Paper 2019/031

Collusion Resistant Broadcast and Trace from Positional Witness Encryption

Rishab Goyal, Satyanarayana Vusirikala, and Brent Waters


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.

Available format(s)
Public-key cryptography
Publication info
A minor revision of an IACR publication in PKC 2019
Witness EncryptionTrace and RevokeBroadcast EncryptionBroadcast and Trace
Contact author(s)
rgoyal @ cs utexas edu
satya @ cs utexas edu
bwaters @ cs utexas edu
2019-01-17: received
Short URL
Creative Commons Attribution


      author = {Rishab Goyal and Satyanarayana Vusirikala and Brent Waters},
      title = {Collusion Resistant Broadcast and Trace from Positional Witness Encryption},
      howpublished = {Cryptology ePrint Archive, Paper 2019/031},
      year = {2019},
      note = {\url{}},
      url = {}
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