Obtaining the public key from the public address

[Shevek]

I'm sure it is a dumb question, answered a lot of times. But it is difficult to search such topic over this forums.

So: the public address (that is propagated) is a hash of the public key. The public key is needed for checking transactions. But reversing the public address to obtain the public key is impossible, because of the nature of hash functions.

What is the solution!?

TIA.

[dust]

The public key corresponding to an address is revealed when coins are first spent from that address.

[fpgaminer]

When bitcoins are sent to an address, they are sent using the standard pay-to-hash output script:

Code:

OP_DUP OP_HASH160 <pubKeyHash> OP_EQUALVERIFY OP_CHECKSIG

For the receiver to spend this output, they need to supply a scriptSig of:

Code:

<sig> <pubKey>

And thus you see that the public key is revealed when the receiver spends the bitcoins.  Until such a time, the public key may remain unknown.

[Shevek]

Yeeeaap!

Thanks!