I don't think I'm understanding your point. The public key is safe for to be used in as many transactions as you want - it's designed for that and does not diminish the security of your key.
In the event of ECDSA being *cracked* (perhaps something that could occur in the future via Quantum Computing) then it could be feasible to determine the private key for any published public key.
As a bitcoin address itself is a hash of the public key (rather than the public key itself) your bitcoins are safe from such an attack *provided* that you do not reuse an address that you have published the public key for (which you will have if you've used a previous UTXO from that address).
So although it may be unlikely that the ECDSA used by Bitcoin will be *cracked* any time soon it is an extra level of safety for you *not* to reuse addresses.
Thanks for the added detail, this makes sense. To replay it:
- the address isn't really a key - its a hash of a key. So it is meaningless for attacking by itself.
- you can receiving coins at an address without exposing your public key
- you can't send coins from an address without exposing your public key
- so once you've sent coins, your public key could be cracked
- but we all generally agree that cracking ECDSA is extremely unlikely and certainly decades away
True?
So, since we do generally agree that ECDSA is safe (see also:
http://bitcoin.stackexchange.com/questions/2847/how-long-would-it-take-a-large-computer-to-crack-a-private-key), does this really matter? Isn't this kind of like putting on sunblock when indoors at night?
Thanks,
Mike