Session Key Proxy Decryption for Secure Content Distribution
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Solution Overview
Problem
Conventional mechanisms for securing content in a one-to-many relationship are inefficient due to the need for significant storage and processing resources, inability to allow new members to decrypt content post-factum, and inapplicability to micro-blogging systems, as they require storing and looking up public keys for all group members and include large encrypted messages.
Innovation Solution
A server-based system that receives identifying information from a client device, determines group membership, and either decrypts or re-encrypts session keys to enable secure content access, reducing storage and processing burdens and allowing new members to access encrypted content by caching session keys and re-encrypting them using user public keys.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the sender encrypts the session key for each member using individual public keys, then security is improved, but storage and processing resources are significantly consumed
Solution Approach 1:
The patent introduces a trusted third party server as an intermediary that holds the group private key. Instead of the sender directly encrypting session keys for each member, the sender only needs to encrypt the session key with the group public key and send it to the server. The server then acts as a mediator to distribute the session key to authorized members, reducing the sender's storage and processing burden while maintaining security through the intermediary's control.
Solution Approach 2:
The group public key serves multiple functions: it can encrypt session keys for distribution to multiple members simultaneously, and it enables the server to manage all group members through a single key pair. This universal approach eliminates the need for the sender to manage individual public keys for each member, reducing complexity while maintaining the ability to securely distribute content to any number of members.
2Reliability
If the encrypted message includes approximately 700 bytes of ASCII text for each member's key, then security is maintained, but the message size becomes too large for micro-blogging systems
Solution Approach 1:
The patent extracts the individual member public key information from the encrypted message itself and places it in the server's database. The encrypted message only contains the session key encrypted with the group public key, which is much smaller. The server extracts and stores the member identification information separately, allowing the message to be minimized for transmission while security is maintained through the server's key management infrastructure.
3Ease of operation
If the sender stores public keys of all group members, then key distribution is enabled, but the sender requires significant storage resources for large groups
Solution Approach 1:
The server acts as an intermediary that stores the group private key and manages member information. The sender no longer needs to store individual public keys for each member; instead, the sender only needs the group public key to encrypt the session key. The server mediates the distribution by matching the encrypted session key with authorized members using its stored group private key and member database, eliminating the sender's storage burden while maintaining key distribution capability.
4Reliability
If conventional encryption mechanisms are used, then existing content can be secured, but new members added to the group cannot decrypt previously encrypted content
Solution Approach 1:
The server acts as a flexible intermediary that can dynamically manage group membership. When new members are added, the server updates its database with the new member's identification information and the group's private key. The server can then decrypt previously encrypted session keys and redistribute them to new members, allowing dynamic access control without requiring the sender to re-encrypt content. This maintains content security while providing adaptability to changing group compositions.
Data Source
AI summary
A server receives identifying information of a user of a client device and data encrypted with a public key of a group, where the encrypted data includes an encrypted session key for secure content. The server determines whether the user is a member of the group using the identifying information of the user. If the user is a member of the group, the server decrypts the encrypted session key using a private key of the group, and causes the client device to obtain a session key to access the secure content.