Bitcoin Forum

I understand that sometimes when receiving bit coins you have to communicate the public key to the sender as well as the address. If this is true then how does one learn the public key of a blockchain.info wallet address?

You've obviously misunderstood something. To receive bitcoins, you need to give the sender either your public key or your address. Never both. The whole point of addresses is so that ordinary users never have to even see a public key or know what one is. Addresses are shorter than public keys making them easier to manage and include a checksum to guard against typos. You shouldn't even think about using public keys if you can use addresses instead.

I see. I remember reading on an online bitcoin wallet site that if you want to send money to a bitcoin address that has never been used before you have to provide the public key as well. I'll see if I can find a link to that statement. But in the meantime, have you ever heard of something like this?

I think I see the source of the misunderstanding. The public key associated with a bitcoin address is broadcast as part of the transaction when sending coins from that address, and it is unusual for a public key to be published any other way. As such, the public key of an address that has not yet been used to send coins will usually not be publicly available. However, the public key is only used to verify that coins sent from an address are legitimate; sending coins to an address does not involve that address's public key in any way, and the non-availability of an address's public key does not prevent anyone from sending coins to it.

Case in point: the donation address in my signature. Anyone can send coins to this address, and a few people already have, even though the public key has never been seen. The public key has never been seen because this address has never been used to send coins anywhere else. None of this is a problem, and ordinary users never have to care about any of it.

Thanks for taking the time to explain it to me.