Towards More Efficient Registration-Based Encryption from LWE

Toi Tomita

Paper 2026/768

Towards More Efficient Registration-Based Encryption from LWE

Toi Tomita

, Yokohama National University

Abstract

Registration-based encryption (RBE) effectively addresses the key escrow problem in identity-based encryption. However, existing post-quantum RBE schemes suffer from prohibitive ciphertext sizes in the gigabyte range for systems with $2^{10}$ registered users. This poor scalability is a major obstacle to the large-scale implementation of RBE in society. In this work, we propose a framework for constructing efficient RBE schemes that can be instantiated from the learning with errors (LWE) assumption. Specifically, the ciphertext size remains around 221 MB even as the number of registered users increases. The core techniques involve introducing decomposable laconic encryption and integrating it with a refined snapshotting trick. Our work represents an important milestone towards achieving practical post-quantum RBEs.

Metadata

Available format(s): PDF
Category: Public-key cryptography
Publication info: Published elsewhere. Applied Cryptography and Network Security (ACNS) 2026
Keywords: Registration-based encryption Post-quantum cryptography Learning with errors
Contact author(s): tomita-toi-sk @ ynu ac jp
History: 2026-04-22: approved; 2026-04-19: received; See all versions
Short URL: https://ia.cr/2026/768
License: CC BY

BibTeX

@misc{cryptoeprint:2026/768,
      author = {Toi Tomita},
      title = {Towards More Efficient Registration-Based Encryption from {LWE}},
      howpublished = {Cryptology {ePrint} Archive, Paper 2026/768},
      year = {2026},
      url = {https://eprint.iacr.org/2026/768}
}