Scalable File System Key Management for Permanent Data Unreadability
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Solution Overview
Problem
Existing file systems that store data in encrypted form face challenges with increased storage overhead and communication overhead due to the need to store and manage large public keys, as well as frequent interactions with key managers for file access and key management.
Innovation Solution
A scalable file system manages file-class keys at a file manager, using these keys to encrypt files and store them in non-volatile storage, with encrypted keys maintained by key managers, reducing storage overhead and interaction frequency by storing only metadata with expiration times and using a k-out-of-n scheme for fault-tolerant decryption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If each file is encrypted with a random key and the key is encrypted with ephemerizer keys stored in metadata, then data security is improved, but storage overhead increases significantly due to large public key sizes
Solution Approach 1:
The patent segments the encryption key management by introducing an intermediate file-class key that is separate from both the file-specific key and the ephemerizer key. This segmentation allows the metadata to store only a small reference to the file-class key rather than the full encrypted key, significantly reducing storage overhead while maintaining security through the hierarchical key structure.
Solution Approach 2:
The patent introduces a file-class key as an intermediary between the file-specific encryption key and the ephemerizer key. This intermediary key acts as a mediator that can be efficiently stored in metadata, eliminating the need to store large encrypted keys directly in file metadata while still enabling secure decryption through the key hierarchy.
2Reliability
If the file system interacts with the ephemerizer for every file operation, then key management security is improved, but communication overhead and file access time increase
Solution Approach 1:
The patent implements preliminary action by pre-establishing file-class keys that are associated with expiration times. These keys are set up in advance and can be efficiently retrieved during file operations without requiring real-time interaction with the ephemerizer, thus reducing file access time while maintaining security through the pre-configured key hierarchy.
Solution Approach 2:
The patent merges multiple file-specific keys under a single file-class key for files with the same expiration time. This consolidation allows the system to manage multiple files efficiently with a single key retrieval operation rather than requiring separate ephemerizer interactions for each file, significantly reducing communication overhead.
3Ease of operation
If public keys are stored in metadata for every file, then key management is simplified, but metadata size increases by thousands of bits per file
Solution Approach 1:
The patent uses copying by storing only a small reference or pointer to the file-class key in the metadata rather than copying the full encrypted key. This reference copying approach maintains the simplicity of key management through the hierarchical structure while dramatically reducing metadata size from thousands of bits to a minimal reference.
Solution Approach 2:
The patent transitions from storing keys in a single dimension (directly in metadata) to a multi-dimensional hierarchical structure where keys are organized by file-class and expiration time. This dimensional change allows efficient key management through the hierarchy while minimizing the actual data stored in metadata to small references rather than full keys.
Data Source
AI summary
One embodiment of the present invention relates to a system for managing files which facilitates making the files permanently unreadable. During operation, the system maintains file-class keys at a file manager, wherein the file-class keys are associated with different classes of files. If a file belongs to a class of files, the system ensures that whenever the file is stored or updated in non-volatile storage that the file is encrypted with an associated key-manager-file-class key for the class of files. The system makes an entire class of files permanently unreadable by causing an associated key-manager-file-class key, which can be used to decrypt the class of files, to become permanently unreadable.