In order to increase the security of cloud email systems, a security attribute known as forward secrecy is now both desirable and necessary for both individuals and cloud email service providers due to the widespread use of cloud emails and the regular reporting on significant email leakage occurrences. In particular, even if the user’s secret key is discovered, forward secrecy can ensure the confidentiality of those previously encrypted
communications. However, conventional ways of attaining forward secrecy, such as Diffie-Hellman key exchange and forward-secure public-key encryption, have not been extensively accepted and used because they cannot simultaneously meet the security and practicality needs of email systems. In this project, we introduce a new cryptographic primitive called forward-secure puncturable identity-based encryption (fs-PIBE), which enables an email user to perform fine-grained revocation of decryption capability in order to capture forward secrecy of encrypted cloud email systems without sacrificing practicability. In more specific terms, the user is permitted to keep the ability to decode emails that have not yet been received while eliminating it for emails that have. As a result, it offers more useful forward secrecy than customary methods, which simultaneously disable the ability to decipher both received and unreceived encrypted emails. We develop a framework for encrypted cloud email systems based on such a basic and implement it using a concrete fs-PIBE design with constant ciphertext size and standard model-provable security. Furthermore, we extend the suggested fs-PIBE scheme to provide end-to-end encryption and outsourced decryption, respectively, in order to increase the security and effectiveness of the presented framework. Additionally, we implement the suggested fs-PIBE method and conduct numerous tests as a proof-of-concept to show that it is workable and accurate.