Cryptology ePrint Archive: Report 2016/123
Robust Password-Protected Secret Sharing
Michel Abdalla and Mario Cornejo and Anca Nitulescu and David Pointcheval
secret sharing (PPSS) schemes allow a user to publicly share its high-entropy secret across different servers and
to later recover it by interacting with some of these servers using only his password without requiring any authenticated data.
In particular, this secret will remain safe as long as not too many servers get corrupted. However, servers are not always
reliable and the communication can be altered. To address this issue, a robust PPSS should additionally guarantee
that a user can recover his secret as long as enough servers provide correct answers, and these are received without
In this paper, we propose new robust PPSS schemes which are significantly more efficient than the existing ones.
We achieve this goal in two steps.
First, we propose a generic technique to build a Robust Gap Threshold Secret Sharing Scheme (RGTSSS) from any
threshold secret sharing scheme. In the PPSS construction, this allows us to drop the verifiable property of Oblivious
Pseudorandom Functions (OPRF).
Then, we use this new approach to design two new robust PPSS schemes that are quite efficient, from two OPRFs.
They are proven in the random oracle model, just because our RGTSSS construction requires random non-malleable
fingerprints. This is easily guaranteed when the hash function is modeled as a random oracle.
Category / Keywords: Password-Protected Secret Sharing, Robust Gap Threshold Secret Sharing Scheme, Oblivious Pseudorandom Functions
Original Publication (with minor differences): ESORICS 2016
DOI: 10.1007/978-3-319-45741-3 4
Date: received 11 Feb 2016, last revised 23 Dec 2016
Contact author: mario cornejo at ens fr
Available format(s): PDF | BibTeX Citation
Version: 20161223:153816 (All versions of this report)
Short URL: ia.cr/2016/123
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