<p>Read about <a href="http://en.wikipedia.org/wiki/Public-key_cryptography" rel="nofollow">Public-key cryptography</a> and <a href="http://en.wikipedia.org/wiki/Digital_signature" rel="nofollow">Digital signature</a>.</p>

<p>For bitcoins you need the private key to spend (by signing) the coins that were "sent" to the address associated with a public key.</p>

CC BY-SA 3.0
2013-05-29T15:58:05.640Z
Thats what I was looking for. Public key cryptography
Enthusiast
CC BY-SA 3.0
2013-05-29T15:18:27.393Z
2013-05-29T15:18:27.393Z
Gigi
<p>I know each user has a public key and private key. The users signs the transaction with his private key and sends it to a Bitcoin address. What prevents me from claiming his coins? I read something about verification with the private key but I didn't really understand. How does Bitcoin ensure that only the eligible person can spend the bitcoin? More specifically I didn't understand the verify and sign part in Satoshi's paper in the diagram on page 2.</p>

<p>Also from <a href="http://thumbnails.visually.netdna-cdn.com/bitcoin-infographic_5029189c9cbaf.jpg" rel="nofollow">this diagram</a>, how is it that a secret key can act as a key to lock a lock, but the public key can open the lock only but can't lock it back? How is this implemented technically?</p>

<private-key><public-key><signature><transaction-verification>
How are transactions verified to ensure only the eligible person can spend a Bitcoin balance?
Enthusiast
# How are transactions verified to ensure only the eligible person can spend a Bitcoin balance?

(Asked by: username_0 on 2013-05-29)

I know each user has a public key and private key. The users signs the transaction with his private key and sends it to a Bitcoin address. What prevents me from claiming his coins? I read something about verification with the private key but I didn't really understand. How does Bitcoin ensure that only the eligible person can spend the bitcoin? More specifically I didn't understand the verify and sign part in Satoshi's paper in the diagram on page 2.

Also from [this diagram](http://thumbnails.visually.netdna-cdn.com/bitcoin-infographic_5029189c9cbaf.jpg), how is it that a secret key can act as a key to lock a lock, but the public key can open the lock only but can't lock it back? How is this implemented technically?

**Tags:** private-key, public-key, signature, transaction-verification


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## 1 answers

### Answer by username_1 on 2013-05-29. Score: 1 | Accepted answer

Read about [Public-key cryptography](http://en.wikipedia.org/wiki/Public-key_cryptography) and [Digital signature](http://en.wikipedia.org/wiki/Digital_signature).

For bitcoins you need the private key to spend (by signing) the coins that were "sent" to the address associated with a public key.

> **Comments:**
> **username_0**: Thats what I was looking for. Public key cryptography  

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