## CryptoDB

### Paper: Knowledge-Binding Commitments with Applications in Time-Stamping (Full Version)

Authors: Ahto Buldas Sven Laur URL: http://eprint.iacr.org/2007/071 Search ePrint Search Google We prove in a non-black-box way that every bounded list and set commitment scheme is knowledge-binding. This is a new and rather strong security condition, which makes the security definitions for time-stamping much more natural compared to the previous definitions, which assume unpredictability of adversaries. As a direct consequence, list and set commitment schemes with partial opening property are sufficient for secure time-stamping if the number of elements has an explicit upper bound N. On the other hand, white-box reductions are in a sense strictly weaker than black-box reductions. Therefore, we also extend and generalize the previously known reductions. The corresponding new reductions are Theta(sqrt(N)) times more efficient, which is important for global-scale time-stamping schemes where N is very large.
##### BibTeX
@misc{eprint-2007-13353,
title={Knowledge-Binding Commitments with Applications in Time-Stamping (Full Version)},
booktitle={IACR Eprint archive},
keywords={cryptographic protocols / bit commitment, white-box reductions, time-stamping},
url={http://eprint.iacr.org/2007/071},
note={A shortened version of this work will be published in PKC2007. ahto.buldas@ut.ee 13567 received 23 Feb 2007},
author={Ahto Buldas and Sven Laur},
year=2007
}