## Cryptology ePrint Archive: Report 2019/031

Collusion Resistant Broadcast and Trace from Positional Witness Encryption

Rishab Goyal and Satyanarayana Vusirikala and Brent Waters

Abstract: An emerging trend is for researchers to identify cryptography primitives for which feasibility was first established under obfuscation and then move the realization to a different setting. In this work we explore a new such avenue — to move obfuscation-based cryptography to the assumption of (positional) witness encryption. Our goal is to develop techniques and tools, which we will dub “witness encryption friendly” primitives and use these to develop a methodology for building advanced cryptography from positional witness encryption. We take a bottom up approach and pursue our general agenda by attacking the specific problem of building collusion-resistant broadcast systems with tracing from positional witness encryption. We achieve a system where the size of ciphertexts, public key and private key are polynomial in the security parameter $\lambda$ and independent of the number of users N in the broadcast system. Currently, systems with such parameters are only known from indistinguishability obfuscation.

Category / Keywords: public-key cryptography / Witness Encryption, Trace and Revoke, Broadcast Encryption, Broadcast and Trace

Original Publication (with minor differences): IACR-PKC-2019

Date: received 13 Jan 2019, last revised 13 Jan 2019

Contact author: rgoyal at cs utexas edu, satya at cs utexas edu, bwaters at cs utexas edu

Available format(s): PDF | BibTeX Citation

Short URL: ia.cr/2019/031

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