But if you're offline (and no blockchain access), how can it get the UTXO?
It can't in that case, thats why it has an optional scriptpubkey argument. 
Topic: How does signrawtransaction know which private key to use? (Read 630 times)
hash and vout index refer to a UTXO record containing a spend script. the spend script refers to a public address, upon which a private key can be matched.
But if you're offline (and no blockchain access), how can it get the UTXO? 
hash and vout index refer to a UTXO record containing a spend script. the spend script refers to a public address, upon which a private key can be matched.
It only has a previous output (hash and vout index) but nothing to tell it which address that output was for, so how can it choose the correct private key to sign the transaction?
Jump to: