<p>Say you see a check for "$50,000 to Bob" that needs to be signed by Ed. What you want to know is whether the signature on the check came from Ed and signs the message "$50,000 to Bob". So the question a signature checker answers is, does the given signature attach the given credential to the given message. How would it check that without the message?</p>

<p>Checking a signature detached from a message would serve no purpose. Say you see that check for $50,000 to Bob. If Ed actually signed "$50 to Alice", the the signature check <em>must</em> fail -- since Ed didn't sign that message. So you <em>can't</em> check the signature without knowing the message.</p>

CC BY-SA 3.0
2015-07-02T22:39:04.047Z
Let me make an example about how is it works. Tugay sends 1 btc to David. Tugay signs it with his private key and broadcasts to the network. Miners verify the transaction like this: 1) solve digital signature with Tugay's public key, 2) compare the result with the hash of transaction 3) if its correct then verify the transaction and the output of this function: transaction = v(message, public key, signature) will be my address because transaction is made by me. Now do i got it right ?
Tugay Öztürk
CC BY-SA 3.0
2015-07-06T07:35:39.527Z
@TugayÖztürk That's pretty close.
David Schwartz
CC BY-SA 3.0
2015-07-02T00:02:37.130Z
2015-07-02T19:15:20.157Z
2015-07-02T19:15:20.157Z
David Schwartz
<p>here is the how bitcoin works under the hood article
<a href="http://www.imponderablethings.com/2013/07/how-bitcoin-works-under-hood.html" rel="nofollow">http://www.imponderablethings.com/2013/07/how-bitcoin-works-under-hood.html</a>
i did not got this why message is needed when using this verify function ?
1 =? v(message, public key, signature)</p>

<signature>
Why the message is need in verify function
Tugay Öztürk
# Why the message is need in verify function

(Asked by: username_0 on 2015-07-01)

here is the how bitcoin works under the hood article
<http://www.imponderablethings.com/2013/07/how-bitcoin-works-under-hood.html>
i did not got this why message is needed when using this verify function ?
1 =? v(message, public key, signature)

**Tags:** signature


---

## 1 answers

### Answer by username_1 on 2015-07-02. Score: 1

Say you see a check for "$50,000 to Bob" that needs to be signed by Ed. What you want to know is whether the signature on the check came from Ed and signs the message "$50,000 to Bob". So the question a signature checker answers is, does the given signature attach the given credential to the given message. How would it check that without the message?

Checking a signature detached from a message would serve no purpose. Say you see that check for $50,000 to Bob. If Ed actually signed "$50 to Alice", the the signature check *must* fail -- since Ed didn't sign that message. So you *can't* check the signature without knowing the message.

> **Comments:**
> **username_0**: Let me make an example about how is it works. username_0 sends 1 btc to username_1. username_0 signs it with his private key and broadcasts to the network. Miners verify the transaction like this: 1) solve digital signature with username_0's public key, 2) compare the result with the hash of transaction 3) if its correct then verify the transaction and the output of this function: transaction = v(message, public key, signature) will be my address because transaction is made by me. Now do i got it right ?  
> **username_1**: @username_0 That's pretty close.  

---

