This document describes a proposed cryptosystem for secure and efficient data sharing in cloud storage. It allows a user to encrypt files with different public keys but send a receiver a single constant-size decryption key that gives decryption rights to any set of ciphertexts. This allows flexible sharing of encrypted data while keeping decryption keys compact. The proposed system aims to address disadvantages of existing approaches like unexpected privilege escalation exposing all data or inefficient key sizes. It provides security based on number-theoretic assumptions without relying on servers for access control.