Key Management System Using Secret Sharing for Authority Updates
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Solution Overview
Problem
Existing key management systems face difficulties in efficiently handling changes, losses, or expirations of keys due to organizational and personnel changes, particularly when a system administrator cannot decrypt data, making it challenging to update or manage user authorities without compromising data security.
Innovation Solution
A key management system comprising user terminals and a key management apparatus that utilizes databases to store and manage user private and public keys, authority private and public keys, and secret sharing mechanisms to securely update and share authority keys among users, ensuring that even if a user loses a key or their authority changes, data access can be maintained without re-encrypting all data.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a key is managed by a user without system administrator involvement, then data security is improved by preventing illegal actions, but key management complexity increases when dealing with organizational changes and key updates
Solution Approach 1:
The key management system segments authority into multiple levels: user keys for individual access and authority keys for group or role-based access. This segmentation allows users to manage their own keys while authority keys can be collectively managed by multiple users, reducing the burden on any single user while maintaining security.
Solution Approach 2:
The system introduces an intermediary mechanism where authority keys are encrypted and stored in a database, and users can retrieve them through authenticated requests. This intermediary layer (the database and authentication system) handles the complexity of key updates and distribution, allowing users to maintain security without directly managing all key operations.
2Reliability
If part keys are shared in secret to enable key recovery, then key availability is improved when owners are absent, but ease of operation deteriorates when owners need to change part keys due to organizational changes
Solution Approach 1:
The system makes key management dynamic by allowing authority keys to be reassigned to different users based on organizational changes. When a user leaves or changes roles, the system can update which users hold the authority key without requiring manual intervention from the departing user, as long as at least one user retains access.
Solution Approach 2:
The system enables self-service key management where users can autonomously update authority key assignments through the database interface. Users can add or remove other users from authority key holdings without requiring the departing user to manually transfer keys, as the system handles the reassignment process.
3Reliability
If all data is re-encrypted when keys change, then data security is maintained, but productivity decreases due to time-consuming re-encryption processes
Solution Approach 1:
The system segments data encryption into two layers: user-level encryption using user keys and authority-level encryption using authority keys. When authority keys change, only the authority-level encryption needs to be updated, not all individual data encryption operations, significantly reducing the scope of re-encryption required.
Solution Approach 2:
The system performs preliminary action by pre-storing authority keys in the database encrypted with user public keys before any key changes occur. This preparation allows rapid key updates without requiring re-encryption of existing data, as the new authority keys are already in place and can be immediately used for new encryption operations.
4Ease of operation
If system administrators can decrypt data, then ease of operation is improved for administrative tasks, but data security deteriorates due to potential illegal actions
Solution Approach 1:
The system extracts the decryption capability from the system administrator role. Administrators can manage keys through the database interface and perform administrative tasks, but they cannot directly decrypt user data. The decryption function is extracted and assigned only to users who possess the appropriate user keys and authority keys, eliminating the security risk of administrator data access.
Solution Approach 2:
The database serves as an intermediary that mediates between administrators and data decryption. Administrators can query and manage key information through the database, but the actual decryption operation requires the user to provide their private key through the authenticated request process, preventing administrators from directly accessing encrypted data.
Data Source
AI summary
A user private key is stored in a database of the user terminal. A user public key and user information are stored in the user management DB. The encryption/decryption unit encrypts an authority private key specific to a first authority given to a user, by using a user public key associated with user information to indicate a user. The secret sharing unit shares in secret an authority private key into two or more shared authority private keys. The encryption/decryption unit encrypts the shared authority private keys, by using an authority public key specific to each of second authorities to manage the first authority in a shared manner. The authority management DB stores the encrypted authority private key and authority public key in association with the first authority, and stores the encrypted shared authority private keys in association with the second authorities.