## CryptoDB

### Paper: On Universal Composable Security of Time-Stamping Protocols

Authors: Toshihiko Matsuo Shin'ichiro Matsuo URL: http://eprint.iacr.org/2005/148 Search ePrint Search Google Time-stamping protocols, which assure that a document was existed at a certain time, are applied to some useful and practical applications such as electronic patent applications and so on. There are two major time-stamping protocols, the simple protocol and the linking protocol. In the former, a time-stamp authority issues a time-stamp token that is the digital signature of the concatenated value of a hashed message and the present time. In the latter, the time-stamp authority issues a time-stamp token that is the hash value of the concatenated value of a hashed message and the previous hash value. Although security requirements and analysis for above time-stamping protocols has been discussed, there are no strict cryptographic security notions for them. In this paper, we reconsider the security requirements for time-stamping protocols and define security notions for them, in a universally composable security sense, which was proposed by Canetti. We also show that these notions can be achieved using combinations of a secure key exchange protocol, a secure symmetric encryption scheme, and a secure digital signature scheme.
##### BibTeX
@misc{eprint-2005-12484,
title={On Universal Composable Security of Time-Stamping Protocols},
booktitle={IACR Eprint archive},
keywords={cryptographic protocols / time-stamping protocol, universal composable security},
url={http://eprint.iacr.org/2005/148},
note={This paper is accepted as a regular paper at IWAP 2005. matsuosn@nttdata.co.jp 12968 received 25 May 2005, last revised 3 Jul 2005},
author={Toshihiko Matsuo and Shin'ichiro Matsuo},
year=2005
}