[Repost] Hashgraph 5 Min Intro @ Silicon Valley Ethereum Meetup

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• What we'll do
Derek Labian will be giving a 5 min introduction to Hashgraph at this event and will be happy to answer any questions you may have afterward. Please see original event link below for more details.

ORIGINAL EVENT: https://www.meetup.com/EthereumSiliconValley/events/245861880/
We're happy to have Yan Michalevsky (https://www.linkedin.com/in/yanmichalevsky/) (PhD student (https://web.stanford.edu/~yanm2/) at Stanford) speak to us on "Ethereum Bugs Through the Lens of Formal Verification". Please note that this is not at our usual time (it's at 4:15), nor location (it's at Stanford). Also see below for more info on an event from the Stanford Bitcoin Meetup in the same room following our event.

The material Yan will present is joint work (http://www.cs.tau.ac.il/~shellygr/pubs/2018-popl-1.pdf) with Shelly Grossman (http://www.cs.tau.ac.il/~shellygr/) of Tel Aviv University, and others at Tel Aviv and VMware Research. Yan's abstract follows: The famous DAO bug employed callbacks to steal $150M. Callbacks are essential in many programming environments, but drastically complicate program understanding and reasoning because they allow to mutate object’s local states by external objects in unexpected fashions, thus breaking modularity. We define the notion of Effectively Callback Free (ECF) objects in order to allow callbacks without preventing modular reasoning. We study the decidability of dynamically checking ECF in a given execution trace and statically checking if an object is ECF. We also show that dynamically checking ECF in Ethereum is feasible and can be done online. By running the history of all execution traces in Ethereum, we were able to verify that virtually all existing contract executions, excluding these of the DAO or of contracts with similar known vulnerabilities, are ECF. Finally, we show that ECF, whether it is verified dynamically or statically, enables modular reasoning about objects with encapsulated state.

At the start of the event, Derek Labian will give a 5-min intro to HashGraph. Also, in the same room at 6pm Charlie Lee will talk to the Stanford Bitcoin meetup; we'll have food of some kind between the events. If you plan to attend the Stanford Bitcoin event, please RSVP at https://www.meetup.com/Stanford-Bitcoin-Meetup/events/246462531/

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