user132107: As I know, signature system is adding signature to end of transaction. And doesn’t hash transaction, so others can know my signature.
If I can send a message directly to the node, can I use other’s signature and send currency to me?
For example, Alice make a transaction sending 1bitcoin to Bob. Then Alice will send her digital signature to nodes. And nodes will verify it is from Alice and share the transaction with address, signature, etc.
At here, I can know her signature and can send a transaction with her signature. Then nodes will verify this transaction is from Alice and share it.
I’m very beginner of cryptocurrency, so can you let me know where has problem?

user63872: The signature Alice creates is not just arbitrarily appended to her transaction. It is created by taking the transaction (or in some cases just parts of the transaction) as input, and then by using the relevant private key, a signature is created over this transaction data.
So when Alice signs the transaction, the signature that is created will only be valid for the specific transaction that was signed. If any part of that transaction is modified, then the signature will no longer be seen as valid by other nodes on the network. Thus you cannot just modify the transaction to pay to a different address, as doing so would make the transaction invalid.

132107: <p>As I know, signature system is adding signature to end of transaction. And doesn’t hash transaction, so others can know my signature.</p>
<p>If I can send a message directly to the node, can I use other’s signature and send currency to me?</p>
<p>For example, Alice make a transaction sending 1bitcoin to Bob. Then Alice will send her digital signature to nodes. And nodes will verify it is from Alice and share the transaction with address, signature, etc.</p>
<p>At here, I can know her signature and can send a transaction with her signature. Then nodes will verify this transaction is from Alice and share it.</p>
<p>I’m very beginner of cryptocurrency, so can you let me know where has problem?</p>
 63872: <p>The signature Alice creates is not just arbitrarily appended to her transaction. It is created by taking the transaction (or in some cases just parts of the transaction) as input, and then by using the relevant private key, a signature is created <em>over this transaction data</em>.</p>
<p>So when Alice signs the transaction, the signature that is created will only be valid for the specific transaction that was signed. If any part of that transaction is modified, then the signature will no longer be seen as valid by other nodes on the network. Thus you cannot just modify the transaction to pay to a different address, as doing so would make the transaction invalid.</p>
