could it be a hard collision?

ahh my mistake, thanks for clarifying.

your randomly created change address seems to be one of the many millions of addresses already in use. you have just won the lottery.

i suggest not using that address as obviously someone else has it too..

i dont think this is the first time a address 'collision' has occured which is why v9 of bitcoin-QT will start using messaged to allow recognition of transactions, to avoid merchants using fresh addresses per transaction. thus reducing the chances of 'collisions' becoming a regular thing.

most people think that there is no chance of a collision unless you create billions of addresses. the actual fact is that you have 1 chance WITHIN those billions of addresses.. so it could be the 10th address you make or the 9,999,999,999th address or so on.

wtf are you talking about? Stop spreading FUD.

You don't own this address do you?

https://blockchain.info/address/1DSu8QqECJFFx9vmTp1MiT3PqHND6LLyTx

The address was already in the block chain. It is known. Someone sent you 0.001 BTC. You didn't get it as change for yourself. The address you posted, has been public since May.

Even with trillions of addresses, there would still be no collision. 2^256 is a very big number, almost as all the atoms in the visible universe.

I agree, that collision is (almost) impossible, but this could be used to create panic between those who do not understand bitcoin very well.

I think this could potentially be very serious (a social "attack" to ruin bitcoin's reputation?), and should be looked into further.

There will be (at least) hundreds of bitcoin users, who will think that their "newly created address" already contains BTC (as I thought at first), and if they are not familiar with bitcoin, they may very well decide it must be an address collision (suspicious fact - the first "answers" to my question "what happened?" were exactly that - "collision!"; luckily I myself know about bitcoin too much, to believe that that was the case, but many others could be easily convinced that it was collision).

I said there will be hundreds (of bitcoin users affected), only judging from this one transaction that I know of. In reality, there may have been hundreds of such transactions, ant the number of such users could be tens of thousands.

Then I'm wondering if your first post isn't quite accurate.

In your transaction list, do you see the 8 btc transaction back in May? Did you create a new address and think it was this one by selecting not the newly created one, but this slightly older one? Also coincidentally, this transaction happened and you didn't notice it until after you made the new address?

Let's toss a number of stars out there per galaxy. 1 trillion. 10^12  (Galaxies range from 10^7 - 10^14) 1,000,000,000
Let's almost halve the number of galaxies in the observable universe and call it a nice round 100 billion or 10^11 100,000,000

That gives us 10^23 stars in the universe.

2^256 always sounded confusing to me. Let's round it down to a nice even 10^77 power.

If you generated as many bitcoin addresses as all the stars in the universe (so the 1 trillion times 100 billion)
Then Sha hashes number of stars in the universe equals

Your chances of collision are then 1 in 1,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000

Give or take a few zeroes because I'm not trying too hard here.

So... no, it's not going to happen.

If EVERY single person on this planet (round up to 10 billion just for fun) also generated 10^23 addresses...

The chance of ONE person generating a collision increases all the way to 1 in 100,000,000,000,000,000,000,000,000,000,000,000,000,000,000

Get the point?