Cryptography – Cryptanalysis
Reexamination Certificate
1997-06-24
2001-05-22
Swann, Tod R. (Department: 2767)
Cryptography
Cryptanalysis
C280S003000, C280S010000, C369S084000
Reexamination Certificate
active
06236727
ABSTRACT:
TECHNICAL FIELD
The present invention relates in general to apparatus and method for protecting digital video/audio data and, more particularly, to an apparatus, method and computer program product for encryption/decryption of data within a computer system for communication from a CPU to an accessible internal structure, such as memory or a bus, without exposing the data in unscrambled form at the accessible structure.
BACKGROUND OF THE INVENTION
Within the past decade, the advent of world-wide electronic communications systems has enhanced the way in which people can send and receive information. In particular, the capabilities of real-time video and audio systems have greatly improved in recent years. In order to provide services such as video-on-demand, video conferencing, and digital video disc (DVD) motion pictures, an enormous amount of bandwidth is required. In fact, bandwidth is often the main inhibitor in the effectiveness of such systems.
In order to overcome the constraints imposed by existing technology, compression systems have emerged. These systems reduce the amount of video and audio data which must be transmitted by removing redundancy in the picture sequence. At the receiving end, the picture sequence is uncompressed and may be displayed in real time.
One example of an emerging video compression standard is the Moving Picture Experts Group (“MPEG”) standard. Within the MPEG standard, video compression is defined both within a picture and between pictures. Video compression within a picture is accomplished by conversion of the digital image from the time domain to the frequency domain by a discrete cosine transform, quantization, variable length coding, and Huffman coding. Video compression between pictures is accomplished via a process referred to as “motion estimation”, in which a motion vector plus difference data is used to describe the translation of a set of picture elements from one picture to another. The ISO MPEG2 standard specifies only the syntax of bitstream and semantics of the decoding process. The particular choice of coding parameters and tradeoffs in performance versus complexity is left to the system developers.
Digital Versatile Disc (DVD) is an emerging technology which due to its nature, requires extensive encryption in order to protect the data, such as a motion picture, against unauthorized copying.
DVD is a specification for the content of video, audio and other compressed data to be used as playback video, audio and, for example, subtitle data by a DVD decoder. The DVD video data is specified in the Moving Picture Experts Group (MPEG) standard (ISO/IEC 13818-2). As well as being represented by this standard, the data is also encrypted using the industry's Content Scrambling System (CSS), which produces an encrypted, encoded data stream for DVD playback. The data stream can be decrypted by hardware licensed to perform CSS decryption. Conventionally, CSS decryption occurs at a PCI card, which also conventionally includes MPEG decompression of the encrypted, encoded data signal.
The present invention is directed in one particular aspect to improving upon this conventional DVD processing of the encrypted, encoded data stream.
DISCLOSURE OF THE INVENTION
Briefly summarized, this invention comprises in a first aspect apparatus for processing a scrambled data stream within a computer system having a central processing unit (CPU) coupled to receive the scrambled data stream. The apparatus includes a descrambling means within the central processing unit to descramble the received, scrambled data stream and thereby produce a clear data stream. Re-encryption means also within the central processing unit reencrypts the clear data stream to produce an encrypted data stream, wherein the scrambled data stream is produced from a different encryption algorithm than the encrypted data stream. Means are provided for transferring the encrypted data stream from the central processing unit to a second structure of the computer system, the second structure being coupled to the CPU. Decryption means coupled to the second structure receives the encrypted data stream for decrypting and produces the clear data stream therefrom, wherein the clear data stream is unexposed when transferred from the central processing unit to the second structure coupled to the CPU, while the descrambling means within the central processing unit accomplishes software descrambling of the received, scrambled data stream.
In another aspect, apparatus is provided for processing a data stream within a computer system having a central processing unit coupled to receive the data stream. The apparatus includes encryption means within the CPU for encrypting identified copyright data within the data stream to produce therefrom encrypted data. Means are provided for transferring the encrypted data from the central processing unit to a structure of the computer system coupled thereto, wherein the copyright data is only transferred from the CPU as said encrypted data. Decryption means are coupled to the structure receiving the encrypted data for decrypting the encrypted data.
Various enhancements to each of the aspects summarized above are also described and claimed. In addition, corresponding methods and computer program products are presented and claimed.
To restate, in accordance with this invention clear data, whether compressed or uncompressed, is not allowed to be resident in an accessible computer system structure, such as a host memory buffer or system bus to prevent theft of the clear data. The invention is particularly applicable to MPEG encoded and CSS encrypted video data such as employed by digital video disc (DVD) technology. The decryption techniques presented herein allow for subsequent changes, for example, through the flexibility of downloading new microcode, of an encryption/decryption algorithm pair. In addition, the particular scrambling/descrambling algorithm employed may vary. The concept is to initiate the descrambling process by host software, rescramble the data at the central processing unit using a different encryption technique, and then complete the descrambling at the receiving module, whether the receiving module comprises an additional software module executing on the central processing unit or a receiving hardware device, such as a decoder resident on a system bus coupled to the central processing unit. The rescrambling subsequent to primary software descrambling of the received encrypted data may be complete or partial. At the receiving module, the rescrambled data can be decrypted for display, output via an audio card, or undergo further processing.
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“Sonic DVD Creator—Blueprint for DVD Premastering”, Sonic Solutions, Apr. 1996, (pp. 2-10).
Ciacelli Mark Louis
Fetkovich John Edward
Kouloheris Jack Lawrence
Lam Wai Man
Urda John William
Heslin & Rothenberg, P.C.
International Business Machines - Corporation
Jack Todd
Steinberg William H.
Swann Tod R.
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