same public key

[schnuber]

I have a stupid question.
How is it prevented that there are accidentally two identical bitcoin addresses in the system? Of course the probability is small but if it happened it would be disastrous, wouldn't it?

[Remember remember the 5th of November]

I have a stupid question.
How is it prevented that there are accidentally two identical bitcoin addresses in the system? Of course the probability is small but if it happened it would be disastrous, wouldn't it?

It wouldn't really be that disastrous. But no, there is no system to prevent two addresses from colliding. If it ever happened, it would mean you can steal the money in there.

[justusranvier]

How do you prevent yourself from being simultaneously struck by lightening and a meteorite while also being bitten by a mosquito that gives you West Nile virus as your house is being swallowed by a sinkhole caused by an earthquake?

[BurtW]

From another thread just yesterday, there are exactly:

p = FFFFFFFF FFFFFFFF FFFFFFFF FFFFFFFF FFFFFFFF FFFFFFFF FFFFFFFE FFFFFC2F

    = 2^256 − 2^32 − 2^9 − 2^8 − 2^7 − 2^6 − 2^4 − 1

possible key pairs in the Bitcoin system.  

However, because of the way Bitcoin addresses are calculated there are "only" 2^160 possible Bitcoin addresses.

So 2^160 is the number you are dealing with when talking about Bitcoin address collisions.  

This number is big.  Really, really big.  The probablity of a collision is so small that it will never happen.

[grue]

From another thread just yesterday, there are exactly:

p = FFFFFFFF FFFFFFFF FFFFFFFF FFFFFFFF FFFFFFFF FFFFFFFF FFFFFFFE FFFFFC2F

    = 2^256 − 2^32 − 2^9 − 2^8 − 2^7 − 2^6 − 2^4 − 1

possible key pairs in the Bitcoin system. 

However, because of the way Bitcoin addresses are calculated there are "only" 2^160 possible Bitcoin addresses.

So 2^160 is the number you are dealing with when talking about Bitcoin address collisions. 

This number is big.  Really, really big.  The probablity of a collision is so small that it will never happen.

Yep, 2^160 ~ 1.46x10^48 = 48 zeros!

[jackjack]

Number of water molecules on Earth: 4.68 x 10⁴⁶
Number of keys possible: 2 ^ 160 = 1.5 x 10⁴⁸ = 30 * Number of water molecules on Earth


Imagine you choose one water molecule on Earth (anywhere: in ocean, your kitchen, your cat's lung, Kim Jung Il's hair, etc) and I do the same without us communicating
The possibility of address collision is 30 times lower than the possibility of us chosing the same water molecule


Even if choose billions of water molecules (which is 1000000000000000 tinier than a glass of water) instead of just one, do you realize how ridiculously impossible it is for us to have even one shared molecule?

[schnuber]

Many commercial entities will use a new address for each transaction. If bitcoin will be widely adopted someday the amount of used bitcoin addresses will be also very big. Of course the probability of two identical addresses will still be very small... but it will be there, nonetheless.
I simply wonder what the implications would be if that happened.

[grue]

Many commercial entities will use a new address for each transaction. If bitcoin will be widely adopted someday the amount of used bitcoin addresses will be also very big. Of course the probability of two identical addresses will still be very small... but it will be there, nonetheless.
I simply wonder what the implications would be if that happened.

has been discussed 9001 times. please search for answer kthx

[threeip]

Many commercial entities will use a new address for each transaction. If bitcoin will be widely adopted someday the amount of used bitcoin addresses will be also very big. Of course the probability of two identical addresses will still be very small... but it will be there, nonetheless.
I simply wonder what the implications would be if that happened.

Chance would be the address was used 10 years ago by someone, and they've lost the privkey by now anyway. Always a good idea to empty old addresses right?

[jackjack]

Many commercial entities will use a new address for each transaction. If bitcoin will be widely adopted someday the amount of used bitcoin addresses will be also very big. Of course the probability of two identical addresses will still be very small... but it will be there, nonetheless.
I simply wonder what the implications would be if that happened.

Obvious lack of sense of proportion
Did you ever wonder about the implications of being hit by 3 lightnings simultaneously on the right eye, the left feet and the belly button?

Also, search

[DeathAndTaxes]

Many commercial entities will use a new address for each transaction. If bitcoin will be widely adopted someday the amount of used bitcoin addresses will be also very big. Of course the probability of two identical addresses will still be very small... but it will be there, nonetheless.
I simply wonder what the implications would be if that happened.

Nope.  Very big and 2^160 big are two different things.   It is like saying if we can go to mars (very far away from the earth) in a year then obviously we could just keep going and get to the nearest star "soon" doing the same thing.

Maybe this helps:
if a billion people, each used a billion new addresses, every second continuously for the next billion years that would be less than 1/460,000,000,000th of 1% of possible addresses in 2^160.

[cbeast]

It would be much easier to crack that SHA256 address. The solution to both is to not keep all your coins in one address.

[kokjo]

give up people.

some people just cannot comprehend so big numbers.

[jackjack]

give up people.

some people just cannot comprehend so big numbers.

I guess so
So disappointing

[kjj]

Hashing takes far less work than generating keypairs, and so far the bitcoin network has done something like 2⁷⁰ hashes in 4.5 years.

[kokjo]

Hashing takes far less work than generating keypairs, and so far the bitcoin network has done something like 2⁷⁰ hashes in 4.5 years.

noob response: oh, we are already half way.

[threeip]

Hashing takes far less work than generating keypairs, and so far the bitcoin network has done something like 2⁷⁰ hashes in 4.5 years.

noob response: oh, we are already half way.

For noobs;

2^70=22 digits
2^140=43 digits

[schnuber]

Amazing how one gets bashed and degraded simply because for asking a legitimate question.

I wasn't asserting that the theoretical possibility of two identical addresses is an imminent weakness of bitcoin.

If you read my post carefully you probably recognize that I am simply asking whether there is a mechanism in the software that somehow prevents two identical addresses (meanwhile I found out from your responses that there's not) and secondly, I wonder what the implications would be if  there were two identical addresses in the system. To this question you have failed to provide a profound answer yet, since you obviously prefer to bash people than to provide instructive explanations (which of course requires more intelligence and respect for other people that don't share the same level of knowledge yet).

I think this attitude is not beneficial for mainstream adoption of bitcoin.

[jackjack]

Amazing how one gets bashed and degraded simply because for asking a legitimate question.

I wasn't asserting that the theoretical possibility of two identical addresses is an imminent weakness of bitcoin.

If you read my post carefully you probably recognize that I am simply asking whether there is a mechanism in the software that somehow prevents two identical addresses (meanwhile I found out from your responses that there's not) and secondly, I wonder what the implications would be if  there were two identical addresses in the system. To this question you have failed to provide a profound answer yet, since you obviously prefer to bash people than to provide instructive explanations (which of course requires more intelligence and respect for other people that don't share the same level of knowledge yet).

I think this attitude is not beneficial for mainstream adoption of bitcoin.

You were bashed for not using the search function

It wouldn't really be that disastrous. But no, there is no system to prevent two addresses from colliding. If it ever happened, it would mean you can steal the money in there.

has been discussed 9001 times. please search for answer kthx

Also, search

[edd]

Amazing how one gets bashed and degraded simply because for asking a legitimate question.

I wasn't asserting that the theoretical possibility of two identical addresses is an imminent weakness of bitcoin.

If you read my post carefully you probably recognize that I am simply asking whether there is a mechanism in the software that somehow prevents two identical addresses (meanwhile I found out from your responses that there's not) and secondly, I wonder what the implications would be if  there were two identical addresses in the system. To this question you have failed to provide a profound answer yet, since you obviously prefer to bash people than to provide instructive explanations (which of course requires more intelligence and respect for other people that don't share the same level of knowledge yet).

I think this attitude is not beneficial for mainstream adoption of bitcoin.

Your question was answered though it might not have been very obvious. The result of such an astronomically unlikely event would be the same as if you were struck by lightning, hit by a car, and attacked by a great white shark in the middle of the Sahara desert at the same time: it would be (potentially) very bad for you, the victim, it would get a lot of attention and many others would probably worry about the same thing happening to them despite the odds against it while the rest of us and our descendants would happily use bitcoins until the universe ended without ever experiencing anything similar.

Hope that satisfies you.