Digital Content Distribution System Time Synchronization

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Solution Overview

Problem

In content distribution systems, inconsistencies in date-time clocks between distribution and reception apparatuses due to malicious alterations or changes can lead to improper usage permission judgments, resulting in unauthorized usage beyond the set usage expiry.

Innovation Solution

A digital content distribution system that includes a distribution apparatus with a first timer and a reception apparatus with a second timer, where usage permission is judged using the date-time clocked by the second timer and the difference between the two timers, ensuring accurate usage permission judgments by adjusting the usage expiry date-time based on the clock differences.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of operation

If date-time clocks are used independently in distribution and reception apparatuses, then each apparatus can operate autonomously, but time synchronization between the two apparatuses deteriorates, leading to improper usage permission judgments

Engineering Contradiction:

Improveautonomous operationVSAvoidusage permission judgment accuracy

Core Design Contradiction:

Ease of operationVSReliability

Solution Approach 1:

The patent introduces an intermediary mechanism (time difference calculation and compensation) between the distribution apparatus and reception apparatus. The reception apparatus calculates the time difference between its own clock and the distribution apparatus clock, and uses this difference to adjust the usage permission judgment, thereby resolving the time synchronization issue while maintaining autonomous operation

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent changes the time parameter by calculating the time difference between two clocks and using this difference to adjust the usage permission judgment. Instead of requiring strict time synchronization, the system adapts to the time difference by modifying the judgment criterion, thus resolving the contradiction between autonomous operation and judgment accuracy

Inventive Principle:

Principle #35Parameter changes

2Reliability

If digital signature verification is performed to ensure content integrity, then security against tampering is improved, but the complexity of the permission judgment process increases

Engineering Contradiction:

Improvecontent integrityVSAvoidpermission judgment process

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent merges the digital signature verification process with the time-based permission judgment process. By integrating these two functions into a unified permission judgment mechanism, the system maintains security while reducing overall process complexity compared to having separate verification and judgment processes

Inventive Principle:

Principle #5Merging (Combining)

Data Source

PatentUS7386618B2Distribution system, distribution apparatus, and reception apparatus for distributing contents having usage expiry

Publication Date: 2008.06.10 PANASONIC INTELLECTUAL PROPERTY CORP OF AMERICA

AI summary

A reception apparatus includes a first timer and sends to a distribution apparatus a first date-time clocked by the first timer. The distributing apparatus includes a second timer, and generates expiry information based on a difference obtained by subtracting, from the first date-time, a second date-time that is clocked by the second timer. The expiry information is used to adjust a usage expiry date-time of content. The reception apparatus judges whether playback of the content is permitted based on the first timer and the expiry information. With this arrangement, unauthorized use of the content beyond the expiry date-time is prevented.