Removing the Depth Bound of Lattice Homomorphism for ABE
- LecturerDr. Yao Ching Hsieh (University of Washington)
Host: Kai-Min Chung - Time2024-06-18 (Tue.) 10:15 ~ 12:00
- LocationAuditorium 101 at IIS new Building
Abstract
In the past decade, lattice-based assumptions have played a very strong role in constructing advanced crypto primitives. One great strength of lattice is its ability to support homomorphism for circuits of polynomial depth. This feature enables various lattice constructions supporting circuit homomorphisms or encoding circuit computations.
One caveat of these lattice homomorphisms is that they typically introduce noise that grows exponentially to the computation depth. Therefore, the resulting homomorphic primitives would need depth-dependent parameter size and have a depth bound for the supporting circuit once the parameters are set. For homomorphic encryption, the seminal bootstrapping technique proposed by Gentry overcame this limit and achieved homomorphism for unbounded depth circuits. However, for most other homomorphic primitives, removing the depth constraint without relying on iO has been a long-standing challenge.
In this work, we demonstrated how to achieve single-key secure attribute-based encryption for unbounded depth assuming circular LWE. At the core of this construction, we give novel techniques to upgrade the underlying homomorphism of the seminal ABE construction by [BGG+14] to support unbounded homomorphisms. Assuming stronger evasive-type assumptions, we can also give unbounded depth ABE secure against unbounded collusion.Based on joint work with Rachel Lin and Ji Luo.
One caveat of these lattice homomorphisms is that they typically introduce noise that grows exponentially to the computation depth. Therefore, the resulting homomorphic primitives would need depth-dependent parameter size and have a depth bound for the supporting circuit once the parameters are set. For homomorphic encryption, the seminal bootstrapping technique proposed by Gentry overcame this limit and achieved homomorphism for unbounded depth circuits. However, for most other homomorphic primitives, removing the depth constraint without relying on iO has been a long-standing challenge.
In this work, we demonstrated how to achieve single-key secure attribute-based encryption for unbounded depth assuming circular LWE. At the core of this construction, we give novel techniques to upgrade the underlying homomorphism of the seminal ABE construction by [BGG+14] to support unbounded homomorphisms. Assuming stronger evasive-type assumptions, we can also give unbounded depth ABE secure against unbounded collusion.Based on joint work with Rachel Lin and Ji Luo.