Same Address generated by 2 Clients

[BitCoinDream]

Is not it possible that a same address is being generated by 2 clients ? Or 2 persons at 2 different parts of the world are creating brainwallet from same passphrase ?

[CrapMan]

Is not it possible that a same address is being generated by 2 clients ? Or 2 persons at 2 different parts of the world are creating brainwallet from same passphrase ?

read this thread! I argued that couple days ago.

https://bitcointalk.org/index.php?topic=557274.0

[DannyHamilton]

Is not it possible that a same address is being generated by 2 clients?

As long as the wallet is using a source of random numbers with significant entropy?  No.

If there is a bug in the computer such that the "random numbers" that the computer provides aren't "random enough", then yes, absolutely.

Or 2 persons at 2 different parts of the world are creating brainwallet from same passphrase ?

This is VERY LIKELY.

This is why people should not use brainwallets.  Most humans aren't capable of creating and memorizing a brainwallet passphrase that is random enough to reduce collision chances to acceptable levels.

[byt411]

Is not it possible that a same address is being generated by 2 clients?

As long as the wallet is using a source of random numbers with significant entropy?  No.

If there is a bug in the computer such that the "random numbers" that the computer provides aren't "random enough", then yes, absolutely.

Or 2 persons at 2 different parts of the world are creating brainwallet from same passphrase ?

This is VERY LIKELY.

This is why people should not use brainwallets.  Most humans aren't capable of creating and memorizing a brainwallet passphrase that is random enough to reduce collision chances to acceptable levels.

That is correct, but I would just like to point out one thing.
It is possible that the wallets are indeed using a source of random numbers with significant entropy, but it can still generate the same address.
The chance is extremely low, so low it is like impossible, but extremely low chance does not equal impossible.

[DannyHamilton]

Is not it possible that a same address is being generated by 2 clients?

As long as the wallet is using a source of random numbers with significant entropy?  No.

If there is a bug in the computer such that the "random numbers" that the computer provides aren't "random enough", then yes, absolutely.

Or 2 persons at 2 different parts of the world are creating brainwallet from same passphrase ?

This is VERY LIKELY.

This is why people should not use brainwallets.  Most humans aren't capable of creating and memorizing a brainwallet passphrase that is random enough to reduce collision chances to acceptable levels.

That is correct, but I would just like to point out one thing.
It is possible that the wallets are indeed using a source of random numbers with significant entropy, but it can still generate the same address.
The chance is extremely low, so low it is like impossible, but extremely low chance does not equal impossible.

It is also possible that all the air in the room will spontaneously collect in one corner suffocating everyone in the room.  The chance is extremely low, so low it is like impossible, but extremely low chance does not equal impossible.

Now ask any lay person if they think that it is possible for all the air in the room to suddenly collect tightly in a corner leaving everyone to suffocate, and we'll see if "impossible" in general use means what you think it means.

[byt411]

Is not it possible that a same address is being generated by 2 clients?

As long as the wallet is using a source of random numbers with significant entropy?  No.

If there is a bug in the computer such that the "random numbers" that the computer provides aren't "random enough", then yes, absolutely.

Or 2 persons at 2 different parts of the world are creating brainwallet from same passphrase ?

This is VERY LIKELY.

This is why people should not use brainwallets.  Most humans aren't capable of creating and memorizing a brainwallet passphrase that is random enough to reduce collision chances to acceptable levels.

That is correct, but I would just like to point out one thing.
It is possible that the wallets are indeed using a source of random numbers with significant entropy, but it can still generate the same address.
The chance is extremely low, so low it is like impossible, but extremely low chance does not equal impossible.

It is also possible that all the air in the room will spontaneously collect in one corner suffocating everyone in the room.  The chance is extremely low, so low it is like impossible, but extremely low chance does not equal impossible.

Now ask any lay person if they think that it is possible for all the air in the room to suddenly collect tightly in a corner leaving everyone to suffocate, and we'll see if "impossible" in general use means what you think it means.

Well, that is why I am pointing out most people are wrong.
Also, why would all the air in a room suddenly collect tightly in a corner?

[CrapMan]

Is not it possible that a same address is being generated by 2 clients?

As long as the wallet is using a source of random numbers with significant entropy?  No.

If there is a bug in the computer such that the "random numbers" that the computer provides aren't "random enough", then yes, absolutely.

Or 2 persons at 2 different parts of the world are creating brainwallet from same passphrase ?

This is VERY LIKELY.

This is why people should not use brainwallets.  Most humans aren't capable of creating and memorizing a brainwallet passphrase that is random enough to reduce collision chances to acceptable levels.

That is correct, but I would just like to point out one thing.
It is possible that the wallets are indeed using a source of random numbers with significant entropy, but it can still generate the same address.
The chance is extremely low, so low it is like impossible, but extremely low chance does not equal impossible.

I greet you Sir for your input, that's why I argued this point couple days ago.
Imagine you are walmart.com or amazon.com ..etc and you get 500 transaction a second/or minutes or whatever, then someone with that very extremely low possibility generated your business address. Oh well... imagine your loss!
But people are so excited and busy about the dream of being so rich one day when the coin hit million dollars and are forgetting the fact that until that day come there is an extremely small chance that someone may generate the same address and all your saving will be gone!

[Ibian]

No, it is not possible. Don't argue about it, go read up on it.

[Flashman]

The chance is extremely low, so low it is like impossible, but extremely low chance does not equal impossible.

You might say a chance of a person having a birthday on a given day is 1 in 365, and therefore the chances of two people having the same birthday are (1/365)*(1/365)= 1/133225

But...

http://en.wikipedia.org/wiki/Birthday_problem

So, while your individual chances of generating the same address as anyone else is very very very very very low, you may hear of such a case in the bitcoin community eventually.

[BitCoinDream]

Is not it possible that a same address is being generated by 2 clients?

As long as the wallet is using a source of random numbers with significant entropy?  No.

If there is a bug in the computer such that the "random numbers" that the computer provides aren't "random enough", then yes, absolutely.

Or 2 persons at 2 different parts of the world are creating brainwallet from same passphrase ?

This is VERY LIKELY.

This is why people should not use brainwallets.  Most humans aren't capable of creating and memorizing a brainwallet passphrase that is random enough to reduce collision chances to acceptable levels.

That is correct, but I would just like to point out one thing.
It is possible that the wallets are indeed using a source of random numbers with significant entropy, but it can still generate the same address.
The chance is extremely low, so low it is like impossible, but extremely low chance does not equal impossible.

It is also possible that all the air in the room will spontaneously collect in one corner suffocating everyone in the room.  The chance is extremely low, so low it is like impossible, but extremely low chance does not equal impossible.

Now ask any lay person if they think that it is possible for all the air in the room to suddenly collect tightly in a corner leaving everyone to suffocate, and we'll see if "impossible" in general use means what you think it means.

Well, that is why I am pointing out most people are wrong.
Also, why would all the air in a room suddenly collect tightly in a corner?

Though, in multiple instances I have seen Danny is quite a knowledgeable person, but I dont understand why sometimes he argues like a kid !!! Why on earth all the air in the room will spontaneously collect in one corner suffocating everyone in the room ? That is against the second law of thermodynamics !!!

[Flashman]

Yah but the "laws" of thermodynamics are misnamed, they are the statistical principals of thermodynamics, so it's statistically unlikely that it will happen, and should be qualified by "should the system be left it it's own devices".... otherwise people start saying ridiculous things like airconditioning and refrigeration being impossible.

Most people who spout "Thermodynamics, BOOYAH!!!" haven't got the first freaking clue what it is and where it comes from.

[DannyHamilton]

Most humans have a very difficult time comprehending just how big some really big numbers are.

why would all the air in a room suddenly collect tightly in a corner?

For the same reason that two people will randomly generate the same address.

Generation of addresses is random.

The motion of the air molecules in the room is random.

There is a "possibility" that two people will just happen to randomly generate the same address.

There is a "possibility" that all the air molecules will just happen to move in the same direction to the corner of the room.

Imagine you are walmart.com or amazon.com ..etc and you get 500 transaction a second/or minutes or whatever, then someone with that very extremely low possibility generated your business address. Oh well... imagine your loss!

2¹⁶⁰ is a very Very VERY big number.

500 transactions per second is not a very Very VERY big number.

Also, Walmart or Amazon or whatever should be using a new address for every transaction.  So even though they won't ever have the same address as anyone else, it wouldn't be a big problem if they did since that address will only have one transaction of bitcoins in it.

there is an extremely small chance that someone may generate the same address and all your saving will be gone!

You don't seem to understand how "extremely small" that chance is.  There are things that are MUCH more likely to happen, that you don't every worry about and that are far more dangerous.

You might say a chance of a person having a birthday on a given day is 1 in 365, and therefore the chances of two people having the same birthday are (1/365)*(1/365)= 1/133225

But...

http://en.wikipedia.org/wiki/Birthday_problem

So, while your individual chances of generating the same address as anyone else is very very very very very low, you may hear of such a case in the bitcoin community eventually.

No you won't.  Not if both addresses were generated using random numbers with sufficient entropy.  2¹⁶⁰ is a very Very VERY big number. 365 is not a very Very VERY big number.

Keep in mind that no matter how many addresses are ever created, there can never be more than 2,099,999,997,690,000 addresses in use at a time, and will almost always be much less than that.

Though, in multiple instances I have seen Danny is quite a knowledgeable person, but I dont understand why sometimes he argues like a kid!!!

Because that is the only way to present a demonstration of "extremely unlikely equals impossible" that anyone seems to understand.

Why on earth all the air in the room will spontaneously collect in one corner suffocating everyone in the room?

It wouldn't.  And no two people generating random addresses with sufficient entropy are going to generate the same address either.  They are both "mathematically possible", but in reality they are both impossible.

That is against the second law of thermodynamics!!!

No, it really isn't.  It is however so unlikely that we can say it is impossible (just like generating identical addresses from completely random sources with sufficient entropy).

[CrapMan]

There have been so many cases reported where people logged on to their accounts and their BTC were gone, how can you know for sure that it wasn't because of address collision?

A lot of people don't take the flue vaccine because they are worried of the side effect of it, even though the percentage is low but it happened

https://www.youtube.com/watch?v=5ztiAN9k584

Now I understand that this address collision is extremely ^160 low, but that doesn't stop the fact that is still possible.

And the more Amazon and Walmart use a new wallet for each transaction, the more possible it might happen, as the more wallets you generate the more you increase the chance for collision.

[DeathAndTaxes]

There have been so many cases reported where people logged on to their accounts and their BTC were gone, how can you know for sure that it wasn't because of address collision?

Math and probability.  Extraordinary claims require extraordinary evidence.

Anything is possible but the odds make it so incredibly improbable that in the absence of extraordinary evidence it is far more likely that there is another possibility.

Nothing in life is certain. Quantum mechanics tells us there is a chance that you could just walk through a wall.  As Danny example points out, by random chance all the air molecules may move away from your head and cause you to suffocate and die before you finish reading this post.  All these things are possible yet we generally consider them impossible because the odds are so incredibly small.  We aren't talking about winning the lottery small, or getting stuck by lightning small, or getting eaten by a shark small.  We aren't even talking about winning the lottery while getting struck by lightning just after getting attacked by a shark small.  

We are talking about probabilities on a scale so unlikely that they are essentially zero.  The odds of an address collision are 2^160.  That is something on the order of the number of atoms in our solar system.  Imagine each key is a single atom somewhere in the solar system picked at random.  The odds that the same atom would be picked again at random is essentially zero.  It doesn't matter if billions or even quadrillions of addresses are in use.  It doesn't matter if you tried millions of billions of key.  The odds are so small that ~0% * a quadrillion * a billion =~ 0%.

Of course these same odds apply to other public key cryptographic systems.  Lets say your gmail account is hacked.  How do you know a hacker didn't just randomly slam a bunch of keys on his keyboard and produce a private key which could decode all your communications with google.  It could happen.  Maybe the reason you got hacked is because a hacker has been doing this for years?  Of course probability tells us the odds of that happening as so low that in normal conversation it can be considered to be zero.  Baring some extraordinary evidence it is far more likely you got hacked by another method.

[CrapMan]

There have been so many cases reported where people logged on to their accounts and their BTC were gone, how can you know for sure that it wasn't because of address collision?

Math and probability.  Extraordinary claims require extraordinary evidence.

Anything is possible but the odds make it so incredibly improbable that in the absence of extraordinary evidence it is far more likely that there is another possibility.

Nothing in life is certain. Quantum mechanics tells us there is a chance that you could just walk through a wall.  As Danny example points out, by random chance all the air molecules may move away from your head and cause you to suffocate and die before you finish reading this post.  All these things are possible yet we generally consider them impossible because the odds are so incredibly small.  We aren't talking about winning the lottery small, or getting stuck by lightning small, or getting eaten by a shark small.  We aren't even talking about winning the lottery while getting struck by lightning just after getting attacked by a shark small.  

We are talking about probabilities on a scale so unlikely that they are essentially zero.  The odds of an address collision are 2^160.  That is something on the order of the number of atoms in our solar system.  Imagine each key is a single atom somewhere in the solar system picked at random.  The odds that the same atom would be picked again at random is essentially zero.  It doesn't matter if billions or even quadrillions of addresses are in use.  It doesn't matter if you tried millions of billions of key.  The odds are so small that ~0% * a quadrillion * a billion =~ 0%.

I agree, and I understand that.
But let's take a minutes and look at the future of BTC if we are going to consider it the world currency.
Let's say 50 Billion addresses are generated each year. in a hundred year that's 5 Trillions Wallets and each year the collision become close to be possible.
Well probably at that time we will have to change the coin.
What about if a hacker came up with a wallet generator software? just use the software to generate a desktop wallets, and then you will have probably half a billion using it to make more and more wallets and increase the possibility of collision.
The point the guy who started the thread is: it is possible to happen because even though it is 2^160 at the end it is LIMITED to a number and the more wallets you generate the more you come closer and closer to the end.
In real life, people die and others are born, there is usually balance in every single physic law.
But for Math there is no infinity as long as you put "=" at the end of the equation.

Tell me about this extremely low collision again when a hacker come up with a wallet generator software!
If the software generate 1 wallet a min
1*60 = 60 an hour
60 * 24 = 1440 a day
1440 * 365 = 525600 a year
Now let's say there is only a million using the software
That's 525,600,000,000
and this is not adding what normal people are generating!

[DannyHamilton]

The odds are so small that ~0% * a quadrillion * a billion =~ 0%.

I agree, and I understand that.

No.  Clearly you don't.  You say you do, and yet you immediately follow that up by demonstrating that you don't.

But let's take a minutes and look at the future of BTC if we are going to consider it the world currency.
Let's say 50 Billion addresses are generated each year. in a hundred year that's 5 Trillions Wallets and each year the collision become close to be possible.

No, it doesn't.

5 Trillion is not a big number.  You feel like its a big number because it's bigger than you can comprehend.  Then you compare a number that is bigger than you can comprehend to another number that is bigger than you can comprehend and you feel like they aren't very far apart.  You are mistaken in that feeling.

Well probably at that time we will have to change the coin.

Perhaps.  Perhaps not.  Either way, it doesn't matter.

What about if a hacker came up with a wallet generator software? just use the software to generate a desktop wallets,

It already exists.  There are already people who are bad at mathematics who are running it continuously.  It doesn't matter.

and then you will have probably half a billion using it to make more and more wallets and increase the possibility of collision.

And they still aren't going to have a collision.  2¹⁶⁰ is bigger than you are realizing.

The point the guy who started the thread is: it is possible to happen because even though it is 2^160 at the end it is LIMITED to a number and the more wallets you generate the more you come closer and closer to the end.

And if every single human being on earth does nothing else except generate addresses as fast as they can continuously until the sun burns out 6 billion years from now, they still won't reach the point where an address collision has any chance of happening.

In real life, people die and others are born, there is usually balance in every single physic law.
But for Math there is no infinity as long as you put "=" at the end of the equation.

There is not infinity, but there is realistic impossibility.

Tell me about this extremely low collision again when a hacker come up with a wallet generator software!
If the software generate 1 wallet a min
1*60 = 60 an hour
60 * 24 = 1440 a day
1440 * 365 = 525600 a year
Now let's say there is only a million using the software
That's 525,600,000,000
and this is not adding what normal people are generating!

See my examples above.  The numbers you are typing are not big.  They don't change the odds in any significant way.

[Ibian]

Let's go back to school.

It is not possible. Not even in theory. Probability forbids it. The only way it could happen is through faulty code.

[byt411]

Let's go back to school.

It is not possible. Not even in theory. Probability forbids it. The only way it could happen is through faulty code.

Yes, there is a probability in theory.
Prove that there isn't.

Also, the point is not about whether we should care about this possibility, it is not about if we should think about things that have a higher probability to occur.

The point is that 0.01^ ∞% ≠ 0%.

[Ibian]

Let's go back to school.

It is not possible. Not even in theory. Probability forbids it. The only way it could happen is through faulty code.

Yes, there is a probability in theory.
Prove that there isn't.

Also, the point is not about whether we should care about this possibility, it is not about if we should think about things that have a higher probability to occur.

The point is that 0.01^ ∞% ≠ 0%.

You are bad at math, and wrong. There is no possibility of it happening. It has been discussed, and mathed out, a number of times before. Use the search feature and read instead of arguing on the internet.

[roslinpl]

Is not it possible that a same address is being generated by 2 clients ? Or 2 persons at 2 different parts of the world are creating brainwallet from same passphrase ?

It would be a RIPEMD-160 collision.
Highly not possible but not impossible