US 20050254645 A1
A data safeguarding system, method, and article for safeguarding an encrypted data-stream transmitting on a first channel from a first system to a second system. The data-stream can be intertwined with other data-streams. The data-stream is arranged in fixed length sequential blocks, each block including a header portion and a payload portion. The first system places a flag marking in the header portion indicating that the payload includes a tag having at least one identifier for selecting the decryption keys from the first system. The second system reads the flag, and if the flag indicates a tag portion, reads the tag portion. The second system transmits the identifier to the first system on a second channel. The first system reads the identifier, retrieves the keys, and transmits the decryption keys to the second system on the second channel. The second system receives the decryption keys and decrypts the data block using the decryption keys.
1. A method comprising:
receiving a data stream from a source device, by a sending system, the data stream comprising a sequence of data blocks, wherein each data block comprises a header and a payload;
the sending system negotiating with each of at least one application decoder to generate a session key shared between the sending system and the at least one application decoder, each session key to encrypt at least a decryption key;
for each data block, encrypting a payload by the sending system, the payload corresponding to the each data block, the encryption using at least one key;
the sending system storing a portion of the encrypted payload to be transmitted later to the application decoder, wherein the stored portion is one of an encrypted portion and an unencrypted portion;
the sending system replacing the stored portion of the encrypted payload with a tag, the tag identifying the data stream and a source of the data stream;
the sending system setting a flag in a header of the data block corresponding to the encrypted payload, the flag indicating that (a) at least one of said payload is encrypted and (b) said payload includes the tag; and
transmitting by the sending system each of the data blocks to an appropriate one of the at least one application decoder.
2. The method as recited in
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7. The method as recited in
8. A machine readable medium having instructions that when executed cause the machine to:
receive a data stream from a source device the data stream comprising a sequence of data blocks, wherein each data block comprises a header and a payload;
negotiate with each of at least one application decoder to generate a session key shared between the sending system and the at least one application decoder, each session key to encrypt at least a decryption key;
for each data block, encrypt a payload, the payload corresponding to the each data block, the encryption using at least one key;
store a portion of the encrypted payload to be transmitted later to the application decoder, wherein the stored portion is one of an encrypted portion and an unencrypted portion;
replace the stored portion of the encrypted payload with a tag, the tag identifying the data stream and a source of the data stream;
set a flag in a header of the data block corresponding to the encrypted payload, the flag indicating that (a) at least one of said payload is encrypted and (b) said payload includes the tag; and
transmit each of the data blocks to an appropriate one of the at least one application decoder.
9. The medium as recited in
10. The medium as recited in
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15. A system for safeguarding protocol-specific data within a device, comprising:
a first transmission channel to transmit at least one protocol specific encrypted data stream;
at least one protected content exchange (PCX) device configured to translate the at least one protocol specific encrypted data stream into a PCX encrypted data stream; and
at least one application decoder configured to decode the PCX encrypted data stream, the decoded PCX data stream comprising a plurality of data blocks each data block having a header and a payload,
wherein the at least one PCX device comprises:
at least one protocol specific registration engine configured to register the at least one application decoder,
at least one negotiator configured to negotiate at least one content decoder key for the at least one application decoder, the negotiator using a second transmission channel to communicate non-data block data between the PCX device and the at least one application decoder,
at least one decryptor configured to decrypt the at least one protocol specific encrypted data stream,
at least one encryptor configured to encrypt at least a portion of the decrypted data stream using the at least one decoder key to produce at least one re-encrypted data stream,
a payload replacement module to replace a portion of a payload of the data block with a tag data that indicates at least one key for the data block in the PCX device,
a header flag setting module that sets a flag in a header of the data block when the data block includes the tag, and
a data-stream sending module that sends a data-stream, the data stream including the data block, to the at least one application decoder after the header flag setting module sets the flag and the encryptor encrypts the data stream and the payload replacement module replaces the portion of a payload.
16. The system as recited in
17. The system as recited in
This application is a divisional application of U.S. patent application Ser. No. 09/675,976, (Attorney Docket No. 042390.P7957), entitled “System And Method For Safeguarding Data Between A Device Driver And A Device,” filed on Sep. 29, 2000 by Keith Shippy et al., assigned to a common assignee, the entire subject matter which is herein incorporated by reference.
1. Field of the Invention
The present invention relates to data encryption. More specifically, the present invention relates to safeguarding the transfer of data within a device.
2. Background Information
With the proliferation of computers and networks, the amount and availability of digitized data available for viewing and listening has grown. However, with this growth in the amount and availability of information, content providers have desired greater protection of the data from unauthorized use.
In order to protect data from unauthorized use, conventional data protection techniques, such as, for example, data encryption, have been used to protect data as it is being transferred over a network or between devices. Content providers use a number of well known encryption techniques to encrypt sensitive data before transmission from one device, such as, for example, a satellite receiving dish, to a second device, such as, for example, a computer or set-top box.
Different conventional types of encryption techniques are used depending upon the source device of the data and the type of data bus being used for the transmission from one device to another. For example, data transmitted from a Digital Video Disk (DVD) player to a computer uses Content Scrambling System (CSS) encryption, and data transmitted over an IEEE 1394 bus use Digital Transmission Content Protection (DTCP). Data transmitted over other bus systems use a number of other encryption techniques. In order to decrypt the data as it is received, devices need to be able to decrypt data using the variety of techniques that are used to encrypt the data. Thus, a device that receives both CSS and DTCP encrypted data needs to know the techniques for decrypting both types of encrypted data.
The various encryption techniques employed only protect the data during transmission. Once the data is received, it must be decrypted in order for the receiving device to be able to process the data. Once the data is decrypted within the receiving device, the data is susceptible to unauthorized access and manipulation.
Moreover, these conventional systems do not protect the data inside an open architecture device, such as a personal computer. Conventional systems do not control what applications access the incoming data-stream, nor allow those applications to access the incoming data stream without being aware of the data originator outside the device.
According to one aspect of the invention, a machine readable medium provides instructions which when executed by at least one processor, cause the processor to perform operations. The operations include encrypting a payload of a data-stream data block with at least one key before transmitting the data-stream from a first system to a second system, replacing a portion of the payload with a tag that identifies at least one decrypting key to the first system before transmitting the data-stream from the first system to the second system, and setting a flag in a header of the data block that indicates that the payload has the tag before transmitting the data-stream from the first system to the second system.
The present invention will be described by way of exemplary embodiments, but not limitations, illustrated in the accompanying drawings. Identical numerals indicate the same elements throughout the figures.
In the following description, various aspects and details of the present invention will be described. However, it will be apparent to those skilled in the art that the present invention may be practiced with only some or all aspects of the present invention. For purposes of explanation, specific numbers, materials and configurations are set forth in order to provide a thorough understanding of the present invention. However, it will also be apparent to one skilled in the art that the present invention may be practiced without the specific aspects and details. In other instances, well known features are omitted or simplified in order not to obscure the present invention.
Some portions of the descriptions that follow are presented in terms of algorithms and symbolic representations of operations on data bits within a computer memory. These algorithmic descriptions and representations are the means used by those skilled in the data processing arts to most effectively convey the substance of their work to others skilled in the art. An algorithm is here, and generally, conceived to be a self-consistent sequence of steps leading to a desired result. The steps are those requiring physical manipulations of physical quantities. Usually, though not necessarily, these quantities take the form of electrical or magnetic signals capable of being stored, transferred, combined, compared, and otherwise manipulated. It has proven convenient at times, principally for reasons of common usage, to refer to these signals as bits, values, elements, symbols, characters, terms, numbers, or the like.
It should be borne in mind, however, that all of these and similar terms are to be associated with the appropriate physical quantities and are merely convenient labels applied to these quantities. Unless specifically stated otherwise as apparent from the following discussion, it is appreciated that throughout the description, discussions utilizing terms such as “processing” or “computing” or “calculating” or “determining” or “displaying” or the like, refer to the action and processes of a circuit that can include a programmed computer system, or similar electronic computing device. A computer system manipulates and transforms data represented as physical (electronic) quantities within the computer system's registers and memories into other data similarly represented as physical quantities within the computer system memories or registers or other such information storage, transmission or display devices.
The present invention also relates to apparatus including circuits for performing the operations herein. This apparatus may be specially constructed for the required purposes, or it may include a general purpose computer selectively activated or reconfigured by a computer program stored in the computer. Such a computer program may be stored in a computer readable storage medium. A machine readable medium includes any mechanism that provides (i.e. stores and/or transmits) information in a form readable by a machine such as a computer. For example, a machine readable medium includes, and is not limited to, read only memory (ROM); random access memory (RAM); magnetic disk storage media; optical storage media; flash memory devices; electrical, optical, acoustical or other form of propagated signals (such as carrier waves, infrared signals, digital signals, and so forth), or any type of media suitable for storing electronic instructions.
The algorithms and displays presented herein are not inherently related to any particular computer or other apparatus. Various general purpose systems may be used with programs in accordance with the teachings herein, or it may prove convenient to construct more specialized apparatus to perform the required method steps. The required structure for a variety of these systems will appear from the description below. In addition, the present invention is not described with reference to any particular programming language. It will be appreciated that a variety of programming languages may be used to implement the teachings of the invention as described herein.
Various operations will be described as multiple discrete steps performed in turn in a manner that is most helpful in understanding the present invention, however, the order of description should not be construed as to imply that these operations are necessarily order dependent, in particular, the order the steps are presented. Furthermore, the phrase “in one embodiment” will be used repeatedly, however the phrase does not necessarily refer to the same embodiment, although it may.
Protocol specific encrypted data is received over protocol specific bus 120 from protocol specific input devices 110. In the
Initially, PCX module 106 negotiates a content channel encryption key with protocol specific input device 110. PCX module 106 then negotiates a PCX session key with the client decoding device 102. Decoding device 102 is the client that, in one embodiment, originally requested the data from device 110. Once the PCX session key is negotiated, PCX module 106 re-encrypts the payload of the protocol specific data using a randomly generated PCX content key and transfers the re-encrypted data (including header and payload) to the appropriate decoding device 102. Once decoding device 102 receives the re-encrypted data, decoding device 102 negotiates with the PCX module 106 to retrieve the PCX content key encrypted by the PCX session key. Once the appropriate PCX content is retrieved, decoding device 102 decrypts the payload data. Decoding device 102 then manipulates the unencrypted data. In one embodiment, decoding device 102 decodes the unencrypted data. For example, if MPEG data is requested by an MPEG decoder, the appropriate input device 110 sends the data over the bus 120 to data safeguarding device 104. CPU 115 executes the PCX module 106 which decrypts the MPEG input data stream using a content channel encryption key for the bus 120. The MPEG decoder and PCX module 106 negotiate a PCX session key. The payload MPEG data is re-encrypted with the randomly generated PCX content key and the re-encrypted data is sent to the MPEG decoder. PCX module 106 encrypts the PCX content key with the PCX session key. The MPEG decoder retrieves the encrypted PCX content key and decrypts the PCX content key with the PCX session key. In addition, the MPEG decoder uses the PCX content key to decrypt the payload data for playback. The MPEG decoder then retrieves the device key and decrypts the payload data for playback.
In one embodiment, data within system 100 is further protected from tampering or from unauthorized access by the use of a number of anti-tampering techniques such as, for example, self-modification of PCX module 106 code, the use of anti-debugging techniques, self-verification of PCX module 106 code, signature verification of PCX module 106 code, and other applicable anti-tampering techniques. The use of these anti-tampering techniques prevents unauthorized access or modification of PCX module 106 code which prevents the unauthorized access or modification of the data as it is being transferred through system 100.
Thus, the data is protected from unwarranted hacking or copying within data safeguarding system 100. Within data safeguarding system 100, the transmission headers of the data are left decrypted while the payload of the data is re-encrypted by PCX module 106. Thus, the payload of the data is protected from unwarranted copying or hacking during transfer within system 100 while allowing untrusted components to access the portions of the data stream they need.
Each data bus transmission protocol requires a corresponding protocol specific decryptor 322. PCX negotiator 328 negotiates a PCX session key with the decoding device 102 that is the intended recipient of the protocol specific data. Once a session key is negotiated, protected content exchange (PCX) encryptor 324 re-encrypts the payload portion of the data with a randomly generated PCX content key to produce re-encrypted data. PCX encryptor 324 transfers the re-encrypted data to protocol specific bus abstractor 320 which, in turn, transfers the re-encrypted data to device specific mini port driver 316. Device specific mini port driver 316 sends the PCX re-encrypted data to the upstream drivers and libraries 330 which in turn transfers the PCX re-encrypted data to splitter 232.
Splitter 232 reads the transmission header of each re-encrypted data block and transfers the data block to the decoding device 102 corresponding to the information contained within the transmission header. In addition, in one embodiment, splitter 232 removes the transmission headers from the data block. Within the data, data blocks are intermingled so that a variety of data blocks are received by splitter 232. Thus, a video block may be received, then an audio block, then another video block, and so forth. The splitter transfers the payload sections of the blocks to the corresponding decoding device as indicated by the transmission header. Once the re-encrypted payload data is received by a decoding device 102, decoding device 102 retrieves the encrypted PCX content key from PCX negotiator 328. Decoding device 102 decrypts the content key using its PCX session key which was originally negotiated with PCX negotiator 328. The unencrypted data is then consumed by decoding device 102.
Once the content channel encryption key is negotiated, IEEE 1394 encrypted data is transferred from protocol specific input device 110 via IEEE 1394 bus driver 210, to class driver 212 and eventually to device specific mini port driver 416. DTCP bus abstractor 420 abstracts the IEEE 1394 encrypted data from device specific mini port driver 416 and transfers the IEEE 1394 encrypted data to PCX module 106. The IEEE 1394 encrypted data is decrypted by DTCP decryptor 422 one block at a time using the content channel encryption key previously negotiated by DTCP registration engine 426. In the IEEE 1394 example, both the transmission headers and the payload are encrypted by protocol specific input device 110. Thus, DTCP decryptor 422 decrypts both the transmission header and payload portions of the IEEE 1394 encrypted data block.
If video decoder 438 has not previously registered with PCX module 106, PCX negotiator 428 authenticates video decoder 438. During authentication, video decoder 438 is registered with PCX negotiator 428 and video decoder 438 negotiates a key exchange with PCX negotiator 428. The key exchange method between video decoder 438 and PCX negotiator 428 is similar to the key exchange method between decoding device 110 and DTCP registration engine 426 described above. Once a session key is negotiated between video decoder 438 and PCX negotiator 428, PCX encryptor 424 encrypts the payload of the data blocks using a randomly generated PCX content key. The re-encrypted IEEE 1394 data blocks are transferred to DTCP bus abstracter 420 for transfer to device specific mini port driver 416. The re-encrypted IEEE 1394 data is transferred via WDM stream class driver 430 and WDM streaming library 432 to source filter 434. At source filter 434, re-encrypted IEEE 1394 data intended for MPEG decoder 435 is split off from the other IEEE 1394 data and transferred to MPEG decoder 435. The re-encrypted IEEE 1394 data is muxed as MPEG transport stream (TS) to MPEG TS splitter 436. MPEG TS splitter 436 splits the video and audio portions of the MPEG TS and removes the transmission headers. The video portion of the TS is transferred to video decoder 438. Video decoder 438 requests the PCX content key from PCX negotiator 428. PCX negotiator 428 encrypts the PCX content key with the appropriate PCX session key and transfers it to video decoder 438. Video decoder 438 decrypts the PCX content key using the previously negotiated PCX session key and used the content key to decrypt the video data. In addition, the video decoder 438 consumes the data. In a similar manner, audio decoder 440 receives the audio TS and decodes the audio TS with a device key retrieved from PCX negotiator 428.
In standard MPEG video, the audio and video blocks are interwoven together within the input data stream. In order to separate the data, the MPEG splitter 436 reads the transport stream headers. Within data safeguarding system 100, MPEG decoder 435 only needs to use the PCX specific protocols in order to interact with PCX negotiator 428 and does not need to be able to use each individual data bus transmission protocol. PCX module 106 is able to translate the encrypted protocol specific data from any specific bus into PCX encrypted data that the MPEG decoder 435 is able to understand and decode. Thus, the re-encryption of the protocol specific data by PCX module 106 is independent of any specific bus protocol used by system 100. Decoding devices 102 are independent of the command protocol of the specific bus. The bus abstractor 420 abstracts the DTCP status structure, encapsulates the status structure in the proper command protocol, and transmits the encapsulated protocols to the driver 416 and vice versa. In this manner, decoding devices 102 are capable of receiving encrypted data from any protocol specific bus 120 without negotiating the content channel encryption key with the input devices 110 or knowing the encryption protocol for the specific buses 120. As existing bus protocols change and new bus protocols are developed, PCX module 106 may be updated. However, decoding devices 102 only need to be able to talk with PCX module 106 and only need to be updated when the PCX module 106 negotiation protocols are updated.
PCX module 106 may be implemented in software or hardware. The PCX module 106 may be incorporated within RAM memory of a personal computer or may be contained within flash memory which is attached to a CPU or other data processing device. Thus, PCX module 106 is easily updated independent of decoding devices 102.
PCX module 106 includes a number of registration modules 520 for the negotiation of content channel encryption keys with protocol specific input devices 110. In one embodiment, PCX module 106 may contain registration module 1 (522) through registration module n (524) corresponding to each protocol specific bus connected to the system.
PCX module 106 contains PCX negotiation modules 530 which are utilized by data safeguarding system 100 to negotiate key exchanges with decoding devices 102. In addition, the negotiation modules authenticate the decoding devices and maintain key synchronization between PCX module 106 and decoding devices 102. In one embodiment, PCX module 106 includes from negotiation module 1 (532) through negotiation module n (534) corresponding to individual decoding device 102.
Referring now to
Referring now to
The source device 110 transmits an exemplary two intertwined data-streams, a video data-stream and an audio data-stream, to a device specific driver stack 1410 of data safeguarding device 104 via a bus 1420 a. Each data-stream includes a sequence of data blocks, each data block having a conventional header and payload. The driver stack 1410 retransmits each data-stream to an appropriate PCX module 106. The PCX module 106 includes at least one decryptor and protocol specific registration engine, and at least one PCX encryptor and PCX negotiator, described herein with reference to
The embodiment portrayed in
The data-stream data transmission path includes the PCX module 106 that sends the exemplary intertwined data-stream to a driver stack 1410. The driver stack 1410 sends the data-stream to a splitter 1432, wherein each separate data-stream is then separated and separately transmitted to an appropriate exemplary application decoder 102 a or 102 b. The video data-stream is routed to the exemplary video application decoder 102 a, and the exemplary audio data-stream is routed to the exemplary audio application decoder 102 b. The non-data-stream data transmission path between the PCX module 106 and the decoder 102 a is exemplary bus 1460 a, and between the PCX module 106 and the decoder 102 b is exemplary bus 1460 b, wherein buses 1460 a and 1460 b may be identical physical devices. The non-data-stream data includes the identifier necessary for the PCX module to access the data block decryptor keys and optional portion of the payload. The non-data-stream data preferably includes a data-stream identification datum and a source identification datum from the decoders 102 a and 102 b, and the encryption keys and the portion of a replaced payload from the PCX module 106. The preferred embodiment non-data-stream data additionally includes an authentication and key exchange (AKE) from the PCX module 106 to the exemplary application decoders 102 a and 102 b to enable a separately encrypted tag and the aforementioned encryption keys to be themselves encrypted, assuring the embodiment of an authorized and secure decoder(s) 102 in communication with the PCX 106 module and receiving the data-stream. The precise method of transmitting and receiving the data-streams, datum identifiers, and encryption keys, shall be described with reference to
Referring now to
The PCX module 1706 additionally replaces a portion of the payload with the tag, and marks a flag, as described with reference to
Referring now to
The data stream transmitted to the safeguarding system is alternatively unencrypted, or encrypted and has been decrypted by the PCX module as described herein. At block 1805, the PCX module not necessarily but preferably performs an AKE procedure with each decoder to create a shared session key with each decoder. This session key will be used to encrypt the decryption keys before they are sent back to the decoder. Additionally this AKE will assure that the applications are authorized to access the PCX module encryption system. At block 1810, the PCX module encrypts the data block payload. The payload is encrypted using at least one key. At block 1815, the PCX source module stores a tag-sized portion of the encrypted payload for subsequent transmission to an application decoder. In the preferred embodiment, the entire payload is encrypted using the key(s). In the present invention, the stored portion can alternatively be encrypted separately with the key(s), or can be optionally left unencrypted. The payload in a following block shall be decrypted in accordance with the encryption characteristic of the stored portion.
At block 1820, a tag is inserted into the payload in the place of the saved payload portion. The tag includes in the preferred embodiment both an identification of the data stream 612 and an identification of the data stream source 614, the source identified because a safeguarding system may include more than one source circuit. The encryption keys and the saved portion of the payload are each referenced to the data-stream identifier. At block 1825, a flag in the header is marked to indicate that the block contains a payload tag. At block 1830, the data block is sent to the appropriate decoder 102 along the data-stream transmission channel described with reference to
At block 1855 the appropriate PCX module reads the data stream identifier. The proper application keys and portion of the payload are determined by reference to the data stream identifier. The second set of encryption key(s) and the stored portion of the payload that was replaced by the tag are transmitted to the target application decoder in accordance with the data stream identifier. In the embodiment in which the application decoder module and the PCX module are physically separate devices, the identifiers are sent back to the PCX module along the separate channel as herein described. At block 1860, the appropriate application decoder receives the decryption keys key(s) and the payload portion transmitted from the PCX module at block 1855, and decrypts the key(s) with the session key, replaces the payload portion from the tag position, and then decrypts the payload using the decrypted key(s).
At processing block 910, the encrypted protocol specific data is translated into protected content exchange (PCX) re-encrypted data. The translation of the data includes decrypting the encrypted protocol specific data using a content channel encryption key to produce decrypted data. Once the data is decrypted, the payload of the decrypted data is re-encrypted using a PCX content key to produce PCX re-encrypted data. The content channel encryption key is negotiated by a protocol specific registration engine 326 with protocol specific input device 110 upon initiation of the transfer of protocol specific data from the protocol specific input device 110 to decoding device 102. Once protocol specific input device 110 and protocol specific registration engine 326 have completed the required AKE procedure, a content channel encryption key may be exchanged between protocol specific input device 110 and protocol specific registration engine 326. This content channel encryption key is used to encrypt the data by protocol specific input device 110 and decrypt the encrypted protocol specific data by protocol specific decryptor 322. The session key is negotiated between PCX negotiator 328 and decoding device 102.
After the data is re-encrypted, the re-encrypted data and the PCX content key encrypted by the PCX session key are transferred to the decoding device 102 at processing block 915. In one embodiment, the re-encrypted data is split into a number of data streams which are transferred to appropriate decoding devices 102. At processing block 920, decoding device 102 decrypts the PCX content key and uses it to decrypt the re-encrypted data. The unencrypted data is further decoded by decoding device 102.
At processing block 1112, the new PCX content key is generated. PCX module 106 uses the existence of natural synchronization points within the original data stream to determine when to create a new PCX content key.
At processing block 1115, PCX module 106 generates PCX tag 610 that is a unique identification for the PCX resync block 720. In one embodiment, PCX tag 610 may be an array index value. In alternate embodiments, PCX tag 610 may be any suitable index value to the PCX resync block 720. At processing block 1120, PCX module 106 copies PCX flag 609, PCX tag 610, TSID 612, and PID 614 into the payload portion of the data stream and saves the original portion in location 820 in the resync block 720.
At processing block 1125, PCX module 106 updates PCX resync data 720. If the PCX content key being used to encrypt the payload is different from the PCX content key used on the previous block for the same decoding device 102, key delta tag 810 is incremented. Otherwise, key delta tag 810 is unchanged. In this manner, PCX content keys may be changed periodically during re-encryption of the data. This increases the security of the data within system 100. In one embodiment, PCX content key is changed on a fixed time interval or after a fixed number of PES headers 608 have been processed.
In order to increase the security of system 100, the PCX content key is altered on each PES header 608 change by using a random initialization vector as a seed value to modify the key. This allows splitter 232 to drop a data block without losing the ability to decrypt the remaining data in the input stream. In one embodiment, key delta tag 810 and random initialization vector 815 are not encrypted. PCX content key 714 is encrypted with the previously negotiated PCX session key.
At processing block 1130, PCX module 106 encrypts the payload containing the resync data using the PCX content key.
At processing block 1211, decoder 102 checks if key delta tag 810 changed. Delta tag 810 indicates if PCX content key has changed. If so, at processing block 1213, decoding device 102 retrieves PCX content key 714 from shared buffer 700. At processing block 1215, decoding device 102 extracts PCX tag 610 and performs a look-up of the resync block 720 within shared buffer 700. Decoding device 102 restores the original payload.
Decoding device 102 then decrypts the PCX content key using the previously negotiated PCX session key. At processing block 1218, decoder 102 reinitializes the decryption cipher using the PCX content key and the random initialization vector 815.
At processing block 1219, decoder 102 decrypts the payload using the decryption cipher. At processing block 1220, the decoding device 102 decodes the payload of the unencrypted data for further processing (for example, playback by MPEG decoder).
The protocol specific data may contain copy control information (CCI) which allows the content owners to assign varying levels of priority for what can and can't be done with the data. The data may be “copy free” which means there is no restriction to copying the data. The other end of the spectrum is “copy never” which means that as soon as the AKE is negotiated, a device must render the data immediately. In this scheme, a device can not make any copies, can not save the data for later use, or anything similar. Thus, when a device receives the data, it is sent to the consumer, and then the data gets thrown away.
The other two schemes are “copy once” and “copy no more.” If a device receives data that is marked as “copy once,” the device may make a single copy of the data if the user chooses to do so. This scheme allows recording for later viewing. When a device receives data that is marked “copy once,” the device may save it, but then once it is saved, when it is retrieved after saving, the device must mark the data as “copy no more.”
In one embodiment, during transfer of data within system 100, if the data is unencrypted, the CCI information is susceptible to interception and unauthorized change. Thus, if the data is marked “copy never” and the information is hacked, the data may be pirated within system 100. The CCI information is contained within transmission header 602. The transmission header 602 is not encrypted during transfer though system 100 and is susceptible to change.
Within system 100, the CCI information is built into the PCX content key. The CCI information retrieved from the data stream in transmission header 602 is used as part of the seed to generate the key. Thus, by combining the PCX content key with the control information before re-encryption, system 100 guarantees that any modification of the CCI information in the transmission header 602 will result in incorrect decryption of the protected data. During decryption of the re-encrypted data by decoding device 102, the CCI information is extracted from the transmission header 602 and combined with the PCX content key to create the decryption key.
The above method may be used to protect any information embedded within the transmission header 602. Thus, information such as, for example, copy quality which may indicate the quality of audio a user is allowed to copy, how many times a device is allowed to copy this content, and similar information may be protected from change while the data is transferred within system 100.
Decoding device 1535 is configured to extract the embedded tag from replacement data 1530 and to retrieve the original payload and synchronization information from shared memory buffer 1540 corresponding to replacement data 1530.
In one embodiment, decoding device 1535 is contained within the same device as shared memory buffer 1540. In an alternate embodiment, decoding device 1535 is a separate device from the device containing shared memory buffer 1540.
While certain exemplary embodiments have been described and shown in the accompanying drawings, it is to be understood that these embodiments are merely illustrative of and not restrictive of the broad invention. The present invention is not limited top the specific constructions and arrangements shown and described, and alternative embodiments will become apparent to those skilled in the art to which the present invention pertains without departing from the scope of the present invention. The scope of the present invention is defined by the appended claims rather than the forgoing description. In the appended claims, a physical embodiment of each recited circuit limitation does not necessarily include completely separate physical devices from another recited circuit limitation. An embodiment of each circuit may share at least one element with another circuit.