Bitcoin Forum

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  ???

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?

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 (http://preshing.com/20110504/hash-collision-probabilities)

Ok, new data, will recalc everything:

• probability of getting struck by lightning in any given year: 1/280000.
• probability of taking a shit at any given point in time: 1/(60*24) = 1/1440 (assuming you take a crap every day and the actual process takes 1 minute)
• probability of getting struck by lightning while taking a crap in any given year: 1/(280000*1440) = 1/1.47E11 = 2.48E-9
• probability of taking a crap while being in a situation where being struck by lightning can actually occur = 1/1440 = 0.25 = 1.74E-4
• probability of finding a collision: 1E-65
• getting hit by lightning while taking a crap for how many years in a row is equally probable as finding a collision: log(1E-65) / log(1.74E-4) = 17.3

is my math roughly correct now?

If so, I can say: "Finding a collision is about as likely as being struck by lightning while taking a crap every year for 17 years in a row".

A graphical explanation of bitcoin security https://i.imgur.com/VjtG3.jpg

https://i.imgur.com/VjtG3.jpg (https://i.imgur.com/VjtG3.jpg)

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

I am a little scared  ???

The chance is extremely low, you better worry how to keep your paper wallet safe & secure.
If you worry about it, split your bitcoin to multiple addresses or using multi-signature address

So you bought this account just recently?
No way you could have been a bitcointalk member for 2 years without ever reading this frequently (asked/answered) question.

The risk is non-zero, but small enough that you don't need to bother (unless you're using software with a broken random number generator). If you bother about duplicate private keys, you should bother more about the possibility of being eaten alive by an ice bear or drowning in a soup bowl - both events are much more likely.

Onkel Paul

Someone already create www.directory.io
but I think this site is only prank

Its good that guy who make this site didnt
implement address search option

There is nothing to be scared of. Lucky guy get others' money. Isn't it cool? ;)

So is it his website real or just fake?
Do we have to worry about is?

Yes, this site is real.
Do we have to worry?

maybe yes, maybe no  :D

But with a private key you can acces the wallet or not?

So you bought this account just recently?
No way you could have been a bitcointalk member for 2 years without ever reading this frequently (asked/answered) question.

So is it his website real or just fake?
Do we have to worry about is?

No, its my account. I know about bitcoin for 3 years....
but never read / think before about this possible problem.

So is it his website real or just fake?
Do we have to worry about is?

So if two people have the same private key, they have the same wallet??

Its real, but you dont have to worry about it. They dont have a database with all keys (there is not enough storage space on the planet for that), they just generate them on the fly.


No, wallet is the software that handles the private keys for you.

So the website is useless?

Or for what do they use private keys than?

Someone already create www.directory.io
but I think this site is only prank

Its good that guy who make this site didnt
implement address search option

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.

 

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.

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  ???

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.

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.

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.

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 :)

You need many more 9s than that.

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Correct.


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.


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?

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.

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.

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  ???

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  :D

Yea, I see that site before.
Its only a prank :D

Well, I would not say it is a prank. If you have the time you can click yourself through all 904625697166532776746648320380374280100293470930272690489102837043110636675 pages and you will find every private key to a bitcoin address you want  :D