Bitcoin Forum

Hi everyone,

1) I was interested in creating a vanity wallet on bitaddress.org, but it points me to the vanity pool website to paste my public key and there's no field to do so. Is the vanity pool website defunct?

2) On directory.io, why do addresses and their corresponding compressed addresses show different transaction information on blockchain.info? Aren't they essentially the same address?

Thanks for any help,

Ag

Yes. If you want to generate a vanity address, it is recommended that you do so yourself on your own hardware using the vanitygen software.

No, they are not the same thing. An address corresponds to the hash of a public key. The hash of an uncompressed public key will be different from a compressed public key, so there are different addresses and thus different transaction histories.

Thanks achow101. I'll check out vanitygen.

Regarding compressed/ uncompressed addresses, why does directory.io list compressed addresses next to uncompressed ones? When you create a compressed address is this in fact a new address from the 2^160 pool of public keys? Confused...

Cheers,

Ag

There is no pool of 2^160 public keys. It is a pool of 2^160 addresses, not public keys. There are 2^256 private keys and each private key has exactly one public key, so 2^256 public keys. Each public key can be represented in two ways, in uncompressed form and in compressed form, so there are 2^257 representations of all public keys. Each representation of a public key corresponds to exactly one address because it is a hash of a representation of a public key. Because of the pigeonhole principle, more than one public key can correspond to the same address (and thus an address can have more than one corresponding private key).

So each private key can ultimately produce two different addresses - one compressed and one uncompressed? And different private keys can produce the same address (i.e. there are 2^96 private keys for each address)?

From the web:
"A compressed key is just a way of storing a public key in fewer bytes (33 instead of 65). There are no compatibility or security issues because they are precisely the same keys, just stored in a different way. "

So they're the same keys but when hashed produce different addresses?

Yes.

Yes, in theory. It has not happened yet.

Not necessarily.

Yes.

There are no addresses at the technical level.  Addresses are something the user interface provides to us humans to make it easier for us to talk about transferring control over value.

I assume you are asking about P2PKH addresses (the addresses that start with a '1').  In that case, yes, each private key can ultimately produce two different addresses.

However, recall that there are also P2SH addresses (the addresses that start with a '3').  

If you include P2SH addresses, then for so long as we choose to compute an address as a RIPEMD160 hash of some information encoded with base58check encoding, there will be 2¹⁶⁰ possible P2SH addresses for every private key.


Correct.  Although, realistically, only one of those private keys will ever be known.


Correct, because they are "just stored in a different way", and what is being hashed is that way of storing it.

Thanks people. Makes sense.