## Cryptology ePrint Archive: Report 2019/365

Fully Secure Attribute-Based Encryption for $t$-CNF from LWE

Rotem Tsabary

Abstract: Attribute-based Encryption (ABE), first introduced by [SW05,GPSW06], is a public key encryption system that can support multiple users with varying decryption permissions. One of the main properties of such schemes is the supported function class of policies. While there are fully secure constructions from bilinear maps for a fairly large class of policies, the situation with lattice-based constructions is less satisfactory and many efforts were made to close this gap. Prior to this work the only known fully secure lattice construction was for the class of point functions (also known as IBE). In this work we construct for the first time a lattice-based (ciphertext-policy) ABE scheme for the function class $t$-CNF, which consists of CNF formulas where each clause depends on at most $t$ bits of the input, for any constant $t$. This class includes NP-verification policies, bit-fixing policies and $t$-threshold policies. Towards this goal we also construct a fully secure single-key constrained PRF from OWF for the same function class, which might be of independent interest.

Category / Keywords: public-key cryptography / attribute-based encryption, ABE, ciphertext policy, full security, adaptive security, constrained PRF, lattice techniques, LWE

Date: received 4 Apr 2019, last revised 2 Jun 2019

Contact author: rotem tsabary at weizmann ac il

Available format(s): PDF | BibTeX Citation

Short URL: ia.cr/2019/365

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