Creating same priv. key two times

[el kaka22]

The number of private keys in the universe is very big, and I've done the following calculation:
My computer have a hashrate of 4 MH/s, and it generate 650K private keys per second on vanitygen, so the estimation of private keys that can be generated by ALL the current hashing power in the world (let them be 400 PH/s for easy calculation), then the WHOLE world generate 6.5*10^16 private keys per second, compared to there are 2^160 (about 1.5*10^48) private keys that would ever exist and the 10^10 keys that may present if 10^9 people using 10 keys, then the whole world needs 4*10^22 seconds, or 1.3*10^15 years to generate a private key that someone owns, not to mention they are empty or not. So generating a duplicate private key is almost impossible.

[Muhammed Zakir]

The number of private keys in the universe is very big, and I've done the following calculation:
My computer have a hashrate of 4 MH/s, and it generate 650K private keys per second on vanitygen, so the estimation of private keys that can be generated by ALL the current hashing power in the world (let them be 400 PH/s for easy calculation), then the WHOLE world generate 6.5*10^16 private keys per second, compared to there are 2^160 (about 1.5*10^48) private keys that would ever exist and the 10^10 keys that may present if 10^9 people using 10 keys, then the whole world needs 4*10^22 seconds, or 1.3*10^15 years to generate a private key that someone owns, not to mention they are empty or not. So generating a duplicate private key is almost impossible.

[Rmcdermott927]

After I made a paper wallet for long-term saving,
I start thinking about posibility that somone can create same priv. key
in their wallet in the future.

I know that posibility for this is very small, but it exist.
If someone want to create billions and billions private keys,
he can generate someone address with positive balance.

What you people think about that? This can become a big problem
for Bitcoin in the future... no?

I am a little scared 

A collision with any of the SHA algorithms has never been recorded.   There are more possible private keys than there are grains of sand on every beach in the world.   Don't be scared.   Just keep you keys safe.   The only theoretical issue is when quantum computing becomes a reality.  But this is many, many years in the future.

[odolvlobo]

There are more private keys than molecules of water on the Earth. If I picked a single molecule of water somewhere -- maybe in an ocean, or in a lake, or in the air, or in a puddle, or in my toilet -- you are more likely to guess which molecule of water I picked than to guess one of my private keys.

[Deathwing]

I don't know if it's a coincidence or not but someone from the Turkish community was mining "private keys" yeah. "mining" and he managed to find 50 BTC, a address that no one used for the last 3 years.

[Amph]

There are more private keys than molecules of water on the Earth. If I picked a single molecule of water somewhere -- maybe in an ocean, or in a lake, or in the air, or in a puddle, or in my toilet -- you are more likely to guess which molecule of water I picked than to guess one of my private keys.

still very far from being impossible  

for example 1B^1B is bigger than the amount of the number of tries required to perform a successful collision

B = billions

[Rmcdermott927]

I don't know if it's a coincidence or not but someone from the Turkish community was mining "private keys" yeah. "mining" and he managed to find 50 BTC, a address that no one used for the last 3 years.

It was likely not a collision.  It is possible that it was generated by some sort of brainwallet or other non-random method of generating keys.  Compute time would be better spent running combinations of words and phrases through the brain wallet format than trying to find collisions.

[shorena]

I don't know if it's a coincidence or not but someone from the Turkish community was mining "private keys" yeah. "mining" and he managed to find 50 BTC, a address that no one used for the last 3 years.

It was likely not a collision.  It is possible that it was generated by some sort of brainwallet or other non-random method of generating keys.  Compute time would be better spent running combinations of words and phrases through the brain wallet format than trying to find collisions.

Yep, IIRC there was someone that was generating a subset of all private keys. 32-bit worth IIRC and they also found several balances. Its not a proper collision if you only use a subset of the whole space. Thats like searching only a certain toilet (to stay with the water example) which is commonly used by badly written software as well.

[RealBitcoin]

After I made a paper wallet for long-term saving,
I start thinking about posibility that somone can create same priv. key
in their wallet in the future.

I know that posibility for this is very small, but it exist.
If someone want to create billions and billions private keys,
he can generate someone address with positive balance.

What you people think about that? This can become a big problem
for Bitcoin in the future... no?

I am a little scared 

Its very small, but i cant describe how small it is, higher odds for you to being hit by a bus then to that happen.

Its also more likely to be hit by a meteorite than for that to happen, so better buy insurance agains meteorite hits than agains duplicate priv key.

[Bitdonator]

After I made a paper wallet for long-term saving,
I start thinking about posibility that somone can create same priv. key
in their wallet in the future.

I know that posibility for this is very small, but it exist.
If someone want to create billions and billions private keys,
he can generate someone address with positive balance.

What you people think about that? This can become a big problem
for Bitcoin in the future... no?

I am a little scared 

Its very small, but i cant describe how small it is, higher odds for you to being hit by a bus then to that happen.

Its also more likely to be hit by a meteorite than for that to happen, so better buy insurance agains meteorite hits than agains duplicate priv key.

I already hited by bus when I was young    LoL
Nothing serious, just my broken bike

[BitcoinNewbie15]

I have heard that the odds of a private key collision taking place are infinitesimally small. It is so incredibly unlikely to happen, that it is almost guaranteed nothing to worry about.

[ClamCoin]

This website also generate and publish private keys.  www.coinfind.cf
New archive with 100,000 priv. keys are published every day.

But seems like this is for good reason, creator of that website
drop some BTC to 5 addresses for others to find.

 

So when peoples get the Same private key, the one got some free bitcoin. But if I am right that will need so much luck to get the same private key,that it will take most likely many years. And what is the good reason u are saying?


Thanks,

ClamCoin

[Hexcoin]

This website also generate and publish private keys.  www.coinfind.cf
New archive with 100,000 priv. keys are published every day.

But seems like this is for good reason, creator of that website
drop some BTC to 5 addresses for others to find.

 

So when peoples get the Same private key, the one got some free bitcoin. But if I am right that will need so much luck to get the same private key,that it will take most likely many years. And what is the good reason u are saying?


Thanks,

ClamCoin

definitely free coins for the other owner. but the chance is so small like it is 99.999999999999999% impossible. maybe in our entire lives it wouldn't happen

[Muhammed Zakir]

This website also generate and publish private keys.  www.coinfind.cf
New archive with 100,000 priv. keys are published every day.
But seems like this is for good reason, creator of that website
drop some BTC to 5 addresses for others to find.

So when peoples get the Same private key, the one got some free bitcoin. But if I am right that will need so much luck to get the same private key,that it will take most likely many years. And what is the good reason u are saying?
Thanks,
ClamCoin

definitely free coins for the other owner. but the chance is so small like it is 99.999999999999999% impossible. maybe in our entire lives it wouldn't happen

You need many more 9s than that.

-snip-

The probability of a collision is found by a standard formula: p = 1 - k! / N^k-1(N-k)!, where k is the number of hashes generated (100x10¹⁰x10³) and N is the number of possible hashes (2¹⁶⁰).

This is a difficult number to calculate, but there is a good approximation: p = 1 - e^-k(k-1)/2N

But even that value is difficult to compute because of the precision needed. Here is another approximation p = k²/2N.

So the answer is that the probability of at least one collision is approximately 7x10^-19 or 0.00000000000000007%


See: http://preshing.com/20110504/hash-collision-probabilities

-snip-

[Reynaldo]

This has been talked different times on this forums, it's not possible, Muhammed posted all the needed information. Please next time use search function it really helps to keep post quality up and you can learn many things from old posts

[Bitdonator]

sorry, but I really tried to find some topics about that on the forum.

maybe I not search too much...
anyway, discusing about this problem
is never enough

[el kaka22]

Oh, I suddenly realized that, there are 2^256 private keys available in the universe, while there is only 2^160 bitcoin addresses available. That is, there are about 2^96 (about 8*10^30) private keys pointing to a same bitcoin address?! Is that true? Then will them collide?

[Muhammed Zakir]

Another interesting post:

there is no risk of collision?

Correct.

I mean 2 person can generate the same btc address

And all the molecules of air can collect in the corner of the room causing everyone in the room to suffocate, but the probability is so low that we consider it impossible.

Even if risks are low, what will happen in this case?

If the users are using faulty software that does not properly generate a random number (so that multiple users end up generating the same number), then all users that generate the same number will have the ability to spend the bitcoins that are sent to the address.  Whoever spends an output and gets confirmed first gets to be the "real" transaction for that output, and any transaction created by any of the others to spend the same output are rejected.

Oh, I suddenly realized that, there are 2^256 private keys available in the universe, while there is only 2^160 bitcoin addresses available. That is, there are about 2^96 (about 8*10^30) private keys pointing to a same bitcoin address?! Is that true? Then will them collide?

See

So there are 2^160 public keys but only 2^96 private keys? Ho does that add up?
Are there private keys than unlock more than one public key?

There are just under 2^256 private keys, just under 2^256 public keys, and 2^160 addresses. There are some addresses that have more than one corresponding public key and thus more than one corresponding private key.

The confusion comes in when two distinct concepts have the same name.

"private key" can mean either the raw 256 bits used to calculate the signature, or it can mean the encoded format that bitcoin stores.

Public key can also mean either the (x,y) point used to verify signatures, or it can mean the encoded version that bitcoin uses.

In the raw sense, both private keys are the same, and both public keys refer to the same (x,y) point.  In the encoded sense, the compressed private key encoding implies the compressed public key encoding, and ditto for the uncompressed encodings.  The addresses are hashed from the encoded forms, so there are two different addresses that technically refer to the exact same keypair.

Since bitcoin deals exclusively with encoded versions, the two formats are totally distinct different things.  If you generate your own raw private key, you can create both encodings and calculate both addresses.  Import the two encodings into different wallets, and neither one will have any idea about transactions sent to the other.  Even though they could calculate signatures for both, they don't know to look for them.

Difference between public keys and addresses:

Your public key is your BTC address. You can go to receive then copy an address that you want to receive at/use.

This is not true.

A public key is a 256 bit number if compressed (or a 256 bit x coordinate and 256 bit y coordinate of a point if not compressed) calculated from the private key using ECDSA with the Secp256k1 curve.

A BTC address is a hash of a public key with a version number prepended, a checksum appended, and then Base58Check encoded.

[Rmcdermott927]

After I made a paper wallet for long-term saving,
I start thinking about posibility that somone can create same priv. key
in their wallet in the future.

I know that posibility for this is very small, but it exist.
If someone want to create billions and billions private keys,
he can generate someone address with positive balance.

What you people think about that? This can become a big problem
for Bitcoin in the future... no?

I am a little scared 

The real question is:  How was this private key created?   If it was created using a brainwallet or something that is non-random with little entropy then that is essentially your only risk.   Remember, there are more private keys than there are molecules of water in all the oceans in the world.    There has never been a collision recorded in any of the SHA algorithms. 

[tyz]

This issue was discussed several times here. For sure, it is possible to create same keys but it is very very very...very unlikely. Even with quantum computers it would last decades.
To make you a little bit more afraid, just visit www.directory.io for example