Lost Bitcoins

[Xav]

What if ....

Someone was a bit nonchalant and did not back up his/her coins, but ... But he/she remembers his/her private key. Is there a way to 'restore' these 'lost' coins? IOW, is there a way to match private key and a specific address in the block-chain?

If you know the private key, then you can access the coins:

https://en.bitcoin.it/wiki/Private_key

Just as if you wrote the key down or printed it.

Thanks for this answer. The info reads:

The private key is mathematically related to the Bitcoin address, and is designed so that the Bitcoin address can be calculated from the private key, but importantly, the same cannot be done in reverse.

That's great. But, just to be sure, assume that I lost my wallet; completely, no back up. And all I do remember is my private key, can I restore (or recreate) the same wallet including all the coins?

[cr1776]

What if ....

Someone was a bit nonchalant and did not back up his/her coins, but ... But he/she remembers his/her private key. Is there a way to 'restore' these 'lost' coins? IOW, is there a way to match private key and a specific address in the block-chain?

If you know the private key, then you can access the coins:

https://en.bitcoin.it/wiki/Private_key

Just as if you wrote the key down or printed it.

Thanks for this answer. The info reads:

The private key is mathematically related to the Bitcoin address, and is designed so that the Bitcoin address can be calculated from the private key, but importantly, the same cannot be done in reverse.

That's great. But, just to be sure, assume that I lost my wallet; completely, no back up. And all I do remember is my private key, can I restore (or recreate) the same wallet including all the coins?

Hey,
If you go to bitaddress.org and click on "wallet details" and then enter your private key, it will give you the public address.  The problem is that most people can't remember their private key, but if you can do so, that is enough.

For example, this private key:
5JntzqqXVhR8SBRvFWQhrtv3UXRqovnnfaij4FFT5nCAswFoqkx

Generates this address:
14MR8Li8Fna4d43PfY2f2XRp6GAbPM5swJ

You can go there, hit single wallet, copy the private key and then hit wallet details and see if it regenerates the address you just created.

You want to be safe doing that though - off-line, incognito window at minimum, quit when done, restart, if you have any significant numbers of bitcoins there.  Bitaddress.org is reputable, however it is best to be safe and those are the minimum steps I'd take.


:-)

[odolvlobo]

That's great. But, just to be sure, assume that I lost my wallet; completely, no back up. And all I do remember is my private key, can I restore (or recreate) the same wallet including all the coins?

Yes, as long as you have memorized the private keys for all the addresses that have coins -- but why would you not back up a wallet? That seems like an obvious mistake (as well as not encrypting it). Furthermore, why would you back up your wallet in your brain?

[Xav]

Thanks guys. Maybe I didn't express my thoughts clearly enough, but I did not lose any coins, yet. I was just wondering why people lose coins if all can be restored by remembering the private key. BTW I think the safest place to store a private key is in your own brain; of course not in the form of a completely random string of characters, albeit as a quite unique sentence, which you encrypt and hash on a stand alone (offline) computer. The FBI confiscated BTC170,000, now why wouldn't these 'criminals' (or their partners) have moved these coins to another wallet, or were the FBI-agents smart enough to do this themselves already. Hmm, just thinking out loud again ...

[DannyHamilton]

- snip -
I think the safest place to store a private key is in your own brain; of course not in the form of a completely random string of characters, albeit as a quite unique sentence
- snip -

This is generally a very bad idea.

[Xav]

- snip -
I think the safest place to store a private key is in your own brain; of course not in the form of a completely random string of characters, albeit as a quite unique sentence
- snip -

This is generally a very bad idea.

Care for an explanation?

[DannyHamilton]

- snip -
I think the safest place to store a private key is in your own brain; of course not in the form of a completely random string of characters, albeit as a quite unique sentence
- snip -

This is generally a very bad idea.

Care for an explanation?

Human minds are wired for patterns and are VERY bad at randomness.  Brain wallets have a significant risk of loss due to collision (either intentional, or accidental).

Just one of MANY examples from this forum:
https://bitcointalk.org/index.php?topic=421559.0

[Xav]

Now tell me, how likely is it that someone would reproduce my sentence (key):

"Ik heb de Mont Ventoux drie keer opgefietst en de Elfstedentocht even vaak geschaatst."

Of course it is stupid to use some sort of general phrase. One has to make it real personal, and certainly not create it via brainwallet. One more thing, if you prefer to generate a random number by a computer (Andreas Antonopoulos warned about a bug in Linux; random is not so random these days) and you lose it then there is no way ever to get your coins back. My brain can. BTW this "drie keer" in itself means three times also implying three hash runs. Let's say, everyone his own bite.

[jeffg]

Thanks guys. Maybe I didn't express my thoughts clearly enough, but I did not lose any coins, yet. I was just wondering why people lose coins if all can be restored by remembering the private key. BTW I think the safest place to store a private key is in your own brain; of course not in the form of a completely random string of characters, albeit as a quite unique sentence, which you encrypt and hash on a stand alone (offline) computer. The FBI confiscated BTC170,000, now why wouldn't these 'criminals' (or their partners) have moved these coins to another wallet, or were the FBI-agents smart enough to do this themselves already. Hmm, just thinking out loud again ...

It's not that easy. The problem is, most Bitcoin clients generate a new address every time you send money where the change is transferred to (see https://en.bitcoin.it/wiki/Change). So you'd have to memorize a new private key everytime you spend money. To circumvent this you can use a deterministic wallet like armory. It generates a unique "seed" that you need to memorize and can regenerate every address then.

[odolvlobo]

Now tell me, how likely is it that someone would reproduce my sentence (key):

"Ik heb de Mont Ventoux drie keer opgefietst en de Elfstedentocht even vaak geschaatst."

The key doesn't have to be random. It just has to be unlikely to be duplicated whether accidently or on purpose. I guess a phrase like that might never be duplicated, but you might be surprised.

Consider the birthday problem: There are 365 days in a year. In a room with 23 people, what are the chances that two people in the room have the same birthday? It's a lot higher than you think. Answer: 50%

[Xav]

Answer: P = 1 - (³⁶⁴₃₄₃) 22!/365^22 ~ 50%

Can you calculate the probability of a classroom with n children, all having different names, all being blindfolded, all taking a seat randomly, and no kid finds their own seat, which is tagged with their name?