A study of key compaction encryption for group file sharing and seeking keyword in cloud storage

Key compaction encryption for group data sharing and retrieval via cloud storage are used for effective management of encrypted data. They have flexibility of selectively sharing the data with multiple users in public cloud storage. Data owner can cluster many sets of secret keys and make them as compact as a single class. This approach provides formal security analysis of schemes in the standard model. Sharing group of selected files with any group of selected users requires different secret keys to be used for each document. However, there is an additional overhead for securely distributing each key to users, as those users will have to store equally large number of keyword cipher text in the cloud in order to perform a search over the encrypted data in cloud server. Large memory requirement for huge number of encrypted keys and computational complexity clearly renders this approach ineffective. To address this practical problem, a concept of Key Compaction Encryption in which a data owner needs to distribute a single aggregated key to the user for sharing huge number of documents has been utilized. The safety analysis and overall performance assessment performed confirmed that proposed scheme is comfortable for implementation. Later several concrete Key Encryption Schemes with distinct security tiers and extensions are tested with the proposed model.