Is it possible a BTC client generate an address identical to another person's?

[rdluffy]

I'm thinking here, sorry if it's a noob question, but if we can create a wallet offline with electrum for example
Is it possible the client generate 2 same adresses with 2 identical seeds?

Thanks

[1715318428]

1715318428

[1715318428]

1715318428

[TryNinja]

What do you mean?

If you use the same seed, it will obviously show the same addresses (it’s the same wallet after all).

Edit: I missed the title. TLDR: chances are way (WAY) too small as explained by HCP right below.

[HCP]

Is it possible the client generate 2 same adresses with 2 identical seeds?

The possibility of randomly generating the same seed as another wallet, while technically "non-zero", is so incredibly small that it's regarded as being "impossible".


For reference, Electrum generates a random 128bit seed... That's 2^128 or 340,282,366,920,938,463,463,374,607,431,768,211,456 different values that are possible (then you get the checksum added on for good measure).

[rdluffy]

Oh, thank's for the clarification, now I can undertand, it's not zero, but technicaly impossible

[numismatist]

Is it possible the client generate 2 same adresses with 2 identical seeds?

The possibility of randomly generating the same seed as another wallet, while technically "non-zero", is so incredibly small that it's regarded as being "impossible".


For reference, Electrum generates a random 128bit seed... That's 2^128 or 340,282,366,920,938,463,463,374,607,431,768,211,456 different values that are possible (then you get the checksum added on for good measure).

On the other hand it is possible to detect that 1 address got used by 2 people. Just no wallet does, since it requires fuzzy logic.
Bitcoin was never designed for keeping all eggs inside single same basket. Every single dollar worth of value should reside on it's own and unique address.
This paper wallet culture messed things up in a serious way.

[joniboini]

On the other hand it is possible to detect that 1 address got used by 2 people. Just no wallet does, since it requires fuzzy logic.

Afaik, you can detect which address belongs to which wallet using tools like walletexplorer (though it's using some kind of wallet clustering iirc). So, if I use an address X, and then I use address Y from the same seed, it will show up as part of one wallet.

Did I misunderstand something on how they work or what did you exactly mean?

[DebitMe]

I haven't seen that one infographic in awhile that does a good job explaining the power output of the sun over trillions of years, still has less of a chance of making a duplicate address.  Anyone have that saved?

[HCP]

So, if I use an address X, and then I use address Y from the same seed, it will show up as part of one wallet.

Did I misunderstand something on how they work or what did you exactly mean?

That's not how it works... it can't know that address X and address Y are from same seed. What Walletexplorer is essentially doing is looking for situations where UTXOs from different addresses (technically public keys) are being spent in the same transaction.

For instance... this recent transaction: ce09079b0588205ceb5c33e3378677d8a6f4eea826b7ec44a29f84c6c1e42c16

We can see the UTXOs came from the following (unique) addresses:
1AxkKhTPHULorCp7weHNCzNsnu7daiQpS9
1HxQg5f5hCi1R6QLme5AnhxxJp9dekEgXN
17nt1tAH2HZYkpzeu89WPQax1Z14itSZEM
1DhrGMNaAPXibS3w37xd7brmBche8fpTmY
1P1P9NTiN69nZas2VtNGcC1SXuABswy4ZN
12PZiFyf4Fzy981M9tiu6Hirzdd6tFYK9t
1GyejomGpaTndNiXdjstTjjMvvVoVonKGd

It is therefore reasonable to assume that ALL of those addresses came from the same wallet (but not necessarily the same "seed", it's quite possible they were just random private keys in the same wallet). Walletexplorer is basically just looking at relationships like this.

They can't just start with say 1AxkKhTPHULorCp7weHNCzNsnu7daiQpS9 and then claim that 1GyejomGpaTndNiXdjstTjjMvvVoVonKGd comes from the same seed... unless you actually know the seed or master private/public key, you can't derive the other public keys.

[CryptoBry]

I haven't seen that one infographic in awhile that does a good job explaining the power output of the sun over trillions of years, still has less of a chance of making a duplicate address.  Anyone have that saved?

I think you meant this image


Source : https://www.reddit.com/r/Bitcoin/comments/1apxbv/bitcoin_security_your_money_is_secured_by_the/

But it's no longer true when quantum computer with sufficient qubit exist and public key of an address is exposed

It is quite reassuring of the chance that a duplicate wallet address can be created but then again I am thinking about the coming of supercomputers which can presumably fry private keys and crack them using less resources. Should we be worrying about quantum computers or is it possible that at that time a counter technology can also be developed?

[bob123]

Should we be worrying about quantum computers or is it possible that at that time a counter technology can also be developed?

Short answer: No.

Slightly longer answer:
Definitely not in the foreseeable future. Quantum computers are not magic machines.
It will still take lots of years until usable QCs will be built.

And if they are finally in a stable state with the ability to program them properly, one would still need to develop an efficient algorithm.
It is not like you would give it the public key and say 'crack it' - and 10 minutes later you have the private key.

Even IF this was the case (which would still take lots of years to reach this state), simple stopping of address-reusing would circumvent it. THEN we would basically be at the same level of security as IOTA.

But instead of stopping address reuse, we can simply fork into a better (quantum proof) algorithm. We will have more than enough time for this.


Now, if we are also talking about attacking hashing algorithms in addition to the elliptic curve (where it wouldn't be enough to stop address-reuse), the world would have far more problems than just BTC's security.
Anything else would also be at risk (TLS, banking, encryption, etc..). 

However, in this case BTC can still simply fork to a new algorithm.


So.. in the end.. No, quantum computer will note harm BTC at all.

And if you here someone else talking garbage that QCs will break BTC in no time - they don't have a clue at all regarding what they are talking about.
Even with existing, fully functional QC's it probably still would take years to create an efficient algorithm to be able to crack private keys.

[rdluffy]

Ok guys, now I'm really satisfied with the answers and it's incredible, even try to imagine the chances to this situation happens is hard