2. Money, Ledgers & Bitcoin

published on July 13, 2020

The following content is provided under a Creative Commons license Your support will help MIT OpenCourseWare continue to offer high-quality educational resources for free To make a donation or to view additional materials from hundreds of MIT courses, visit MIT OpenCourseWare

At ocwmitedu PROFESSOR: So today, what we're going to be doing is– last week, you gave us some feedback what you wanted to do in the class We're going to go through that and talk about the readings

I'm going to do a little calling on you and helping you take the class through the readings And then the six or seven things I'm going to do– history of money; ledgers; fiat currency, central banks, and credit cards; the role of money; some early digital money

You had the Clark reading as to a bunch of failed attempts All the way through a little bit of mobile money, all the way up to Starbucks and Alipay And yet, the riddle remains We're going to get really deep into Bitcoin in the next three classes

But this is to give some foundational bits of money and ledgers and central banking and technology And then, of course, I always like to finish the class talking a little bit about why we're doing what we're doing between now and then Even though the readings are required,

I know you're all busy I know that you've all got a bunch of classes And like good business students and business people, you optimize So I'm trying to give you a sense of why you might read it, rather than it's required, at the end of each class

And how it fits into the course narrative And then we'll do a little bit of conclusions So the survey results What did you want to learn? This is really your class, and I'm going to learn as much from you

But hopefully, we're going to cover what you want So here's a list of those things that were at least written by two of you First was technical things 18 of you said understanding blockchain technology Hopefully, we get to that, but you

Might find that you'll want to do more after this class The ecosystem and being able to have an educated discussion, sort of the dinner party conversation around blockchain I think we'll be successful But at the end of the semester, we're going to pull these slides up again,

And we'll see how we did as a group You all talked a lot about applications How can you actually apply it, learning in the venture space and thinking about where it really works in the world And I think we're going to spend a lot of time on that in the second half

But all throughout, we're going to be talking about the economics and what's the reality versus the hype You also wanted to understand its impact on people's lives, the regulation About six of you said something about regulation

I'm glad, because we're only doing one lecture on that But we're going to spread it out, because as we talked about in our first class– and I'm honored Larry's here again– but we're going to always be thinking about Larry's four ways

And I see– is it Jihei? What are Larry Lessig's– you shook your head yes AUDIENCE: I know– let's see It is code and architecture, market, law, and norms PROFESSOR: You got it

Does anybody want to say how that relates to blockchain, why we're chatting about that? Oh, my god, I'm going to have to cold call fast, right? You're from R3

Joe? AUDIENCE: No, I remember we saw it last class, but I can't relate it now to blockchain PROFESSOR: Can you relate it to anything in life? Maybe not Alan, help your tablemate out

AUDIENCE: I'm waiting for my moment to shine PROFESSOR: This isn't it AUDIENCE: This isn't it PROFESSOR: I'm having fun This is what I'm going to do I'm just going to have–

Don't worry about it So why do markets, code, law– I can't see your name, but is it ?? Yeah, why? Why does that relate to all this? AUDIENCE: Can you repeat the question?

PROFESSOR: Jihei, you're going to repeat the question, because you went through it AUDIENCE: So how does Larry's four forces relate to our topic of blockchain PROFESSOR: And the four forces, again, are market, so business; law; code or architecture,

Call it technology; and social norms AUDIENCE: So I think it's because it brings a new way of doing those things, like a new tool in order to– so what I got from the reading is these ledgers already existed, but given that now we have big data, for example,

Then more things going on helps our society roll it out better PROFESSOR: Good way to say it Look, it's unfair of me It wasn't one of the readings I'm just saying, in everything in life, I find these things grind up against each other

I spent a lot of time in Washington in politics, but the markets and how the commercial enterprise and the economy grinds up against technology and sort of grinds up against the law– and then, of course, just social normative behavior These four forces, in almost everything one does in life,

You will find And so I just ask you to always, whether it's one reading or another reading, bring that into your thought process of this class I'm not going to assign Larry's assignment I didn't know he was even going to be here

But I've always thought it's a good discipline to think, OK, what are the commercial realities, the markets? What's the technology, even if it's in an earlier day and it's the technology of the car replacing the horse and carriage?

How does government or the official sector put it into a set of standards that are required? And then how do we, as a society, even if it's not required, just have our behaviors? Those are the four forces

So that's why I probably just failed Larry's class, but that's how I've thought about it I did, probably, right? No, he's shaking his head But regulation is just one of those four forces

And that's why I pause there And so we'll have it in every class, but only one lecture Money and markets, that's one of the other forces Five of you said you want to make money, and I applaud those who said that, because own it You're in a business school

Why not? But investing and trends Now, there was a bunch of other miscellaneous topics I'm not going to go through them I kind of thought the last two were interesting– anecdotes from my past

I'm not sure who said that I'm not sure what you want to know about– my three daughters, my running, or this Wall Street stuff and finance And I'd like to understand hyperbitcoinization, as well, but I don't know who asked that question I don't know what it is, so I'll try

To figure out what hyper– does anyone want to own up to that question? They were anonymous All right All right So today's study questions

What's the role of money historically and in today's digital economy? And this is when I'm going to look for discussion So does anybody want to tell me what the role of money– what would be your answer to this? Anton?

AUDIENCE: The medium of the transaction, and the unit of– like a counting unit And also, the state of the value PROFESSOR: So the three classic rolls of money that people talk about Kelly, you want to repeat what he just said?

AUDIENCE: the question, but I think historically, it was pay off debts, starting and conquering various lands and wards, and then also funding trade wars, cutting taxes So a lot of societal things that drove civilization forward PROFESSOR: And what we'll discuss today

And what it is, is that money is a social construct It's something that societies came together– it's hard to tell whether it was 5,000 years ago or 8,000 or 10,000 years ago Really, it's a social consensus mechanism But we're going to chat about the readings in a minute

And come back to that question What is fiat currency? Does anybody want to– Tom, you want to tell us what fiat currency is? It's a shame, Tom See, I recognize you

AUDIENCE: This is like a established currency by a central government, by a government that proposed a market or PROFESSOR: Right So you said it's a central currency,

And it's by government Anybody else want to add some things? Is it Kyle? AUDIENCE: I would just add that it's not backed by any physical commodity PROFESSOR: So it's not backed by any physical commodity

AUDIENCE: Yeah Really just the good faith and credit of the nation that issues it PROFESSOR: Daniel, did you want to add anything? AUDIENCE: I was just going to say somewhere that it's not gold backed or anything like that

PROFESSOR: But was it always that way? AUDIENCE: It wasn't originally that way PROFESSOR: Right A fiat currency might be backed by something physical Was there other– remind me your name I'm sorry

AUDIENCE: Josh PROFESSOR: Josh AUDIENCE: Specifically used to settle debts, specifically those to the government, so taxes PROFESSOR: All right, so it can be used for taxes And remind me of your name, because I can't see a card

What? AUDIENCE: Sean PROFESSOR: Sean AUDIENCE: So, basically, there's no inherent value in fiat currency So basically, there's no one recognize

That specific currency itself There's no government PROFESSOR: So here's a question for the class Is there inherent value to non-fiat currencies? Because Sean's saying that maybe a distinguishing characteristic of fiat is it has no inherent value

AUDIENCE: Terry PROFESSOR: Terry AUDIENCE: Well, actually, the same applies to any commodity that's used to– currency in general

Because it's just the scarcity of some specific resource and social common agreement that that's going to be the parameter PROFESSOR: So how many people are more in line with Eric or– there's not one right answer to this This is a question that's been debated

For decades or centuries How many are more in Sean's camp? AUDIENCE: I think it depends For example, gold is definitely a social construct We decide that, as a human society, that gold is going to be something valuable

But if it's, like, grains that humans can and that, I think, has an inherent value So I think there are non-fiat currencies that does have inherent values and that does not have inherent values PROFESSOR: All right, anybody– what's your–

Jihi, yeah Tom? Tomas? AUDIENCE: Tomas I just want to say that the is another component which the fact that it is a legal tender

So the government and some forced the society to use the currency, which makes more comfortable for people to use PROFESSOR: So Tomas is saying that fiat currency is legal tender So first, we have to discuss, what is legal tender?

Does anybody want to knock that one out of the ballpark who hasn't raised their hand yet? No? All right AUDIENCE: I think that's maybe my earlier comment It can be used to settle debts, and specifically

Those to the government So you can use gold as a money It can be a stored value It can be a means of exchange But you can't pay your taxes in gold, right? You have to–

PROFESSOR: Is that correct? So 19th century, could you pay your taxes in gold in the US and in Britain and other countries that had gold currency? This is just a yes or no, but James?

AUDIENCE: It's yes, but after 1970s, the paper currency is attached to the gold standard So inherently, there is an exchange of value that is picked by the government or the central bank So it's almost one of the same thing at that time, until more recent years

PROFESSOR: James is saying you could use gold as legal tender Legal tender, again, is something that a society comes together and creates a law– back to the Lessig four Society together says– it's not just a social normative behavior

It's a law One must accept this And the US and the UK and many countries it says for all debts, public and private So a debt to the government or a debt in a store We're going to get to, later, as to when

Is it true that somebody has to take your cash But I'm going to hold off on that in a minute and talk about it But I think, also, Jihei said– it was somewhere between Sean and Eric, both physically in the class and in terms of her articulation–

That fiat currency might not have anything inherently behind it But gold mostly doesn't have anything inherently behind it And then some forms of currency, like grain, had more So maybe it's a continuum Maybe it's not black and white, 100% or 0%

And then we're going to talk a little bit about how Bitcoin fits into it And our next three classes are going to be really into the technology of Bitcoin, but just a little bit of teasing out before I go through some lecture slides

Who wants to talk about how Bitcoin might fit into this history of money? And then I'm going to return to that question in about 45 minutes and ask you again Does anybody want to say from the readings? And you remind me your name?

AUDIENCE: Isabel PROFESSOR: Isabel AUDIENCE: So with Bitcoin, it's kind of the same, where the value is given by society, except with Bitcoin, it's not backed by a central bank

So people don't think that there is an inherent value But the readings pointed out that there's sort of that same history, except it doesn't have PROFESSOR: So Isabel is saying that Bitcoin fits into the history of money because, like fiat currencies

And like Jihei said about gold, it doesn't necessarily have any inherent monetary value, but it's a societal set of norms that people are accepting it as having value But the key distinction that Isabel said was that it's no central

AUDIENCE: It's not backed by any kind of central bank PROFESSOR: It's not backed by a central bank or a central authority Alan? AUDIENCE: Yes So Bitcoin, in my opinion, is unique,

Because I think the value of Bitcoin changes over time, not the fluctuation that we see like $6,000 or $90,000, but in terms of the utility of the coin itself So today, for example, we might be able to buy pizza or coffee or whatever with Bitcoin, so there is an inherent value in terms of medium of exchange

And it will change as society adopts it more and more So I think it's hard to define if there is inherent value or not PROFESSOR: So Alan is raising that Bitcoin– if I can put some words in your mouth, and tell me if I'm correct, that Bitcoin

Might have some distinguishing features from even fiat currency, that its value is shifting over time with adoption Is that– I mean, you didn't use that word Please let me know your name again

AUDIENCE: Brotish PROFESSOR: Right Like British, but with an O, you told me earlier– Brotish AUDIENCE: Another way I was thinking of

The evolution of the later technology like accounting and the evolution of money, along with– so initially, we saw in the reading how it happened in the prehistoric age and then the advent of the and then later, which is kind of one of the fundamental blocks

Of Bitcoin PROFESSOR: Right AUDIENCE: So that is another way kind of natural progression of how money PROFESSOR: Brotish? AUDIENCE: Yeah

PROFESSOR: So what Brotish has raised is also Bitcoin fits into the history of ledgers, whether it's double entry ledgers as recognized through T accounts or other forms of ledgers, that it adds to this whole long history of ledgers I agree with that

And it's a new form of keeping ledgers Alan? AUDIENCE: So Bitcoin is also similar to gold There is an element of scarcity PROFESSOR: Of scarcity AUDIENCE: Yeah

So you cannot generate that many Bitcoin PROFESSOR: Correct AUDIENCE: You can only generate 50 bitcoins every 10 minutes, and it keeps happening every four years PROFESSOR: So it seems like scarcity and ledgers are important components

Aviva? AUDIENCE: Yes So it does have a fixed demand– sorry, a fixed supply, like you said, in terms of scarcity But the more we adopt it, the more it becomes divisible in terms of units

And so we can increase its use, because now you can divide them up to PROFESSOR: This is good So divisibility is another characteristic of money, scarcity, adoption as Alan said, ledgers Sorry, Tomas?

AUDIENCE: We mention decentralization, because this implementation make feasible the Bitcoin and makes feasible to implement this kind of thing in the decentralized environment So without any central authority to design or dictate the supply and all the aspects of the concepts

PROFESSOR: We'll take one more, and then I'll start to talk about the history Why don't we go here? And remind me your name AUDIENCE: Alexis PROFESSOR: Alexis

AUDIENCE: of like money and other forms of currency, even if it's controlled by central government or central bank, there's no fixed exchange rate It trades extremely quickly with other types of currency, so I mean, it's still very different

PROFESSOR: So, Alexis, if I understand Alexis' point, it's that there's no fixed exchange rate about Bitcoin we're talking about But couldn't we really broaden that to all forms of currency? I mean, what really is the exchange rate between an ounce of gold and a bushel of corn?

AUDIENCE: Yes and no I mean, yes, that, for example, some states do control exchange rates with other counties PROFESSOR: All right, good point So Alexis is saying yes and no, because some governments try to fix

Now back to markets How well does that work when governments try to fix an exchange rate? I mean, just as a sense of the class, does that work well? So it sort of might work well in temporal, short periods Works less well for decades on end

I'll take one more, and then I'm just– I want to go through a couple– AUDIENCE: Just one comment That way you can teach hours of work That's how economies define it previously, right? But I just want to ask, what is a ledger?

PROFESSOR: What is a ledger? Very good question I'm going to be chatting about that in a minute But does anybody want to hit that? I'm sorry No, over here

AUDIENCE: I was going to say, it's just a numerical record of everything recorded, in a fashion PROFESSOR: A numerical record I think that's a good thing A ledger is basically a way to record economic activity

Or social relationships or financial relationships I would say it's both a way to record economic activity, and it's a system of recording financial relationships And while I didn't assign these readings, some very good academic research suggests that the first methods of writing and symbols of writing

Had to do with numbers and had to do with ledgers, rather than words and communication Because it's so fundamental to society to record various economic transactions or to record the financial relationships amongst and between members of a community,

Whether it was a small village or when society burst out of villages thousands of years ago Does that help? We'll be back to it And better that you ask that here than in your accounting fundamentals class

I don't know So the readings– we've sort of talked about the readings How many of you actually watched the little three-minute video? What'd you think? I mean, just as a– I'm sorry, here

We haven't chatted yet AUDIENCE: I think the broad-based message was that any currency, or anything, for that matter, has value equivalent to what the society assigns it with Because the video basically just showed a guy who created his own currency and was just

Selling it to the public And his whole claim was that it is real if you believe it is real PROFESSOR: So it was just a nice little ditty, in a way Matthew, I'm sorry? AUDIENCE: I would have given him $1 for it

PROFESSOR: You would have given him $1? Great AUDIENCE: Seeing how much the pizzas went for AUDIENCE: Who knows? PROFESSOR: Would anybody else have given him $1 for it? No?

Oh, you would have? AUDIENCE: Actually, I'm working with local currencies And it's kind of the same, but you can use them just locally I mean, it keeps the money inside the community that decides to use that way of transactions PROFESSOR: We're going to refer back to each of these readings

As we go through the next 45 minutes Yeah? AUDIENCE: I was wondering if he was actually breaking the law by launching his own competing currency to the US dollar? Is that a legitimate–

Obviously, it didn't compete with the US dollar, but– PROFESSOR: You raise a very good question I'm not aware of any statute, federal or state, that says there's an absolute monopoly on forms of currency as there is in other things, like you know that slot in the door that's called the–

Where you can put a letter through the door or a mailbox? There's actually a law that says that the US Postal Service has a monopoly, and that's why UPS is not allowed to put their boxes or anything in there There's a government fiat monopoly But you raise a very good question

What we've found in the last 10 years with Bitcoin, with really oversimplifying, is that it is legal to create your own form of money, as Bitcoin is possibly this money But you have to comply with all the other laws And all those other laws that we'll talk about

In other lectures, in essence, fall into buckets of guarding against illicit activity, so the Bank Secrecy Act and all the laws related to anti-money laundering and terrorism finance and so forth One still has to pay your taxes if you're gaining or losing

On this investment The Federal Reserve and other authorities around the globe still want to insure for financial stability The fellow on the streets of– I don't remember what city New York?

Selling his dollars, when Matthew bought it for $1 and I think over here– Brianna? AUDIENCE: PROFESSOR: What's that? AUDIENCE: My name?

PROFESSOR: Yes AUDIENCE: PROFESSOR: Bought it The society's still going to be stable It's going to be all right But if millions of people were buying it,

Then people might worry And then there's the third big bucket that we look at is investor and consumer protection But I think it's allowed So we'll refer to these, Joaquin, and then I'm going to go on

AUDIENCE: Can you legally pay, for example, salaries in bitcoin in the US? PROFESSOR: Yes And why is it that you can legally pay for wages in bitcoin in the US? I know it's outside of the readings,

But why do you think it is allowed in this society? Is it Kyle? AUDIENCE: Wouldn't those compensation forms be allowed under any contract? PROFESSOR: Most things– you could pay somebody

In these placards I doubt, really, that you're going to value them much But you could pay somebody in this You could pay somebody in gold, euros, bitcoin And there are firms that are paying– usually, they're developing blockchain applications

And interestingly, they have to compute the value of the wages to do withholding taxes, because the US government will not accept taxes in bitcoin So they figure out the fair market value– and there are companies in the US that pay people in bitcoin who are doing development work

Around blockchain applications But the taxes need to be computed and analyzed and then paid in US dollars There was a legislative initiative in Arizona earlier this year where a state legislature wanted to have Arizona be the first state in the land

To accept bitcoin for taxes But it failed in committee It didn't even get a full vote of– I can't remember if it was the Arizona Senate or the Arizona House of Delegates

So just a little walk through the history I was going to do a little history of money and have some fun So in Ethiopia, people put together salt bars This is not that long ago Salt, as Jihei said earlier, is really valuable in society,

And they standardize the shape and size And so here's salt bars We're going to get to, a little bit later, all the characteristics of money But what else do you think a salt bar in Ethiopia, as opposed to maybe some other country–

What did it have, as well, as to why people might use that? AUDIENCE: Oil PROFESSOR: What's that? AUDIENCE: Crude oil PROFESSOR: Crude oil All right, I hadn't thought of that

I'm going to keep thinking about that It's not a common characteristic of money But why salt bars? What else might it have in Ethiopia? AUDIENCE: Are you going to say that you

Can use salt to preserver food? PROFESSOR: Well, you can preserve food, but because it was mined, there was some scarcity, as well And a lot of currencies, a lot of moneys over time, have that fundamental issue Cowrie shells from West Africa

Does anyone know the history of when cowrie shells got really debased and stopped being used, from the readings? I can't remember if that was in the readings or not They got debased when Europeans started

To realize that they were accepted as a value And it's a very sad and terrible history, too, because it's related to the whole slave trade But that the Europeans could figure out that societies accepted this as something of value, but they also debased that currency

And they debased the land and captured people as slaves It was quite a collection of not particularly good things going on Tally sticks in England Does anybody, from the readings– because there was a little bit of the debate in the first

Reading about the history of money– want to chat? And I'll pull up the Rai stones from Yap How this fits into that first reading and the debate between did money come from a history of barter, or did money come from a history of ledgers and credit,

Which is kind of a setup of that first reading? Any thoughts? Which ones of these four bits of money, early money, are more about maybe barter?

AUDIENCE: There are two theories, right? Debt, which corresponds to this one This was a way to measure debt PROFESSOR: Which one? AUDIENCE: The sticks

PROFESSOR: The sticks The tally sticks, yes, correct Which is the second one on here that has to do with debts, actually, and credits? AUDIENCE: The stones PROFESSOR: The stone, the Rai stones

So it's remarkable The Rai stones were so heavy that on this island of Yap, they couldn't possibly lug it around and use it in a traditional medium of exchange But it was viewed as, well, I have 1/6 of this Rai stone You have 1/16

And then if I make an exchange, we'd remember And the society was small enough to keep a form of ledgers, even to the extent that when a Rai stone was lost in a river, they said, you know, the river Rai stone, we each have this piece So on the island of Yap, I can assure you,

These stones could not be used for anything else Does anyone know, because it was outside the readings, what made these stones so scarce? So Rai stones were quarried on an island about 200 kilometers away from Yap, so were they exceedingly

Hard to get, like gold, like mining of gold What else is mined these days that might be a money? AUDIENCE: Lithium PROFESSOR: What's that? Can I hear everybody? AUDIENCE: I'm saying lithium

PROFESSOR: What's that? AUDIENCE: For batteries For batteries It's going to be very difficult in the future for electric batteries and whatnot PROFESSOR: But what's mined right now that's

At the center of this class? AUDIENCE: Bitcoin PROFESSOR: Bitcoin, right? The Yap stone was, in essence, quarried a couple kilometers away And what debased that currency was when sailors from England

Came There's a specific sailor– I think his name was O'Keefe– in the late 19th century, and he realized that these stones were valuable And he went to the other island, and he started quarrying

And came back and forth And within a few years, the whole economic system collapsed We moved to metal money At first, it wasn't really stamped It was just heavy

It was hard to quarry Bronze in Rome There was some China and Sweden These were starting to be stamped by the official sector And then we had minted money starting somewhere around 2,500 years ago

And there's debates as to whether it started in Greece or in China But where an official emblem was placed upon a scarce resource that was used Paper money came along, in a sense, for what reason?

Why did society first tip in to paper money? AUDIENCE: Because there's not enough gold to back it up I mean, like because there's– PROFESSOR: All right One reason is not enough gold I'm sorry, I haven't–

AUDIENCE: I think it's just easy to– PROFESSOR: Ease of use It's kind of heavy, especially if there wasn't gold and if it was copper or bronze It was just heavy Or if it was wheat, you'd have to put it in a storage unit

So the first paper monies from China were basically warehouse receipts And I spent five years running something called a Commodity Futures Trading Commission, and so I guess I learned a lot about warehouse receipts, commodity receipts, where you put a commodity in a warehouse

And then you got a piece of paper that said, yes, you have that commodity there So the first paper monies were basically warehouse receipts in China Because whatever it was– grain or gold And then you had a piece of paper backing it

These are five pound notes from England and the continental notes of the US But that note in China is about 700 years old But between that first paper money and the 18th century, who do you think we're kind of the first bankers in the late 17th century, early 18th century?

What craft had they been in before they were in banking? AUDIENCE: Trading AUDIENCE: Trading AUDIENCE: Trading PROFESSOR: Alpha? AUDIENCE: International trading

PROFESSOR: International trade They actually did something more local AUDIENCE: I just talked about this The ones that have lands and all the– the ones that have lands and all the

PROFESSOR: Lanes? AUDIENCE: Lands AUDIENCE: Land PROFESSOR: Land Land No, they had something else that they were doing

Tom? AUDIENCE: Printmakers PROFESSOR: They were printmakers I like that We're not there yet AUDIENCE: Money lenders?

PROFESSOR: What's that? AUDIENCE: They're underwriting insurance PROFESSOR: A little bit later AUDIENCE: They were doing agriculture? PROFESSOR: It's definitely outside of the reading They were goldsmiths

Some of the first dominant bankers in London, they were small goldsmiths And they took the gold, they gave you a piece of paper, and then they went from there And then, all of a sudden, they figured out how to do credit

Later in the semester, we're going to talk about Bitcoin credit It's not there yet, by the way I think in the next 18 to 36 months, we're going to start seeing cryptolending and cryptofinance in the form similar to what the goldsmiths were doing

In the early 1700s in England Alan? AUDIENCE: Is that scalable with a finite number of bitcoins, in your opinion? PROFESSOR: It's a very good question Is it scalable to lend against a finite currency?

I think so, but it's not done yet, right? AUDIENCE: Yeah, because when you lend money to someone, I guess it could be in the form of bitcoin But you lend someone dollars, they could redeem in bitcoin You'd be increasing kind of the money supply

So you don't need– you're not moving money around You're actually PROFESSOR: So this is exactly the central of commercial banking today It's called fractional banking

We'll be talking about that in a bit But yes, you could lend and then have a multiplier effect You also had, then, banks come up and started to issue private bank notes Private bank notes effectively a liability of that bank and saying it would trade

And the history of private bank notes is usually what? Good until it's really bad And the history of money, a lot of private banks went bust in this country around the revolutionary period, again around the Civil War And in essence, that's what we have now

With 1,600 different cryptocurrencies We have sort of a new period of a little bit of private currencies And I only ask you to remember that as we start to look at ICOs, Initial Coin Offerings, and so forth

So ledgers– the earlier question is, what was a ledger? You asked it Can you remember, what's a ledger? AUDIENCE: It's a way to record economic transaction PROFESSOR: There you go

Principal recordings of accounts And 5,000 years ago– you had a little reading on this, just a medium post It wasn't meant to be a deep economic, academic paper But it was to try to get the class thinking about ledgers This is the personal ledger of George Washington,

Our first president He was 15 years old when he kept this ledger And he apparently kept ledgers until his death in– let's see 52 years later

So ledgers could be kept just to record the transactions of the day He's got one up there– Mary Washington It must have been a cousin, or I can't remember if it was his mother

So if they're the principal recordings of accounts– and I've already sort of said this– they record economic activity and financial relationships Economic activity in a sense of transactions Financial relationships– what's a key financial relationship a ledger might record?

I'm sorry? AUDIENCE: Debt PROFESSOR: Kelly said it– debt And it goes back to the debate you had in the reading Is money a history of barter– did it come out of barter?

Did it come out of a sense of debts and credit and store of value? For this purpose today, it doesn't really matter It may have come from both But know that it has both sides And ledgers have both sides, too

And when we're talking about Bitcoin, Bitcoin, you will see, is a mechanism to store transactions Some other blockchains, like Ethereum, stores balances So even in the blockchain world, you will see some that are balance ledgers and some which are transaction ledgers, not

To lose you and confuse you It's an important part of what is blockchain Some types of ledgers I just mentioned one– transactions versus balance George Washington's ledger, by the way, I think was a transaction ledger

He was just keeping a list of sales and movements But I haven't studied President George Washington's ledger close enough Does anybody know enough accounting to tell me the difference between a general ledger and a subledger or a general ledger and a supporting ledger?

I mean, I don't want to do the whole lecture myself How many of you have taken accounting? Uh-huh I taught undergraduate accounting once Sorry So those of you who just put up your hand who took accounting–

Did I see, in the back of the room, did you take accounting? And that's Aviva AUDIENCE: I'm an accountant, actually PROFESSOR: You're an accountant? All right, all right Did you pass the CPA?

Oh, we have a Certified Public Accountant who's going to tell us the difference between a general ledger and a subledger AUDIENCE: So a general ledger is one that records all kinds of transactions Any kind of activity that takes place, you

Record in the general ledger And subledgers, you can call them as like a specialization So let's say if there's a salary to be paid, you have your salary subledger But it'll also go in the general ledger, and the other part of the transaction's

In the salary ledger Or if there's capital or if there's new stuff that you buy, so all of that goes specifically in the general ledger And each of them have their own specific ledgers If you want to say how much you spent on Saturdays for the month, then you go to your Saturday ledger

And see But if you want to see, overall, how much money you've spend and how much has moved around, then you look at your general ledger PROFESSOR: Aviva clearly said it better than I could have Thank you

Now we know we have one CPA in the class But the importance– it's not just a passing note The importance of a general ledger and subledgers is there is a hierarchy, as well Subledgers have more detail, and maybe the net number is kept in the general ledger

That is at the heart of our system of banking and is at the heart of our system of financial markets, where the central bank is like a general ledger for money, and every commercial bank, all 9,000 of them or so in the US, in essence keep a subledger for money But they do not have control of what

I will call the master ledger or general ledger at the Federal Reserve Then, a third distinction about ledger is a single entry A little, young, 15-year-old George Washington was keeping a single entry ledger–

Just a list of things that was going on And I didn't think I was going to bore the class with readings about double-entry bookkeeping, because you've taken accounting But does anybody want to tell me, other than Aviva, what double-entry bookkeeping– and she'll bail you out

? AUDIENCE: Double-entry bookkeeping basically means any transaction has two places in the lender– one on the credit side and one on the debt side Because every transaction involves one person lending, whereas the other person

Is getting the thing PROFESSOR: It works for me Anybody else want a different view? AUDIENCE: In other words, asset and liability two sites and then

To balance each other PROFESSOR: So there's a balancing between assets and liabilities, and then the resulting bit of capitalism in it is if assets are more than liabilities, the rest is capital So at the heart of capitalism, in a sense,

Is double-entry bookkeeping And in fact, while it probably goes back a little over 1,000 years, when it was truly written up by the Italians in the 1300s, it started to help Europe come out of the Dark Ages I mean, the commercial Renaissance of the Middle Ages,

Some would say, was in part– not entirely, but in part– on the backs of double-entry bookkeeping So ledgers matter is my point They're not going to be the heart and soul of this class, but Bitcoin, which is a transaction ledger, Ethereum,

Which is a balance ledger, our financial system, which is all set up on ledgers is a relevant sort of subtext You don't have to be afraid of it, just as you don't have to be afraid of hashing power that we'll be talking about on Thursday and cryptography You have to have some sort of basic sense of where

Does Bitcoin fit in, in terms of ledgers I didn't feel this slide in You'll find out it's blank Does anybody want to tell me what are some characteristics of a good ledger?

Because again, as you start to think about your blockchain projects later in the semester, it's like, what makes a good ledger? I don't have any answers here AUDIENCE: The bitcoin were immutable PROFESSOR: So you want it to be immutable, maybe

Thalita can you do me a favor and keep these? We'll put them on the slides We'll keep the class's list, and we'll put them in the slides Immutable, I like that Anybody else want to grab something which is a good ledger?

AUDIENCE: Time stamped PROFESSOR: What's that? Time stamped, all right, so that you know when you made your entry Kelly? AUDIENCE: Ownership

PROFESSOR: Ownership What do you mean by ownership? AUDIENCE: Essentially, the receiver and the person giving So essentially, who's taking what and who's giving what PROFESSOR: So if there's a transaction, the two counterparties to the transaction, right?

And if it's a balance, then who owns the balance? I was just adding a little bit Let's see if we have a new name or face Back here, on the back table I haven't chatted with you yet AUDIENCE: Ross

PROFESSOR: What is that? AUDIENCE: Ross PROFESSOR: Ross Thank you, Ross Good to meet you AUDIENCE: Pleasure to meet you, as well

Accuracy PROFESSOR: Accuracy So Ross says accuracy And can we take one or two more, just to– AUDIENCE: So a description of the transaction PROFESSOR: Andrew says a description of the transaction

And last, Mr ? AUDIENCE: Comprehensive PROFESSOR: What's that? AUDIENCE: Comprehensive PROFESSOR: Comprehensive So all good attributes of a–

Characteristics Somebody's burning desire that we missed one or two? Jihei? All right AUDIENCE: I just was curious Consistency, maybe?

But I don't know if that's– PROFESSOR: Consistency Well, I think that's inside of immutability, that, in essence, that it's valid, that you can't change it You can't counterfeit it and the like And what you'll find is the characteristics

Of a good ledger is also, in some part, similar to the characteristics of good money They're not identical, but they overlap a lot Payment systems– I'm just going to say one line about it It's a method, basically, to amend and record changes in a ledger for money

I know it's not what you usually think about a payment system But if you go into Starbucks and buy a cup of coffee and use your cell phone, aren't you really just amending a set of ledgers? Starbucks' ledger goes up, and yup, your ledger goes down Well, your monetary ledger goes up

Your utility, your fulfillment from that latte might go up I'm talking about the financial ledger So I just wanted to ground– when we talk about payment systems, think about it's really just a way to amend, usually, two parties ledgers'– one going up, one going down Now, in an earlier time, it was handing somebody a bit of gold

Or a bit of silver, and it was not recorded on central ledgers But we already live in an age of electronics, so this is really what a payment system largely is It's not entirely There's still some other ways to do finance

So what were some early forms of payment systems that did just that, that moved and changed ledgers? They're called negotiable orders I would dare say that most of you probably have not used negotiable orders of withdrawal that much in the last week or the last month

Has anybody here written a personal check in the last week? But in an earlier era, it would have been the whole class Anybody in the class not even have a checkbook? 3/4 of the class

Larry, how's that make you feel? AUDIENCE: Old PROFESSOR: But a checkbook is, in essence, with a– what do you put on a check? This is all about Bitcoin now

I'm not doing this just as a walk down memory lane for Larry and myself What are the important pieces of negotiable order, withdraw, or a check? AUDIENCE: Signature

AUDIENCE: Put your signature on it PROFESSOR: So there's a signature What else is there? I want to get to people I haven't talked to In the back I can't remember your name

AUDIENCE: Me? I'm Dana You put who you're paying to, how much, and what it's for PROFESSOR: All right, so there's a bunch So a signature, a payee, how much, and what it was for What else?

AUDIENCE: There's an account number and routing number PROFESSOR: Account numbers and routing numbers So think about it Account numbers and routing numbers is to say, in essence, what ledger is this coming from? And the payee is the ledger to whom it's going

And I'm sorry, Dan? AUDIENCE: Also a date, and a day PROFESSOR: So there's a timestamp, a signature, a payee, the payor in the form of the account number, and an amount Those five are really critical, and you'll

Find them all are going to be right in the middle of all this Bitcoin And then the reason why you're– you know, some other information I'm sorry, was there something else? AUDIENCE: Kyle

PROFESSOR: Kyle AUDIENCE: I just have a question Would you consider something like PayPal or Venmo like a negotiable order? PROFESSOR: They may be They may be new forms

They're certainly parts of the payment system They might not be negotiable orders to withdraw They might not be a direct authorization for a bank with one ledger to move money to another ledger They might be moving it on their own ledger

You're asking the right question So some early money that we already talked about that was ledger where the tally sticks in England and the Yap stone These were ledger types and forms of money and was kind of interesting

So ledgers didn't just come with electricity and computers So now let's get back to fiat currency, the heart of the earlier question We already talked about it, so let's see how the professor did, because you already

Said some of the things that you said were fiat currency One, social and economic consensus I'm in the school that it's just part of the history It's not that different than everything that came, even though it built on that promissory note from China 700 years ago and the private bank notes and the goldsmiths

In the 1700s But ultimately, governments took control It represents central bank liabilities, and that's important It's a liability of a central bank It's not an asset

It's their liability side But it's also– guess what? There's a second form of money And that's when you have a deposit in a bank, that's a liability of a commercial bank Central bank is the top gold standard, in a sense

Using the word gold, but it's the top ledger Commercial banks are like subledgers, in a sense Please, Alan? AUDIENCE: Sure I'm not an economist or anything, but what does it mean for a coin or a note

To be a liability of the central bank? What does that actually mean? PROFESSOR: So before I answer, does anybody want to try to answer what it is? Eric? AUDIENCE: Liability is basically an obligation to, in this case,

Pay someone an amount PROFESSOR: So because it's a social consensus, it's a very good question that Alan asked, is what does it mean to be a liability of a central bank when it's just the currency in our pocket, right? This Federal Reserve note, this says

Federal Reserve note on it We can pass it around I'm not afraid It's only $1 Right?

If you want me to pass around 20's, then I want them But it says Federal Reserve note, right? So it's a liability of the commercial bank In an earlier day, it said you could exchange it for gold or silver

AUDIENCE: Right, so that's what I don't understand PROFESSOR: By the 1930s, for retail deposits in the middle of the Depression, President Roosevelt said, no more You cannot redeem gold and silver And then President Nixon, in the 1970s,

Said in the official sector that he was going off of the– until that point in time, other governments could redeem in gold But when paper money started, it was not backed by gold We had a period of the gold standard We were on and off of it

We fell off of it during World War I We went back on it It would be a false narrative to say that we were on the gold standard for our first 140 years I just wanted to clear that up I mean, we sort of went on the gold standard, we went off,

We went back on, and so forth But it is a liability on the books and records So it is a matter of accounting in double-entry bookkeeping I will show you in a minute the balance sheet of the Federal Reserve, and I'll come back to this question

Is that all right? AUDIENCE: Can you clarify what is the bank liable for? So before, it gave me $1, and I could go to $1 and get back the gold, right? PROFESSOR: Right AUDIENCE: Now, what are they liable for now?

PROFESSOR: It is, in essence, a social– it's the first point I'm going to separate it The central bank is liable that they will move on its ledgers if you want to move that to somewhere else So you could take that physical $1 in and say,

I want to deposit this in a bank And they have to record it on the ledger of that bank That is what they are– and the US government, which is technically separate from the central bank– or the UK government or the Chinese government

They're all technically separate from their banks– People's Bank of China or the Bank of England Their governments are saying they will accept it for payments against taxes So there's a set of social constructs

I'm going to just go through this to answer your question It relies on a system of ledgers, and it's an integration of those ledgers between the banking system and the commercial banks In the US, we have about 9,000 commercial banks And what the Federal Reserve is saying–

But it's true about the People's Bank of China It's true about the European Central Bank Each of these central banks are basically saying, if you bring your paper money in, we'll record it on the ledger of a commercial bank And you can pay your taxes to our sister

Over here called the government I'm sorry to let you down It's not more than that Sorry, Alan AUDIENCE: I have a potential answer I might be totally wrong

PROFESSOR: Please, no AUDIENCE: I think it's a legal and sustainable way to conduct a Ponzi scheme with a proper Ponzi scheme, where the value will increase by 1% to 3% if the central bank reaches the goal of inflation PROFESSOR: All right, any other points of view on that?

I saw– I'm not sure of your name Oh, no, you don't want to say anything? No? All right AUDIENCE: I think I'll go back to point one It's a construct that someone would give you something

So your dollar with the central bank, the central bank owes you that dollar's worth of whatever you desire And someone will happily take that dollar from the central bank and give you the goods that you want So it's a roundabout way of– it's a way of transacting something, whatever value that dollar has

AUDIENCE: It's also central bank liability, because whenever the government has sovereign debt, it can't just issue new notes It's liable So that's why it's a liability, because you can only issue notes against a certain amount of reserves

That you carry So that's why you refer to it as a liability Because you can't just issue new notes whenever you need them You can't just make new money out of thin air So you're liable for every new note PROFESSOR: I'm going to take one more comment on this

And then give a couple more things Eric? AUDIENCE: The currency is actually a small part of the total reserves of the Federal Reserve System I think maybe the bank reserves are maybe

A more applicable application, because a bank can actually require the Fed to print money by making more loans So in that way, there's this mechanism to ensure that liability PROFESSOR: I'm very pleased with this discussion, even Alan's contributions about the schemes

This is the debate If Jay Powell were here– how many of you know who Jay Powell is? Who's Jay Powell? AUDIENCE: It's a lab PROFESSOR: Jay Powell

No Who's Jay Powell? AUDIENCE: Head of the Federal Reserve PROFESSOR: Head of the Federal Reserve Thank you Sorry

But if Jay Powell were here, he'd have a laugh along with what Alan just said, but he would say, also, the liability is a social liability, as well That a central banker, to their core, believes what they are trying to do

Is ensure for the stability of this social thing we call money and to make sure that it doesn't get debased and it has some value So it's accepted for taxes, we talked about Notes and coins are legal tender for all debts, public and private

I walk into a Starbucks and I say, I'd like a cup of coffee Here's my $5 or whatever it costs these days Does the person behind the counter have to brew the coffee? Is just a yes or no? Can I see?

Who wants to go for it? There's a no from Christopher What, Chris? There's a no from Chris Who agrees with Chris?

OK They brew a cup of coffee I go to the other side of the counter The coffee's sitting there Now, do they have to accept my $5 at that point? Yes

Before they brew the coffee, nobody has to take dollars But once a debt is established, they've produced the good, they've provided the service, they have to take it Just a small, little thing That's what legal tender is And so there's many establishments

Around the globe that are basically now putting little signs out, we don't take Swedish krona We don't take this We don't take that in paper form They'll still take it electronically And there's a new little bit of definitional thing

Going on about legal tender There's also some unique tax treatments, but I'm not going to go through the currency So central banking and money we talked about a little bit This is a kind of chart that I borrowed from somebody else's paper

But the central banks at the top is at the center And if Alice and Bob– and we'll be talking about Alice and Bob in Bitcoin time, so you can pull this chart down later– want to transact and they're at the same commercial bank, Bank Number 1, then commercial Bank Number 1

Has to change their ledgers, moving money from Alice to Bob In essence, if you're both two people at Bank of America, you can move your balance at Bank of America But if you're at Bank of America going over to Citicorp, then something has to go between two ledgers, Bank of America's ledger and Citicorp's ledger

And the only way to transact between two banks' ledgers is some balancing act has to happen at the top ledger, called the central bank And later, when we talk about payment systems– and I'm going to use this slide again later in the semester That's why I'm not going to spend as much time now on it

We're going to talk about ledgers And when you move money between two banks, it's all within one closed system– that country's or that society's central banking system But then it gets really a little bit more iffy and woolly when you're moving from one currency

To another currency Because how do you make two closed ledger systems operable? Not for today, but we'll go through that later when we do payment systems and the like The central bank, the US central bank– this

Was the only good slide I could find, which was about a year old Its liabilities and assets are about 4 and 1/4 trillion dollars, $43 trillion $17 trillion of that is in currency Do I get my $1 back, by the way?

I mean, my liability So $17 trillion of those greenbacks are in circulation And remarkably, even though half of you probably don't use cash that much, you don't even have checking accounts, the amount of cash in circulation is growing faster than the economy

In most developed nations Why do you think that is? What probably one word? AUDIENCE: The amount of 2008 crisis PROFESSOR: Oh, that's more than one word AUDIENCE: Trust

PROFESSOR: Drugs AUDIENCE: Trust PROFESSOR: Oh, trust I thought you said drugs Trust Well, it does have to do with trust,

But it also has to do with drugs Paper currency is a wonderful method of money laundering, drug running, and a store of value So there's certain segments of our economy and segments of the worldwide economy that does not want to be in the electronic banking system

I'm going to slip through these quickly, but there's another piece that we need for this whole class and for the semester is credit and credit intermediation But just a little thing– credit cards started only 60 or 70 years ago, but they go back to a book a little over 100 years ago

The word "credit card" is used 18 times in this book, where a science fiction writer in 1887 said, what would the world be like in the year 2000? And it was the first use of the word "credit card" And he said that society would have a form of money, and you would have credit against it

And it's a fascinating thing that somebody could be that visionary But there were merchant cards starting, so maybe he wasn't so visionary Oil companies in the 1920s, charge cards were starting, but they were single-merchant cards

You could have credit from that merchant In 1946, in a bank in Brooklyn, a guy named Biggins started with that That was the first real charge it You could charge things in a few dozen places in Brooklyn, literally

And then, all of a sudden, it took off Diner's Club started in the early 1950s They found that they could get a bunch of restaurants to say, wouldn't you want to extend credit, and we'll back it? American Express in the mid-1950s And then, finally, in the mid-1960s,

Bank of America, which at that time was a California bank, figured out they would create a co-operative with a bunch of other US banks to extend credit And the credit boom took off And what was interesting, the laws to regulate all this didn't come until the 1970s, at least in the US–

The Fair Credit Reporting Act and all the other laws There's three big ones in the 1970s I go to conferences sometime and talk about Bitcoin regulation, and they say, well, why can't the government solve this now? I sort of remind them that it took 15 to 20 years from the introduction of credit cards kind of in the early to mid

1950s and the real take-off in the 1960s– it was 1974, 1970, '77, the three big credit laws So if you're going to be an entrepreneur in Bitcoin, know that it could be 15 years until there's some cryptolaws in the future That was the processing machine from the 1950s

I made it too small, sorry Visa made it better And then, of course, that's what we all see today, how your cards get processed So the role of money we've talked about So I'm going to skip over that

But now the characteristics of money What makes a good money? We talked about some of this earlier It's durable, meaning that that salt cube wasn't the greatest, because if a lot of rain came, that would wash away Gold and silver, metals, are durable

They're portable The heavier it is, the less portable it is, and that's why gold was a better money than silver You could move it– and better than copper and bronze It was divisible easily

You could slice things up Uniform and fungible And anyone who's who down the rabbit hole on this stuff, if you really want to learn about money, read about Crawford versus Royal Bank in 1749 There was a gentleman at the early part of paper money

That mailed two 20-pound notes, and he wrote his name on them They got lost in the mail, and he took the banks to court to say, those were mine, when they were found And there was no law in Scotland or in England at the time as to what to do about it But if you lose or somebody stole a piece of art,

You get it back And the law was settled in 1749 that you actually don't get your money back Does anybody want to guess as to why the courts– it was a matter of first interpretation The courts had no jurisprudence on this before 1749

Why did the courts decide that a piece of art was different than currency? And it goes to the fundamental of what money is, fiat money is Anybody want to take a guess as to why the courts– they could have gone the other way

AUDIENCE: How could you tell if someone really owned money? How could you ? PROFESSOR: He signed it Actually, the facts were clear it was the currency he signed I'm just helping you out so that– that's a good point, but he signed it

AUDIENCE: It can't be used as a medium of exchange if it doesn't belong to the person PROFESSOR: In essence, if you were to go back and read– there's some history on this, and read the court cases This was the point

The court basically said, we have to make this a medium of exchange, the greater social good It has to be fungible And the Royal Bank of Scotland was, of course, kind of closer to the courts than this gentleman, Crawford

But the banks were also saying, we can't keep track of this So it was a mixture of the two, but it made it fungible Eric? AUDIENCE: Was it those specific notes that he had signed ? PROFESSOR: Yeah

Yeah AUDIENCE: PROFESSOR: And in 1749, they all had serial numbers, and they were signed in a way that not today Of course, they're acceptable, and they're stable And we're going to talk a lot about the last point

They're stable because they're hard to mine, and Bitcoin has that embedded in it, as well The design of money is really important, as well You can make it a token– a token is like something physical– or account based

We're of course now living in a world of account-based money, and it's digital, not physical It can be issued by the private sector, just like banknotes in the 18th century, or private sector like Bitcoin, or it can be central

It can be widely acceptable or just wholesale There are forms of wholesale money One of the biggest forms of wholesale money is the central bank's reserves are only available to the commercial banking system We're going to study this money flower later,

But I put it in the slides because this– I didn't create this flower You have a reading later in the semester from the Bank of International Settlement that has this money flower in it But it's basically across these four things–

Is it token our account based, physical or digital, private or central, or widely accessible? And then all monies fall into one piece of this money flower There's a Professor Garrett that came up with this flower, and there's an optional reading later in the semester from him

You had a reading from Clark There's not enough time, but all this stuff failed Does anybody want to give me a flavor for one or two reasons why a bunch of digital cash failed? Did anybody read the Clark reading, the history of some DigiCash?

Oh, Alan read it Anybody else read it? Over here I can't remember– AUDIENCE: Zhan PROFESSOR: Don

So what did you– AUDIENCE: Zhan PROFESSOR: What? AUDIENCE: Zhan PROFESSOR: Zhan Zhan, what did you take from the reading?

Why did these all fail? What's the one or two biggest reasons they failed? AUDIENCE: Most of them still relied on kind of some form of a central authority PROFESSOR: All right, they relied on central– DigiCash certainly did it, David Chaum's case,

And some of the others Any other big reason? Alan, did you have– AUDIENCE: There wasn't enough adoption by merchants, I recall PROFESSOR: Definitely not adoption by merchants

Very good Third reason why they failed? One that's at the core of what Bitcoin solved AUDIENCE: Incentivizing like a decentralized network to keep that ledger, maintain the ledger

PROFESSOR: All right, incentivizing the ledger Behind Eric AUDIENCE: They couldn't solve the double spend problem PROFESSOR: That's it Couldn't spend the double spend problem Could a currency be spent not just once, but twice?

So there's four things that were raised Four things about centralization, the double spend They couldn't get merchants to adopt it, and there was couldn't– some form of consensus as to what the ledger was

I'm going to flip through these quickly, but digital and mobile money did happen We were asked about PayPal earlier It was 1998 In Norway, Ericsson and Telenor had the first mobile app And it was to get movies on your mobile phone

1999, Alipay comes along that we'll talk a lot about when we do payments later And of course, M-Pesa that we talked about a little last week in Kenya, where Safaricom noticed that a bunch of money– near money It was mobile minutes that was being used as money in Kenya,

And now there's 20 million users of that And of course, there's a bunch of regulations now and so forth Starbucks started in 2011 And then, of course, it's now off to the races in mobile money

One of the key things about mobile money we will discuss and learn together is the question each one of these is, where is the stored value? And I have to tell you, sometimes I get quite confused when I research a new app

Are they storing the value? Or are they just a processing provider to move– as we said earlier, payment systems move and change and amend other ledgers In a number of these, like M-Pesa, initially they were storing the value

And mobile apps Starbucks stores the value But many of them are just applications, computer code, to move the ledger somewhere else But the riddle remained You remember that riddle– how to move money peer to peer without a central authority

And that's what I'm asking for next class, Thursday, to actually read I wouldn't wing it, and I wouldn't be afraid of it Satoshi Nakamoto wrote a paper that everybody in this class– if you're at MIT, and a few of you are at Harvard

I'm telling you, you can read it You'll understand maybe 1/2 to 2/3 of it It's not deeply technical And it's only eight or nine pages I've also assigned National Institute

Of Science Technology, about 20 pages of reading from NIST The question is whether that's Bitcoin I'm going to skip through the study questions, but the study questions are really about cryptography and how append-only timestamping We are going to get into the nitty-gritty over three

Lectures I couldn't commit the whole course, the whole semester But I think three lectures– Thursday and the two next week Anytime you want to come to see me– Sabrina is somewhere here on the floor, who's

One of our TAs, who's a computer science master's student and knows more about all of this Madores, who was here last week– I don't know if Madores is here, who's part of the Digital Currency Initiative Over three lectures, we're going to try

To work through what's the cryptography, and why does that matter? How does the time stamping happen? How's this look like money, and how are the transactions kept? Yes? You get to close it out, almost

AUDIENCE: Can you just answer the question posed about the longest running blockchain? PROFESSOR: I can answer that, but the assignment was to answer it by Thursday, right? AUDIENCE: Oh, Thursday OK

PROFESSOR: So by Thursday What's your first name? AUDIENCE: Caroline PROFESSOR: Caroline Did I say I was going to answer it today? AUDIENCE:

PROFESSOR: Oh, did I say today? No, is there a mutable record of what I said? I'll answer it now if you want Does anyone have the answer in the whole class? AUDIENCE: Yeah It's a service called Surety that Gillespie

Begun working in 1995, was a timestamp service for digital documents And the way they did it was use a hash function to create a seal with a timestamp on the document And then present the weekly batch of seals And they actually published it in the New York

Times PROFESSOR: So Caroline, it's good to raise the question I thought it was for Thursday, but thank you Stewart Haber, a cryptographer, and a colleague at Bell Labs in the early '90s, said, how do we notarize information, digitally notarize?

And we're going to be talking about this Thursday a lot They used a cryptographic method called hash functions And they were just trying to notarize information And by 1995, they took– they were entrepreneurs They created a company called Surety

And once a week, they published, in the New York Times– and they still do it You can get a New York Times– I believe it's on Saturday or Sunday And they take– it's in the classifieds section And they have the hash function, which you'll read about

Between now and Thursday They have the hash of all the pre-existing information And so they timestamp it by using the New York Times, and they use cryptography And it's currently 23 years in running AUDIENCE: So that's the longest in terms

Of time, not the longest with how many ledgers or how many– PROFESSOR: Correct, because Bitcoin is about 550,000 blocks, and this would be whatever 23 years times 52 is Longest in time Thank you

I look forward to seeing you

Related Videos

24. Conclusion

1 year ago
The following content is provided under a Creative Commons license. Your support will help MIT OpenCourseWare continue to offer high quality educational resour...

23. Digital ID

1 year ago
The following content is provided under a Creative Commons license. Your support will help MIT OpenCourseWare continue to offer high quality educational resour...
The following content is provided under a Creative Commons license. Your support will help MIT OpenCourseWare continue to offer high quality educational resour...
The following content is provided under a Creative Commons license. Your support will help MIT OpenCourseWare continue to offer high quality educational resour...
The following content is provided under a Creative Commons license. Your support will help MIT OpenCourseWare continue to offer high-quality educational resour...
The following content is provided under a Creative Commons license. Your support will help MIT OpenCourseWare continue to offer high quality educational resour...
The following content is provided under a Creative Commons license. Your support will help MIT OpenCourseWare continue to offer high-quality educational resour...
The following content is provided under a Creative Commons license. Your support will help MIT OpenCourseWare continue to offer high quality educational resour...
The following content is provided under a Creative Commons license. Your support will help MIT OpenCourseWare continue to offer high-quality educational resour...
The following content is provided under a Creative Commons license. Your support will help MIT OpenCourseWare continue to offer high quality educational resour...
The following content is provided under a Creative Commons license. Your support will help MIT OpenCourseWare continue to offer high quality educational resour...
The following content is provided under a Creative Commons license. Your support will help MIT OpenCourseWare continue to offer high quality educational resour...
The following content is provided under a Creative Commons license. Your support will help MIT OpenCourseWare continue to offer high-quality educational resour...
The following content is provided under a Creative Commons license. Your support will help MIT OpenCourseWare continue to offer high quality educational resour...
The following content is provided under a Creative Commons license. Your support will help MIT OpenCourseWare continue to offer high quality educational resour...
The following content is provided under a Creative Commons license. Your support will help MIT OpenCourseWare continue to offer high quality educational resour...
The following content is provided under a Creative Commons license. Your support will help MIT OpenCourseWare continue to offer high-quality educational resour...
The following content is provided under a Creative Commons license. Your support will help MIT OpenCourseWare continue to offer high-quality educational resour...
The following content is provided under a Creative Commons license. Your support will help MIT OpenCourseWare continue to offer high quality educational resour...
The following content is provided under a Creative Commons license. Your support will help MIT OpenCourseWare continue to offer high quality educational resour...