Name: 7.カテナビットコインによる効率的な非等価化 (7. Catena: Efficient Non-equivocation via Bitcoin)
Uploaded: 2021-01-14T10:26:52.000Z
Duration: 1 h 21 min 19 s
Description: VoiceTubeの動画で発音を聞きながら英語表現を覚えよう！学べる英語：

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I'm a PhD student there in my fifth year.

And today we're going to be talking about one

And Catena is a really nice way of using bitcoin

And a lot of people have been using it to put data in it.

And if there is time, we'll talk about a tax and maybe colored

We'll talk about the what, the how and the why.

And that's the overview of the presentation.

So let's talk about this problem called the equivocation

In general, non-equivocation means saying the same thing

So for example, if you have a malicious service

should say the same thing to Alice and Bob.

Let's say s1, s2, s3 over time and Alice and Bob

So this is very similar to what bitcoin provides, right?

In bitcoin you see block one, block two, block three.

And everybody agrees on these blocks in sequence, right?

So this is non-equivocation and in some sense

what you might get is some of these statements

that this statement is a correct statement.

But it just guarantees you that everybody

And then they can detect incorrect statements.

You actually know that if this is a block,

it's a valid block, assuming there are enough blocks on top

So equivocation means saying the same thing to everybody.

So for example, this malicious service at time four,

he might show Bob a different statement than Alice.

This is what happens in bitcoin sometimes.

And that's how you can double spend in bitcoin

by putting the transaction here sending money to the merchant,

Suppose we have Jimmy and we have Jimmy's mom and Jimmy's

But he knows that mom and dad usually don't let him play.

So what he does is he tells dad, hey dad,

And let's say mom and dad are in different rooms

and they're watching soap operas and they're not

You know, mom can confirm that dad really said that.

And dad can really confirm that mom said that.

So you see how equivocation can be really problematic

go outside as long as the other person said that, right?

But let me give you a more practical example.

So let's look at something called a public-key directory.

A public-key directory allows you to map user's public keys--

Right, so here I have the public key for Alice

And they look up each other's keys in this directory.

And then they can set up a secure channel.

How many of you guys use Whatsapp, for example?

So the Whatsapp server has a public-key directory.

I look up your phone number in that directory

If that directory equivocates, the following thing can happen.

What the directory can do is it can create a new directory

at time two where he puts a fake public key for Bob

And at time two also, he creates another directory for Bob

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7.カテナビットコインによる効率的な非等価化 (7. Catena: Efficient Non-equivocation via Bitcoin)

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