Part 5/11:
The user constructs a transaction in their wallet software and generates a PSBT (Partially Signed Bitcoin Transaction).
Instead of exporting private keys, the software communicates with the seed signer to sign the transaction via the smart card.
When ready to sign, the user inserts the SATA smart card, enters the PIN, and authorizes the signing process.
The seed signer communicates with the smart card, which signs the transaction internally and returns the signature.
The fully signed transaction is then broadcasted.
This approach ensures private keys remain isolated in the secure element, never arriving at or stored on the seed signer or connected device. The setup significantly mitigates the risk of private key extraction or malware compromise.