Hash Chain Digital Content Access Control
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Solution Overview
Problem
Existing digital content protection systems face issues such as degradation of audio and visual quality, inefficient public key infrastructure operations, and user-managed access limitations that can be modified or illegally disseminated, making them ineffective for securely limiting access to digital content.
Innovation Solution
A method and apparatus using a hash chain to securely limit access to digital content by generating a series of hash values from a seed value, where each access deletion reduces the number of available hash values, ensuring secure and controlled access management by the content supplier.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If digital contents are protected using traditional copyright systems, then copyright protection is provided, but the contents can be copied and reproduced unlimited times without degradation
Solution Approach 1:
The patent applies preliminary action by pre-generating a hash chain with a predetermined number of hash values before content distribution. Each hash value serves as an access key, and the chain is structured so that each subsequent hash value can be derived from the previous one. This preliminary preparation enables controlled access without requiring real-time verification computations, thus limiting reproductions while maintaining copyright protection.
Solution Approach 2:
The patent segments the access control mechanism into discrete hash values within a hash chain. Instead of using a single access control token, the system divides access rights into multiple sequential hash values (H1, H2, H3, ... Hn), where each hash value permits one access. This segmentation allows precise control over the number of reproductions while maintaining security through cryptographic hash functions.
2Manufacturing precision
If audio and visual quality is maintained during reproduction, then content quality is preserved, but existing systems cause quality deterioration with each reproduction
Solution Approach 1:
The patent replaces traditional mechanical or procedural quality control mechanisms with a cryptographic hash chain system. Instead of relying on physical degradation or complex verification processes that may compromise quality, the system uses mathematical hash functions to control access. This substitution allows unlimited reproductions in terms of quality preservation while imposing cryptographic limits on the number of valid access instances through the hash chain structure.
3Reliability
If public key infrastructure is used for secure distribution, then security is improved, but operational efficiency deteriorates
Solution Approach 1:
The patent extracts the computationally intensive public key infrastructure operations from the content distribution process and replaces them with lightweight hash chain verification. The complex cryptographic key pair generation and verification are removed, leaving only simple hash function evaluations. This extraction maintains security through the cryptographic properties of hash functions while dramatically improving operational efficiency by eliminating heavy computational overhead.
Solution Approach 2:
The patent changes the cryptographic parameter from public key infrastructure (asymmetric cryptography requiring key pairs and complex verification) to hash function-based symmetric verification. This parameter change reduces computational complexity from O(n log n) or worse in PKI operations to O(1) hash evaluations, thereby improving operational efficiency while maintaining security through the one-way property and collision resistance of cryptographic hash functions.
4Ease of operation
If user manages access limitation information, then ease of operation is improved, but security deteriorates due to potential modification or illegal dissemination
Solution Approach 1:
The patent introduces a hash chain structure as an intermediary between the content provider and the user, eliminating the need for users to directly manage access control information. The hash chain, generated and controlled by the provider, serves as a trusted mediator that automatically enforces access limits. Users simply present successive hash values for verification without needing to understand or manage the underlying access control logic, thereby maintaining ease of operation while ensuring security through the cryptographic integrity of the hash chain.
Data Source
AI summary
A method and apparatus are provided for simply and securely limiting a number of times that contents can be accessed using a hash chain. The apparatus limiting a number of times contents are accessed by a user terminal includes a hash chain generator receiving information indicating selected contents by the user terminal and information indicating how many times (n) the user terminal has authority to access the selected contents and generating a hash chain including n hash values derived from a seed value, and a contents access manager deleting the hash values one by one from the hash chain whenever the user terminal accesses the selected contents such that the number of times the contents can be accessed by the user terminal is decreased by the number of deleted hash values.