(AGENPARL) - Roma, 20 Marzo 2026 -
ePrint Report: Ciphertext-Policy ABE for $mathsf{NC}^1$ Circuits with Constant-Size Ciphertexts from Succinct LWE
Jiaqi Liu, Yuanyi Zhang, Fang-Wei Fu
We construct a lattice-based ciphertext-policy attribute-based encryption (CP-ABE) scheme for $mathsf{NC}^1$ access policies with constant-size ciphertexts. Let $lambda$ be the security parameter. For an $mathsf{NC}^1$ circuit of depth $d$ and size $s$ on $ell$-bit inputs, our scheme has the public-key and ciphertext sizes $O(1)$ (independent of $d$), and secret-key size $O(ell)$, where the $O(cdot)$ hides $operatorname{poly}(lambda)$ factors. As an application, we obtain a broadcast encryption scheme for $N$ users with ciphertext size $operatorname{poly}(lambda)$ independent of $log N$ and key sizes $operatorname{poly}(lambda,log N)$. Our construction is selectively secure in the standard model under the $operatorname{poly}(lambda)$-succinct LWE assumption introduced by Wee (CRYPTO 2024).
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