Hierarchical Key Derivation for Secure File Systems
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Solution Overview
Problem
Current methods for secure hierarchical referencing systems, such as cryptographic file systems, face inefficiencies and complexities in key management and revocation, particularly in untrusted environments, where lazy revocation methods interrupt key derivation algorithms and require excessive storage and processor power, while existing solutions like key management by Atallah, Frikken, and Blanton lead to key loss and high overheads.
Innovation Solution
The method involves maintaining a temporary volatile data node key list and a non-volatile data node key parameter list to derive and update keys efficiently, allowing for active revocation without storing multiple keys, by tracing the tree path to ensure data encryption with valid current keys and minimizing storage needs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If lazy revocation approach is used, then re-encryption overhead is reduced, but key storage requirements increase
Solution Approach 1:
The patent extracts the key storage burden from the system by using key derivation functions. Instead of storing multiple keys for each data element, the system stores only derivation parameters (seed values, path identifiers) and derives actual encryption keys on-demand. This removes the need for extensive key storage while maintaining lazy revocation efficiency.
Solution Approach 2:
The patent changes the nature of stored data from complete encryption keys to key derivation parameters. By storing compact parameter sets (seed + path) instead of full keys, the system reduces storage requirements while enabling efficient key regeneration for lazy revocation without storing multiple actual keys.
2Quantity of substance
If key derivation algorithm is used, then key storage is minimized, but active revocation requires complete re-encryption
Solution Approach 1:
The patent segments the key hierarchy into derivable components using path identifiers. When revocation is needed, only the specific path/branch affected by the revocation needs to be re-encrypted, not the entire dataset. This segmentation enables selective re-encryption while maintaining key derivation benefits.
Solution Approach 2:
The patent makes the key derivation process dynamic by allowing path identifiers to be updated selectively. When a user is revoked, the system dynamically generates new path identifiers for affected data elements and re-encrypts only those elements, enabling efficient active revocation without complete system re-encryption.
3Adaptability or versatility
If independent keys are distributed to each user for each element, then access control precision is improved, but key management complexity increases
Solution Approach 1:
The patent creates a universal key derivation mechanism that works across all data elements and users. A single key derivation function, given a seed and path identifier, can generate the appropriate encryption key for any user-element pair. This universal approach enables precise access control without requiring separate key management processes for each user-element combination.
Solution Approach 2:
The patent implements self-service key generation where the system automatically derives encryption keys from stored parameters without manual key distribution. When a user needs access to an element, the system automatically generates the appropriate key using the derivation function, eliminating complex manual key distribution and management overhead.
4Reliability
If multiple encrypted keys are stored for sharing with third parties, then security is improved, but storage overhead and complexity increase
Solution Approach 1:
The patent extracts the security mechanism from storing multiple encrypted key copies to using a single stored parameter set with on-demand derivation. The system stores one seed and path identifier combination, and when security is needed, derives the appropriate encryption key without storing multiple encrypted versions, reducing storage overhead while maintaining security.
Data Source
AI summary
A performance-optimized secure hierarchical referencing system, for example to implement a cryptographic file system (CFS) in which files or other data are stored in a cryptographic tree structure on a untrusted environment. The system operates by using adaptive cryptographic access control (ACAC) whereby the data on the client (user) side is encrypted using keys. All said keys (with the exception of an entry key) are not stored but are calculated, and a dedicated symmetric key is used for each element in the referencing system (e.g. files, records, comments) to ensure that read/write permissions can be distributed to selected third parties at element level and actively revoked where required (sharing/revocation).