Proxy HSM Wrapped-Key Storage for Expanded Signing Capacity
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Solution Overview
Problem
Hardware security modules (HSMs) face limitations in key storage capacity due to physical memory constraints, necessitating multiple modules and complex key management, which can be addressed by using a proxy HSM to manage signing keys externally.
Innovation Solution
A proxy HSM receives signing requests, retrieves wrapped signing keys from remote storage, provides them to the HSM for unwrapping and signing operations, and destroys the keys upon completion, reducing the need for continuous storage at the HSM.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If keys are stored externally outside the hardware security module, then storage capacity is increased, but security is compromised because external databases or memory can be accessed and compromised
Solution Approach 1:
The system segments key management into two parts: the HSM securely generates and wraps keys, while external storage holds the wrapped keys. This segmentation allows external storage to be used without compromising security, as the external storage only contains encrypted key material that cannot be used without the HSM's unwrapping capability.
Solution Approach 2:
The patent introduces wrapped keys as an intermediary form between the original key and external storage. The wrapping process creates an intermediate encrypted version that can be safely stored externally, acting as a mediator that protects the security of the original key while enabling external storage.
2Quantity of substance
If multiple hardware security modules are used to accommodate key storage, then key storage capacity is increased, but system complexity increases due to routing requirements
Solution Approach 1:
The HSM is designed to perform multiple functions: it can generate keys, wrap keys for external storage, unwrap wrapped keys, and perform signing operations. This multi-functionality eliminates the need for separate dedicated key storage HSMs, reducing overall system complexity while maintaining the ability to store and manage multiple keys.
3Quantity of substance
If wrapped keys are stored externally and retrieved for signing operations, then storage requirements at the HSM are reduced, but additional processing steps are required
Solution Approach 1:
The system performs preliminary action by pre-wrapping keys with the HSM's wrapping key before storing them externally. This preliminary wrapping process enables efficient retrieval and unwrapping operations later, as the wrapped keys are already in the correct format for secure external storage and can be quickly unwrapped when needed for signing operations.
Data Source
AI summary
A proxy hardware security module (HSM) is disclosed, useable with an existing HSM for expansion of key storage for the HSM. The proxy HSM receives a signing request that is targeted to the HSM, and retrieves a wrapped version of a signing key from a storage location separate from the HSM. The proxy HSM provides the wrapped signing key to the HSM, and provides the signing request to the HSM. Upon receipt of a response to the signing request indicating successful execution of a signing operation by the HSM, the proxy HSM transmits a key destroying request to the HSM, and a confirmation message to the device from which the signing request was received. Upon completion of the signing request, the HSM does not retain the signing key.