Multi-User Searchable Encryption via Secret Key Distribution

The user key is segmented into multiple distribution keys through secret distribution. Each share-target user receives a unique distribution key instead of the full user key. This segmentation enables multi-user access while maintaining security, as no single distribution key alone can decrypt the encrypted index or perform search operations without collaboration from other holders.

The patent introduces an intermediary verification mechanism where the server acts as a mediator to verify search requests. The server performs homomorphic hash calculations on received distribution keys and compares them with stored hash values. This intermediary verification layer enables secure multi-user search without direct key sharing between users.

The system performs preliminary actions by pre-calculating and storing hash values of distribution keys on the server during the key distribution phase. When search requests are made, the server only needs to perform homomorphic hash calculations on received keys and compare them with pre-stored values, rather than performing full encryption/decryption operations. This preliminary preparation significantly reduces processing time during actual search operations.

The patent replaces traditional mechanical encryption/decryption operations with homomorphic hash calculations. Instead of decrypting the encrypted index to perform searches (which is computationally intensive), the system uses homomorphic properties to verify search requests through hash comparisons. This substitution of cryptographic mechanisms dramatically reduces processing load while maintaining security.