same private key?

[cauciuc08]

hey,
I wonder, even if the probability so small is, if someone else get the same private key as me could he/she spend my Bitcoins and viceversa? would we have the same Bitcoin Adress?

[1714856994]

1714856994

[1714856994]

1714856994

[1714856994]

1714856994

[1714856994]

1714856994

[BlackHatCoiner]

Simple answer: Yes.

Advanced answer: The possibility is so small that we should not even discuss it. It's like finding a random number between 1 and 115,792,089,237,316,195,423,570,985,008,687,907,853,269,984,665,640,564,039,457,584,007,913,129 that has already been chosen from another person.

It's more possible to win 10 jack pots on a row than finding the same private key with someone else.

Except if you choose a number that is not random. Like 5, because you can. Then some developers may steal your bitcoins because there are people who do that kind of researches.

Although everything is possible. The problem is that it's very unlikely to happen.

[cauciuc08]

@BlackHatCoiner
thank you

[minairia3]

Indeed. But chances are not that high and one out of million times. But there are cases of stolen funds by guessing.

Check out these articles:
[1]Guess My Bitcoin Private Key
[2]A 'Blockchain Bandit' Is Guessing Private Keys and Scoring Millions

[Yatsan]

Private keys are generated uniquely, there is no way that there are 2 identical/ same pattern private keys. Same as the question " Is it possible to guess someone's private key?, the answer is nearly impossible because private keys are set of codes paired to public key which is used for encryption and decryption, for cryptography the common size of the private key is 256 bit, if someone wants to guess it he needs to perfectly guess each of it, it's like winning a toss coin for 256 times or more!

[BlackHatCoiner]

Private keys are generated uniquely, there is no way that there are 2 identical/ same pattern private keys. Same as the question " Is it possible to guess someone's private key?, the answer is nearly impossible because private keys are set of codes paired to public key which is used for encryption and decryption, for cryptography the common size of the private key is 256 bit, if someone wants to guess it he needs to perfectly guess each of it, it's like winning a toss coin for 256 times or more!

Yeah that. Think the coin, OP.
If we toss it once then you have 1:1 possibilities. H or T.
If we toss it 2 times then you have 1:4. HH, TT, TH, HT
3 times even bigger.

It becomes HHH, TTT, HHT, TTH, HTH, THT, THH, HTT.

Imagine tossing it for 256 times

[Bitcoinislife09]

Indeed. But chances are not that high and one out of million times. But there are cases of stolen funds by guessing.

The private key is really important. These are things that are must not be shared. But then there are also times that it may be guessed.
Bitcoin transactions are traceable, public, and stored permanently in networks of bitcoin. If you have an account anyone may see your transactions and can see your balance. If one address are used, in every transaction it can be involved with. I think the answers are yes just like what the other says but the private key is just so many letters and numbers so we could assume that there is only a very small chance it having the same private, maybe a small percentage of users only could have the same private key but it would never happened in the same wallet or platform I assumed.

[Nhor1011]

Private keys are generated uniquely, there is no way that there are 2 identical/ same pattern private keys. Same as the question " Is it possible to guess someone's private key?, the answer is nearly impossible because private keys are set of codes paired to public key which is used for encryption and decryption, for cryptography the common size of the private key is 256 bit, if someone wants to guess it he needs to perfectly guess each of it, it's like winning a toss coin for 256 times or more!

You are right,it is possible to have the same private key but it is possible to have only one number or letter different from other private like what happened to my own private key which i think i lost because i can't open my wallet using it but when i tried what Myetherwallet team told me to do,i recovered my own private key and open my wallet again and i found out that there is another wallet with private key almost the same with mine,only one number is different. But if you want to guess someones private key,it is difficult because every private key has a ramdom number with letters.

[joniboini]

i recovered my own private key and open my wallet again and i found out that there is another wallet with private key almost the same with mine,only one number is different.

Of course it is. Which means if you have one unknown variable then it will be much easier to crack/brute force it. However, finding/guessing private key of a given address is another story.

[milesfull]

Simple answer: Yes.

Advanced answer: The possibility is so small that we should not even discuss it. It's like finding a random number between 1 and 115,792,089,237,316,195,423,570,985,008,687,907,853,269,984,665,640,564,039,457,584,007,913,129 that has already been chosen from another person.

Sounds interesting. Some times even mad things in terms of probability really could happen, it would be interesting for researchers.

[Kong Hey Pakboy]

Private keys are generated uniquely, there is no way that there are 2 identical/ same pattern private keys. Same as the question " Is it possible to guess someone's private key?, the answer is nearly impossible because private keys are set of codes paired to public key which is used for encryption and decryption, for cryptography the common size of the private key is 256 bit, if someone wants to guess it he needs to perfectly guess each of it, it's like winning a toss coin for 256 times or more!

You are right,it is possible to have the same private key but it is possible to have only one number or letter different from other private like what happened to my own private key which i think i lost because i can't open my wallet using it but when i tried what Myetherwallet team told me to do,i recovered my own private key and open my wallet again and i found out that there is another wallet with private key almost the same with mine,only one number is different. But if you want to guess someones private key,it is difficult because every private key has a ramdom number with letters.

Indeed. It is impossible for someone to have the same private keys because it is generated uniquely. It is really possible for you to have the almost same letter and numbers in your private with another wallet that only one letter and number is different, yet it is still a unique private key because you are the only one who has that private key.

[btccoffee]

Cleared answer is yes, if he got your wallet and your private key then he can use all of your bitcoins. But if you mean that he can generate the same wallet and the same key in your own wallet then that is impossible to happen because bitcoin or any blockchain wallets are generated together as one. What i mean is they are encrypt and decrypt each other, means you can’t generate the same public key wallet without generating the same private key.

[o_e_l_e_o]

Advanced answer: The possibility is so small that we should not even discuss it. It's like finding a random number between 1 and 115,792,089,237,316,195,423,570,985,008,687,907,853,269,984,665,640,564,039,457,584,007,913,129 that has already been chosen from another person.

That number is not right. You've taken 2²⁵⁶, but missed out the last 6 digits of 639,935, giving a number that is closer to 2²³⁶ rather than 2²⁵⁶.

However, 2²⁵⁶ isn't correct either. Because of the secp256k1 curve that bitcoin uses, the upper limit to the number of private keys is slightly less than 2²⁵⁶. In decimal, the number is:

Code:

115,792,089,237,316,195,423,570,985,008,687,907,852,837,564,279,074,904,382,605,163,141,518,161,494,336

However, that number isn't actually correct either. Although there are just less than 2²⁵⁶ private keys, there are "only" 2¹⁶⁰ addresses, meaning on average there are around 2⁹⁶ private keys for each address.

[BlackHatCoiner]

Advanced answer: The possibility is so small that we should not even discuss it. It's like finding a random number between 1 and 115,792,089,237,316,195,423,570,985,008,687,907,853,269,984,665,640,564,039,457,584,007,913,129 that has already been chosen from another person.

That number is not right. You've taken 2²⁵⁶, but missed out the last 6 digits of 639,935, giving a number that is closer to 2²³⁶ rather than 2²⁵⁶.

However, 2²⁵⁶ isn't correct either. Because of the secp256k1 curve that bitcoin uses, the upper limit to the number of private keys is slightly less than 2²⁵⁶. In decimal, the number is:

Code:

115,792,089,237,316,195,423,570,985,008,687,907,852,837,564,279,074,904,382,605,163,141,518,161,494,336

However, that number isn't actually correct either. Although there are just less than 2²⁵⁶ private keys, there are "only" 2¹⁶⁰ addresses, meaning on average there are around 2⁹⁶ private keys for each address.

I didn't get the first part. Why is it closer to 2²³⁶ rather than 2²⁵⁶?

You say that there are "only" 2¹⁶⁰ addresses. Why their private keys aren't 2¹⁶⁰ too?

Guide me.

[o_e_l_e_o]

I didn't get the first part. Why is it closer to 2²³⁶ rather than 2²⁵⁶?

Because you wrote the wrong number, and missed out the last 6 digits. 2²⁵⁶ is equivalent to 1.158*10⁷⁷. The number you wrote is 1.158*10⁷¹.

You say that there are "only" 2¹⁶⁰ addresses. Why their private keys aren't 2¹⁶⁰ too?

Private keys are limited by the order of the secp256k1 elliptical curve used in bitcoin. The order n is as follows:

Code:

FFFF FFFF FFFF FFFF FFFF FFFF FFFF FFFE BAAE DCE6 AF48 A03B BFD2 5E8C D036 4141

Private keys can range from 0 to n-1. In hex, n-1 is:

Code:

FFFF FFFF FFFF FFFF FFFF FFFF FFFF FFFE BAAE DCE6 AF48 A03B BFD2 5E8C D036 4140

In decimal, it is:

Code:

115,792,089,237,316,195,423,570,985,008,687,907,852,837,564,279,074,904,382,605,163,141,518,161,494,336

This number is so close to 2²⁵⁶ that we often just say there are 2²⁵⁶ private keys for ease of communication. The difference between this number and 2²⁵⁶ is tiny.

Addresses, on the other hand, are limited by the RIPEMD160 hash function. To turn a public key in to an address, it is first hashed using SHA256 and then use RIPEMD160. The result of this will be a number which is 160 bits long, meaning the upper limit is 2¹⁶⁰ unique addresses. (Assuming of course we are talking about 1 type of address. There are 2¹⁶⁰ P2PKH "1" addresses, 2¹⁶⁰ P2SH "3" addresses, and 2¹⁶⁰ P2WPKH "bc1" addresses.)

So yes, there are many more private keys than there are addresses, meaning multiple private keys can lead to the same address.

[noorman0]

I have another related question.
When I generate a new address/privkey through a custodian/non-custodian wallet even on the exchange, is it possible to get someone else's address or will it be skipped?
if at least 1% of the total privkey was generated, it's not impossible that one day someone will get someone else's privkey.
And I think this is more possible for people who want vanity addresses.

[o_e_l_e_o]

is it possible to get someone else's address or will it be skipped?

Theoretically it is possible, but in reality it will never happen. There is certainly no mechanism or database that wallets or exchanges use to check if an address has already been used when generating new private keys.

The reason it will never happen is simply down to math. The numbers we are dealing with here are unimaginably large. For example, if every human on the planet each generated 1 million new addresses every second, and had been doing so since the birth if the universe 13.7 billion years ago, we would only have generated approximately 0.0000000000002% of all possible addresses.

[samcrypto]

hey,
I wonder, even if the probability so small is, if someone else get the same private key as me could he/she spend my Bitcoins and viceversa? would we have the same Bitcoin Adress?

That's not going to happen considering the probability and I'm sure if the limit for the private keys has been reach, no new users will allowed to create a wallet. We have so much words to use in private keys, and I'm confident that those system can generate that much. Though we might think about the system error and if you think someone is also using the same private keys with you better to inform the developer and create a new wallet right away, this can be a very rare situation.

[TheArchaeologist]

The reason it will never happen is simply down to math. The numbers we are dealing with here are unimaginably large. For example, if every human on the planet each generated 1 million new addresses every second, and had been doing so since the birth if the universe 13.7 billion years ago, we would only have generated approximately 0.0000000000002% of all possible addresses.

Thanks for these numbers. I see a lot of "get rich fast" posts/questions from new members to this forum lately in which they think it is possible to find private keys to well funded addresses by bruteforcing. I think most of these questions arise when people just don't have a grasp about the near infinite candidates. So I'm probably gonna use your number example as reply in the future to point out there's a difference between "theoretical possible" and "practictal feasible".

[Reid]

Learned a lot here.
Thanks to those who answered the question from the OP.

I didn't even think about it since there is a very low chance for it to happen or we could even say "none".
But, it is still better to find an explanation for it. 
The math though is getting me dizzy especially the answers from o_e_l_e_o.