Can two computers use the same wallet keys concurrently?

[Schland]

I know I can't double money, but theoretically I think this should be possible, as a redundancy. Does anyone have experiences with that?

[jackjack]

Of course
And as one would use the money, the other one will see the transaction and know it can't use it anymore

[ct1aic]

I know I can't double money, but theoretically I think this should be possible, as a redundancy. Does anyone have experiences with that?

Greetings.

I exported the private key (encrypted) of my Bitcoin-wallet Android application, from my Galaxy S3, to Blockchain.info. From there, I exported the same private key, this time not encrypted, and imported it into the Multibit software of my windows laptop and my MacBook.

Now I can send BTC from any of this 4 places. The transaction appears in all places and the balance is updated also in all 4.

[telemeh]

I know I can't double money, but theoretically I think this should be possible, as a redundancy. Does anyone have experiences with that?

Yes, you can have the same wallet on multiple machines and all transactions will be visible from all of them.

[Stephen Gornick]

I know I can't double money, but theoretically I think this should be possible, as a redundancy. Does anyone have experiences with that?

The Bitcoin-Qt/bitcoind client does not handle a situation where you've double spent very well at all.   If you were, for instance, to spend from one client while a second was offline, then launched the second right after making the transaction then the second client wouldn't know of the transaction until either the first client re-broadcasts the transaction (perhaps not until an hour later) or else if the transaction gets included in a block.       So then let's say you make another spend transaction from the second client and if it uses the same coin as was already spent then that transaction will be invalid and will never confirm.

It gets worse, ... the Bitcoin-Qt/bitcoind client doesn't have any easy way to remove that invalid transaction that you've made.   So that transaction and any coins it used will be locked in a 0/unconfirmed status on the second client.

Additionally, the key pool will start to diverge between the two wallets.  So your balance on one client will eventually show different from the wallet on another.   And both will need to be backed up and kept separate.

So, in other words .. for most people, sharing a Bitcoin-Qt/bitcoind wallet among multiple computers ends up going badly.  

[ThomasV]

Of course
And as one would use the money, the other one will see the transaction and know it can't use it anymore

this is why you can use the same Electrum wallet on different devices.
Two Electrum wallets that have the same seed will use the same sequence of addresses, and remain synchronized on different machines, with no need to communicate.

[ct1aic]

Of course
And as one would use the money, the other one will see the transaction and know it can't use it anymore

this is why you can use the same Electrum wallet on different devices.
Two Electrum wallets that have the same seed will use the same sequence of addresses, and remain synchronized on different machines, with no need to communicate.

Interesting... I tried Electrum wallet, but I could not figure out how to import a private key... Tried several unencrypted formats (base 58, base 64, HEX, Bitcoin-qt), always the same error: The following inputs could not be imported...

UPDATE: I was using the wrong password. I could import the private key with the Bitcoin-QT format...