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?

1 Answer 1


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.

  • Please explain why there are still dusty attacks on the blockchain? Is this related to "sigops"?
    – Izi Tors
    Commented Oct 15, 2019 at 12:02
  • 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. Commented Oct 15, 2019 at 12:09
  • What happens if an attacker increases SIGOPS? How can he get the private keys from Bitcoin Addresses in this block?
    – Izi Tors
    Commented Oct 15, 2019 at 12:13
  • 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. Commented Oct 15, 2019 at 12:14

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