Data Storage Encryption Key Splitting for Offline Access
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Solution Overview
Problem
Existing data storage solutions fail to provide secure offline access and full control for data owners, as encryption keys must be shared, risking confidentiality and access control when the owner is offline, and existing access control methods are not secure against misconfigurations or malicious actions.
Innovation Solution
Implementing a method where each authorized client and a Trusted Third Party (TTP) share parallel copies of the encryption key, allowing secure access without the owner being online, using two-part secret sharing schemes like Shamir's polynomial-interpolation or Vernam/Shannon's modulo-2 scheme, ensuring only the owner can access the entire key.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If encryption is used to protect data confidentiality, then data security is improved, but the owner must be online to provide decryption keys, reducing system availability
Solution Approach 1:
The encryption key is segmented into multiple parts distributed among different entities (owner, TTP, and authorized clients). Each entity holds a portion of the key, and no single entity except the owner has access to the complete decryption key, enabling offline access while maintaining confidentiality.
Solution Approach 2:
A Trusted Third Party (TTP) is introduced as an intermediary that holds a portion of the decryption key. The TTP mediates access by providing its key portion to authorized clients who need to access data when the owner is offline, thus improving availability without compromising confidentiality.
2Reliability
If the owner provides full control over decryption keys, then access control security is improved, but the system cannot provide secure offline access when the owner is unavailable
Solution Approach 1:
The decryption key is divided into segments distributed among the owner, TTP, and authorized clients. The owner maintains control by holding a critical segment, while other segments are distributed to enable offline access by authorized clients through the TTP intermediary.
Solution Approach 2:
The key segmentation and distribution is performed in advance during system setup. Authorized clients receive their key portions beforehand, enabling them to access data offline without requiring real-time owner involvement, thus improving ease of operation while maintaining security.
3Productivity
If split keys are distributed among multiple clients, then offline access is improved, but the complete key can be reconstructed without involving the data owner
Solution Approach 1:
The decryption key is segmented such that the owner holds a critical portion that cannot be derived from other segments. This ensures that while offline access is enabled through distributed key segments, the owner maintains ultimate control and cannot be bypassed for key reconstruction.
Solution Approach 2:
The key distribution is asymmetric: authorized clients and TTP hold equivalent key segments for operational purposes, but the owner holds a distinct, critical segment that provides ultimate control. This asymmetric structure prevents unauthorized reconstruction while enabling offline access.
4Ease of operation
If access policies are enforced by the data storage provider, then ease of operation is improved, but security is reduced due to potential misconfiguration or malicious actions
Solution Approach 1:
The critical security function of key management is extracted from the data storage provider and distributed to the owner, TTP, and authorized clients. This removes the single point of failure and trust vulnerability in the provider's access control system, improving security while maintaining ease of operation through automated key distribution.
Data Source
AI summary
A method of performing an operation on a data storage for storing data being encrypted with a key KD associated with an owner of the data is provided. The method includes deriving, for each authorized client Cj, a first key KCj and a second key KTj, providing the client Cj with the first key KCj, and providing a Trusted Third Party (TTP) with the second key KTj. The method further includes, at a Policy Enforcement Point, receiving a request for performing the operation on the data storage from a client Ck of the authorized clients, acquiring a first key KCk from the client Ck, acquiring a second key KTk from the TTP, deriving the key KD from the first key KCk and the second key KTk, and performing the operation on the data storage using the derived key KD. The disclosed trust model uses two-part secret sharing.