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Paper 2013/642

Multiparty Key Exchange, Efficient Traitor Tracing, and More from Indistinguishability Obfuscation

Dan Boneh and Mark Zhandry

Abstract

In this work, we show how to use indistinguishability obfuscation (iO) to build multiparty key exchange, efficient broadcast encryption, and efficient traitor tracing. Our schemes enjoy several interesting properties that have not been achievable before: - Our multiparty non-interactive key exchange protocol does not require a trusted setup. Moreover, the size of the published value from each user is independent of the total number of users. - Our broadcast encryption schemes support distributed setup, where users choose their own secret keys rather than be given secret keys by a trusted entity. The broadcast ciphertext size is independent of the number of users. - Our traitor tracing system is fully collusion resistant with short ciphertexts, secret keys, and public key. Ciphertext size is logarithmic in the number of users and secret-key size is independent of the number of users. Our public key size is polylogarithmic in the number of users. The recent functional encryption system of Garg, Gentry, Halevi, Raykova, Sahai, and Waters also leads to a traitor tracing with similar ciphertext and secret key size, but the construction in this paper is simpler and more direct. These constructions resolve an open problem relating to differential privacy. - Generalizing our traitor tracing system gives a private broadcast encryption scheme (where broadcast ciphertexts reveal minimal information about the recipient set) with optimal size ciphertext. Our proof of security for private broadcast encryption and traitor tracing introduces a new tool for iO proofs: the construction makes use of a key-homomorphic symmetric cipher which plays a crucial role in the proof of security.

Metadata
Available format(s)
PDF
Category
Public-key cryptography
Publication info
Preprint. MINOR revision.
Keywords
obfuscationmulti-party key exchangebroadcast encryptiontraitor tracing
Contact author(s)
mzhandry @ stanford edu
History
2014-06-16: last of 8 revisions
2013-10-10: received
See all versions
Short URL
https://ia.cr/2013/642
License
Creative Commons Attribution
CC BY
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