Secure DMA Module for Mobile UE Security Domain Translation
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Solution Overview
Problem
Current cryptographic computing systems face inefficiencies and security risks when switching between secure and non-secure execution environments, particularly in mobile User Equipment (UE) for DRM content transfer, requiring frequent CPU mode changes and potential data interception or copying.
Innovation Solution
A mobile UE architecture with a CPU, secure DMA module, secure cryptographic module, and secure memory, where the CPU manages cryptographic keys and initializes DMA transfers in secure mode, and performs encryption translation and data transfer in non-secure mode, minimizing CPU mode switches and ensuring secure data transfer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the CPU switches between secure and non-secure modes for every data packet encryption/decryption, then security requirements are met, but processing efficiency and power consumption deteriorate
Solution Approach 1:
The system segments security-critical operations (key management, mode switching) from data processing operations. The CPU enters secure mode only once to initialize cryptographic modules and keys, then exits to non-secure mode for bulk data processing. This segmentation reduces frequent mode switching while maintaining security boundaries.
Solution Approach 2:
A secure cryptographic module acts as an intermediary between the CPU and data streams. This module handles encryption/decryption operations in secure mode while the CPU operates in non-secure mode for data management, reducing direct CPU mode switching overhead.
2Reliability
If the CPU switches between secure and non-secure modes for every data packet, then security is maintained, but power consumption increases
Solution Approach 1:
The system segments power-intensive secure mode operations from routine data processing. The CPU enters secure mode only for key management and cryptographic module initialization, then remains in power-efficient non-secure mode for data transfer operations, significantly reducing overall power consumption.
Solution Approach 2:
Cryptographic keys and security parameters are pre-loaded into secure memory and cryptographic modules during system initialization in secure mode. This preliminary action eliminates the need for repeated secure mode entries during data processing, reducing power consumption.
3Ease of operation
If clear text data is transferred to external devices, then data accessibility is improved, but security is compromised due to potential copying
Solution Approach 1:
The secure cryptographic module and secure memory act as intermediaries that enable controlled data transfer. Clear text data can be accessed by authorized applications while remaining protected in secure memory, and encrypted transfers to external devices are managed through the cryptographic module without exposing keys to non-secure processes.
Solution Approach 2:
Different security levels are applied to different data locations and access contexts. Clear text data exists in secure memory with restricted access, while encrypted data is used for external transfers. This local differentiation of security properties enables both accessibility and protection.
Data Source
AI summary
A mobile UE includes a CPU, a secure DMA module, a secure cryptographic module, secure memory, and non-secure memory. The secure cryptographic module and secure memory allow access only by secure processes, including the secure DMA module. The CPU manages cryptographic keys and initializes DMA transfers in secure mode. The CPU executes the DMA transfers in non-secure mode. A first DMA transfer moves data encrypted in a first security domain to the secure cryptographic module, and moves clear text data to the secure memory. A second DMA transfer moves the clear text data to the secure cryptographic module, and data encrypted in a second security domain out of the secure cryptographic module. The data encrypted in the second security domain are transmitted to an external device. The secure memory protects the clear text data from being copied; only encrypted data is accessible by non-secure processes.