Security enhancement in a data processor through use of dynamic parameter authentication

Abstract: A descrambler for descrambling scrambled information signals (10) through use of a predetermined decryption key (12) includes processing means (13) and a memory (14) for storing data (19, 27) for use in said data processing routines. The processing means are adapted for processing data in accordance with a number of different data processing routines to descramble said scrambled information signals, including a routine (16) for descrambling said scrambled information signals that utilizes said predetermined decryption key (12), and a routine (18) for generating said predetermined decryption key. The processing means includes means for responding to an instruction (20) for generating said predetermined decryption key by processing a first signal (22) provided by the processing means with a second signal (24) to generate said predetermined decryption key; and means for providing at least a portion of said second signal for processing with said first signal by retrieving a portion (25) of said stored data (27) from a portion of said memory identified by a dynamic pointer (26) contained in said instruction for generating said decryption key, with said retrieved data being data that is also used in a said data processing routine other than said routine for generating said predetermined decryption key.

Description: The present invention generally pertains to secure data processing systems and is particularly directed to enhancing the security of a given data processing routine in which an essential predetermined signal is utilized. The invention is particularly, but not exclusively, directed to enhancing the security of a data processing routine in which the essential predetermined signal is a decryption key used for descrambling scrambled information signals. Examples of data processing systems using a decryption key for descrambling scrambled information signals are described in United States Letters Patents Nos. 4,613,901 to Klein S. Gilhousen, Charles F. Newby, Jr. and Karl E. Moeder; 4,712,238 to Klein S. Gilhousen, Michael V. Harding, Jerrold A. Heller and Robert D. Blakeney, II; and 4,864,615 to Christopher J. Bennett. GB-A-2 161 680 describes a data processing system that includes an exclusive-OR gate for descrambling a scrambled signal in accordance with a data processing routine by which the scrambled signal is exclusive-OR'd with a descramble signal; a random number generator for processing data in accordance with a second data processing routine; and a memory for storing data for use in said data processing routines. The data processing system is adapted to respond to an instruction to generate the descramble signal that is essential to the data processing routine performed by the exclusive-OR gate by causing the random number generator to process an initial signal with a tier key in accordance with the second data processing routine to generate the descramble signal. At least a portion of the tier key is provided for said processing with the initial signal by retrieving a cipher signal from a portion of the memory identified by a dynamic reference page flag pointer received by the data processing system with the scrambled signal. According to a first aspect of the present invention, a secure data processing system comprises processing means for processing data in accordance with a number of different data processing routines; and memory means for storing data for use in the data processing routines; wherein the processing means includes means for responding to an instruction to generate a predetermined decryption key that is essential to the descrambling of a scrambled information signal in accordance with at least one of the said data processing routines by processing a first signal with a second signal in accordance with one of the data processing routines to generate the predetermined decryption key; and means for providing at least a portion of the second signal for processing with the first signal by retrieving a portion of the stored data from a portion of the memory means identified by a dynamic pointer; characterised by means operable to provide the dynamic pointer from the said instruction whereby the security of the said at least one data processing routine is enhanced. The second signal may include the pointer and the retrieved data. According to a second aspect of the invention, there is provided a method of operating a secure data processing system having a processor for processing data in accordance with a number of data processing routines, and a memory for storing data for use in the data processing routines, wherein the method comprises receiving an instruction in the processor, causing the processor to respond to the instruction to generate a predetermined decryption key that is essential to the descrambling of a scrambled information signal in accordance with at least one of the said data processing routines by processing a first signal with a second signal in accordance with one of the data processing routines to generate the said predetermined decryption key, and causing the processor to provide at least a portion of the second signal for processing with the said portion with the first signal by retrieving a portion of the said stored data from a portion of the memory identified by a dynamic pointer, characterised in that the dynamic pointer is provided from the said instruction whereby the security of said at least one data processing routine is enhanced. Security of the data processing routines executed by the data processing system may be further enhanced by including in said retrieved data dynamic data that is also used in a said data processing routine other than said routine for generating said predetermined decryption key. The term "dynamic" is used to indicate a changeable parameter. A dynamic pointer is a pointer that may be changed from time to time. Dynamic data is data that may change with time and/or with execution of the data processing routines. Utilization of these dynamic parameters makes unauthorized descrambling of scrambled information signals by a pirate more difficult since the dynamic parameters have to be authenticated to enable descrambling. The preferred embodiment of the invention is a communication system including a descrambler as described above in combination with a scrambler for scrambling information signals. The scrambler includes processing means for processing data in accordance with a number of different data processing routines, including a routine for scrambling said information signals and a routine for encrypting a predetermined decryption key that is required for descrambling said scrambled information signals; and memory means for storing data for use in said data processing routines; and wherein the scrambler processing means includes means for responding to an instruction to encrypt said predetermined decryption key, by processing said predetermined decryption key with a second signal to encrypt said predetermined decryption key; and means for providing said second signal. Additional features of the present invention are described in relation to the description of the preferred embodiment. BRIEF DESCRIPTION OF THE DRAWING Figure 1 is a block diagram of a preferred embodiment of the system of the data processing system of the present invention embodied as a descrambler. Figure 2 is a block diagram of a preferred embodiment of a scrambler that is combined with the descrambler of Figure 1 in a communication system. Figure 3A is a block diagram of a preferred embodiment of a portion of the descrambler of Figure 1 utilized for decrypting an encrypted decryption key. Figure 3B is a block diagram of a preferred embodiment of a portion of the scrambler of Figure 2 utilized for encrypting the decryption key that is decrypted in the portion of the descrambler shown in Figure 3A. DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of a data processing system of the present invention is embodied as a descrambler in a microprocessor, as shown in Figure 1. The descrambler descrambles scrambled information signals 10 through use of a predetermined decryption key 12. The microprocessor includes a central processing unit (CPU) 13 and a memory 14. The memory 14 may include a random access memory (RAM) and a read only memory (ROM). The CPU 13 is adapted for processing data in accordance with a number of different data processing routines, including a routine 16 for descrambling scrambled information signals that utilizes a predetermined decryption key 12, and a routine 18 for generating the predetermined decryption key 12. The CPU 13 also processes data in accordance with other routines (not shown) incident to the descrambling of information signals in accordance with the various data processing steps described in the aforementioned U.S. Patents Nos. 4,613,901; 4,712,238 and 4,864,615. The predetermined decryption key may be any of the decryption keys described in these patents, including intermediate keys and signals created at different stages during the generation of such decryption keys. The memory 14 stores data 19 that is used in the data processing routines 16, 18. The CPU 13 responds to an instruction 20 for generating the predetermined decryption key by executing the routine 18. In accordance with the routine 18, a first signal 22, such as an encrypted decryption key, provided by the CPU 13 is processed with a second signal 24 to generate the predetermined decryption key 12. At least a portion 25 of the second signal 24 is provided by retrieving a portion of the stored data 19 from a portion of the memory 14 that is identified by a dynamic pointer 26 contained in the instruction 20 for generating the predetermined decryption key 12. The retrieved second-signal data 25 preferably includes dynamic data that is also used in a data processing routine other than the routine 18 for generating the predetermined decryption key 12. The decryption key generation routine 18 of the present invention may be utilized in generating multiple predetermined signals, such as decryption keys, and in generating an intermediate key or signal that is essential to the generation of the ultimate predetermined signal, such as the decryption key 12. The data which is retrieved from the memory 14 as the second-signal data 25 may be data that is dynamically stored in the memory 14 as such data is being processed by the CPU 13 in the various data processing routines executed by the CPU 13, such as data 27 which is processed and stored during the descrambling routine 16. Alternatively, the data which is retrieved from the memory 14 as the second-signal data 25 may be data that is otherwise stored in the memory 14 for processing by the CPU 13. The predetermined decryption key 12 ultimately generated in accordance with the routine 18 is stored in the memory 14. The CPU 13 responds to an instruction 28 for descrambling the scrambled information signal 10 by executing the routine 16. In accordance with the routine 16, the predetermined decryption key 12 is retrieved from the memory 14 and utilized in descrambling the scrambled information signal 10 to produce a descrambled information signal 30. The descrambler of Figure 1 is used in a communication system that further includes a scrambler, such as shown in Figure 2, and a plurality of such descramblers. The scrambler of Figure 2 is embodied in a data processing system that includes a CPU 32, a first memory 34 and a second memory 36. The memories 34 and 36 may include RAM and/or ROM. The CPU 32 processes data in accordance with a number of different data processing routines, including a routine 38 for scrambling said information signals 30 and a routine 42 for encrypting a predetermined decryption key 12 that is required for descrambling the scrambled information signals 10. The CPU 32 also processes data in accordance with other routines (not shown) incident to the scrambling of information signals in accordance with the various data processing steps described in the aforementioned U.S. Patents Nos. 4,613,901; 4,712,238 and 4,864,615. The CPU 32 responds to an instruction 43 for scrambling the information signal 30 by executing the routine 38. In accordance with the routine 38, the predetermined decryption key 12 is utilized in scrambling the information signal 30 to produce the scrambled information signal 10. The CPU 32 responds to an instruction 44 to encrypt the predetermined decryption key 12 by executing the routine 42. In accordance with the routine 42, the predetermined decryption key 12 is processed with a second signal 46 to encrypt the predetermined decryption key and thereby produce an encrypted decryption key 22. The second signal 46 is provided from the memory 36. At least a portion of the second signal 46 is provided by retrieving a portion 48 of the data stored in the memory 14 that is identified by a dynamic pointer 50. The encrypted decryption key 22 is transmitted to the descramblers together with the scrambled information signal 10. In the preferred embodiment of the communication system, the predetermined decryption key 12 is encrypted differently for different groups of descramblers. Accordingly, different second-signal components 48 are stored in the memory 36 for differently encrypting the predetermined decryption key 12 for the different groups of descramblers. The different second-signal components 48 are selected from the memory 36 in response to the pointer 50 for use in encrypting the predetermined decryption key 12 to provide different encrypted decryption keys 22 for transmission to the different groups of descramblers. The pointer 50 thus serves as a selection-control signal that is different for each of the different groups of descramblers. The memory 34 provides different pointers 50 corresponding to the different groups of descramblers in response to a descrambler identification (ID) signal 52 and a pointer data signal 53. The pointer data signal 53 is combined with the descrambler ID signal 52 to indicate the portions of the memory 34 from which the pointers 50 and 26 are to be provided so that the pointers 50 and 26 related to a given descrambler can be changed to access the second-signal components 48 (and components 25 in the descrambler of Figure 1) from different portions of the memory 36 (and memory 14 in the descrambler of Figure 1). The pointers 26 for the different descramblers are also transmitted to the descramblers, where they are included in the key generation instruction 20. The transmitted pointers 26 may or may not be identical to the pointers 50. In order for the pointers 26 to be identical to the pointers 50 the CPU 32 of the scrambler simulates the operation of a descrambler of each of the different groups of descramblers in order to produce and dynamically store in the memory 36 of the scrambler the same second-signal data as is dynamically stored in the memory 14 of a descrambler in each of the different groups of descramblers. Accordingly the scrambler executes a descrambling routine 54 so as to process the scrambled information signal 10 in the same manner as the scrambled information signal 10 is processed in the descrambler and thereby provide the same data 27 for dynamic storage in the memory 36 and retrieval in response to the pointer 50 as is dynamically stored in the memory 14 of the descrambler and retrieved as second-signal data 25 in response to the pointer 26. The stored data 19 used in executing the routines 42 and 54 are provided from the memory 36 in the same manner as said data 19 is provided from the memory 14 in the descrambler for use in executing the routines 16 and 18. The data which is retrieved from the memory 36 as the second-signal data 48 may be data that is dynamically stored in the memory 36 as such data is being processed by the CPU 32 in the various data processing routines executed by the CPU 32, such as data 27 which is processed and stored during the descrambling routine 54. Alternatively, the data which is retrieved from the memory 32 as the second-signal data 48 may be data that is otherwise stored in the memory 36 for processing by the CPU 32. In an alternative embodiment (not shown), the second signal 46 is provided independently of the memory 36 and/or the pointers 50. In one preferred embodiment, as shown in Figures 3A and 3B, second-signal data retrieved from the respective memories of the scrambler and the descrambler is divided and used in separate subroutines of the respective encryption and decryption routines. Referring to Figure 3A, the CPU of the descrambler causes thirteen bytes of second signal data 25 to be retrieved from the memory 14 in response to a two-byte pointer 26. A first part of the second signal 24a consisting of seven bytes of the retrieved second-signal data 25 is exclusive-ORed (XORed) with a seven-byte unit key 56 in accordance with a subroutine 58 to provide a first intermediate signal 60 of seven bytes. The seven-byte unit key 56 is provided within the descrambler CPU in the manner described with reference to Figure 8 in the aforementioned U.S. Patent No. 4,864,615 for providing the unit key identified by reference numeral 148 in said patent. The CPU executes a decryption subroutine 62 in which the predetermined decryption key 22 (eight bytes) is processed with the seven-byte first intermediate signal 60 to provide a second intermediate signal 64 of eight bytes. Preferably the subroutine 62 is in accordance with the Data Encryption Standard (DES) algorithm. A second part of the second signal 24b consisting of six bytes of the retrieved second-signal data 25 and the two-byte pointer 26 is XORed with the eight-byte second intermediate key 64 in accordance with a subroutine 66 to provide the decryption key 12. Referring to Figure 3B, the CPU of the scrambler causes thirteen bytes of second signal data 48 to be retrieved from the memory 36' in response to a two-byte pointer 50. The thirteen bytes of second-signal data 48 are identical to the thirteen bytes of second-signal data 25. A first part of the second signal 46a consisting of seven bytes of the retrieved second-signal data 48 is exclusive-ORed (XORed) with a seven-byte unit key 68 in accordance with a subroutine 70 to provide the first intermediate signal 60 of seven bytes. The unit key 68 is is identical to the unit key 56 provided within the descrambler CPU. A second part of the second signal 46b consisting of six bytes of the retrieved second-signal data 48 and the two-byte pointer 50 is XORed with the eight-byte decryption key 12 in accordance with a subroutine 72 to provide the second intermediate key 64. The scrambler CPU executes an encryption subroutine 74 in which the second intermediate key 64 (eight bytes) is processed with the seven-byte first intermediate signal 60 to provide the encrypted decryption key 22. Preferably the subroutine 74 is in accordance with the Data Encryption Standard (DES) algorithm.

Claims: A secure data processing system, comprising a processing means (13) for processing data in accordance with a number of different data processing routines (16, 18); and memory means (14) for storing data (19, 25, 27) for use in said data processing routines; wherein the processing means includes means for responding to an instruction (20) to generate a predetermined decryption key (12) that is essential to the descrambling of a scrambled information signal (10) in accordance with at least one of said data processing routines (16) by processing a first signal (22) with a second signal (24) in accordance with one of said data processing routines (18) to generate said predetermined decryption key (12), and means for providing at least a portion of said second signal for processing with said first signal by retrieving a portion (25) of said stored data from a portion of said memory means identified by a dynamic pointer (26); characterised by means operable to provide said dynamic pointer from said instruction (20) whereby the security of said at least one data processing routine is enhanced. A system according to claim 1, characterised in that said second signal (24) includes said pointer (26) and said retrieved data (25). A system according to any preceding claim, characterised by a scrambler for scrambling information signals (30), including processing means (32) for processing data in accordance with a number of different data processing routines (36, 42, 54), including a routine (38) for scrambling said information signals and a routine (42) for encrypting said predetermined decryption key (12) that is required for descrambling said scrambled information signals; wherein the scrambler processing means are adapted to provide said second signal, and to respond to an instruction (44) to encrypt said predetermined decryption key, by processing said predetermined decryption key with said second signal. (46) to encrypt said predetermined decryption key. A system according to claim 3, characterised in that said descrambler includes means for dynamically storing as said second-signal data in said descrambler memory means (14) data (27) that is processed by the descrambler processing means (13) in a said data processing routine (16) that is executed by the descrambler processing means as said data (27) is being processed; and in that said scrambler includes means (32) for processing said scrambled information signal (10) in the same manner as said scrambled information signal is processed in the descrambler in order to provide said second-signal data (27), and memory means (36) for dynamically storing said second-signal data. A system according to claim 4, characterised in that said scrambler processing means includes means for providing at least a portion of said second signal (46) by retrieving said second signal data (48) from a portion of said scrambler memory means (36) identified by said pointer (50), and in that said descrambler memory means (14) store said second-signal data (27) in portions that are accessed in response to said pointer (26) corresponding to the portions of the scrambler memory means (36) from which said second-signal data (48) is accessed in response to said pointer (50). A system according to claim 3, characterised in that said scrambler processing means includes memory means (36) for storing said second-signal data (27), and means for providing at least a portion of said second signal (46) by retrieving said second signal data (48) from a portion of said scrambler memory means identified by said pointer (50); and in that said descrambler memory means store said second-signal data (27) in portions that are accessed in response to said pointer (26) corresponding to the portions of the scrambler memory means (36) from which said second-signal data (48) is accessed in response to said pointer (50). A system according to claim 3, characterised in that the means for providing the second signal (46) in the scrambler comprises memory means (36) for storing a number of different predetermined said second signal components, and means for providing a selected said second signal (48) by retrieving a selected predetermined said second signal component from said scrambler memory means in response to a selection-control signal (50). A system according to claim 7, characterised by a plurality of said descramblers, and characterised in that the scrambler processing means are adapted for providing different said selection-control signals (50) for selecting different said predetermined second signal components (48) for use in differently encrypting said decryption key (12) for different descramblers. A system according to any preceding claim, characterised in that the first signal is an encrypted said decryption key (22), and in that the descrambler processing means are adapted to generate said predetermined decIyption key (12) by executing the following routines: (a) providing a third signal (56); (b) processing said third signal with a first part (24a) of said second signal that includes a first part of said retrieved second-signal data to provide a fourth signal (60); (c) processing said encrypted decryption key (22) with said fourth signal to provide a fifth signal (64); and (d) processing said fifth signal with a second part (24b) of said second signal that includes at least a second part of said retrieved second-signal data to provide said predetermined decryption key (12). A system according to any of claims 1, 2, 3, or 9, characterised in that said retrieved data (25) includes dynamic data (27) that is also used in a said data processing routine (16) other than said routine (18) for generating said predetermined decryption key (12). A system according to claim 9, characterised in that routine (d) comprises processing said fifth signal (64) with a second part (24b) of said second signal (24) that includes both said pointer (26) and at least a second part of said retrieved second-signal data (25) to provide said predetermined decryption key (12). A system according to claim 4 and claim 9 or claim 11, characterised in that said scrambler processing means are adapted to encrypt said predetermined decryption key by executing the following routines: (a) processing said decryption key (12) with said second part (46a) of said second signal to provide said fifth signal (64); (b) providing said third signal (68); (c) processing said third signal with said first part (46a) of said second signal to provide said fourth signal (60); and (d) processing said fifth signal with said fourth signal to provide said encrypted decryption key (22). A system according to claim 1 or 3, characterised in that the first signal is encrypted said decryption key (22), and in that the descrambler processing means are adapted to generate said predetermined decryption key by executing the following routines: (a) providing a third signal (56); (b) processing said third signal with said retrieved second-signal data (25) to provide a fourth signal (60); and (c) processing said encrypted decryption key (22) with said fourth signal to provide said predetermined decryption key (12). A system according to claims 3 and 13, characterised in that said scrambler processing means are adapted to encrypt said predetermined decryption key by executing the following routines: (a) providing said third signal (68); (b) processing said third signal with said retrieved second signal data (48) to provide said fourth signal (60); and (c) processing said decryption key (12) with said fourth signal to provide said encrypted decryption key (22). A method of operating a secure data processing system having a processor (13) for processing data in accordance with a number of data processing routines (16,18), and a memory (14) for storing data (19,25,27) for use in the data processing routines (16,18), wherein the method comprises: receiving an instruction (20) in the processor (13), causing the processor (13) to respond to the instruction to generate a predetermined decryption key (12) that is essential to the descrambling of a scrambled information signal in accordance with at least one of the said data processing routines (16) by processing a first signal (22) with a second signal (24) in accordance with one of the data processing routines (18) to generate the said predetermined decryption key (12), and causing the processor (13) to provide at least a portion of the second signal for processing with the said portion with the first signal by retrieving a portion (25) of the said stored data from a portion of the memory (14) identified by a dynamic pointer, characterised in that the dynamic pointer is provided from said instruction (20) whereby the security of said at least one data processing routine is enhanced.

Inventors: ANDERSON STEVEN EDWARD, ESSERMAN JAMES NEIL, GRIFFIN III ROY ALLEN, ANDERSON, STEVEN EDWARD, ESSERMAN, JAMES NEIL, GRIFFIN III, ROY ALLEN
Applicants: GEN INSTRUMENT CORP, GENERAL INSTRUMENT CORPORATION
Application year: 1991
Main classification: H04L9
IPC codes: H04L9, G06F12, G06F21