Stuff Yaron Finds Interesting

Technology, Politics, Food, Finance, etc.

How much will it cost to send our kids to college?

The short answer is that we don’t know. And before someone says ”what about the 529 prepaid plans?!?!” (which I discuss here) please keep in mind that those plans only track instate tuition fees and so don’t cover expenses like room and board, books, etc. So bottom line is - we don’t know, in fact, I would argue, we can’t know. The guiding light of finance being ”the future’s not our’s to see.” So I’m going to guess. My guess, assuming both our kids go out of state for college in 7 and 16 years and attend college for 4 years is that our total bill (tuition, fees, room, board, etc.) will be $315,322.37 and $404,998.28 in current dollars. That’s a grand total of $720,321 for two kids.
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The block chain and the CAP Theorem

In this article I argue that depending on how one programs one’s client, one can build a Consistent and Partition Tolerant or Available and Partition Tolerant system on top of Bitcoin or really any block chain. And no, that isn’t a contradiction and no this doesn’t violate the CAP theorem.
[Note: Lots of updates in response to feedback]

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How to make block chains strongly consistent

Block chains can be strongly consistent but not in the normal deterministic sense we are used to from consensus protocols like Paxos. Instead the strong consistency is probabilistic. That is, if one waits for long enough then the probability of a particular transaction being removed from the chain falls to negligible levels. This then provides the basis for a protocol that can treat the block chain as strongly consistent, where the protocol is “Wait until a transaction is X blocks deep in whatever chain one sees”.
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Going off chain for storage

It turns out that building a distributed database with ACID behavior (aka a block chain) isn’t easy, it requires a lot of code and a lot of processing. As a result block chains like Bitcoin can process around 4 transactions/second. A pretty slow pace for a globe spanning system. To work around this and other issues I explore below, we hear more and more about off block chain storage. But it turns out that if you store off the chain then you lose the chain’s ACID guarantees. In many cases that loss is fine but it does call into question if the use case that can leverage off chain storage really needs the chain at all.
[Update: Thank you to Shawn Cicoria for pointing out that my original price quote for storing a Gigabyte of data in Ethereum was off by a factor of 32. My mistake is that I did the calculations forgetting that the gas price is per Ethereum Word which is 32 bytes.]
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How do we build apps for this wonderful mesh based Internet anyway?

Previously I waxed poetic about the amazing powers of Serval to create mesh based Internet infrastructure for developing and less developed countries (LDCs). The thesis being that if we had meshes of Wifi endpoints that could move data around without charge then people could have local applications on their smart phones that run peer to peer and could take advantage of this infrastructure. But how do we build those apps? That is where Thali comes in. But yes, we need more. See below.
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Building local Internet infrastructure for disadvantaged communities

Smart phones are showing up in the poorest of countries. Even the Internet is showing up but it’s still quite expensive. But for a reasonable price we can deploy Wifi based local mesh infrastructures that can let people run applications on their smart phones and communicate locally with people around them. We have the technology! Below I explain what that technology is and why it’s all Serval's fault.
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Serval and Thali

Serval is a project that wants to enable mobile phones to work no matter what. They have built mesh technology to let mobiles make voice calls as well as share data and have an app available on Android to use this technology. This is a technology that Thali could potentially really leverage. In the first section below I give a quick walk through of Serval. In the next section I compare and contrast Serval and Thali’s ways of solving similar problems. Then I conclude that hopefully we can reach a point where Thali just runs on top of Serval.
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