[Resource Topic] 2024/1416: Circuit ABE with poly(depth, λ)-sized Ciphertexts and Keys from Lattices

Welcome to the resource topic for 2024/1416

Title:
Circuit ABE with poly(depth, λ)-sized Ciphertexts and Keys from Lattices

Authors: Hoeteck Wee

Abstract:

We present new lattice-based attribute-based encryption (ABE) and
laconic function evaluation (LFE) schemes for circuits with sublinear
ciphertext overhead. For depth d circuits over \ell-bit inputs, we obtain

  • an ABE with ciphertext and secret key size O(1);

  • a LFE with ciphertext size \ell + O(1) and digest size O(1);

  • an ABE with public key and ciphertext size O(\ell^{2/3}) and
    secret key size O(1),

where O(\cdot) hides \mbox{poly}(d,\lambda) factors. The first two results achieve almost optimal ciphertext and secret key / digest sizes, up to the \mbox{poly}(d) dependencies. The security of our schemes relies on \ell-succinct LWE, a falsifiable assumption which is implied by evasive LWE. At the core of our results is a new technique for compressing LWE samples \mathbf{s}(\mathbf{A}-\mathbf{x} \otimes \mathbf{G}) as well as the matrix \mathbf{A}.

ePrint: https://eprint.iacr.org/2024/1416

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