Is your upgraded client "up to date"?

Your balance will show as zero if it has ended up re-loading the blockchain until it gets to the point when you "acquired the coins" (i.e. it might just "come good" if you wait).

Also - "don't panic" and make sure that your backups are kept intact.

(and yes - use blockchain.info to check the balances of individual addresses to verify whether or not any coins have *moved*)

There is only *one fee* and it is calculated according to a formula that depends upon the "size of the tx" (due to the number of *inputs* and *outputs*) and the *age/amount* of the inputs.

Basically the bigger the tx is (in terms of bytes) the more fees will have to be paid (and there is a *maximum size limit* that is currently 1MB).

(I hope your question isn't because you are trying to work out how to send thousands of 0.00000001 BTC outputs as "spam" for advertising)

For "cold storage" this is never going to be an issue - tx sizes are an issue only when one is trying to be a "wallet" (such as Armory).

Also a QR code can actually handle a fair amount of data provided that your cam is good enough quality (at least 4K is no problem at all from my own practical experience).

You *can't* print *fake Bitcoins* full stop.

Anyone thinking you can doesn't understand Bitcoin.

Guys - the "who is right and wrong" about this is really "not important" (apart from perhaps yourselves).

The sane advice is that you "don't accept 0 confirmations" for anything that you can't *also reverse* (such as web-hosting).

(the whole "I'm right and he's wrong" stuff is really just rather *boring*)

Assuming the website does what "it says it does" it still cannot "undo a confirmed tx" (only a 0 confirmation tx).

So the basic advice of "don't use 0 confirmations" remains.

I didn't check - but even if they are not in existence "today" that doesn't mean that they won't be readily available "tomorrow".

I think that varies from "client to client" (the protocol won't stop it - but you'll end up with "stuck txs" due to the dependencies).

From memory the most recent versions of "bitcoin-core" won't use unconfirmed "inputs" (but don't quote me on that - as I am not 100% certain).

Not surprised - which is why accepting 0 confirmations is "not a smart idea" in general.

Yup - the easiest way to "game" is to send a tx with "no fee" (that has reasonably aged inputs and a not too tiny output amount) through the "normal channels" (which looks legit but has "low priority") and then send the same tx with a "fee" (and of course a *different output address*) directly to a "friendly mining pool" (i.e. one that prefers fees over no fees) very shortly afterwards.

It is always possible to "game" 0 confirmations - so yes you are taking the risk of getting played if you do this.

Of course this depends upon "what you are selling" (if it is a service like a VPS you can always *switch it off* when the payment later fails - but if it is a "coffee" then you "probably don't want it returned after it has been consumed").

Small re-orgs (of 1-2 blocks) do happen fairly often but generally don't involve such "tx replacements" (although that of course *could happen*) this is why you should care about confirmations (the more valuable the tx the more you'd generally want to wait).

If I was say accepting BTC for something as valuable as a *house* then I'd probably want to wait for 100 confirmations (although maybe you think that would be "going overboard").

For a face-to-face situation involving even a few thousand dollars I would be basically happy with just a couple.

Perhaps the "wording" used in blockchain.info could be better (i.e. "double-spend attempt" vs. "double-spend").

Of course until at least 1 confirmation has occurred it is impossible for them to identify which one is the one that "will go through" (apart from perhaps guess by looking at the tx fee which would not have helped in this case - but they should probably change the wording after x confirmations as the other is never going to confirm then).

Note that https://blockchain.info/tx-index/65484044 has 47 confirmations (so it is a *real* tx) whereas https://blockchain.info/tx-index/65484042 has no confirmations (and is never going to get any unless Bitcoin has a major disaster).

Yes - the term "double spend" seems to imply that someone "spending the same BTC twice" has been recorded in the blockchain (but no such event has or *can* occur - because if it *could* then Bitcoin would be *pointless*).

What the term is generally referring to is a "double-spend attempt" whereby one tx spending certain UTXO's can end up being "replaced" by another (most usually when 0 confirmations have occurred - and in fact I'm not aware of any such events happening when there was 1 or more confirmations although potentially that might have happened we had the "fork" back in early 2013).

The easiest way to perform such an attack is to provide *no fee" in the initial tx and provide a "generous fee" in the "replacement tx".

Depending upon how you do this it can be actually successful (and is not so hard) so it is never advised for vendors to accept zero confirmations (especially those without any fee).

You might want to take a look at CIYAM Safe https://susestudio.com/a/kp8B3G/ciyam-safe.

Although not (yet) so user friendly it does let you do 100% air-gapped offline tx signing (i.e. you just use QR codes to do all the "comms").

For the "offline" computer I specifically bought an old laptop (without WiFi) and further *mangled* it to prevent it from ever (at all easily) being "connected" to the internet.

BTW - it also uses GPG (and QR codes of GPG encrypted data) to let you safely keep "back ups" of your "encrypted offline keys" on your "online system".

Agreed and there are mods trying their best already to "clean up the mess" but their job has been made very hard by the ad-sponsored posts (this was all discussed in another thread - maybe someone would be kind enough to find that and link it here).

I am not against "freedom of speech" (i.e. would never try to people stop posting because of political content that some governments might not like). I just don't think "freedom of speech" == "freedom to spam".

I am in HK now and man walking down Nathan Road (yes - poor choice of location I'll agree) is a bit like reading this forum (at every corner some guy trying to hassle you to buy a watch or some other thing).

I'm not angry at all - just trying to point out that the line "just hit ignore" when you see post after post of crap is "not very useful advice".

Stop being a *dick* then (you might think you're *terribly clever* but everyone *adult* here does not).

Yeah - very funny (not).

Some people think "freedom of speech" actually means *freedom to be a dick*.

I don't bother with the Ignore (from memory I only have one person on that) - my point is that if I wanted "to rid my eyes of all the rubbish" then I'd be using it for most of the forum members (as most now are just ad-sponsored rubbish posters as has been discussed in another topic).

I am not "easily offended or annoyed" but it is "tiring to bother reading topics that just have posts with *no purpose*" (as I am very sure will start happening with this topic as the ad-sponsored posters start adding their effective "+1" posts).