Cryptographic Metadata Compression for Low-Latency Memory Encryption
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Solution Overview
Problem
Current memory encryption engines face significant bandwidth and latency issues due to the frequent transfer of cryptographic metadata between on-die and off-die memory during enclave operations, particularly in multi-threaded server architectures, which also leads to increased power consumption.
Innovation Solution
Implementing a compression-decompression engine within the memory encryption engine to compress cryptographic metadata, such as counter values and MACs, and storing them in a dedicated cache to reduce the need for off-die memory access, using techniques like run-length encoding and dictionary schemes to optimize storage and retrieval.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If cryptographic metadata is frequently transferred between on-die and off-die memory during enclave operations, then memory encryption security is maintained, but bandwidth requirements and latency increase significantly
Solution Approach 1:
The patent pre-loads cryptographic metadata (counter values and MACs) into an on-die buffer before they are needed for encryption operations. This preliminary action allows the memory encryption engine to access metadata from the fast on-die buffer rather than repeatedly accessing off-die memory, thereby reducing latency while maintaining security requirements.
Solution Approach 2:
The patent introduces an intermediary buffer structure located on-die that sits between the off-die memory and the memory encryption engine. This buffer acts as a mediator, caching frequently accessed cryptographic metadata and reducing the need for direct off-die memory accesses, thus lowering latency without compromising the integrity of the encryption process.
2Reliability
If cryptographic metadata is frequently transferred between on-die and off-die memory, then memory encryption functionality is maintained, but bandwidth requirements increase
Solution Approach 1:
The system pre-loads cryptographic metadata into the on-die buffer in advance, so that subsequent encryption operations can proceed using the cached metadata without requiring additional bandwidth for real-time off-die memory accesses. This reduces the overall bandwidth consumption while maintaining full encryption functionality.
Solution Approach 2:
The on-die buffer serves as an intermediary that captures and retains cryptographic metadata, preventing repeated traversals of the off-die memory interface. This intermediary structure significantly reduces bandwidth requirements by localizing metadata access to the fast on-die memory subsystem.
3Quantity of substance
If cryptographic metadata is stored in off-die memory, then sufficient storage capacity is available, but power consumption increases due to frequent transfers
Solution Approach 1:
The system proactively loads cryptographic metadata into the on-die buffer before encryption operations commence, eliminating the need for repeated power-consuming transfers between off-die memory and the encryption engine. This preliminary loading action reduces overall power consumption while maintaining adequate storage capacity through the buffer.
Solution Approach 2:
The on-die buffer acts as a power-saving intermediary by intercepting metadata access requests and serving them from local storage rather than triggering high-power off-die memory transfers. This intermediary approach significantly reduces power consumption associated with metadata access operations.
4Quantity of substance
If compression-decompression engine is implemented, then bandwidth requirements and power consumption are reduced, but device complexity increases
Solution Approach 1:
The patent applies compression algorithms that transform cryptographic metadata into a more compact representation, changing the parameter of data size. This parameter change reduces the bandwidth requirements and power consumption associated with metadata transfers, while the added complexity of compression/decompression logic is offset by the significant resource savings.
Data Source
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AI summary
Examples include techniques for compressing counter values included in cryptographic metadata. In some examples, a cache line to fill a cache included in on-die processor memory may be received. The cache arranged to store cryptographic metadata. The cache line includes a counter value generated by a counter. The counter value to serve as version information for a memory encryption scheme to write a data cache line to a memory location of an off-die memory. In some examples, the counter value is compressed based on whether the counter value includes a pattern that matches a given pattern and is then stored to the cache. In some examples, a compression aware and last recently used (LRU) scheme is used to determine whether to evict cryptographic metadata from the cache.