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Showing posts from March, 2018

Book review: Last lecture by Randy Pausch

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Of course you have watched the late Prof. Randy Pausch's last lecture. If for some reason you haven't, please right that wrong now.

I recently read the book "Last Lecture" by Randy Pausch. I got the book from my local library, yes, a physical library building. They still exist, and they are a great resource.

It is a short book, and I have a very brief review.

The book does not repeat the "last lecture" presentation. It tells mostly disjoint and complementary story, and it gets into more personal stuff. I learned several more interesting anectodes about Randy in this book.

It is of course a very heartbreaking story. The book is a "memento mori".

It makes you think about "What would you want to be known for?" and "How would you prioritize your life if you had 5 years left?"

I am still thinking about those long after I returned the book to the library.

I am currently reading about "Crypto: How the Code Rebels Beat the Governm…

Master your tools

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Couple months ago, a friend sent me this article about "Speed learner Max Deutsch challenging chess grandmaster Magnus Carlsen". My friend called the story a life-hack story, and remarked that this is the "Silicon Valley bro" frame of mind in action: "Nobody deserves any respect because I am so confident and valley savvy I could naturally write an app and do it better".

This was my reply on the article.
This is a very nice illustration of a hack versus expert: Expert had years of battle-scar, and internalized everything. Hacks/shortcuts are going to take you only to where the expert's domain starts.
Also another take away is, we humans are dumb. We don't have anything to be proud of about our mental prowess. I make so many stupid mistakes every week, it is frustrating. It is a shame we can't get much smarter on the spot. But in the offline mode (doing research/thinking by writing), I think we can do better. We can only make up for the shortcom…

Replying to why decentralization matters

Last month Chris Dixon published "Why decentralization matters".

I felt it was one-sided and lacked solid arguments. I picked up some populist vibes as well.
"There go my people. I must find out where they are going, so I can lead them." --Alexandre Auguste Ledru-Rollin
At that time, I had jotted down my criticisms to some of the paragraphs in that article in my draft posts folder. Then I saw Todd Hoff's (from High Scalability fame) brief write up about the article. It captures nicely my reactions to the article. So I will start with Todd's response and cover only the remaining parts of my criticisms in the rest of this post.
"Nerds always dream of decentralization, I certainly do, but every real world force aligns on the side of centralization. We still have NAT with IPv6! Ironically, the reason given why decentralization will win is exactly why it won't: "Decentralized networks can win the third era of the internet for the same reason they w…

Blockchain applications in Supply Chain Management

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Here is the whitepaper that started this post, which is admittedly outside my domain of expertise. Also here is some discussion we had on this on Twitter. 

The white paper includes quotes like "7 in 10 consumer industry executives expect to have a blockchain production network in 3 years" and "Blockchains are expected to greatly reduce nine frictions. Including: inaccessible marketplaces, restrictive regulations, institutional inertia, invisible threats, imperfect information, inaccessible information."

Man, if that last statement is true, the companies should just employ blockchain and fire their CEO's and management teams as they are no longer needed. Blockchain is a miracle worker indeed. It enters inaccessible marketplaces, it loosens restrictive regulations, eliminates institutional inertia, makes visible the invisible threats (watchout ninjas), corrects/curates the imperfect information, and makes all information accessible.

I know that I tend to go hyper…

Anatomical similarities and differences between Paxos and blockchain consensus protocols

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Now that we read through some blockchain papers in our seminar, I started to develop some understanding of the "blockchain way". Since I already know about the "Paxos way", I thought it would be instructive and fun to compare & contrast Paxos and blockchain consensus protocols. If you know about either of these protocols well, this post can help you get a headstart on learning the other one.

I will be referring to the below Paxos figure for the protocol phases, so let's pin it here.


Leader election: silent vs loud
A couple days ago I tweeted that. That is how leader election is done in blockchain consensus protocol. The first miner to solve the puzzle first becomes the leader for the current round. For blockchain it is par for the course that for each round another leader (the one who solves the next puzzle first) serves. In other words, instead of Phase1a "propose leadership" and Phase1b "promise to follow" back-and-forth communication a…

Leveraging data and people to accelerate data science (Dr. Laura Haas)

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Last week Dr. Laura Haas gave a distinguished speaker series talk at our department. Laura is currently the Dean of the College of Information and Computer Sciences at University of Massachusetts at Amherst. Before that, she was at IBM for many years, and most recently served as the Director of IBM Research’s Accelerated Discovery Lab. Her talk was on her experiences at the Accelerated Discovery Lab, and was titled "Leveraging data and people to accelerate data science"

Accelerated Discovery Lab The mission of the lab was to "help people get insight from data -- quickly".
The lab aimed to manage the technology and data complexity, so that clients can focus on solving their challenges. This job involved providing the clients with:

expertise: math, ml, computingenvironment: hosted big data platformsdata: curated & governed data sets to provide contextanalytics: rich collection of analytics and tools.
By providing these services, the lab "accelerated" aro…

Paper review. Enhancing Bitcoin Security and Performance with Strong Consistency via Collective Signing.

This paper appeared in USENIX Security in 2016, and is by Eleftherios Kokoris Kogias, Philipp Jovanovic, Nicolas Gailly, Ismail Khoffi, Linus Gasser, and Bryan Ford at EPFL.

The link includes the conference presentation video which is useful. Kudos to USENIX for providing this. Other organizations should take a hint. It is 2018-- how hard is it to make the conference videos and presentation material available online?

The problem Bitcoin does not provide instant irreversibility. Bitcoin protocol needs 6 consecutive blocks to be appended to conclude the irreversibility of a block with very high probability. A useful analogy here is to imagine the 6 additional blocks trapping the original block in amber layers. After that the adversaries don't have the computing power to go back 6 blocks to rewrite history and catch up and beat the current longest chain.

Instant irreversibility would be helpful, because it would save you from having to wait 6 more blocks to be added (which amounts to…

Paper review. A secure sharding protocol for open blockchains.

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This paper appeared in ACM CCS'16. It is authored by Loi Luu, Viswesh Narayanan, Chaodong Zheng,  Kunal Baweja, Seth Gilbert, and Prateek Saxena.

Here is a video of the conference presentation.

The problem The Bitcoin transaction throughput does not scale. Bitcoin's PoW blockchain consumes massive computational power yet can only process up to 7 transactions per second.

The paper proposes, Elastico, a new distributed agreement protocol, based on a non-PoW Byzantine consensus protocol, for permissionless blockchains.

The challenge is that classical/non-PoW Byzantine consensus protocols do not work in an open environment:

many of those protocols assume that the network nodes have pre-established identities. practical byzantine consensus protocols such as PBFT require at least a quadratic number of messages in the number of participants, hindering scalability. 
The main idea The key idea in Elastico is to partition the network into smaller committees, each of which processes a disj…

Paper review. Service-oriented sharding with Aspen

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This week in our seminar, we discussed this linked whitepaper/shortpaper from Adem Efe Gencer, Robbert van Renesse, Emin Gün Sirer.

The problemBlockchains provide trustless auditability, tamper-resistance, and transparency due to the face of Byzantine participants.  As such there is a community of users that would like to use blockchains to record in an authoritative manner transactions/provenance for many assets (in addition to the prevalent use of cryptocurrencies), such as gold, silver, diamonds, gems, land records, deeds, mortgages, boat titles, fine art, health records, and domain names.

The simplest approach address this demand is to layer these additional blockchains on top of an existing secure blockchain such as Bitcoin. The OP_RETURN opcode is adopted for this purpose, and its use has been increasing rapidly. However, this is not scalable, as it leads to a stream of costly and burdensome transactions. And Bitcoin blockchain is already overburdened and crawling.

The other app…

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