Should websites refuse to send coins to an already used address?

[1000000]

I think most of us know that address reuse is a bad idea and it's better to use a unique one for every transactions to avoid security and privacy issues. If a website owner accepts bitcoin deposits and a user wants to withdraw coins to an address which was already used in the past, should there be a warning or even an error message or would that be too annoying for the user?

I'm curious about your opinions!

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[achow101]

I don't think so. There are many legitimate uses for reusing an address. For example, many people on this forum have tip jar addresses. A lot of people also use web wallets. If those services began blocking used addresses, then those with tip jars may not be able to get tips.

[c-cex-finch]

Doesn't make much sense blocking used addresses, all recurring payments or repeat payments to an address just wont work. For one-off transactions it might make sense but I think the onus should lie on the user (my personal opinion).

[gmaxwell]

Warning about it, at least, would be productive-- as there has been a fair amount of loss from people accidentally using the wrong address (in addition to the other ways reuse causes systemic harm).  If you mean "already used" ever, then prohibiting it requires a forever growing database, which isn't all that scalable.

A middle ground would be warning (or refusing) any that the site itself had previously sent to; and I think there was general agreement to do that kind of warn on (wallet local) reuse in bitcoin core in the past.

[RocketSingh]

I don't think so. There are many legitimate uses for reusing an address. For example, many people on this forum have tip jar addresses. A lot of people also use web wallets. If those services began blocking used addresses, then those with tip jars may not be able to get tips.

I think, the Address re-use problem refers to spending. One may receive as many times as they want without any issue.

[SFR10]

It's better to use a unique one for every transactions to avoid security and privacy issues.
- Honestly I have to disagree with you as this makes the whole process a lengthy one due to the fact that each address should be created each time for every single transaction


If a website owner accepts bitcoin deposits and a user wants to withdraw coins to an address which was already used in the past, should there be a warning or even an error message or would that be too annoying for the user?
- If the address was used in the past by a different IP address then yes, there should be some sort of warning of "This address was used before with the following IP" and on top of that for the user to be able to use the same address, there should be some verification system implemented upon getting the said error

[Envrin]

I don't believe it's something the core dev team should worry about / implement, no.  I think it's something best left up to the market, and individual merchants / online operations.

Everything I develop has generates a new address for every transaction by default, but sometimes clients will want things like change sent back to the originating address.  I explain to them why the practice is discouraged and so on, but at the end of the day, it is their business and they can do what they like.

[belcher]

You realize "leaving it up to the market" could ruin bitcoin's privacy. That's what "systemic" harm means. The damage doesn't just go to the individual but to the entire system.

[jacee]

I think most of us know that address reuse is a bad idea and it's better to use a unique one for every transactions to avoid security and privacy issues. If a website owner accepts bitcoin deposits and a user wants to withdraw coins to an address which was already used in the past, should there be a warning or even an error message or would that be too annoying for the user?

I'm curious about your opinions!

Well I don't it's a bad practice. Bitcoin is anonymous and so does the bitcoin address we use( for some). I think reusing the same address all over again makes it more secure for both party, let's say as a proof of ownership. Just like how it works in a staked address here in the forum, same thing as in a website, it also proves ownership or in a transaction to someone else. It proves that you are still the same person that uses the same address. Someone can claim to be that person yet can't use the old address so ye, I think the address is like a signature that proves who really is doing the transaction.

[Wintermute]

I think most of us know that address reuse is a bad idea and it's better to use a unique one for every transactions to avoid security and privacy issues. If a website owner accepts bitcoin deposits and a user wants to withdraw coins to an address which was already used in the past, should there be a warning or even an error message or would that be too annoying for the user?

I'm curious about your opinions!

Well I don't it's a bad practice. Bitcoin is anonymous and so does the bitcoin address we use( for some). I think reusing the same address all over again makes it more secure for both party, let's say as a proof of ownership. Just like how it works in a staked address here in the forum, same thing as in a website, it also proves ownership or in a transaction to someone else. It proves that you are still the same person that uses the same address. Someone can claim to be that person yet can't use the old address so ye, I think the address is like a signature that proves who really is doing the transaction.

Bitcoin is not anonymous. The transaction history reveals a lot about addresses and connections between addresses.

Re-using addresses is bad from a security and anonymity point of view:
1) it reveals more about the owner of the address
2) when doing a transaction the public key of the address is revealed - this means that the additional protection layer by the hashing algorithm is gone

But forcing anything up on the user, is not the right way to do things. Wire transfers are less anonymous than cash, but still there are a lot of use cases why people prefer wires.

[Envrin]

You realize "leaving it up to the market" could ruin bitcoin's privacy. That's what "systemic" harm means. The damage doesn't just go to the individual but to the entire system.

Understood, but again, I believe that's up to the individual users / merchants / market.  Everyone has a different usage for bitcoin, and some people don't mind their privacy being compromised in exchange for a more user-friendly system.  If your primary aim is privacy, then you should know how to do it, as it's not difficult to setup intermediate addresses for incoming funds, then split-up and bounce those funds around the blockchain enough times to skew where they went, before they hit your actual wallet.

[medUSA]

I understand there are advantages of having one-time addresses. There are also good reasons to reuse addresses if the owner do not need the extra privacy. Reusing an address should be a choice made by the recipient, not forced upon by any website or the network.

[Delek]

I may sound paranoid, but the creation of a new address shouldn't never be done online and automatically. Creating a new private key every time you spend gives me chills.

[Hugroll]

i would say no, but im probably biased. personally i like to use 1address so that i can see easily the transactions that came in and out. if i had to replace my address everytime i used it thats just not organized enough for me 

[cellard]

I think that the wallets should have a way to automatically generate a new address each time so the average Joe doesn't get an headache and can still enjoy the increased privacy of not reusing addresses, but still have to option to reuse an address if you want to. Overall we need to simplify the functionality of stuff like this thinking on the average consumer which will not understand (and will not bother) with anything deeper that isn't clicking send, receive and whatnot.

[NeuroticFish]

I think most of us know that address reuse is a bad idea and it's better to use a unique one for every transactions to avoid security and privacy issues. If a website owner accepts bitcoin deposits and a user wants to withdraw coins to an address which was already used in the past, should there be a warning or even an error message or would that be too annoying for the user?

I'm curious about your opinions!

Reuse of an address is the sole business of its owner. It's a matter of choice, for most people simplicity is the most important.
So imho, while talking about a coin that's about freedom.. asking about banning / blocking the freedom of choice is absurd.
Hence my answer is clearly NO! No blocking!

A warning can be done, because it helps the users learn and get more aware of what their choices mean. But that's all.

[letsplayagame]

I think most of us know that address reuse is a bad idea and it's better to use a unique one for every transactions to avoid security and privacy issues. If a website owner accepts bitcoin deposits and a user wants to withdraw coins to an address which was already used in the past, should there be a warning or even an error message or would that be too annoying for the user?

I'm curious about your opinions!

Reuse of an address is the sole business of its owner. It's a matter of choice, for most people simplicity is the most important.
So imho, while talking about a coin that's about freedom.. asking about banning / blocking the freedom of choice is absurd.
Hence my answer is clearly NO! No blocking!

A warning can be done, because it helps the users learn and get more aware of what their choices mean. But that's all.

Privacy matters a lot to me but so does free will. This answer seems appropriate.

[unamis76]

The website obviously should not refuse it, in my opinion. That's basically refusing a withdrawal... And that could raise suspicion and it's just not the right thing to do. That would also be discriminating Bitcoin addresses...

I'm definitely thumbs up for a warning tho

[gmaxwell]

Reuse of an address is the sole business of its owner. It's a matter of choice, for most people simplicity is the most important.

Pedantically, the reuse of address harms third parties... and the decision to send coins is the sole business of the sender. I don't think you can answer this questions with simplistic reductions to arguments about free choice: there are multiple people involved in the question, and their free choices may conflict.

I may sound paranoid, but the creation of a new address shouldn't never be done online and automatically. Creating a new private key every time you spend gives me chills.

New addresses can be generated without generating new private keys.

Monero, for example, has no address reuse at all in the blockchain-- it's required for the prevention of double spending there. It seems to do okay with it.  The original bitcoin software never addresses w/ pay-to-ip; and even with addresses in use it the practice of reusing is somewhat inexplicable from a technology standpoint: it _really_ screws up your privacy along with that of people you transact with, and you can't reliably tell which of the payments you had outstanding were confirmed.... I think if it had been realized that people would behave the way they do, it likely would have been prohibited in the Bitcoin system from the start.

[I make these points as points of correctness, not to further argue it-- I think warning is more prudent, and will also have the effect of educating on this matter).

[Delek]

New addresses can be generated without generating new private keys.

Monero, for example, has no address reuse at all in the blockchain-- it's required for the prevention of double spending there. It seems to do okay with it.  The original bitcoin software never addresses w/ pay-to-ip; and even with addresses in use it the practice of reusing is somewhat inexplicable from a technology standpoint: it _really_ screws up your privacy along with that of people you transact with, and you can't reliably tell which of the payments you had outstanding were confirmed.... I think if it had been realized that people would behave the way they do, it likely would have been prohibited in the Bitcoin system from the start.

Two more.questions regarding to that:
1) It was known how to generate a new address without a ptivate key back in 2009? If I'm right, this comes from a modern BIP (deterministic wallets)
2) I don't care about privacy, I prefer to have a working Donation address all the time rather than being 100% a ghost. :p

[bitbaby]

I think most of us know that address reuse is a bad idea and it's better to use a unique one for every transactions to avoid security and privacy issues. If a website owner accepts bitcoin deposits and a user wants to withdraw coins to an address which was already used in the past, should there be a warning or even an error message or would that be too annoying for the user?

I'm curious about your opinions!

Websites don't need to babysit it's users and worry about their privacy and the security concerns of re-using an address which as of now afaik are none cmiiw and I don't think there is any need for websites to implement a warning or any such feature, maybe in future when we have quantum computers we need to worry about such things.

[gmaxwell]

Two more.questions regarding to that:
1) It was known how to generate a new address without a ptivate key back in 2009? If I'm right, this comes from a modern BIP (deterministic wallets)

I invented it in 2011: https://bitcointalk.org/index.php?topic=19137.msg239768#msg239768  as a response to people reusing addresses because they didn't want to have private keys online. It was later standardized as BIP32.

2) I don't care about privacy, I prefer to have a working Donation address all the time rather than being 100% a ghost. :p

You may not currently care, and its your right to screw over your future self (which you may well be doing)-- but reuse also harms _other_ users in Bitcoin, who do care about privacy, and this degrades the fungibility of coins; since coins which are linked to this or that party are clearly different, and differently valuable than coins which are linked to other parties or are not linked.

[Delek]

reuse also harms _other_ users in Bitcoin, who do care about privacy, and this degrades the fungibility of coins; since coins which are linked to this or that party are clearly different, and differently valuable than coins which are linked to other parties or are not linked.

If that's so harmful for Bitcoin why there's was never prohibited in Core?, I mean, the address reuse should be disabled if you are 100% right. 

Btw, how do we can have working donation addresses this way? Only using it for sending the inputs to another random addresses? 
"Mined addresses" (vanitygen) are harmful then too? 

This is very shocking for me. 

[philipma1957]

I think most of us know that address reuse is a bad idea and it's better to use a unique one for every transactions to avoid security and privacy issues. If a website owner accepts bitcoin deposits and a user wants to withdraw coins to an address which was already used in the past, should there be a warning or even an error message or would that be too annoying for the user?

I'm curious about your opinions!

I don't want to be anonymous so I use the same address. Over and over and over.

Can you explain to me how this is harmful?

Don't tell me if everyone did this no one would be anonymous as that is not particularly harmful.  IMO


I want  a public repeatable addy.

I realize I can have a wallet with hundreds of addy's if I want or I can use one over and over and over if I want.

I suppose some people want to remain hidden via changing of addresses so let them change every time.  Or let them have a common address that repeats over and over and over plus a set of hidden multi addresses.

[makcik]

Bitcoins address are used for sending and receiving bitcoins from one wallet to another, so I think Websites should send coins multiple times to one address as person may use same address twice for transaction. If websites don't do , people will obviously get loss, which is not correct. As bitcoins address are allotted to one wallet, and one wallet is usually to one person.

[bob123]

I dont think they should do that.

This just would be so unuseful for payments made each week/month.

[virtualx]

Some websites create a new bitcoin address to deposit every time. Users can always change their bitcoin address on sites, even on bitcointalk. I don't think there is a reason to force the users. However, I agree with Delek and generation of bitcoin addresses should never be online.

[Erkallys]

I don't see why they should do such a thing. Some people have their own personalised address, doing this would make those address obsolete. Also faucets pay users to a single address that plays the role of user's account. Also if you apply this, they won't be enough addresses for everyone until 2030.

[cr1776]

I don't see why they should do such a thing. Some people have their own personalised address, doing this would make those address obsolete. Also faucets pay users to a single address that plays the role of user's account. Also if you apply this, they won't be enough addresses for everyone until 2030.

There are 2^160 addresses, the sun will expire before bitcoin "runs out" of addresses.

It is best practices to not re-use addresses, but people are free to do as they wish.  Some places may require a new one, others may not.

[Erkallys]

I don't see why they should do such a thing. Some people have their own personalised address, doing this would make those address obsolete. Also faucets pay users to a single address that plays the role of user's account. Also if you apply this, they won't be enough addresses for everyone until 2030.

There are 2^160 addresses, the sun will expire before bitcoin "runs out" of addresses.

It is best practices to not re-use addresses, but people are free to do as they wish.  Some places may require a new one, others may not.

I was not aware there was so much available addresses. I think that 2^160 is enough for the whole humanity .

[Alphabit]

Well this is a very informative post. Just when I thought there were too many address, I know better now reading though it all. My practice is to change the addresses it can be a little complex at times to keep check of all. My suggestion and practice is to list them on a spreadsheet.   

[btckold24]

isnt their some sites like gambling sites that when you deposit you have to get the money back to that wallet? I remember a site saying dont send btc from a wallet you cant access cause we have to return the btc to that wallet in which we received it from.

[alrachid]

I think most of us know that address reuse is a bad idea and it's better to use a unique one for every transactions to avoid security and privacy issues. If a website owner accepts bitcoin deposits and a user wants to withdraw coins to an address which was already used in the past, should there be a warning or even an error message or would that be too annoying for the user?

I'm curious about your opinions!

I dont even see an option to change my address anymore in coinbase so I would be greatly upset if someone wouldnt send me my coins because I have to use that addy atm.

[EngiNerd]

As others may have mentioned, wouldn't this practice completely eliminate sites like FaucetBox (and with it a significant amount of faucets)?

In my opinion, faucets and platforms like FaucetBox are a great tool for introducing people to bitcoin. Without them I think getting started in bitcoin becomes much more difficult. Some of you feel that the security implications are severe enough to warrant mandating more complex requirements on address management, but I think others here aren't so sure it's worth the tradeoff.