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Abstract
Multi-authority/input attribute-based encryption (MA-/MI-ABE) are multi-party extensions of ABE which enable flavours of decentralised cryptographic access control. This work aims to advance research on multi-party ABE and their lattice-based constructions in several directions:
- We introduce the notion of multi-client (MC-)ABE. This can be seen as an augmentation of MI-ABE with the addition of a ciphertext identity (CID) in the syntax, or a specialisation of multi-client functional encryption (MC-FE) to the ABE setting.
- We adapt the 2-input (2I-)ABE of Agrawal et al. (CRYPTO'22), which is heuristically secure yet without a security proof, into a 2-client (2C-)ABE, and prove it satisfies a variant of very-selective security under the learning with errors (LWE) assumption.
- We extend Wee's ciphertext-policy (CP-)ABE (EUROCRYPT'22) to the MA setting, yielding an MA-ABE. Furthermore, combining techniques in Boneh et al.'s key-policy ABE (EUROCRYPT'14) and our MA-ABE, we construct an MC-ABE. We prove that they satisfy variants of very-selective security under the evasive LWE, tensor LWE, and LWE assumptions.
All our constructions support policies expressed as arbitrary polynomial-size circuits, feature distributed key generation (for MA) and encryption (for 2C/MC), and are proven secure in the random oracle model. Although our constructions only achieve limited security against corrupt authorities/clients, the fully distributed key generation/encryption feature makes them nevertheless non-trivial and meaningful.
Prior to this work, existing MA-ABEs only support up to NC1 policies regardless of their security against corrupt authorities; existing MI-ABEs only support up to constant-many encryptors/clients and do not achieve any security against corrupt encryptors/clients; and MC-ABEs only existed in the form of MC-FEs for linear and quadratic functions.
- We introduce the notion of multi-client (MC-)ABE. This can be seen as an augmentation of MI-ABE with the addition of a ciphertext identity (CID) in the syntax, or a specialisation of multi-client functional encryption (MC-FE) to the ABE setting.
- We adapt the 2-input (2I-)ABE of Agrawal et al. (CRYPTO'22), which is heuristically secure yet without a security proof, into a 2-client (2C-)ABE, and prove it satisfies a variant of very-selective security under the learning with errors (LWE) assumption.
- We extend Wee's ciphertext-policy (CP-)ABE (EUROCRYPT'22) to the MA setting, yielding an MA-ABE. Furthermore, combining techniques in Boneh et al.'s key-policy ABE (EUROCRYPT'14) and our MA-ABE, we construct an MC-ABE. We prove that they satisfy variants of very-selective security under the evasive LWE, tensor LWE, and LWE assumptions.
All our constructions support policies expressed as arbitrary polynomial-size circuits, feature distributed key generation (for MA) and encryption (for 2C/MC), and are proven secure in the random oracle model. Although our constructions only achieve limited security against corrupt authorities/clients, the fully distributed key generation/encryption feature makes them nevertheless non-trivial and meaningful.
Prior to this work, existing MA-ABEs only support up to NC1 policies regardless of their security against corrupt authorities; existing MI-ABEs only support up to constant-many encryptors/clients and do not achieve any security against corrupt encryptors/clients; and MC-ABEs only existed in the form of MC-FEs for linear and quadratic functions.
| Original language | English |
|---|---|
| Pages (from-to) | 1-67 |
| Number of pages | 67 |
| Journal | IACR Communications in Cryptology |
| Volume | 1 |
| Issue number | 4 |
| DOIs | |
| Publication status | Published - 13 Jan 2025 |
| MoE publication type | A1 Journal article-refereed |
Funding
Russell W. F. Lai and Ivy K. Y. Woo are supported by the Research Council of Finland grants 358951 and 358950 respectively. We thank Chris Brzuska for helpful discussion at the early stage of this project.
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Brzuska ICT: Limits of Lattice-based Cryptography: A New Era of Hinted and Structured Assumptions
Brzuska, C. (Principal investigator), Woo, I. K. Y. (Project Member), Puniamurthy, K. (Project Member), Karanko, P. (Project Member), Haapaniemi, A. (Project Member) & Rajabi, A. (Project Member)
01/01/2024 → 31/12/2026
Project: RCF Academy Project targeted call