Paper 2026/1960 Original: eprint.iacr.org/2026/1960 ↗
Unbounded Broadcast and KP-ABE with Sublinear Ciphertext from Pairings
Abstract
We present the first pairing-based unbounded broadcast encryption and key-policy attribute-based encryption (KP-ABE) with sublinear ciphertext size. Here, unbounded means set-up and the public parameters do not impose a bound on the size of the broadcast set, attribute length, or policy size. - Our broadcast encryption scheme supports an unbounded number of users, and achieves \[ |mpk| = O(1), |ct| = O(\sqrt{N}), |sk| = O(\sqrt{N})\] where $N$ denotes an upper bound on the size of the broadcast set. - Our KP-ABE supports boolean formula and span programs, and achieves \[ |mpk| = O(1), |ct| = O(\sqrt{N}), |sk| = O(\sqrt{N} \cdot |f|)\] where $N$ is the attribute length and $|f|$ the policy size. We prove adaptive security for the broadcast encryption and selective security for the KP-ABE, based on the $k$-Lin assumption in the standard model without random oracles.
Metadata
- Available format(s)
PDF- Category
- Public-key cryptography
- Publication info
- Preprint.
- History
- 2026-09-10: last updated
- 2026-09-10: published
- Short URL
- https://ia.cr/2026/1960
- License
- https://creativecommons.org/licenses/by/4.0/
BibTeX
@misc{cryptoeprint:2026/1960,
author = {Junichi Tomida and Hoeteck Wee},
title = {Unbounded Broadcast and KP-ABE with Sublinear Ciphertext from Pairings},
howpublished = {Cryptology {ePrint} Archive, Paper 2026/1960},
year = {2026},
url = {https://eprint.iacr.org/2026/1960}
}