File-Level Encryption Key Management for Secure Data Obliteration
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Solution Overview
Problem
Existing encryption methods for mobile devices are inadequate as they encrypt all data with a single symmetric key, making it accessible to attackers if the device is compromised, and complicate data erasure and backup processes.
Innovation Solution
Implementing a file-level encryption scheme where each file is encrypted with a unique key, and those keys are further encrypted with a class key, allowing for secure data protection and erasure by managing key bags and using additional encryption keys.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single symmetric encryption key is used to encrypt all data on the device, then the encryption process is simple and fast, but the security is inadequate because an attacker can obtain the key and decrypt the entire file system
Solution Approach 1:
The patent divides the encryption system into multiple segments: a file system encryption key for encrypting the file system, individual file encryption keys for each file, and a key encryption key for protecting the file encryption keys. This segmentation ensures that compromising one key does not expose all data, resolving the security vulnerability of single-key encryption while maintaining manageable complexity through hierarchical organization.
2Ease of operation
If encryption keys are stored on the device, then decryption and access to encrypted data is enabled, but the security is compromised because attackers can run code to obtain the encryption key
Solution Approach 1:
The patent extracts the most sensitive encryption key (the key encryption key) from the device storage and stores it securely in a separate location (such as a secure element or external key management system). This extraction prevents attackers from obtaining the master key by compromising device storage, while still enabling data access through secure key release mechanisms when needed.
Solution Approach 2:
The patent introduces a new dimension of key storage by separating the key encryption key from the file system encryption key. The key encryption key is stored in a different security domain (hardware security module or external server) rather than alongside file data, creating a spatial and security architectural separation that prevents single-point compromise.
3Ease of manufacture
If the entire file system is encrypted with one key, then the encryption process is straightforward, but erasing data becomes complex because the encryption key must be managed carefully to prevent unauthorized access
Solution Approach 1:
The patent creates a backup copy of the key encryption key stored securely outside the device (in a key management server or secure element). When data erasure is needed, the system can securely delete the local copy of the key encryption key, and the backup copy can be used to control whether the encrypted data can be recovered. This copying mechanism simplifies erasure by decoupling it from the complexity of key regeneration and distribution.
Data Source
AI summary
Disclosed herein are systems, methods, and non-transitory computer-readable storage media for erasing user data stored in a file system. The method includes destroying all key bags containing encryption keys on a device having a file system encrypted on a per file and per class basis, erasing and rebuilding at least part of the file system associated with user data, and creating a new default key bag containing encryption keys. Also disclosed herein is a method of erasing user data stored in a remote file system encrypted on a per file and per class basis. The method includes transmitting obliteration instructions to a remote device, which cause the remote device to destroy all key bags containing encryption keys on the remote device, erase and rebuild at least part of the file system associated with user data, and create on the remote device a new default key bag containing encryption keys.