IRJET - Efficient Public Key Cryptosystem for Scalable Data Sharing in Cloud Storage

This document summarizes and evaluates several existing approaches for securely sharing data stored in the cloud. It discusses key aggregate cryptosystems that allow a user to generate a single aggregate key to decrypt a set of ciphertexts. It also reviews other techniques such as attribute-based encryption with proxy re-encryption, dynamic auditing services using random sampling and fragment structures, the Oruta system using ring signatures for public auditing of shared data, and privacy-preserving public auditing using message authentication codes. The document analyzes the advantages and disadvantages of each approach, such as increased key sizes with attribute-based encryption and the storage overhead of fragment structures.