Modifying outputs before forwarding?

DannyHamilton

legendary

Activity: 3472

Merit: 4801

Quote from: casascius on December 07, 2012, 10:40:05 AM

The signatures sign a hash of the whole transaction with blanks in place of the signatures (obviously, since the signatures aren't known before signing).

Changing a txout will change the hash and therefore require a different signature.

I knew it would be something simple and obvious, I just wasn't seeing it. Thanks.

casascius

vip

Activity: 1386

Merit: 1140

The Casascius 1oz 10BTC Silver Round (w/ Gold B)

The signatures sign a hash of the whole transaction with blanks in place of the signatures (obviously, since the signatures aren't known before signing).

Changing a txout will change the hash and therefore require a different signature.

DannyHamilton

legendary

Activity: 3472

Merit: 4801

I'm sure I'm missing something simple and obvious, but as I look through the protocol I'm not seeing what keeps me from creating a client that modifies the tx_out of all transactions that it receives before relaying them.

The tx_in is already signed in the transaction, so I don't need the private key. All I need to do is change the address in the pk_script of tx_out to one that I have the primary key to before relaying it.

What am I missing here?

Topic: Modifying outputs before forwarding? (Read 785 times)