I generated an address that already exists

[willphase]

it's impossible* to generate an address already used.

what happened here is that the user had already used the address for a change address sending a transaction, or mining - and when he clicked 'generate' it just assigned that.

I repeat - it's impossible* for this to happen.

Will

* practically impossible - i.e. 1 in 2^160 which is less chance that you entering every lottery worldwide every week since lotteries were invented and winning the jackpot each time.

[Spekulatius]

it's impossible* to generate an address already used.

what happened here is that the user had already used the address for a change address sending a transaction, or mining - and when he clicked 'generate' it just assigned that.

I repeat - it's impossible* for this to happen.

Will

* practically impossible - i.e. 1 in 2^160 which is less chance that you entering every lottery worldwide every week since lotteries were invented and winning the jackpot each time.

You just drew that out of your ass right now, didnt you?   

[willphase]

You just drew that out of your ass right now, didnt you?  

yup!  Totally out of my ass, because I know that it's not possible to comprehend odds so astronomical as 2^160 so anything I can write down will be more likely.

Will

[gmaxwell]

@OP: did your wallet balance increase when you generated that address? If not, then it's a previous address of yours. If it did, err, wow…

It wouldn't have. That isn't how the software works. This is why doing a gettransaction is a pretty useful: had it just generated an address that was used before the wallet wouldn't know about any of the transactions. But in this case it did.

A coredev should look into this ASAP...

What am I?  Chopped liver?

In any case, people need to relax. See my prior post. This looks like he managed to get an address out of key-pool twice, e.g. due to some error in losing the write that marked the key spent after an unclean shutdown. (Or pilot error of some kind, e.g. generate a new one, then mis-click on the copy and copy an old one instead)

[zeroday]

IT IS POSSIBLE to generate address which is already used when you use weak passphrase to generate private key.
This already happened because the flaw in Android random number genretator.
Another example is brainwallet. Just look at 1JwSSubhmg6iPtRjtyqhUYYH7bZg3Lfy1T, This address is in hundreds wallets belonging to different people.

[msc]

My records go back to 2011 but I don't see any transactions made in Jun or Jul 2012 at all and I didn't use mtgox in 2012.

I also do not see any mention of those two other addresses involved in previous transactions in my wallet.

I will assume that some kind of glitch made the client to reuse that address twice, that's more probable than a collision I guess.

Thank you!

If the 50 BTC was not your transaction, then it's a collision. 

[jackjack]

IT IS POSSIBLE to generate address which is already used when you use weak passphrase to generate private key.
This already happened because the flaw in Android random number genretator.
Another example is brainwallet. Just look at 1JwSSubhmg6iPtRjtyqhUYYH7bZg3Lfy1T, This address is in hundreds wallets belonging to different people.

[wachtwoord]

IT IS POSSIBLE to generate address which is already used when you use weak passphrase to generate private key.
This already happened because the flaw in Android random number genretator.
Another example is brainwallet. Just look at 1JwSSubhmg6iPtRjtyqhUYYH7bZg3Lfy1T, This address is in hundreds wallets belonging to different people.

LOL, Zeroday is mixing up brainwallets with passphrases as seeds and the password used for encrypting the wallet in Bitcoin-QT

[darkmule]

IT IS POSSIBLE to generate address which is already used when you use weak passphrase to generate private key.
This already happened because the flaw in Android random number genretator.
Another example is brainwallet. Just look at 1JwSSubhmg6iPtRjtyqhUYYH7bZg3Lfy1T, This address is in hundreds wallets belonging to different people.

Incidentally, don't add this address to your own wallet just to test it.  I can assure you this is a really bad idea, because, well. . .just because.

[darkmule]

* practically impossible - i.e. 1 in 2^160 which is less chance that you entering every lottery worldwide every week since lotteries were invented and winning the jackpot each time.

You just drew that out of your ass right now, didnt you?   

I think he could throw in getting struck by lightning on the way to the convenience store to purchase each winning ticket, then getting struck by lightning again on the way back home, every time, and still be within tolerances.

[wachtwoord]

* practically impossible - i.e. 1 in 2^160 which is less chance that you entering every lottery worldwide every week since lotteries were invented and winning the jackpot each time.

You just drew that out of your ass right now, didnt you?  

I think he could throw in getting struck by lightning on the way to the convenience store to purchase each winning ticket, then getting struck by lightning again on the way back home, every time, and still be within tolerances.

iirc 1 in 2^160 is correct. Therefore I don't really believe this topic. Interesting though, although there is no way to prove anything either way


Edit:

May be this image helps clarify this for some people:

[darkmule]

iirc 1 in 2^160 is correct. Therefore I don't really believe this topic. Interesting though, although there is no way to prove anything either way

I think it's somewhat less, actually, because of the birthday problem.  It's not the odds of a 160 bit hash colliding with one arbitrary address, but with every currently existing address.  The odds are still astronomical but would require estimating the number of currently existing addresses in use.

ETA:  This being the odds of us ever "seeing" a collision.  It's also entirely possible there would be a collision but it would never even be noticed, because either the other "owner" of the address never used it, or because the new "owner" never bothered checking.  (Possible but, of course, very, very unlikely.)

[Ente]

Edit:

May be this image helps clarify this for some people:

https://i.imgur.com/vCkuFAY.jpeg

Fck'n saved! Nice one!

Ente

[the joint]

You just drew that out of your ass right now, didnt you?  

yup!  Totally out of my ass, because I know that it's not possible to comprehend odds so astronomical as 2^160 so anything I can write down will be more likely.

Will

2^161

Wow!  Did it on my first try!

[zeroday]

LOL, Zeroday is mixing up brainwallets with passphrases as seeds and the password used for encrypting the wallet in Bitcoin-QT

I meant exactly passphrase as seed, not the password of Bitcoin-QT which is obviously not involved in the generation of private key.

Duplicate private keys can also be generated if there is some flaw in seed generation like it was on Android.

[ASICSRUS]

Wow... didn't think it would ever happen

it keeps happening?lol

[ASICSRUS]

it's impossible* to generate an address already used.

what happened here is that the user had already used the address for a change address sending a transaction, or mining - and when he clicked 'generate' it just assigned that.

I repeat - it's impossible* for this to happen.

Will

* practically impossible - i.e. 1 in 2^160 which is less chance that you entering every lottery worldwide every week since lotteries were invented and winning the jackpot each time.

anything is possible, i wonder if you could bruteforce an old addy into someone elses client throught compromised hijack?

[Inkvor]

all address are unique you cant generate the same address

[ASICSRUS]

all address are unique you cant generate the same address

read op he just did!!! 

[darkmule]

all address are unique you cant generate the same address

Wrong.  All addresses are probably unique, to a high degree of probability and it is entirely possible to generate the same address, especially using a method like brainwallet with a poor passphrase, or using a broken PRNG.  There is absolutely nothing other than chance preventing generating the same address, assuming robust PRNG.