Bitcoin Forum

what is the total number of private keys that can ever be generated and what percentage of keys has been generated as of now..

how long will it take to run out of all possible keys?

Deep question there. I remember reading somewhere that it would take millions of years to run out of bitcoin addresses. Would anyone like to clarify/expand on this? I too would like to hear a more simple/explaining answer.

Having just imported the blockchain into a Mysql DB I see a total of 42,150,031 (as of block 311761) public key hashes and total amount of address out there I believe are 16^160 or 4.5624406176221952186411716057003e+192

The 42.1M number are only addresses that sent or received bitcoin so far, it is not a reflection of all addresses that have been generated.

So it will be a while before we run out.

If I remember, ripemd160 is the limiting factor so there are 2^160 possible public addresses.

For private keys, 2^256 is often cited but it is actually slightly smaller, some in the top of range are not used by the ECC algorithm bitcoin uses.

But it doesn't matter because 2^160 is smaller, so there are going to be collisions where two different private keys produce the same public address.
I doubt we'll ever find one, but they have to exist. Mapping a larger set to a smaller set guarantees they exist.

So 2^160 is how many addresses are available.

Or 1.4615016e+48, which is the same for...

http://weknowmemes.com/generator/uploads/generated/g1363653526683975009.jpg

Yup I forgot about ripemd160 2^160 or 16^40 = 1.4615016373309029182036848327163e+48

Still a very large number.

If a billion people each continuously generate a billion keys per second, it will take 46,343,913,000,000,000,000,000 years to generate all possible keys.

It is estimated that the solar system is only 4,600,000,000 years old.

It is estimated that the sun will last less than 10,000,000,000 more years, and that it will destroy the earth billions of years before that.

I think we have more pressing issues to worry about than the number of keys that have been used.

And long time before we reach 1/2 of all addresses it fails because when there is a chance that you get a key that already been taken, it fails. Luckily we ain't reach that far as previous post says :)

Nothing will fail when "you get a key that already been taken".
The problem will be that you will be able to spend what's already there, to the detriment of the "existing owner".

Atleast it's good to know how many years we still can generate btc addresses  ;D

At most 21 quadrillion addresses can have some balance in them. What you describe is picking up an address that has had some balance in the past, not that currently has it.

A long time before we reach that point humans and machines will probably have melded and we could upload our digital signature to the cloud - that would be our own biometric key.

Statistically the solar system is more likely to get destroyed than the chance of grabbing somebody's stash.

You have a probability of having a collision of two addresses greater than 50% at around the square root.
So at around 2^80 addresses, there is a 1/2 chance of having two people generating the same address.
2^80 ~ 10^24. It's still a gigantic number.

Such huge numbers to even be able to possibly grasp.

Even if you generate all addresses, to run out of addresses, all of them must have to be used simultaneously, which is pretty much impossible.