Portable Medium Encryption Key Binding

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Solution Overview

Problem

Existing digital content distribution systems lack effective mechanisms to ensure that encrypted content is rendered only according to specified rules, particularly when the content is distributed across multiple devices, leading to potential unauthorized use and redistribution.

Innovation Solution

A method that ties the encrypted decryption key to a portable medium using a unique identifier, ensuring the key can only be accessed when the medium is present, by employing public-private key pairs and a media secret table to authenticate and verify the medium's identity, thus enforcing usage rules and preventing widespread redistribution.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If encrypted digital content is distributed to users for rendering on multiple devices, then content accessibility and user convenience are improved, but content security and control over unauthorized redistribution deteriorate

Engineering Contradiction:

Improvecontent accessibilityVSAvoidcontent security

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

The decryption key is segmented and bound to specific portable medium identifiers rather than being universally accessible. The content encryption key is divided into multiple parts, each associated with different medium identifiers, so that complete decryption requires the correct medium-bound key segments.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

A portable medium acts as an intermediary carrier that physically binds the decryption key to the content. The medium serves as a trusted intermediary object that users must possess and present to access the encrypted content, creating a physical control layer between the content and rendering devices.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Ease of operation

If decryption keys are made accessible to multiple devices for content rendering, then rendering flexibility is improved, but the risk of key extraction and unauthorized copying increases

Engineering Contradiction:

Improverendering flexibilityVSAvoidkey extraction risk

Core Design Contradiction:

Ease of operationVSObject-affected harmful factors

Solution Approach 1:

The decryption key is nested within the portable medium's identification data structure. The medium identifier contains embedded key material that is hierarchically organized, requiring sequential verification layers before key access is granted, making unauthorized extraction difficult.

Inventive Principle:

Principle #7Nested doll (Nesting)

Solution Approach 2:

The decryption key is pre-bound to specific medium identifiers during content creation. Before rendering can occur, the system performs preliminary verification to ensure the presented medium's identifier matches the pre-bound key association, preventing unauthorized key usage before it can occur.

Inventive Principle:

Principle #10Preliminary action

3Reliability

If content is tied to specific portable mediums for copy protection, then unauthorized redistribution is prevented, but device compatibility and user convenience are reduced

Engineering Contradiction:

Improvecopy protection effectivenessVSAvoiddevice compatibility

Core Design Contradiction:

ReliabilityVSAdaptability or versatility

Solution Approach 1:

The portable medium is designed with universal identification capabilities that can be recognized by multiple rendering devices. The medium identifier uses a standardized format that different devices can verify, allowing the same protected content to work across compatible devices while maintaining medium-based control.

Inventive Principle:

Principle #6Universality (Multi-functionality)

Solution Approach 2:

The system changes the control parameter from device-specific binding to medium-specific binding. Instead of tying encryption to particular device hardware identifiers, the encryption key is bound to portable medium identifiers, allowing the content to move with the medium across different devices while maintaining protection.

Inventive Principle:

Principle #35Parameter changes

Data Source

PatentUS7644446B2Encryption and data-protection for content on portable medium

Publication Date: 2010.01.05 MICROSOFT TECHNOLOGY LICENSING LLC

AI summary

A source generates a medium key (KM) and a media secret table including a plurality of entries, each entry including (KM) encrypted by a public key (PU-PD) of a plurality of devices, obtains the medium ID of a medium therefrom, generates a content key (KD) for a piece of content, encrypts the content with (KD) to result in (KD(content)), encrypts (KD) with (KM) to result in (KM(KD)), generates a package for the content including (KD(content)), (KM(KD)), the medium ID, and a signature based on at least the medium ID and verifiable with (KM), and copies the generated package and the media secret table to the medium. Thus, a device with the medium and a private key (PR-PD) corresponding to an entry of the media secret table can access and render the content.