How Does the UTXO Model of Bitcoin Relate to the Concept of ‘Spent’ Funds?
The Unspent Transaction Output (UTXO) model is how Bitcoin tracks ownership. 'Spent' funds refer to a UTXO that has been consumed as an input in a new transaction.
When a UTXO is spent, the script that unlocks it (which includes the public key and signature) is revealed on the blockchain. This is the moment the full public key is exposed, which relates to the preimage attack risk.
A UTXO is an atomic unit of value that is either spent entirely or unspent.
