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The context is on this section: “What if the input and output amounts don’t match?” of this page: http://www.coindesk.com/information/how-do-bitcoin-transactions-work/

I find it strange as it seems that reusing address is a bad practice (https://en.bitcoin.it/wiki/Address_reuse). (i.e. When Person A makes a transaction with Person B, then Person A makes a transaction with Person C, there should be two different addresses (instead of one) from Person A involved.) Or does the “address” here actually mean bitcoin wallet?

Aqqqq
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many different transactions tied to a particular bitcoin address

The sentence refers to the fact that the address can be involved in many different transactions. This is most likely seen with the address working as a receiving address, or destination address. For instance, imagine that you want to have an address posted in your personal website where you receive donations from people. It would be tedious to change it every time you receive a transaction.

As you already mentioned, reusing an address is not usually a good practice, since it could involve some privacy issues. By using a different address each time you perform a payment, you make it harder to link different bitcoin addresses owned by you (however, not impossible). By using always the same address when paying you make way easier for a third party to analyse your behaviour, based on where you are sending bitcoins.

Finally you should not mix up Bitcoin address with wallet. Think in a wallet as a collection of tools that let you manage your Bitcoin address (or addresses), such managing public/private keys to create transactions. What is said to be a bad practice in the Bitcoin wiki is referring to use the same Bitcoin address multiple times. The wallet is a collection of tools, the Bitcoin address will be more like an endpoint.

sr_gi
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  • So the "address" in "many different transactions tied to a particular bitcoin address" really mean bitcoin address, but in the context of bad practice? – Aqqqq Feb 18 '17 at 19:20
  • You should not mix up wallet with address. A bitcoin wallet can hold multiple addresses, actually it usualy does. Bitcoin Core wallet for example creates a new address every time a transaction is performed to get the change returned, if there is change. That is: imagine that you have 2 BTC in address A1 form a single previous transmission, and you want to transfer 1 BTC to address B1. You should send 1 BTC back to yourself, otherwise it will be treated as fees (that is normally done to a new generated address, for example A2). – sr_gi Feb 18 '17 at 21:09
  • So the "address" in this context should be "wallet" instead, am I correct? – Aqqqq Feb 19 '17 at 14:48
  • No, unfortunately you are not, it means Bitcoin address. Think in a wallet as a collection of tools that let you manage your Bitcoin address (or addresses). What is said to be a bad practice in the Bitcoin wiki page you provided is referring to use the same Bitcoin address multiple times. The wallet is a tool, the Bitcoin address will be more like an endpoint. – sr_gi Feb 19 '17 at 18:17
  • Sorry I am confused. What does "many different transactions tied to a particular bitcoin address" really mean if it is not referring to the bad practice involving using the same bitcoin address multiple times? – Aqqqq Feb 19 '17 at 20:37
  • Forget for a moment about the bad practice. Imagine that you can only have a single Bitcoin address. Then, all the transactions in which you will be involve will be tied to that address. Now, if we take into account the "bad practice" consideration, it is not recommended to reuse addresses, but this do not mean that you can't do it. Hence, many different transactions can be tied to a single address. – sr_gi Feb 21 '17 at 20:55
  • Nice! Is that all? – sr_gi Feb 22 '17 at 08:36
  • Yes (for now at least). It was a misunderstanding to begin with. – Aqqqq Feb 22 '17 at 08:45
  • @Aqqqq: If this post answered your question, please accept it, so that the question no longer gets bumped to the frontpage periodically. Otherwise, please update your question to further clarify what information you're looking for. Thanks. – Murch May 20 '17 at 18:45
  • @sr_gi: Comments are supposed to be for transient information only. Please edit your post to incorporate the relevant bits from the comments. – Murch May 20 '17 at 18:47
  • @Murch Sure, we extended the discussion so much. I've updated the answer. – sr_gi May 20 '17 at 19:03
  • @Murch Thanks for the reminding me. I upvoted your answer as well. – Aqqqq May 22 '17 at 16:07
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The section is simplifying to make the topic easier to access. Unfortunately, it is not being consistent with its simplification. This results in conflating wallets, users, and addresses as well as transaction records, transactions, and transaction outputs making the section confusing and borderline wrong. Also, "Jane" is a user or address first, then a transaction input. First transactions are being spent, then there is talk about inputs and outputs out of nowhere. It seems to me that the section should be rewritten.

  • Of course Alice could actually be only using a single address, but as you've noted this is not recommended.
  • People are however not spending transactions, they are spending transaction outputs (also see What is an “unspent output”?)
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Murch
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