iUC-Secure Distributed File Transfer From Standard Attribute-based Encryption

International audience ; Attribute-Based Encryption (ABE) stands as a cryptographic cornerstone, enabling access control to messages based on user attributes. The security definition of standard ABE is shown to be impossible in Universal Composability (UC) against an active adversary. To overcome this issue, existing formal UC security definitions of ABE rely on additional properties for ABE, necessary to prove security against an active adversary, excluding standard ABE by definition. In light of the composability feature offered by UC and the absence of ideal functionality tailored for standard ABE, we propose the two following contributions: (1) We construct the first ideal functionality FABE for ABE which, under reasonable hypothesis against static corruption, can be realized using an IND-CCA2-secure ABE scheme; and (2) our FABE leads us to propose a protocol solving a simple yet highly practical, world-scaled company-focused problem: efficient file transfer. The proposed construction provides data integrity, sender authentication, attribute-based fileaccess, featured with constant data size transferred between users. This is achieved by relying on two efficient building blocks: ABE and signature,which are layered atop of the hash-based distributed storage system IPFS. Our protocol, strengthened by a formal security definition andanalysis under the Universally Composable (UC) framework called iUC, is proved to realize our problem-oriented authenticated attribute-based file transfer ideal functionality. Finally, we implement our proposal with a proof-of-concept written in Rust, and show it is practical and efficient.