Topic: My bitcoin wallet address - Mine forever? (Read 6670 times)

Your answer to number 2 is wrong! Please don't answer unless you know what you are talking about!

@OP: If bitcoin-qt is your bitcoin client you need to take regular backups. Old backups won't restore your wallet 100%. The reasons are as follows:

a) Change addresses as Birdy has explained above.
b) New addresses that you generate. I think bitcoin-qt also generates new addresses itself from time to time.

The accepted wisdom seems to be that you backup your bitcoin-qt wallet every 100 transactions.

If you want a wallet that you can restore easily I suggest switching to a client with a deterministic wallet. Something like electrum (electrum.org).

Your wallet is actually made up of many addresses.  So you need to differentiate between "wallet" and "address".  Each time you do a transaction your wallet can generate a new address and send your remaining bitcoins to that.  So your wallet will grow as it adds more addresses and it is possible that an old backup won't have all the addresses that you have your coins at.

Bitcoin-qt may have an option to keep reusing the same address.  Then you won't have to worry about that.  I use electrum and it has that option, it's nice to have.

1. Yes, unless you give someone your private-key.  Then they can use your address.

2. Will be the same, just wait for the blockchain to update on your computer.

Thank you both for the info, very helpful. 

Your first question is tricky to answer, because wallet software isn't what core Bitcoin is.

Understand that Bitcoin works based on public/private key pairs that are cryptographically linked. You start with a private key which is a 256 bit number - a really really big number, so big in fact the chance anyone else randomly picks your same number is infinitesimally small even if they make thousands of guesses per second for years. The private key is what gives permission to spend/send bitcoins and only you know it; so if you lose it you lose that ability. So the answer to your first question is yes, any address you generate is yours forever as long as only you know the private key.

However, the Bitcoin wallet software you use generates new addresses for some transactions and when you click to generate new addresses. These addresses are taken from a key pool (containing 100 keys by default) so if you make a backup which knows all of the addresses in your key pool, but then do 150 sending transactions, for example, your wallet software will replenish the key pool back to 100 with some keys your backup doesn't know about. It will use the oldest addresses first, but if you ever receive coins to one of the addresses not in your backup and your computer crashes then you lose those coins. That's why it's good to refresh your backups periodically depending on your usage patterns. Here is backup advice from Gavin:


You might check out that thread on the subject anyway if interested as it may be cool to read a thread Satoshi actually participated in

1. Some wallets create new adresses every time you create a transaction. But old adresses are reusable (Note: This is only true for local wallets! Some websites give you other adresses every time!).
When you create a backup of your wallet, you backup the key to the adresses, so it will work only for adresses you have at that time.
Every coin send to this adress is aviable, if you have the key. It doesn't matter when it was sent.

But attention: When you have 2 BTC on your wallet and you send 1 BTC to somewhere, all wallets will send the whole 2 BTC and some (like the bitcoin qt client) will create a new adress for the 1 BTC change (-> you need a new backup or send this to one of the other adresses)!
This is kinda like actual banknotes/coins, you have them in the value that is sent to you and you need to spent it all+receive change back.

I have downloaded the bitcoin client and the client has synced with the network.  I have made a few transactions with my wallet, both inbound and outbound.  I have also encrypted my wallet with a password. I have also backed up my wallet, locally, and also emailed it to my gmail account.  Two questions...

1. will the wallet address that I have used in the past continue to be mine forever? Or will it change after X number of transactions?

2. If I backed up my wallet 2 months ago, then made several more transactions after the backup, then my PC crashed, then restored from a 2 month old backup, would my restored wallet be 100% exactly the same as the one that crashed? Would I have the transactions that occurred after the backup?