Long-term safe storage of Bitcoins

[tinyapps]

If Bitcoins are stored long-term offline or on paper as described in these links:

How to set up a secure offline savings wallet
https://en.bitcoin.it/wiki/How_to_set_up_a_secure_offline_savings_wallet

Paper wallet
https://en.bitcoin.it/wiki/Paper_wallet

Offline USB/CD and Paper Bitcoin Wallets
http://bitcoinmagazine.com/offline-usb-cd-and-paper-bitcoin-wallets/

will they be useable forever, even after the various soft and hard forks we've been hearing about lately? Or is there some chance they could become unusable?

The reason I ask is this: After not firing up Bitcoin-Qt for a year or so, I upgraded to the latest version and had a bit of a scare when it initally reported all of my Bitcoins as unconfirmed:

https://bitcointalk.org/index.php?topic=150802.0

It took a 7GB+ download of the blockchain to restore them to my balance.

[vm1990]

yes there safe the bitchain keeps all info on bitcoins so in theory you could get 1 bitcoin not use the wallet for 5 years and then start from where you where 

[TradersEdgeDice]

I did this. Ignored Bitcoin for over a year. Various configuration changes.

20 minutes to review the latest changes in Bitcoin. 20 minutes to set up and get the money in my wallet reconfirmed.

[Tirapon]

I *think* that they're still safe, even in the event of a hard fork. If this were to happen, your coins would still be 'valid' on whichever chain survives the hard fork, as long as you upgraded to using whichever version of the protocol becomes widely accepted.  I might be wrong but in the event of a hard fork where both chains survive, I think you'd be able to spend the coins once on each branch of the fork?

If my understanding is correct (I'm still learning too...)

[tinyapps]

Thanks everyone for your replies!

Here's to hoping that we see an Illustrated Guide to Bitcoin from O'Reilly soon! 

[WorldOfBitcoin]

I *think* that they're still safe, even in the event of a hard fork. If this were to happen, you're coins would still be 'valid' on whichever chain survives the hard fork, as long as you upgraded to using whichever version of the protocol becomes widely accepted.  I might be wrong but in the event of a hard fork where both chains survive, I think you'd be able to spend the coins once on each branch of the fork?

If my understanding is correct (I'm still learning too...)

what is the difference from a hard fork and a soft fork?

is what we are going though now .7 to .8 considered a soft?

[theymos]

Not forever. ECDSA will probably become too weak in 10-30 years.

[tinyapps]

Thanks for your reply, theymos! I wasn't aware of this eventual pitfall and started digging around. This thread was especially interesting:

How long would it take a large computer to crack a private key?
http://bitcoin.stackexchange.com/questions/2847/how-long-would-it-take-a-large-computer-to-crack-a-private-key

and this link found there:

Why not use larger cipher keys?
http://security.stackexchange.com/questions/25375/why-not-use-larger-cipher-keys/25392

Any thoughts on this comment from http://www.schneier.com/blog/archives/2012/10/analysis_of_how.html#c929588?

Breaking ECDSA would only allow one to steal bitcoins that have been sent to an address which has sent coins already. This is because the public key of an address is revealed when it spends coins. Use a new address for every transaction and ECDSA flaws will not be a threat to your coins (eg it is astronomically harder to brute force BOTH the public key and private key).

[theymos]

That's true. If the public key hasn't been revealed, ECDSA can't be attacked. And Bitcoin's hash algorithms will likely last much longer than ECDSA.

[tinyapps]

Thanks again, theymos!

Speaking of long-term concerns with Bitcoin, have you read this critique?

On the fact that Bitcoin has a Kill Switch; and how to disconnect it.
http://www.loper-os.org/?p=1009

The basic thrust is that a very few individuals own the vast majority of Bitcoins, that they actively conceal this fact through obfuscation, and that they will "kill" Bitcoin at some point by flooding the market. (This last claim strikes me as rather remote - what possible gain could they hope to achieve?)

[tinyapps]

Looking for a definitive answer to the safety of long-term storage, I emailed Gavin:

Barring any unusual attacks/bugs, should a paper wallet essentially last indefinitely, enduring hard/soft forks, etc? Or is it conceivable that the coins could become unusable in the normal course of Bitcoins growth?

His reply:

No.