Bitcoin Q&A: Public Keys vs. Addresses

What is the difference between public keys and addresses? How are new addresses generated? How are change addresses generated? Why have two outputs? Do you still pay fees if you are sending bitcoin to new addresses in your own wallet? What is the VanityGen command? What does the SIG_HASH flag do?
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Chapters
0:00 What is the difference between public keys and addresses?
0:57 If my wallet automatically generates a new address for each transaction, will bitcoin previously sent to me on a different address be transferred to the new address just generated? If someone is going to send me funds to a previously-used address, will I still receive them?
3:54 How can we generate a new address to receive change?
4:17 Why not have a single output with the exact amount of BTC, instead of two outputs, one of which is change?
5:17 Do transactions with multiple inputs and one output pay a fee, even if the wallet is just reorganizing funds?
7:00 Can you explain the VanityGen command? What is a vanity address?
10:55 SIGHASH_ALL is for signing all inputs and outputs. How can all inputs be signed with one signature, when each of the inputs have a different private key?
These questions are from the MOOC 9.3 and 9.5 sessions which took place on March 2nd and March 16th, 2018 respectively. Andreas is a teaching fellow with the University of Nicosia. The first course in their Master of Science in Digital Currency degree, DFIN-511: Introduction to Digital Currencies, is offered for free as an open enrollment MOOC course to anyone interested in learning about the fundamental principles.
If you want early-access to talks and a chance to participate in the monthly live Q&As with Andreas, become a patron: / aantonop
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Andreas M. Antonopoulos is a technologist and serial entrepreneur who has become one of the most well-known and respected figures in bitcoin.
Follow on Twitter: @aantonop / aantonop
Website: antonopoulos.com/
He is the author of two books: “Mastering Bitcoin,” published by O’Reilly Media and considered the best technical guide to bitcoin; “The Internet of Money,” a book about why bitcoin matters.
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[@BitcoinOnlyCentral]

The fact that andreas has only 147k subscribers let’s you know how truly early we still are.

[@prakhargupta2113]

isolate2elevate I don't think he will amass a huge following He is no fluff. That doesn't sell well

[@niklasb3365]

That only shows how dumb humans are...

[@johncandlewick6561]

no, its just lets you know that people dont really care about the tech only about money. i care about both

[@Tobyee]

*196K now, but still so early.*

[@LClarke]

I have never listened to anyone so smart, yet _so very adept_ at explaining technical concepts in such an understandable manner.

[@yohan9747]

OMG! I've spent days trying to find information on the topic of addresses and all is here explained clearly. Liked and subscribed!

[@JoeKazemi]

This is very insightful and helpful. Thank you so much.

[@desther]

Andreas is so amazing speaker. I can listen to his talks all day and i always learn something new.

[@wesleyashley99]

I think of it like this. The public key is what ties together all the generated addresses where you receive from others who send to those multiple addresses. So the public key is like your home address. You don't want people who send you stuff to know where you live so you give them a PO box address. Thats like a wallet address. It ends up at your house which is like it being connected to your public key.

[@livingbeings]

Looking forward to your upcoming Joe Rogan appearance

[@Shadow_-ry6km]

Thanks for that information

[@siewanoatelek4081]

Thank you professor Andreas :-)

[@Sion_6EQUJ5]

Thanks Andreas! You are the best!

[@guillaumepato7423]

Very clear

[@doffmancrypto162]

Thanks for the info.!!

[@surendrashekhawat4155]

I didn’t understand a thing 😒 he didn’t talked about uses of private key and stuff?

[@bitmau5]

What happens when I use multiple wallets? How do I consolidate all of my transactions?

[@cooldog60]

I did not label some of my address and keys for some tokens. How can I tell which is the addresses and which are the keys?

[@dark_joo19]

Do I have to pay a higher fee when I send 1 output out of various inputs instead of sending 1 transaction from 1 adress? Thank you for your answer in advance, I really like your videos!

[@dark_joo19]

Infected exe Thanks for your answer! What do you consider a low fee for a transaction?

[@nion456789]

Smashed the like.....

[@cryptowelt]

how can i generate a vanitiy adress and be sure that is safe?

[@nion456789]

First....nice explination.......:-D

[@ruia3157]

Hi. Bitcoin addresses changes every time you receive a transaction. But for other crypto assets (Ethereum, etc.) the address stays the same. how do we can change the addresses for other crypto to stay with privacy like in bticoin? thanks

[@bartoszs6156]

do I need to make kyc when I buy crypto wallet like trezor or ladger? and if no, does cryptowalets providers match my public key with my personal details like name, address, ip... ???

[@Garfi28]

The parent public key, chain code, and the index number are combined and hashed with the HMAC-SHA512 algorithm to produce a 512-bit hash. This 512-bit hash is split into two 256-bit halves. The right-half 256 bits of the hash output become the chain code for the child. The left-half 256 bits of the hash are added to the parent private key to produce the child private key. Why is this last step needed? why not just take left-half 256 bits of the hash as child private key?

[@michaelsane6136]

Especially with Vanity address creation, wont we run out of possible addresses? How many possible addresses can there be.. 58 to the power of 58?

[@splazukeen3924]

2^160

[@vishnuvarma8019]

Is there a vanity gen command in the Bitcoin client or is it the website only that provides it? And if so, is it legitimate????

[@Chris-zu4es]

if I generate a watch only wallet will it show all my addresses together or will every new address be separate?

[@seniarosadeoliveira473]

how do I generate a bitcoin wallet address from a public key ?????????????????????????

[@TheMiamiTiger69]

Can somebody give this man a microphone and some egg cartons for echo dampening?

[@brainstillalive4213]

i have 1 question sir, Suppose transaction A of .5 btc and transaction B of 20 btc. is A and B both transaction will use same mining power if not why the fee is same for both.

[@pcgurupontro]

because it implies the same amount of miner work; same puzzle solved for 0.000001 BTC as for 100000 BTC. Percentage fees are used by banks, crypto is a different world

[@brainstillalive4213]

pcgurupontro thanks

[@thirdnormalform]

Is it likely that someone could create public / private keys with a CPU array and then scan the blockchain, waiting for a user to move coins to an address where a private key is known?

[@gianluca.g]

thirdnormalform it is happening right now. It's called brainwallet mining. Try to create a wallet from a very weak passphrase and send some funds to it... it will be emptied in seconds

[@thirdnormalform]

Gianluca Ghettini follow up question, should a typical user worry about losing coins in this manner if they have a proper pass phrase? Thank you!

[@gianluca.g]

a proper seed is a true random 256 bit private key, any wallet (both software and hardware) will take care of that

[@hasanadnan1100]

Can the vanity addresses be reversed ,I mean finding the private key by using graphic cards to try private keys?

[@daktak07]

As Andreas said at the start of this video, you cannot derive public key from address. And connot derive private key from public key.

[@ziomanzo]

He is very good! Keep teaching us👍

[@Lesmas]

It looks like you've provided a Bitcoin address. Is there something specific you'd like assistance with regarding this address?

[@kennethstauffer9220]

could the old hack of using floating point rounding errors to steal bitcoins? what numeric encoding is used for fractions of bitcoins is used?

[@michaelsane6136]

Accept BAT in Brave Browser for your KZbin Channel and other sites.

[@illam11]

Michael Sane How to get bat

[@leapbtw]

oh boy did this not age well, 10:50 i genned a vanity address with 8 chars in two hours with my 5800X lmao

[@themanofpower12]

How can I get the public key from the bitcoin address?

[@zoomjohnson9046]

did you ever find out?

[@wesleyashley99]

He answers this at 0:40

[@chetandosco]

I love you andreas but i didnt understand anything. I think i should just give up and buy Doge

[@nowygold]

Welcome Poland

[@dereenaperi2381]

Hi Andreas could you help me get my Bitcoin address.

[@iamlove7096]

Does anyone understand what you talk about?

[@martinezjames83]

Hell no

[@illam11]

I have a doubt If I can count 0 to 2^256 can I hack any bitcoin coin accounts 🤔

[@alexsloan4976]

Yes, but you can’t count to 2^256

[@davef5916]

So basically vanity addresses are ridiculously irresponsible from an environmental/energy consumption point of view.