<p>The method described in the post has nothing to to with OP_RETURN, but is concerned with the SIGOP limits in a block.</p>

<p>Each block has a limit on the number of SIGOPs that can be present in transactions in that block. Signature validation is a CPU intensive operation, and the limit exists to ensure that no block gets too big to validate on regular hardware.</p>

<p>The post describes how a single transaction can be made to consume up to 225 SIGOPS fairly trivially, limiting the number of such transactions in a block to 88. These utxos can be redeemed to any regular output, or an OP_RETURN.</p>

<p>Note that the post is from 2015, and the activation of segwit has increased the total SIGOPs allowed by a factor of 4, so this attack could cost more now.</p>

CC BY-SA 4.0
2019-10-15T12:02:28.340Z
Please explain why there are still dusty attacks on the blockchain? Is this related to "sigops"?
Izi Tors
CC BY-SA 4.0
2019-10-15T12:09:54.200Z
Dust attacks are also unrelated to all this, they are mostly used for tracking which addresses belong to a single wallet, and as spam attacks to bloat the utxo size.
Raghav Sood
CC BY-SA 4.0
2019-10-15T12:13:44.793Z
What happens if an attacker increases SIGOPS? How can he get the private keys from Bitcoin Addresses in this block?
Izi Tors
CC BY-SA 4.0
2019-10-15T12:14:49.163Z
There is no relation between SIGOPS and private key retrieval. Recovering a key from duplicate R values can be done with any regular transaction, provided someone is using bad software that duplicates R values, which no sane wallet does.
Raghav Sood
CC BY-SA 4.0
2019-10-15T11:44:46.947Z
2019-10-15T11:44:46.947Z
Raghav Sood
<p>Please explain something about OP_RETURN to me?
<a href="https://bitcointalk.org/index.php?topic=1166928.0" rel="nofollow noreferrer">https://bitcointalk.org/index.php?topic=1166928.0</a></p>

<p>I saw a discussion that the contents of OP_RETURN can open the value of access to the private key. I am not good at client scripting language. But I assume this is something related to the values of RawTX (R, S) where, when summing the additional value, you can calculate the value of X (that is, the private key). Am I right or wrong?</p>

<transactions><private-key><public-key><attack><op-return>
Is OP_RETURN dangerous for Bitcoin?
Izi Tors
# Is OP_RETURN dangerous for Bitcoin?

(Asked by: username_0 on 2019-10-15)

Please explain something about OP\_RETURN to me?
<https://bitcointalk.org/index.php?topic=1166928.0>

I saw a discussion that the contents of OP\_RETURN can open the value of access to the private key. I am not good at client scripting language. But I assume this is something related to the values of RawTX (R, S) where, when summing the additional value, you can calculate the value of X (that is, the private key). Am I right or wrong?

**Tags:** transactions, private-key, public-key, attack, op-return


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## 1 answers

### Answer by username_1 on 2019-10-15. Score: 4

The method described in the post has nothing to to with OP\_RETURN, but is concerned with the SIGOP limits in a block.

Each block has a limit on the number of SIGOPs that can be present in transactions in that block. Signature validation is a CPU intensive operation, and the limit exists to ensure that no block gets too big to validate on regular hardware.

The post describes how a single transaction can be made to consume up to 225 SIGOPS fairly trivially, limiting the number of such transactions in a block to 88. These utxos can be redeemed to any regular output, or an OP\_RETURN.

Note that the post is from 2015, and the activation of segwit has increased the total SIGOPs allowed by a factor of 4, so this attack could cost more now.

> **Comments:**
> **username_0**: Please explain why there are still dusty attacks on the blockchain? Is this related to "sigops"?  
> **username_1**: Dust attacks are also unrelated to all this, they are mostly used for tracking which addresses belong to a single wallet, and as spam attacks to bloat the utxo size.  
> **username_0**: What happens if an attacker increases SIGOPS? How can he get the private keys from Bitcoin Addresses in this block?  
> **username_1**: There is no relation between SIGOPS and private key retrieval. Recovering a key from duplicate R values can be done with any regular transaction, provided someone is using bad software that duplicates R values, which no sane wallet does.  

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