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Topic: What are the chances of an address collision? and what happens when it does? - page 5. (Read 22435 times)

donator
Activity: 1218
Merit: 1079
Gerald Davis
The odds in colliding with a specific address is 1 in 2^160.

If there are a billion users and each have one million active addresses (1 quadrillion funded addresses in the blockchain) the odds in colliding with any address would be roughly 1 in 2^110 (1*10^33).

Vanitygen can produce 20 million keypairs per second.  Lets say you build a super ASIC on 12nm (4 generations ahead of current tech) process that could create, validate, and steal one trillion keypairs per second (1 TK/s). That would be about 50,000x more powerful than faster GPU today.  Lets also say you built a thousand of them and ran them continually with no downtime 24/7/365.   In 1 year you could brute force 3*10^28 possible addresses.  

If there are 1 quadrillion funded addresses you would still have a ~1% chance of colliding with a random funded address in the next 1,000 years.

TL/DR Vlad's answer works.
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Chance are negligible. If collision occurs with a funded address, attacker you can transfer funds elsewhere.
legendary
Activity: 1264
Merit: 1008
Every time this questions pops up people start flooding the board with zeros.  Scientific notation people!

I grabbed this response from stackexchange, Thomas Pornin:

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If we have a "perfect" hash function with output size n, and we have p messages to hash (individual message length is not important), then probability of collision is about p^2 / 2^(n+1) (this is an approximation which is valid for "small" p, i.e. substantially smaller than 2n/2). For instance, with SHA-256 (n=256) and one billion messages (p=109) then the probability is about 4.3*10-60.

A mass-murderer space rock happens about once every 30 million years on average. This leads to a probability of such an event occurring in the next second to about 10-15. That's 45 orders of magnitude more probable than the SHA-256 collision [in 1b messages]. Briefly stated, if you find SHA-256 collisions scary then your priorities are wrong.



hero member
Activity: 815
Merit: 1000
But probability also says, I could have a success on my first run? isn't it?
Yes.

In conclusion don't store everything on one address. (Also minimizes risk of a given generator being malignant.)
hero member
Activity: 742
Merit: 500
Chance are negligible. If collision occurs with a funded address, attacker you can transfer funds elsewhere.



Chances are still negligible when 1 billion people are using it?  also can't I just run some kind of bots, that randomly generate addresses to see if
they have funds in them?

Yes, chances remain negligible. You could run your bot, but it'd be a waste of electricity. Chances are you'd wait the lifetime of the universe before finding a collision.

Not to mention that even if you could find addresses, if the block reward went to zero TODAY without a billion people using Bitcoin, even today's minute amounts of transaction fees would still be worth more per cpu/gpu/fpga cycle than if you'd spent that same cycle looking for populated addresses. Given that the same equipment you'd use in such an address search should, because of the similarity of the tasks, be capable of mining as well, it would be more profitable to use that equipment for mining purposes.
legendary
Activity: 1806
Merit: 1003
Chance are negligible. If collision occurs with a funded address, attacker you can transfer funds elsewhere.



Chances are still negligible when 1 billion people are using it?  also can't I just run some kind of bots, that randomly generate addresses to see if
they have funds in them?

Yes, chances remain negligible. You could run your bot, but it'd be a waste of electricity. Chances are you'd wait the lifetime of the universe before finding a collision.

But probability also says, I could have a success on my first run? isn't it?
legendary
Activity: 905
Merit: 1012
Chance are negligible. If collision occurs with a funded address, attacker you can transfer funds elsewhere.



Chances are still negligible when 1 billion people are using it?  also can't I just run some kind of bots, that randomly generate addresses to see if
they have funds in them?

Yes, chances remain negligible. You could run your bot, but it'd be a waste of electricity. Chances are you'd wait the lifetime of the universe before finding a collision.
hero member
Activity: 742
Merit: 500
can't I just run some kind of bots, that randomly generate addresses to see if they have funds in them?

See this question on the StackExchange site for a rundown of why brute-forcing private keys (which is essentially what you're describing) is also a no-go.
hero member
Activity: 742
Merit: 500
Given your example of 1 billion users at 10 addresses each:

There are 2^160 or about 1,460,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000 possible addresses
In your scenario, 1,000,000,000 people are using 10 addresses each for a total of 10,000,000,000 possible addresses
10,000,000,000 / 2^160 should yield the probability of a collision occurring
10,000,000,000 / 2^160 = 0.00000000000000000000000000000000000000684

So the chances of a collision occurring in your scenario are approximately 0.000000000000000000000000000000000000684%

See why we don't consider collisions an issue?
legendary
Activity: 1806
Merit: 1003
Chance are negligible. If collision occurs with a funded address, attacker you can transfer funds elsewhere.



Chances are still negligible when 1 billion people are using it?  also can't I just run some kind of bots, that randomly generate addresses to see if
they have funds in them?
hero member
Activity: 812
Merit: 1001
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Chances are negligible. If collision occurs with a funded address, attacker you can transfer funds elsewhere.

legendary
Activity: 1806
Merit: 1003
What are the chances of an address collision? when for example 1 billion people are using bitcoin and on average they generate 10 address per person.

also what exactly will happen when address collision occurs?
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