7
Is there some way in which I could get the public key of a Bitcoin user ?
Lets say I have transaction with another Bitcoin user. Is there some means by which I can retrieve the public key of the Bitcoin address they used in our transaction?
How does https://slock.it/ guys does it ? From where do they get the public key from ?
9
You cannot compute the public key of an address (that is not yours), because the address is computed from the hash of the public key.
You can find the public key of your own address with the Bitcoin-QT debug window or with a validateaddress RPC call.
Sounds like OP is asking about getting the public key AFTER a transaction has happened. Then it IS possible to get the public key from the transaction, or multiple public keys depending on how many inputs were used. – Jannes – 2016-06-06T09:21:35.987
What direction did the transaction go? There's a difference whether the address' balance was spent, or it only received bitcoins. – Murch – 2016-06-06T09:55:38.367