Probabilistic encryption

Gene

Transformation (genetics)

Computer security

Encryption

Operating system

Biochemistry

Attribute-based encryption

Computer science

Cloud computing

Acoustics

Functional encryption

Public-key cryptography

Computer network

Alternative medicine

Physics

On-the-fly encryption

Identity (music)

Multiple encryption

Broadcast encryption

Client-side encryption

Medicine

Chemistry

Filesystem-level encryption

Ciphertext

Data sharing

Pathology

IEEE Transactions on Information Forensics and Security

With the rapid development of cloud computing, an increasing number of individuals and organizations are sharing data in the public cloud. To protect the privacy of data stored in the cloud, a data owner usually encrypts his data in such a way that certain designated data users can decrypt the data. This raises a serious problem when the encrypted data needs to be shared to more people beyond those initially designated by the data owner. To address this problem, we introduce and formalize an identity-based encryption transformation (IBET) model by seamlessly integrating two well-established encryption mechanisms, namely identity-based encryption (IBE) and identity-based broadcast encryption (IBBE). In IBET, data users are identified and authorized for data access based on their recognizable identities, which avoids complicated certificate management in usual secure distributed systems. More importantly, IBET provides a transformation mechanism that converts an IBE ciphertext into an IBBE ciphertext so that a new group of users not specified during the IBE encryption can access the underlying data. We design a concrete IBET scheme based on bilinear groups and prove its security against powerful attacks. Thorough theoretical and experimental analyses demonstrate the high efficiency and practicability of the proposed scheme.

Identity-Based Encryption Transformation for Flexible Sharing of Encrypted Data in Public Cloud