception of the signal and to determine if the feedback signal actually originated from the second communication device. This distance is measured by a secure and certified means of ensuring that this distance is not measured to a third communication device (not aware of the secret) when measuring the distance by. Using a common secret that modifies the signal is a convenient way to perform secure authenticated distance measurements.</p><p num="0017"> In a particular embodiment, the first signal is a diffusion spectrum signal. It provides high resolution and can cope with adverse transmission conditions (eg, wireless environments with many reflections).</p><p num="0018"> In another embodiment, the step of checking if the second signal has been modified according to the common secret is -The step of generating the third signal by modifying the first signal according to the common secret, -With the step of comparing the third signal with the received second signal Is executed by.</p><p num="0019"> Although this method is an easy and convenient way to perform the confirmation step, both the first and second communication devices show how the first signal is modified with a common secret. You need to know.</p><p num="0020"> In certain embodiments, the first signal and common secret are bitwords, and the second signal has information generated by performing an exclusive OR operation between these bitwords. What should be done is a very simple operation, which requires very few resources for the first and second communication devices.</p><p num="0021"> In an embodiment where the common secret is shared before performing the distance measurement, this sharing step is -Steps to perform an authentication verification for the second communication device from the first communication device by verifying that the second communication device complies with a set of pre-specified compliance rules, and -If the second communication device complies, the step of sharing the common secret by transmitting the secret to the second communication device, and Is executed by.</p><p num="0022"> This is a secure means of implementing secret sharing and ensures that only devices that comply with the applicable rules can receive the secret. In addition, the shared secret can then be used to create a SAC channel between the two devices. The secret may be shared, for example, using the key transport mechanisms described in ISO 11770-3. Alternatively, a key agreement protocol can be used, for example, this protocol is also described in ISO 11770-3.</p><p num="0023"> In another embodiment, the authentication confirmation has a step of confirming whether the identifier of the second device conforms to the intended identifier. This ensures that the second device is indeed the device it should be. This identity can be obtained by confirming the proof stored in the second device.</p><p num="0024"> The present invention relates to a method of determining whether data stored in a first communication device should be accessed by a second communication device, which method measures the distance between a first communication device and a second communication device. It has a step of performing and confirming whether the measured distance is within a predetermined distance interval, where the distance measurement is an authentication type distance measurement according to the above. Unauthorized distribution of content can be reduced by using authenticated distance measurements related to data sharing between devices.</p><p num="0025"> In a particular embodiment, if it is determined that the data stored in the first device should be accessed by the second device, the data stored in the first device is transmitted to the second device.</p><p num="0026"> The present invention relates to a method of determining whether data stored in a first communication device should be accessed by a second communication device, the method of measuring a distance between a third communication device and a second communication device. To confirm whether the measured distance is within a predetermined distance interval, where the distance measurement is an authentication type distance measurement according to the above. In this embodiment, the distance is not measured as the distance between the second communication device and the first communication device in which data is stored. Instead, the distance is measured between the third communication device and the second communication device, such that the third communication device can be private to the owner of the content.</p><p num="0027"> The present invention is a communication device that performs an authentication type distance measurement to a second communication device, in which the communication device shares a common secret with the second communication device, and the communication device uses the common secret. It also relates to communication devices that have a means of measuring the distance to the second device.</p><p num="0028"> In certain embodiments, the device is -A means for transmitting a first signal to the second communication device at the first time t1, the second communication device receives the first signal, and the received first signal follows the common secret. Means configured to generate a second signal by modification and transmit the second signal, -Means for receiving the second signal at the second time t2, -Means to confirm whether the second signal has been modified according to the common secret, -Means for determining the distance between the first communication device and the second communication device according to the time difference between t1 and t2, and Have.</p><p num="0029"> The present invention also relates to a device for reproducing multimedia contents having the above-mentioned communication device.</p>

<figref num="1">Figure 1 shows an authenticated distance measurement used for content protection.</figref><figref num="2">FIG. 2 shows a flow chart showing how to perform an authenticated distance measurement.</figref><figref num="3">FIG. 3 shows in more detail the steps to perform the authenticated distance measurement shown in FIG.</figref><figref num="4">FIG. 4 shows a communication device that performs an authenticated distance measurement.</figref>

In the following, preferred embodiments of the present invention will be described with reference to the figures.

FIG. 1 shows an example in which authenticated distance measurement is used for content protection. The calculator 103 is placed in the center of the circle 101. The calculator has content such as multimedia content that is video or audio stored on a hard disk, DVD or CD, for example. Since the owner of the Calculator owns the Content, the Calculator is authorized to access and perform the Multimedia Content for this User. If this user wants to legally duplicate this content to another device, for example via SAC, the distance between the other device and computer 103 is measured and is indicated by device 105,107,109,111,113 in circle 101, pre-specified. Only devices within range are allowed to receive content. In this case, devices 115,117,119 having a distance to the computer 101 that is greater than the predetermined distance are not allowed to receive the content.

In this example, the device is a calculator, but as long as the device has a communication device that performs distance measurements, the device can also be, for example, a DVD drive, a CD drive, or a video.

In certain cases where the distance between the computer on which the data is stored and the other device does not need to be measured, the other device is the third device, i.e. content that is within a predetermined distance. It can also be a device that is private to the owner of the device.

In FIG. 2, the flow diagram shows a schematic idea of performing an authenticated distance measurement between two devices 201 and 203, each having a communication device that performs an authenticated distance measurement. In this example, the first device 201 has the content requested by the second device 203. This authentication type distance measurement is performed as follows. In step 205, the first device 201 authenticates the second device 203. This step may include a step of confirming that the second device 203 is a compliant device, and also a step of confirming that the second device 203 is indeed the device specified to the first device 201. Can be done. Then, in step 207, the first device 201 exchanges the secret with the second device 203, and this step can be performed, for example, by transmitting a randomly generated bitword to the device 203. The secret must be securely shared, for example, in accordance with some key management protocol such as ISO 11770.

Then, in step 209, the signal for distance measurement is transmitted to the second device 203, which corrects the received signal according to the secret and returns the corrected signal to the first device. To do. The first device 201 measures the round-trip time between the departure signal and the feedback signal to confirm that the feedback signal has been modified according to the exchanged secret. Modification of the feedback signal according to some secret is most dependent on the transmission system and the signal used for distance measurement, ie, specific for each communication system (such as 1394, Ethernet®, Bluetooth and IEEE 802.11). Is.

The signal used for the distance measurement may be a normal data bit signal, or a special signal other than that for data communication may be used. In certain embodiments, the diffuse spectrum signal is used so that high resolution can be obtained and that adverse transmission conditions (eg, wireless environments with many reflections) can be addressed.

In certain examples, a direct sequence diffusion spectral signal is used for distance measurement. This signal is modified by exclusive-ORing the sequence code chips directly with secret bits (eg, secret consists of 127 bits) (eg, extending the 127 chip code as well). Can be done. Other mathematical operations similar to the exclusive OR operation can also be used.

Certification 205 and Confidential Exchange 207 can be performed using the protocols described in ISO 9798 and ISO 11770 of several known ISO international standards. For example, the first device 201 can authenticate the second device 203 according to the following communication scenario. 1st device 2nd device:<maths num="1"><img id="000002" he="15" wi="39" file="JP6134469B2_D0001.tif" img-format="tif" img-content="drawing" /></maths>Where R_B Is a random number. 2nd device 1st device:<maths num="2"><img id="000003" he="15" wi="55" file="JP6134469B2_D0001.tif" img-format="tif" img-content="drawing" /></maths>Where CertA is a proof of A,<maths num="3"><img id="000004" he="16" wi="131" file="JP6134469B2_D0001.tif" img-format="tif" img-content="drawing" /></maths>R_A Is a random number, Identifier B is optional and sS_A Is the code set by A using the private key.

If TokenAB is replaced with a token defined by ISO 11770-3, private key exchange can be performed at the same time. This step is<maths num="4"><img id="000005" he="14" wi="89" file="JP6134469B2_D0001.tif" img-format="tif" img-content="drawing" /></maths>Can be used by substituting Text2 such as Where eP_B Is encrypted with public key B, A is an identifier for A K is a secret to be exchanged.

In this case, the second device 203 determines the key (ie, has key control), which is also called the key distribution protocol, but a key sharing protocol can also be used. This can be undesirable if it can be inverted, such as when the first device determines the key. Here, the private key was exchanged according to step 207 in FIG. Again, the private key can be exchanged, for example, by a key distribution protocol or a key sharing protocol.

After the distance has been measured by the secure authentication procedure as described above, the data may be transmitted between the first and second devices in step 211.

FIG. 3 shows in more detail the steps to perform an authenticated distance measurement. As described above, the first device 301 and the second device 302 have exchanged keys, and the keys are stored in the memory 305 of the first device and the memory 307 of the second device. To perform the distance measurement, the signal is transmitted to the second device via the transmitter 309. The second device receives the signal via receiver 311 and 313 modifies the signal by using a locally stored secret. The signal is modified by the first device 301 according to a known rule and returned to the first device 301 via the transmitter 315. The first device 301 receives the modified signal via the receiver 317, and at 319 the received modified signal is compared to the locally modified signal. The local modification is at 321 by using the signal transmitted by transmitter 309 to the second device and modifying the signal with the same locally stored secret as the modification rule used by the second device. Will be executed. If the received modified signal and the locally modified signal are identical, the received signal can be authenticated and used to determine the distance between the first and second devices. If the two signals are not identical, the received signal cannot be authenticated and therefore cannot be used to measure distance as indicated by 325. At 323, the distance between the first device and the second device is calculated. This step is performed, for example, by measuring the time when the signal is transmitted from the first device to the second device by the transmitter 309 and when the receiver 317 receives the signal from the second device. .. Therefore, the time difference between the transmission time and the reception time can be used to determine the physical distance between the first device and the second device.

FIG. 4 shows a communication device for performing an authenticated distance measurement. The device 401 has a receiver 403 and a transmitter 411. The device further comprises means for performing the steps described above, which can be achieved by running software with microprocessor 413 connected to memory 417 via a communication bus. The communication device may be placed inside a device such as a DVD, computer, CD, CD recorder, television or other device to access the protected content.