I think Merkle authentication trees allow you to do this, if you don't care about specific time, but just about the ordering of events. Most of the time-stamping services are based on this, where they publish a daily master hash somewhere.
I can't seem to find an online copy of the Merkle paper as it's quite old. The patent has expired. A Merkle Authentication Tree is basically a tree of hashes to allow the efficient verification of a particular leaf in the tree with log(n) queries. Imagine a binary tree representing a set of events with names as the leaf nodes. The parent of a leaf node is the hash of the pair of events below it. The parent of that node with it's neighbor is the hash of it and the neighbor hash, and so on up to the root which is the master hash of all the hash of hashes of events down to the leaves. The time-stamping service application just publishes on a daily basis the master hash. Each days master hash should also include the previous days. Now even if the time-stamping service were corrupt it can not after the fact create a stamp in a previous days epoch without being caught. Adam On Fri, Mar 22, 2002 at 05:34:42PM -0800, Kevin A. Burton wrote: > -----BEGIN PGP SIGNED MESSAGE----- > Hash: SHA1 > > > Does anyone have any references they would recommend which talk about the > problems of time in a secure and distributed environment? > > Specifically how do you keep others from cheating and saying that an event > happened in the past when it actually happened in the present? > > I have tried to get some resources from google and other crypto hackers but I > can't seem to find anything substantial. > > There HAS to be some prior research in this area! > > Kevin
