Say I have created a paper wallet with one bitcoin address in a vault. What are chances that someone else will find the private key for this wallet?

Related: what are the chances of vanitygen address - private key pair collision?


There are around 1,461,501,637,330,902,918,203,684,832,716,283,019,655,932,542,976 posible bitcoin addresses according to BitcoinTalk.org. This makes it a very small posibility of finding another address that is being used. So the chance is around %0.

  • The method used to figure it this number is through ripemd-160 – nelruk Dec 27 '17 at 16:18
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    You should give a exact number not just around 0% – Omid Sadeghi Sep 10 '19 at 13:01

Essentially zero. They would have to find a private key whose public key hash matched yours. The public key hash is 160 bits long. If they had a billion computers, each of which could try a billion keys a second, and they tried for a billion years, they'd have much, much less than a one in a billion chance of getting it.

  • I understand this if you're trying to match a single public key. But with the entire blockchain freely available and the entire world possibly working on checking each private key, constantly on thousands of different computers, the chances should be slightly different than the model you described. – Luca Matteis Feb 4 '14 at 13:22
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    I assumed a billion computers, and I gave a billion years. There are only 21 million Bitcoins. So if you figure it's not worth much trouble to steal less than 0.01 Bitcoin, that means at most there are 2 billion keys worth stealing. That doesn't change the numbers much (when you make the number of computers and number of years reasonable). – David Schwartz Feb 4 '14 at 13:24
  • There are 21 million bitcoins yes, but many more addresses. – Luca Matteis Feb 4 '14 at 13:25
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    Since there are 21 million Bitcoins, that means at most 2.1 billion keys could hold at least 0.01 Bitcoins. – David Schwartz Feb 4 '14 at 13:27
  • Not wanting to revive this, just adding the actual numbers… 2¹⁶⁰ BTC addresses / 2,100,000,000,000,000 Satoshi = a fraction more than 695,953,160,633,763,294,382,707,063,198,230 addresses per Satochi. – e-sushi Nov 24 '14 at 10:16

There is a guy who has been testing this. He has ran a computer which generates addresses and checks the balances. Out of several years, processing millions of addresses per day, to my knowledge, he has found 3 with small balances. So, you can talk theoretical, where the chances are practically zero, but when there is someone who has attained at least 1, then perhaps it's not as unlikely as the math suggests.

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    You are new here. (1) It's not ok to put your LTC/BTC/ETH... adress in your comments. This will give you a lot of downvotes. The reason of this platform is not earning money. (2) If you tell that someone found 3 private keys of adresses, then prove it (with a link to a website/video for example). I'm pretty sure, it's not possible. – ndsvw Dec 27 '17 at 9:17

I have been thinking this same question myself. If someone is checking against 100s of public addresses wouldn't that increase the odds of finding a correct private key?

At the same time it checks against 100s of addresses it can effectively dismiss those same addresses. In addition by using what some have noted as not so 100% randomness of private keys made with poor RND generators. If there is even a very slight normal distribution then a person could save more time by concentrating on a certain range of private keys (would still be in the billions).

In fact, what if the person cross-checked with multiple public addresses from different cryptocurrencies? One random seed number producing multiple private keys to check against 10,000s of public address for many cryptocurrencies.


Random Seed 1 used to produce bitcoin, ethereum, monero, ltc, bch, ethereum classic, etc private keys to check against 1000s of public addresses from each cryptocurrency.

Then going to Random Seed 2. And Random Seed 3. Etc.

I am sure that a very resourceful person would find address with non-zero balances much faster than the maths tell us since the math is only looking at 1 private key brute force hacking.


Unfortunatly the chance of finding randomlly using private key is greate , becuase wallets uses almost the same algoritm to generate private keys

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    It is what? Great? No, the chance is approximately zero for all intents. – Anonymous May 13 '19 at 5:52
  • This is an interesting take. It might be true if wallets used deterministic algorithms (or bad randomness) to generate private keys. However, that would be a bad implementation mistake. Such problems do exist in practice, of course, and people have searched the blockchain for such patterns for a long time (and found/recovered/stolen lots of bitcoins in brainwallets and such). However, any good wallet should use 256 bits of randomness in generating a private key, and then the probability of collision is unimaginably small - 1 / 2^256. – stefanwouldgo May 16 '19 at 8:04

The only true way to defend against this is to avoid large balances with each private key. But if people do that then it will be much easier to find something if adoption happens and active addresses continued to double every 5 years.

Assuming btc is eventually $ 2 million per bitcoin and average person saves say 200k in bitcoin. They would need 2000 keys with 0.00005 to avoid losing more than $100 though a random collision attack.

I guess there should be some kind of insurance against this happening but it goes against this idea consolidating uxtos to save fees is a good idea. It’s another reason why low fees are required for btc to work.

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