Electrical computers and digital processing systems: support – Computer program modification detection by cryptography
Reexamination Certificate
1999-04-23
2002-05-14
Hayes, Gail (Department: 2132)
Electrical computers and digital processing systems: support
Computer program modification detection by cryptography
Reexamination Certificate
active
06389537
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to the field of cryptography. In particular, this invention relates to a system and method to protect digital content resident in a digital platform.
2. General Background
For many years, there has been a growing demand for platforms that provide video programming for entertainment purposes. Normally, the video programming (e.g., pay-per-view movies) is transmitted in an analog format such as National Television Systems Committee (NTSC) or Phase Alternating Line (PAL). Due to the inherent nature of analog signaling, video programming is protected because recorded copies normally would have poorer image quality than the original master. Also, copy protection signals may be added to the signaling in order to prevent its successful recordation. The inherent nature of content in a digital format, however, fails to provide these safeguards against modification and recordation.
Currently, original equipment manufacturers (OEMs) are developing open, re-programmable digital platforms to receive content in a digital format. For example, in the case of pay-per-view movies, a customer issues a request to a content provider (e.g., a cable company) to download a movie to the digital platform. Upon receiving authorization, the movie is downloaded and, in accordance with one purchasing scheme, an appropriate charge is debited from a prepaid balance maintained by the digital platform. This purchasing scheme is referred to as “metered content.” When the prepaid balance has been exhausted, the customer initiates contact with the content provider or an independent third-party source to establish additional credit.
Unfortunately, since many digital platforms are open and programmable, their functional elements (e.g., hardware, software, or firmware) can be observed and modified by an unauthorized user or by a malicious program. As a result, it is difficult for content providers to ensure that a digital platform is operating as intended. Encrypting the communication channels or using conventional digital signatures may prevent content from being unknowingly modified during transmission; however, these techniques do not provide assurances to the content provider that the content, once loaded within the digital platform, has not been illicitly modified. For example, there is no protection against disabling content metering software responsible for debiting the prepaid balance or modifying content metering software responsible for crediting the prepaid balance.
Moreover, even if the software has not been corrupted, there are no assurances to the content provider that communication or processing circuitry within the digital platform has not been compromised. For example, substitute circuitry or software (e.g., motherboard circuitry, basic input/output system “BIOS”, operating systems, etc.) may be deployed within the digital platform which does not comply with the desired content metering scheme. Additionally, hardware-based methods, such as use of a logic analyzer, may compromise the scheme. These security threats have greatly impeded the expansion of digital content distribution.
Therefore, it is desirable to provide a digital platform and protocol to ensure that the digital platform and its implemented functional elements are authorized and are operating as intended.
SUMMARY OF THE INVENTION
A cryptographic device comprising a processing logic and memory associated with the processing logic. The memory is loaded with a first segment of code to control execution of cryptographic functions and hash functions, and a second segment of code to perform operations on behalf of a third party having no physical control of hardware employing the cryptographic device.
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Davis Derek L.
Herbert Howard C.
Hayes Gail
Smithers Matthew
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