eprint.iacr.orgpaperRegistered ABE via Predicate Encodings, Revisited
Registered ABE via Predicate Encodings, Revisited is an ePrint paper by Junichi Tomida (October 2026) that gives a new definition of predicate encodings suited to registered attribute-based encryption. It yields the first Reg-ABE schemes for (non-)zero inner product and for conjunctions/disjunctions with O(log L)-size ciphertexts. It also gives a registered broadcast encryption scheme with O(log L)-size ciphertexts under the standard k-Lin assumption, not the generic group model.
What it is
Junichi Tomida's ePrint 2026/2558 (received 19 October 2026, approved 20 October 2026) is a minor revision of a paper at ASIACRYPT 2026. It redefines predicate encodings, the framework Wee introduced at TCC'14, so that they fit registered attribute-based encryption (Reg-ABE). The earlier Reg-ABE construction from predicate encodings, by Zhu et al. (Asiacrypt'23), reused the definition from vanilla ABE.
What changes for ciphertext size
Here L is the maximum number of users and ℓ is the vector length or policy size. The abstract gives the prior and new bounds:
| Predicate | Prior ciphertext size | This paper |
|---|---|---|
| (Non-)zero inner product | O(ℓ log L) | O(log L) |
| Conjunctions and disjunctions | O(ℓ log L) | O(log L) |
| Registered broadcast encryption | Relied on the generic group model | O(log L) under k-Lin |
The saving removes the factor ℓ, so ciphertext size no longer grows with the vector length or policy size. All three schemes are proven under the standard k-Lin assumption on pairings.
Caveats
The page is an abstract and metadata only. It gives no concrete parameters, benchmarks, key or public-parameter sizes, or implementation. It does not say whether the new schemes change the cost of registration or of key updates. The abstract claims efficiency gains only for predicates that predicate encodings capture.
Organisations named here
- ASIACRYPT 2026
- Hoeteck Wee
- Junichi Tomida
- k-Lin assumption
Technologies named here
- Predicate encodings
- Registered ABE
Also named here
- Zhu et al.
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