Encrypted AES Round Key Protection via TPM Segmentation
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Solution Overview
Problem
Existing software implementations of symmetric encryption, such as AES-NI, expose underlying encryption keys to software and hardware attacks, compromising security and requiring costly key revocation and re-encryption processes.
Innovation Solution
A method that generates and uses encrypted AES round keys, which are decrypted only by the CPU, ensuring that even if stolen, the keys are worthless after a reboot and reducing exposure during early platform boot, with a mechanism to efficiently cache transformed keys for minimal overhead.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If software implementations (including AES-NI) are used for symmetric encryption, then performance and ease of operation are improved, but security deteriorates because encryption keys are exposed to software and hardware attacks
Solution Approach 1:
The encryption key is segmented into two parts: a secret key stored securely in a trusted platform module (TPM) and a public key stored in a public key infrastructure (PKI). The secret key never leaves the TPM, while the public key is used for encryption operations. This segmentation allows software implementations to maintain ease of operation while improving security by preventing exposure of the actual secret key.
Solution Approach 2:
A key transformation mechanism acts as an intermediary between the secret key in TPM and the encryption operations in software. The TPM transforms the secret key into a transformed key using a key transformation algorithm, and this transformed key is then used by software for encryption. This intermediary approach allows software to perform encryption operations without directly accessing the secret key, thereby maintaining both ease of operation and security.
2Reliability
If hardware accelerators or IP blocks are used for AES encryption, then security is improved by keeping keys inside the hardware boundary, but performance and power consumption vary and may be less efficient for certain workloads
Solution Approach 1:
The invention creates a universal key protection mechanism that works across multiple platforms and implementation types (software, hardware accelerators, IP blocks). The key transformation approach can be applied regardless of the underlying encryption implementation, allowing systems to achieve improved security without being constrained to specific hardware solutions. This maintains performance efficiency while achieving hardware-level security protection.
3Adaptability or versatility
If encryption keys are stored in software implementations, then ease of operation and flexibility are improved, but the keys become vulnerable to attacks requiring costly revocation and re-encryption processes
Solution Approach 1:
The system performs preliminary key transformation before encryption operations. The secret key is transformed into a protected form using the TPM's key transformation algorithm, and this transformed key is then used for encryption. This preliminary action ensures that the actual secret key never exposes the system to attacks, eliminating the need for costly key revocation and re-encryption processes while maintaining flexibility in software implementations.
Data Source
AI summary
Systems and methods for protecting symmetric encryption keys when performing encryption are described. In one embodiment, a computer-implemented method includes retrieving at least one real key from a secure area and executing, with a processor, a key transform instruction to generate at least one transformed key based on receiving the at least one real key. The at least one transformed key is an encrypted version of at least one round key that is encrypted by the processor using the at least one real key. The processor is able to decrypt the at least one transformed key and encrypt the at least one round key.