Method for transmitting encrypted data via a broadcast network, where the decryption data is obtained through a bidirectional communication link

State of the art

0001The invention is based on a method for the transmission of encrypted data or according to the category of the independent claim.

0002It's already out of the brochure <img file="EP1081884A2_D0001.tif" />Digital Audio Broadcasting ", Eureka-147 Project, April 1996 discloses that programs and / or data for a specific group of receivers can be broadcast in DAB (Digital Audio Broadcasting) Access to these programs and / or data. For this purpose, these programs and / or data are encrypted, the authorized recipients either being given a key to decrypt the programs, or have a storage facility on their recipient, such as a smart card, which at least contains the data to decrypt a key or even to decrypt the entire program and / or the data. A smart card has a microprocessor that stores, processes and manages information. A high degree of security is added to a smart card by means of a secret number and / or encryption techniques.

0003If the access authorization by means of the smart card is time-limited, the customer will obtain a valid smart card after the validity of his smart card has expired or have the validity of his smart card extended.

Advantages of the invention

0004The method according to the invention with the features of the independent patent claim has the advantage that the key for decrypting the encrypted programs and / or data that are transmitted using a radio transmission method such as DAB is transmitted using a duplex transmission method, such as a mobile radio transmission method, so that the user can decrypt the received data. This enables the user to obtain the necessary key to decrypt the encrypted data at any time and from any location. He gains a great deal of flexibility. In addition, the user only needs to obtain the necessary key if he actually wants to receive the encrypted programs and / or data.

0005In addition, it is advantageous that the invention uses existing infrastructure, because both a radio distribution system and various mobile radio systems are already installed and can be used.

0006A further advantage is that a data set is transmitted to a user by means of the duplex transmission method, and that additional data that is used with this data set are then continuously transmitted by means of the radio transmission system. This makes it possible for a user to receive a data record only once using a duplex transmission method and then to update it using the additional data which are transmitted via a radio transmission system. This method of updating is extremely cost-effective for both the data service provider and the customer.

0007The measures listed in the dependent claims allow advantageous developments and improvements of the methods specified in the independent claims.

0008It is particularly advantageous that the user, if he wants to decrypt the encrypted data or if he wants to load a data record, selects the data provider by means of the duplex transmission method and loads either the key or the data record from the data service provider. As a result, the user is completely free to determine when, where and what he wants to use for data services. It should be noted that such data services and encrypted data are offered by different data service providers, so that the user selects the data service provider he desires on an opportunity basis.

0009It is also advantageous that both the key and the data record that the user loads using the duplex transmission method are valid for a limited time. This makes it possible for the data service provider to offer and calculate its data service for a certain time. In addition, it is transparent to the user how long the data service he wants is available.

0010In addition, it is advantageous that the data service provider calculates the transmission time for the decryption data and / or the data record for the user, so that the user pays an amount corresponding to the period of validity for the transmission time of this necessary data in order to use the data service. This is then a very simple billing system for a data service provider, since it rents its data service at the same time as the amount that it demands for the transmission time of the key or the data record. In addition, this billing system is also of great transparency for the user, since he can, for example, see the costs for the data service via his phone bill when using a mobile network.

drawing

0011Embodiments of the invention are shown in the drawing and explained in more detail in the following description. FIG. 1 shows a method for the transmission of encrypted data and FIG. 2 shows a method for the transmission of data records.

Description of the embodiments

0012The introduction of digital radio transmission methods such as DAB offers attractive options for transmitting data services over the radio distribution network.

0013DAB is a digital broadcasting method that is particularly suitable for mobile reception. By using the so-called orthogonal frequency division multiplex, frequency-selective attenuation in particular is greatly reduced in its effect on the transmitted signal. The signal that is transmitted by means of orthogonal frequency division multiplex is distributed at DAB on several frequencies, whereby the signal components on the different frequencies do not influence each other. This behavior is described as orthogonal. It is thereby achieved that frequency-selective attenuation only interferes with the signal component which is transmitted at the frequency which is subject to strong attenuation.

0014In addition, the signal is subjected to channel coding in the transmitter, with additional data being added to the original data, so that errors in the receiver can be corrected using this additional data. DAB also has the property that, in addition to the audio data, other data are also transmitted at the same time, the size and distribution of these data being freely configurable. DAB has a frame structure which has frame fields by means of which a receiver recognizes which content is transmitted in the respective frame. A frame field contains, for example, the information that data for a navigation system from a certain data service provider are contained in this frame. If the recipient searches for this data, the recipient evaluates this frame in order to obtain the data.

0015However, other digital radio and television transmission methods such as DVB (Digital Video Broadcasting) or DRM (Digital Radio Monial) also offer the option of transmitting data. These transmission methods also have orthogonal frequency division multiplexing; they differ from DAB in particular in the transmission frequency range, the frame structure and the transmission bandwidth.

0016Digital cellular mobile radio transmission methods such as GSM (Global System for Mobile Communication) or UMTS (Universal Mobile Telecommunication System) have the property in comparison to the radio transmission methods that a connection is established to certain users and not an entire area is served without the individual users in select this area directly. The users must therefore be dialed directly here, while every switched-on receiver receives the data in a radio transmission method.

0017If the combination of a radio transmission method and a duplex transmission method, as are mobile radio transmission methods, is used in the distribution of a data service, there are advantageous possibilities for making a data service available only to a certain group of users.

0018Duplex transmission methods have the property that data is transmitted in both directions, that is to say that communicating stations are both transmitters and receivers. Telephone and cell phone connections are examples of this.

0019In contrast, broadcast transmission methods are simplex transmission methods, since only one station transmits and many other stations receive. In some radio transmission systems, a so-called half-duplex is used, ie if one station transmits, the other station can only receive, whereas in a duplex transmission method both stations can transmit simultaneously.

0020If a data service is only made accessible to a certain group of recipients, this is achieved with encryption. Encryption is performed here in such a way that the data is combined with pseudo-random numbers, these pseudo-random numbers being generated with a pseudo-random number generator, and this pseudo-random number generator being initialized with an initialization word generated by a random number generator . A random generator is, for example, a noise generator with which random numbers can be generated.

0021Other types of encryption are also conceivable, for example, scrambling of data structures.

0022Alternatively, a large number of random numbers once generated can be stored in a memory in order to be used for the initialization of the pseudo random generator if necessary.

0023Pseudo-random numbers have the property that if one knows the initialization word, all subsequent pseudo-random numbers can be calculated because the calculation rule with which the pseudo-random generator generates the pseudo-random numbers is known to the recipient. In order to decrypt data that has been encrypted with pseudo-random numbers, it is necessary that the initialization word is known in the receiver. So it serves as the key. The recipient can then use a pseudo-random generator to generate the same pseudo-random numbers and, by further linking these pseudo-random words with the encrypted data, decrypt this data again.

0024If you link the data with the pseudo-random words in the transmitter using an exclusive-OR link, then you decrypt the data in the receiver by a further exclusive-OR link of the encrypted data word with the same pseudo-random number. Because, if a number x1 is exclusively-or-linked twice with another number x2, the result is the original number x1 again.

0025In Figure 1, a method for transmitting encrypted data is shown as a flow chart. The process is started in process step 1. In method step 2, a user selects a data service provider via a duplex transmission method in order to request a key from a data service provider for decrypting the encrypted data.

0026In step 3, the data service provider uses the duplex transmission method to transmit the key for decrypting the encrypted data that is sent using a radio transmission system. For this purpose, a transceiver station for a duplex transmission method is connected to a radio receiver, so that data transfer from the transceiver station to the radio receiver is possible. The key is therefore received by the transmitting / receiving station and transferred to the radio receiver as a date so that the radio receiver can decrypt the encrypted data.

0027The user selects the data service provider by making direct entries on his radio receiver, or the radio receiver has stored a list of different data service providers from which the user selects a data service provider and the radio receiver then automatically selects this data service provider using the transceiver station.

0028In method step 4, the user receives the encrypted radio data by means of a radio receiver. In method step 5, the user decrypts the received encrypted data in the radio receiver using his key.

0029In method step 6, the user displays the decrypted data by means of acoustic and / or optical means so that they can be viewed or read. The data is used, for example, in a navigation system to show the current traffic situation on a display, to calculate the fastest possible route for a driver to his destination and to show the driver his optimal route to his destination.

0030Other possibilities are that the user selects current stock exchange data or that a user listens to encrypted radio programs or that a construction company transfers certain data to a building site or that the police uses this procedure to get important data from databases to its location. The encryption ensures that only the authorized participants can decrypt the data with the key. If a high level of security is required, as is the case with the police, a smart card is also used, for example, to receive the key for decryption using a duplex transmission method.

0031In method step 7 it is checked whether the key is still valid, a key being valid for a predetermined time, ie the user uses his radio receiver to check whether the time has already been reached from which the key loses its validity. The radio receiver has a chronometer for this. If the key is still valid, encrypted data are received again in method step 4. If the key is no longer valid, step 8 checks whether the user is still interested in this data service. The user expresses this by making entries on his radio receiver. If this is the case, the data service provider is selected again in method step 2 via the duplex transmission method in order to obtain a new key, the radio receiver activating the connected transceiver station with which the data service provider is dialed. If the user is no longer interested in using this data service, the method is ended in method step 9.

0032The GSM transmission method is used here as a duplex transmission method and DAB as the radio transmission method. For this purpose, a GSM transceiver station is integrated or connected in a DAB receiver. The DAB receiver then receives the key from the GSM transceiver station which it uses to decrypt the encrypted data received. Alternatively, a modem can be operated as the transceiver station, which is connected to the telephone network if the radio receiver is not mobile.

0033In a development of the invention, FIG. 2 shows a method for transmitting data records as a flow chart.

0034The method is started in method step 20. In method step 21, a user requests a data record from a data service provider via a duplex transmission system. The user either directly selects the respective data service provider again, or the user selects a data service provider from a list stored in the radio receiver, whereupon the radio receiver selects the selected data service provider by means of a connected transceiver station in order to load the data record.

0035In method step 22, the user receives the requested data set from the data service provider by means of the duplex transmission method, the data set being received by the transceiver station and then being transmitted to the connected radio receiver.

0036In method step 23, the user uses the received data record in order to present the data with means for acoustic and / or optical display, which the radio receiver has. Thus, for example, a navigation system is initialized, with current traffic data now being added in addition to the distance data in order to determine an optimal route to a destination.

0037In method step 24, the user receives encrypted additional data by means of his radio receiver, with which the user updates his data set in method step 25. This means that the navigation system always has the latest traffic data. For example, the existence of a traffic jam can be recognized that would not have been recognized with the original data record. In order to enable privileged access to this additional data, decryption data are contained in the original data record, with which the encrypted additional data can be decrypted.

0038In method step 26 it is determined whether the data record is still valid, ie a data record that the user receives from the data service provider is only valid for a predetermined time. The radio receiver determines this by means of a chronometer, which the radio receiver has. This enables the data service provider to sell its data service on an opportunity basis without having to have a fixed customer base. This is a method currently offered by telephone companies (call-by-call) and internet access providers (internet-by-call).

0039By transferring the original data record, the customer pays for the specified time for how long he can use the data service. This is done by the data service provider setting a certain price for transmission over the duplex transmission system. In the case of a duplex transmission method, as is a mobile radio transmission method, this is done by setting the telephone charges. As a result, the price that the customer has to pay for the data service is also fully transparent to the customer.

0040If it is now determined in method step 26 that the data record is still valid, then it is continued in method step 24 to receive additional data again in order to keep the original data record up to date. If the data record is no longer valid, it is checked in method step 27 whether the user wishes to load a new data record from the data service provider, the user now being able to select a new data service provider. If this is the case, then in method step 21 the user requests a new data record via the duplex transmission system by means of the transmitting / receiving station. If the user is no longer interested in this data record, the method is ended in method step 28.

0041Again, the GSM mobile radio system is used for the duplex transmission method and the DAB radio transmission method for the distribution of the additional data.

0042This method is particularly suitable for navigation systems. Using the duplex transmission method, the user loads a data record that contains current traffic data. Updated data is then received via a radio transmission system in order to renew the data set for the navigation system.

0043Alternatively, however, other combinations are possible in which a duplex method with a radio transmission method is used. If the customer is in a place where there is a connection to the wired telephone network, such a telephone connection can be used as a duplex transmission method, either to receive the key for decrypting the encrypted data or to receive the data record.

0044In addition to the digital radio transmission methods, analog radio transmission methods are also suitable for the transmission of data if, for example, an additional digital signal for the transmission of data is transmitted with the analog radio signals. The well-known Radio Data System is an example of this.