Encrypted Session Key Update for Secure Data Sharing
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Solution Overview
Problem
Existing data sharing systems face challenges in updating encrypted data stored on a server without decrypting it on the server side when a user leaves or is deleted, and ensuring that deleted users cannot access decrypted data.
Innovation Solution
A data sharing method and system that involves a data sharing server and a key generation server, where the session key is updated using a generation identifier, allowing only valid communication terminals to access the encrypted data, ensuring that deleted users cannot decrypt the data.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the session key is updated when a user leaves or is deleted, then security is improved by preventing deleted users from accessing data, but the complexity of key management increases and requires updating encrypted data without decrypting it on the server side
Solution Approach 1:
The system performs preliminary encryption of the session key using the user's public key before the user leaves. This pre-encrypted session key is stored on the server, so when the user departs, the key material is already prepared and cannot be decrypted by the departed user, eliminating the need for complex real-time key rotation and re-encryption operations.
Solution Approach 2:
The patent introduces a key generation server as an intermediary that manages key pairs and session keys separately from the data sharing server. This mediator handles the complex cryptographic operations, allowing the data sharing server to focus on data storage while the key generation server manages the security infrastructure, thereby reducing overall system complexity.
2Reliability
If encrypted data is updated with a new session key on the server side, then deleted users cannot decrypt the data, but the data must be decrypted on the server side which creates security vulnerabilities
Solution Approach 1:
The patent segments the cryptographic functions by separating data encryption (performed by communication terminals using session keys) from key management (performed by the key generation server). The server stores only encrypted session keys and encrypted data, never possessing decryption capabilities. This segmentation ensures that even if the server is compromised, attackers cannot decrypt data without the session keys that remain distributed among communication terminals.
Solution Approach 2:
The patent converts the potential harm of server-side data storage into a benefit by implementing a scheme where the server stores encrypted data and encrypted session keys but cannot decrypt them. The server's lack of decryption capability, which could be seen as a limitation, actually becomes a security feature that prevents server-side vulnerabilities from compromising data security.
3Reliability
If cloud-based data sharing is implemented without leaving data on communication terminals, then security against terminal loss is improved, but the ability to update encrypted data for deleted users becomes difficult
Solution Approach 1:
The key generation server acts as an intermediary that maintains the connection between communication terminals and encrypted data on the data sharing server. It manages session keys and provides them to authorized terminals while preventing access by deleted users. This intermediary enables the cloud-based architecture to function securely by handling key distribution and revocation without requiring data to be present on terminals.
Solution Approach 2:
The system implements a feedback mechanism where the key generation server receives notifications when users are added or removed from groups, and automatically responds by generating new session keys or revoking old ones. This automated feedback loop ensures that encrypted data on the server is continuously updated with appropriate access controls without manual intervention, making the operation easy despite the security requirements.
Data Source
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AI summary
There is provided a data sharing technique in which it is possible to update data stored in a server before to such data that is decryptable on the communication terminal side using an updated session key without the data being decrypted on the server side, and a deleted user cannot decrypt the decryptable data. There are included: a generation identifier generation step of a data sharing server generating a generation identifier showing a generation of a group; a session key encryption step of a communication terminal to perform encrypted session key update using the generation identifier received from the data sharing server and a public parameter and a session key recorded in a recording part to generate an encrypted session key, which is a session key encrypted; and an encrypted session key management step of the data sharing server recording the encrypted session key received from the communication terminal to perform encrypted session key update as a currently valid encrypted session key.