Hi all,

I've been reading a lot about how the sending address is determined

https://bitcointalk.org/index.php?topic=189894.msg1972257#msg1972257

https://bitcointalk.org/index.php?topic=198048.0

But there is one thing I was not able to figure out:
If my client (Bitcoin-Qt) uses more than one address to send the appropriate funds like in this transaction



Which address is the "Sending" one?

do I sign a message with "..7hE" or "..PrL"? or can I choose and sign a message with any one of them to prove I'm the sender?

Thanks in advance.