Dynamic Key Generation for Reduced-Round XTS Encryption
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Solution Overview
Problem
Reduced-round block ciphers used in mobile computing devices for data encryption compromise key security, making data vulnerable to attacks as the primary key (K1) can be compromised, affecting the confidentiality of all data within the address space.
Innovation Solution
A modified XTS block cipher mode is implemented where the data unit index is dynamically encrypted using a full block cipher to generate a modified key (K1′), which is then used with a reduced-round encryption cipher, ensuring that only the data corresponding to the specific index is at risk if the key is disclosed, rather than the entire address space.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a reduced-round block cipher is used to encrypt data, then the encryption speed is improved and read latency is reduced, but the key security is compromised and data confidentiality is weakened
Solution Approach 1:
The patent divides the address space into separate data units, each encrypted with a unique key derived from the base key through encryption of the data unit index. This segmentation ensures that compromise of one key affects only a specific data unit, not the entire address space, thereby maintaining overall system security while using reduced-round ciphers for speed.
Solution Approach 2:
The patent dynamically generates unique keys for each data unit by encrypting the data unit index with the base key. This dynamic key derivation allows the system to use reduced-round ciphers for fast encryption while maintaining security through per-unit key differentiation, resolving the contradiction between speed and security.
2Device complexity
If a fixed key is used for encrypting all data in the address space, then the implementation is simple, but a key compromise exposes the entire address space
Solution Approach 1:
The patent segments the single fixed key into multiple unique keys, one for each data unit, by encrypting the data unit index with the base key. This segmentation limits the impact of key compromise to only the affected data unit, improving data confidentiality without requiring complex key management infrastructure.
Solution Approach 2:
The patent applies local quality by assigning unique encryption keys to specific data units based on their indices. Each data unit has its own key derived locally from the base key and its index, ensuring that security properties are localized to each unit rather than applied uniformly across the entire address space.
Data Source
AI summary
One feature pertains to encrypting data to improve data confidentiality. In one aspect, a modified form of XTS encryption is provided for use with reduced-round block ciphers. A data unit index of data to be applied to the reduced-round cipher is encrypted under a secret key to generate or otherwise obtain a modified secret key for applying to the reduced-round cipher. That is, data to be encrypted by the reduced-round cipher is not encrypted under a static key but is instead encrypted under a dynamic key that varies according to the index of the data. If an attacker were to derive the value of the key applied to the reduced-round cipher by analyzing data encrypted by the cipher, the attacker would only obtain the dynamic key corresponding to one particular data unit index, rather than a global static key applied to an entire address space. Decryption procedures are also described.