Stacked IC Die Protection Using Sacrificial Split-Key Layers
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Solution Overview
Problem
Conventional integrated circuit (IC) dies are vulnerable to physical attacks such as laser probing and focused ion beam attacks, which compromise confidentiality and authentication, especially in stacked die assemblies where internal signals can be exposed, leading to unauthorized access.
Innovation Solution
The implementation of a sacrificial IC die with split key information sources, such as unique physical characteristics and physical unclonable function (PUF) devices, is used to generate encryption keys in a primary IC die, making it difficult for attackers to access or modify the primary die without destroying the split key information, thus enhancing security against physical attacks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional chip packaging schemes utilize a plurality of IC dies mounted to a single package substrate, then component density and functionality are increased, but security against physical attacks is reduced
Solution Approach 1:
The encryption key is segmented into multiple key splits, with each key split stored in a separate IC die within the stacked assembly. This segmentation ensures that no single die contains the complete key, making physical attacks ineffective unless all dies are compromised simultaneously.
Solution Approach 2:
Multiple IC dies are stacked in a nested configuration where each die contains a portion of the security mechanism. The hierarchical stacking provides layers of protection, with each layer contributing to the overall security while maintaining compact form factor.
2Reliability
If die stacking is introduced to enhance security, then protection level is improved, but device complexity and attack surface are increased
Solution Approach 1:
The stacked die assembly serves multiple functions: it provides security through distributed key storage, maintains compact form factor for high density, and enables standard packaging processes. Each die in the stack can be independently manufactured using standard processes, reducing overall complexity.
3Adaptability or versatility
If internal signals are transported across TSVs and die-to-die interfaces in stacked assemblies, then functionality is enhanced, but vulnerability to probing attacks is increased
Solution Approach 1:
The critical security function (key storage) is extracted from the main functional dies and distributed across separate sacrificial dies. This extraction removes the vulnerability point, as the functional dies no longer contain sensitive key material that could be probed.
Solution Approach 2:
Sacrificial dies act as intermediaries between the functional dies and the external environment. These intermediary layers protect the internal signals and key material by providing a physical barrier that must be penetrated to access sensitive information.
4Reliability
If split key information is distributed across multiple dies, then security is improved, but manufacturing and assembly difficulty are increased
Solution Approach 1:
Key splits are pre-distributed to individual dies during the manufacturing process, before final assembly. This preliminary action ensures that each die is correctly configured with its designated key portion, simplifying the final stacking and assembly process.
Data Source
AI summary
Stacked integrated circuit devices, chip packages and methods for operating a chip package are described herein that provide an increased level of backside protection from physical attacks that could compromise confidentiality or authentication of the integrated circuit device. In one example, a chip stack includes a sacrificial integrated circuit (IC) die stacked with a primary IC die. The sacrificial IC die includes a first split key information source. The primary IC die has security circuitry configured to generate an encryption key based at least in part on first split key information transmitted from the sacrificial IC die across a die-to-die interface to the primary IC die. Separation of the dies to probe or modify of the primary IC die would cause the destruction of split key information required to operate the functional circuitry of the primary IC die.