Key Refresh in SAE/LTE Systems
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In mobile communication systems, particularly in SAE/LTE, the reuse of cryptographic keys and counters can lead to security vulnerabilities, as attackers can exploit the same key and counter for different messages, compromising integrity and confidentiality protection.
Innovation Solution
A method is introduced where entities share cryptographic keys and exchange nonces to derive new temporary keys, ensuring key freshness and counter initialization, particularly in state transitions, allowing for secure communication between user equipment, mobility management entities, and evolved NodeB.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the same cryptographic key and counter are reused with different messages, then key management complexity is reduced, but security is compromised allowing attackers to break integrity and confidentiality protection
Solution Approach 1:
The patent implements dynamic key generation by deriving multiple cryptographic keys from a single master key through a key derivation function. Each communication session or message type receives a unique derived key, making the keying material dynamic rather than static. This resolves the contradiction by automatically generating fresh keys for each use without requiring complex manual key management procedures.
Solution Approach 2:
The patent segments the cryptographic keying material by deriving separate keys for different purposes (e.g., encryption keys, integrity protection keys, session-specific keys) from a master key. This segmentation ensures that each message or communication channel uses its own dedicated key, preventing key reuse attacks while maintaining a single master key for management purposes.
2Reliability
If cryptographic keys are frequently refreshed to ensure security, then security against replay attacks is improved, but key management complexity and processing overhead increase
Solution Approach 1:
The patent performs preliminary key derivation during an initial authentication or setup phase, generating a hierarchy of keys before actual communication begins. This preliminary action ensures that secure, fresh keys are already in place for subsequent communications, preventing replay attacks without requiring complex real-time key management during active communication.
Solution Approach 2:
The system implements self-service key generation where entities autonomously derive their own cryptographic keys from shared secret material using standardized key derivation functions. This eliminates the need for complex centralized key distribution and management infrastructure, as each party independently generates its own secure keying material.
3Reliability
If counters are used with cryptographic keys for message authentication, then detection of replayed messages is improved, but vulnerability to attacker substitution increases when counters are reused
Solution Approach 1:
The patent changes the parameters of the cryptographic system by deriving unique keys for different message types, directions, and sessions rather than reusing the same key with incrementing counters. This parameter change ensures that even if message sequences are observed, attackers cannot substitute messages because each message is protected by a unique key, making substitution attacks ineffective.
Data Source
Figure 1
Figure 2
Figure 3
AI summary
The present application describes a key handling in mobile communication systems where first and second numbers are exchanged between entities of a mobile communication system. The first and second numbers are respectively used only once with respect to the respective system parameters of the communication system.