How the Cryptocurrency Community Interacts on Twitter

co-written with Jona Harris (@realjonaharris on Twitter)

Anyone who has been following the cryptocurrency scene already knows how lively the discussion is on Twitter. We wanted to have a bit of a look at the relations between the different parts of the community so we turned to some basic social network analysis. We took a look at who “liked” whose tweets, and ran algorithms meant to find the social groups in the graphs.

The map that we get very clearly shows the social relations between various sub-communities as you’d expect if you’re following the cryptocurrency scene (for example, Bitcoin cash…

By Tamar Berenblum and Aviv Zohar.
A tale of our sudden unexpected Bitcoin wealth and the ensuing beaurocratic mess we had to resolve in order to sell it.

Our small bitcoin fortune turned out to be worth a bit more than what we paid for it

This post was born when we acquired a small amount of Bitcoins for research purposes, which like most of the cryptocurrency market climbed in value in late 2017 (our bitcoins were actually worth 35 times what we originally paid for them at some point). We got a bit nervous and decided to sell them. Then we realized:

How Alice, Bob, and Charlie used Zero-Knowledge and Blockchains to launch The Global Sudoku Revolution.

This post is inspired by two great papers that make zero-knowledge proofs accessible to a wide audience:
[1] How to Explain Zero Knowledge Protocols to Your Children (Quisquater et. al.)
[2] Cryptographic and Physical Zero-Knowledge Proof Systems for Solutions of Sudoku Puzzles (Gradwohl et. al.).

Alice, Bob, and Charlie loved to solve Sudoku problems.The three friends liked challenging each other with puzzles all the time (in fact, sometimes they solved Sudoku problems that were REALLY large — not just 9x9 taken from here). Alice was…

How Auction Theory and Algorithmic Game Theory Can Improve Bitcoin’s Transaction Fee Mechanism

In a new paper (pdf) that we (Ron Lavi, Or Sattath, and Aviv Zohar) just published online, we apply techniques from the field of Algorithmic Game Theory to Bitcoin’s fee market. Our goal is to improve several key aspects of the market:

  1. Simplify fee determination for users.
  2. Improve (or at least maintain) the revenue miners collect from fees, which in turn attracts more mining and thus improves security.
  3. Separate the issue of block size from the mechanism that determines fees as much as possible (in this way…

Ethical dilemmas and economic problems surrounding the disclosure of vulnerabilities in cryptocurrencies.

Any complicated piece of software is likely to contain bugs, some of which can be weaponized into harmful exploits and potentially even monetized to yield financial gains to attackers. Cryptocurrencies are complex systems themselves so it isn’t very surprising by now that many exploits, hacks, and attacks are found on a regular basis. This often results in theft and other damages that can cost millions of dollars.

Responsible Disclosure

Suppose you stumble upon a vulnerability in a software system. Being the responsible law abiding nice guy that you are, you…

A Fast and Scalable Distributed Ledger Protocol
(by Yoad Lewenberg, Yonatan Sompolinsky, and Aviv Zohar)

It is by now well known that the classic Bitcoin protocol laid down by Satoshi Nakamoto doesn’t remain secure when block sizes are increased or block creation rates are sped up. This has caused quite a lot of turmoil in the Bitcoin community, as heated debates began regarding the best ways to scale the protocol.

In a new paper that we just wrote we describe a DAG-based protocol for a permissionless distributed ledger that establishes high throughput and fast confirmation times while maintaining resilience to…

Bitcoin has its own obscure terminology and inside jokes — nearly impenetrable to outsiders. The short story below is just the result of playing around with the terminology (probably due to some stories by Etgar Keret lingering on my mind). Whatever you do, don’t take it too seriously.

The Contract

“Here’s my peg” I say, showing him the chain at my side.

He just sits there chewing on a raw onion.

“How many sigops?” he swallows, and finally asks.

“Not many.” I say.

He glances over. “Any tainted inputs?”

“NOP.” I reply and hope I mixed enough so he can’t tell.


Aviv Zohar

Prof. at The Hebrew U and Chief scientist @ QED-it

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