The patent's inventor is Verma, Sanjeev (
This patent was filed on
From the background information supplied by the inventors, news correspondents obtained the following quote: "This section is intended to provide a background or context to the invention that is recited in the claims. The description herein may include concepts that could be pursued, but are not necessarily ones that have been previously conceived or pursued. Therefore, unless otherwise indicated herein, what is described in this section is not prior art to the description and claims in this application and is not admitted to be prior art by inclusion in this section.
"The current OMA BCAST protection system only works with the ISMACryp-based service protection mechanism promulgated by the
"In addition, the current OMA BCAST content protection system for smartcards unfortunately possesses a number of severe security problems. One such problem occurs in a 'rental phone' scenario, where a first person rents a mobile telephone and subscribes to a broadcast service, which allows him to view recorded content, which is stored on the telephone. At some later point in time, the first person will remove the smartcard from the telephone and return the telephone to a rental company. However, the first person will occasionally forget to transfer or delete some of the recorded content from the telephone. At some later point in time, a second person may rent the same telephone, insert his own smartcard, and subscribe to the same broadcast service. As part of this subscription, the broadcast service will deliver a service key to the second person. In this situation, and assuming that the service key is still valid, the second person would be able to view the content that was purchased by the first person, even if the second person did not pay for that content.
"Another problem area for the current OMA BCAST protection system involves the viewing of recorded content before a subscription is initiated. Currently, any device with an active broadcast interface can record broadcasted content in a PDCF format. Assuming that a broadcaster changes its SEK at the beginning of each month, a user can keep the broadcast interface in his telephone active and record content at will. However, if the user subscribes to the broadcast service near the end of a month and obtains the SEK from the service provider, he will be able to play all previously-recorded content that is located on the telephone, even though he is subscribing to the service for only a few days.
"It would therefore be desirable to develop a system and method which addresses the shortcomings identified above."
Supplementing the background information on this patent, VerticalNews reporters also obtained the inventor's summary information for this patent: "The present invention provides a simple stateless solution for providing content protection to a broadcast stream delivered using smartcard-based key management. According to the present invention, a broadcast service provider indicates the need for content protection after the removal of service protection through a protection_after_reception flag in a short-term key message (STKM). The terminal needs to store the content in encrypted form if the protection_after_reception flag indicates so. According to the present invention, the terminal first removes the service protection by decrypting the delivered content and then temporarily stores the decrypted content if the protection_after_reception flag is set to TRUE. Otherwise, the terminal immediately renders/plays the content if the protection_after_reception flag is set to FALSE. If the protection_after_reception flag is set to TRUE, the terminal then checks whether the protection_after_reception flag in STKM indicates the need for content protection after the removal of service protection. If the answer is yes, then the terminal generates a random number (CEK_RAND) and sends a message (CEK_Request) to the smartcard, also known as the universal subscriber identity module (USIM). This message carries two parameters: CEK_RAND and SEK_id. The smartcard uses the SEK_id to retrieve the SEK and generate a content encryption key (CEK) using its key derivation function: CEK=KDF(IMSI, SEK, CEK_RAND), where CEK_RAND is a random number and, in one embodiment, the key derivation function (KDF) is the same as that used by Generic Bootstrapping Architecture (GBA) to generate a MBMS Request Key (MUK) and a MBMS User Key (MRK), as suggested in 3rd
"With the present invention, the content protection system is independent of the traffic protection system used by the underlying service protection mechanism. This is a substantial improvement over the current system, which only works with ISMACryp. Additionally, the content protection system of the present invention binds the CEK to both the service and the subscriber, while the existing system binds the content to only the service. This protects against the type of problems discussed previously. Furthermore, the content protection system of the present invention is simple to implement since the smartcard and device do not need to maintain any state; the CEK is calculated on the fly. The system of the present invention also consumes less time in decrypting at the time of rendering, as one CEK is used to decrypt the stored content. This can be achieved with as few as two messages. In contrast, the conventional system requires the device to store both STKM messages in a traffic encryption key (TEK) track along with the content. The number of messages required to decrypt the content with the current system is twice the number of traffic keys used to protect the protected content. This adversely impacts the viewing experience of the user. Lastly, the system of the present invention does not mandate many changes in the existing USIM implementation, as it reuses the existing functionalities of USIMs. The present invention can be incorporated into a wide variety of electronic devices which implement broadcast multimedia services.
"These and other advantages and features of the invention, together with the organization and manner of operation thereof, will become apparent from the following detailed description when taken in conjunction with the accompanying drawings, wherein like elements have like numerals throughout the several drawings described below."
For the URL and additional information on this patent, see: Verma, Sanjeev. Content Protection for OMA Broadcast Smartcard Profiles. U.S. Patent Number 8619993, filed
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