> For the complete documentation index, see [llms.txt](https://hub.bsvblockchain.org/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://hub.bsvblockchain.org/higher-learning/bsv-academy/introduction-to-bitcoin-script/chapter-5-op_push_tx/03-op_push_tx.md).

# 03 - OP\_PUSH\_TX

OP\_PUSH\_TX is a scripting technique where the transaction script requires the user to submit a transaction pre-image as part of the solution.

Within the script, the pre-image is signed and then checked using one of Bitcoin's CHECKSIG opcodes (e.g. OP\_CHECKSIG, OP\_CHECKSIGVERIFY).

The SIGHASH flags applied to the signature can give you a means to check things such as total quantity of inputs and outputs, output script types and more. More detail on Sighash flags can be found [HERE](https://wiki.bitcoinsv.io/index.php/Sighash_flags).

There are different versions of the `OP_PUSH_TX` technique, but for the purposes of this module, we will use a simplified version known as 'Optimised OP\_PUSH\_TX'.

To simplify the calculation process, Optimised OP\_PUSH\_TX uses pre-set values for both the private key and ephemeral key, allowing OP\_PUSH\_TX to be executed with a script of less than 100 bytes.

<figure><img src="/files/gQ7t8DJisL3bBTepqe7k" alt=""><figcaption></figcaption></figure>


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