<p>They could be lost in a few rare scenarios. For example:</p>

<ul>
<li>If substantial weaknesses are found in Bitcoin's crypto, or if quantum computing becomes usable on a large scale, your coins could be stolen. Most likely, the crypto will simply be weakened and attacks will still be very slow, so you'll have some time to send your coins to new addresses that use improved crypto.</li>
<li>When you go to redeem your coins, your CPU may err in a way that causes Bitcoin to send your coins into oblivion. There are no known cases of this actually happening, but CPUs are not perfect, and it is possible.</li>
<li>If Bitcoin develops critical scalability problems, and nothing else solves it, one "nuclear option" for improving things would be to require everyone to "renew" their coins every few months (or whatever). Old coins that that aren't renewed would be destroyed. If this policy is implemented, you will have to follow it. You'd have plenty of warning if something like this was approaching.</li>
</ul>

<p>To protect yourself against these things and other possibilities, you should:</p>

<ul>
<li>Not store too much in any one address.</li>
<li>Not send huge amounts at once.</li>
<li>Never send <em>from</em> any high-value address more than once. The best way to do this is to only pay to an address once.</li>
<li>Make sure that you're able to access your wallet with only a few days of notice.</li>
</ul>

<p>There isn't any value in moving coins before you need to.</p>

CC BY-SA 3.0
2013-10-18T00:39:42.620Z
2013-10-18T00:39:42.620Z
theymos
<p>Sounds to me like you are taking good care of your Bitcoins, so you should be able to sleep easy at night.</p>

<p>Of course, there is always a risk that your account could be hacked through a scam.</p>

<p>Bitcoin is the realm of technophiles, so always be careful when conducting transactions. The sad truth is that there are some scammers out there looking to hack into accounts. And as they are often very bright, there is always a risk that you could be tricked.</p>

CC BY-SA 3.0
2013-10-18T12:01:42.820Z
Your answer misses the point here: Since he created his key offline there is no risk that the funds could be accessed through hacking/scam since they are literally not accessible from his day-to-day computing equipment.
Murch
CC BY-SA 3.0
2013-10-18T15:40:31.277Z
Hey boss, my assumption is that he will still be conducting some trading and activities online. Correct me if I am wrong, but he will have to reload the bitcoins no? Also, if he used a flash drive, then he used his fingers to type, and there are spyware programs out there that can and will read what you type.
BTC_Hamster
CC BY-SA 3.0
2013-10-18T16:15:50.507Z
The asker wrote "I'm pretty sure I'm not touching that wallet for a long time." as in, he will not be conducting trades and activities with this particular wallet. Of course some point in the far future he will re-import his private key to access his funds, but before then, the situation is such as he described in detail: He keeps his private key offline in two different usb sticks and two paper copies. While these types of storage pose their own security risks, they definitely cannot be attacked by hacking or scam.
Murch
CC BY-SA 3.0
2013-10-18T16:25:26.220Z
Also he wrote that he created the wallet *offline*: If he went about that in a sensible manner, he did that as follows or similarly: He disconnected his machine from the internet, booted it with a clean live cd, created and backed-up a new wallet, then shut down the computer again. That way only a hardware spy-tool that stores information through shut-downs could have sniffed out anything, which I find implausible.
Murch
CC BY-SA 3.0
2013-10-18T09:31:14.140Z
2013-10-18T09:31:14.140Z
BTC_Hamster
<p>I'll go through your question clause by clause:</p>

<blockquote>
  <p>I've made an offline address</p>
</blockquote>

<p>You're doing good.</p>

<blockquote>
  <p>and only have the key stored on 2 encrypted flash drives stored in different locations </p>
</blockquote>

<p>As long as only you know the password and the password is sufficiently strong, this is <em>probably</em> secure.</p>

<blockquote>
  <p>with the private key written physically on paper and stored in 2 locations. </p>
</blockquote>

<p>If either of these two locations are accessible by anyone other than you, then they are vulnerable. If someone else found either paper, and your keys are in plain text, then you could consider them compromised.</p>

<blockquote>
  <p>Do I ever have to worry about my coins? </p>
</blockquote>

<p>Yes.</p>

<blockquote>
  <p>That is, could they ever be lost in software changes </p>
</blockquote>

<p>Extremely unlikely, as the whole of Bitcoin depends on the safety of balances through upgrades. There are people who have very vested in ensuring that this never happens. Even a bug in the protocol could not erase history in an unrecoverable way, as a single offline client copied online or bootstrap.dat would refresh anyone affected.</p>

<blockquote>
  <p>or is that as big of a never-going-to-happen as the 21 million limit being lifted? </p>
</blockquote>

<p>Pretty much.</p>

<blockquote>
  <p>I'm pretty sure I'm not touching that wallet for a long time. Is there any benefit to repeating this process for a more "fresh" address ever or does that not make sense?</p>
</blockquote>

<p>Theoretically, you would never need to regenerate keys unless some kind of vulnerability was found in the software that generated your key, ala the <a href="http://arstechnica.com/security/2013/08/google-confirms-critical-android-crypto-flaw-used-in-5700-bitcoin-heist/" rel="nofollow">Android random number generator flaw</a>.</p>

<p>An unlikely occurrence would be some kind of change to the way private keys are imported, and your private key generated in 2013 cannot be <em>securely</em> converted to whatever format is expected in 2063, or whenever. I wouldn't get too paranoid about this.</p>

CC BY-SA 3.0
2013-10-18T00:23:59.717Z
2013-10-18T00:23:59.717Z
Colin Dean
<p>I've made an offline address and only have the key stored on 2 encrypted flash drives stored in different locations with the private key written physically on paper and stored in 2 locations. Do I ever have to worry about my coins? That is, could theyever be lost in software changes or is that as big of a never-going-to-happen as the 21 million limit being lifted? I'm pretty sure I'm not touching that wallet for a long time. Is there any benefit to repeating this process for a more "fresh" address ever or does that not make sense?</p>

<security><backup><paper-wallet>
if my wallet is sufficiently secure, can I ever lose my coins?
hedgedandlevered
# if my wallet is sufficiently secure, can I ever lose my coins?

(Asked by: username_0 on 2013-10-17)

I've made an offline address and only have the key stored on 2 encrypted flash drives stored in different locations with the private key written physically on paper and stored in 2 locations. Do I ever have to worry about my coins? That is, could theyever be lost in software changes or is that as big of a never-going-to-happen as the 21 million limit being lifted? I'm pretty sure I'm not touching that wallet for a long time. Is there any benefit to repeating this process for a more "fresh" address ever or does that not make sense?

**Tags:** security, backup, paper-wallet


---

## 3 answers

### Answer by username_4 on 2013-10-18. Score: 4 | Accepted answer

I'll go through your question clause by clause:

> I've made an offline address

You're doing good.

> and only have the key stored on 2 encrypted flash drives stored in different locations

As long as only you know the password and the password is sufficiently strong, this is *probably* secure.

> with the private key written physically on paper and stored in 2 locations.

If either of these two locations are accessible by anyone other than you, then they are vulnerable. If someone else found either paper, and your keys are in plain text, then you could consider them compromised.

> Do I ever have to worry about my coins?

Yes.

> That is, could they ever be lost in software changes

Extremely unlikely, as the whole of Bitcoin depends on the safety of balances through upgrades. There are people who have very vested in ensuring that this never happens. Even a bug in the protocol could not erase history in an unrecoverable way, as a single offline client copied online or bootstrap.dat would refresh anyone affected.

> or is that as big of a never-going-to-happen as the 21 million limit being lifted?

Pretty much.

> I'm pretty sure I'm not touching that wallet for a long time. Is there any benefit to repeating this process for a more "fresh" address ever or does that not make sense?

Theoretically, you would never need to regenerate keys unless some kind of vulnerability was found in the software that generated your key, ala the [Android random number generator flaw](http://arstechnica.com/security/2013/08/google-confirms-critical-android-crypto-flaw-used-in-5700-bitcoin-heist/).

An unlikely occurrence would be some kind of change to the way private keys are imported, and your private key generated in 2013 cannot be *securely* converted to whatever format is expected in 2063, or whenever. I wouldn't get too paranoid about this.


---

### Answer by username_1 on 2013-10-18. Score: 2

They could be lost in a few rare scenarios. For example:

* If substantial weaknesses are found in Bitcoin's crypto, or if quantum computing becomes usable on a large scale, your coins could be stolen. Most likely, the crypto will simply be weakened and attacks will still be very slow, so you'll have some time to send your coins to new addresses that use improved crypto.
* When you go to redeem your coins, your CPU may err in a way that causes Bitcoin to send your coins into oblivion. There are no known cases of this actually happening, but CPUs are not perfect, and it is possible.
* If Bitcoin develops critical scalability problems, and nothing else solves it, one "nuclear option" for improving things would be to require everyone to "renew" their coins every few months (or whatever). Old coins that that aren't renewed would be destroyed. If this policy is implemented, you will have to follow it. You'd have plenty of warning if something like this was approaching.

To protect yourself against these things and other possibilities, you should:

* Not store too much in any one address.
* Not send huge amounts at once.
* Never send *from* any high-value address more than once. The best way to do this is to only pay to an address once.
* Make sure that you're able to access your wallet with only a few days of notice.

There isn't any value in moving coins before you need to.


---

### Answer by username_2 on 2013-10-18. Score: -1

Sounds to me like you are taking good care of your Bitcoins, so you should be able to sleep easy at night.

Of course, there is always a risk that your account could be hacked through a scam.

Bitcoin is the realm of technophiles, so always be careful when conducting transactions. The sad truth is that there are some scammers out there looking to hack into accounts. And as they are often very bright, there is always a risk that you could be tricked.

> **Comments:**
> **username_3**: Your answer misses the point here: Since he created his key offline there is no risk that the funds could be accessed through hacking/scam since they are literally not accessible from his day-to-day computing equipment.  
> **username_2**: Hey boss, my assumption is that he will still be conducting some trading and activities online. Correct me if I am wrong, but he will have to reload the bitcoins no? Also, if he used a flash drive, then he used his fingers to type, and there are spyware programs out there that can and will read what you type.  
> **username_3**: The asker wrote "I'm pretty sure I'm not touching that wallet for a long time." as in, he will not be conducting trades and activities with this particular wallet. Of course some point in the far future he will re-import his private key to access his funds, but before then, the situation is such as he described in detail: He keeps his private key offline in two different usb sticks and two paper copies. While these types of storage pose their own security risks, they definitely cannot be attacked by hacking or scam.  
> **username_3**: Also he wrote that he created the wallet *offline*: If he went about that in a sensible manner, he did that as follows or similarly: He disconnected his machine from the internet, booted it with a clean live cd, created and backed-up a new wallet, then shut down the computer again. That way only a hardware spy-tool that stores information through shut-downs could have sniffed out anything, which I find implausible.  

---

