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.

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.