Multi-party computation (MPC) enhances the security and privacy of Bitcoin custody solutions by allowing multiple parties to collectively compute a function or transaction without revealing their individual inputs. This means that no single party has access to the complete information or private keys required to access the Bitcoins, increasing security against single points of failure or attacks. Additionally, MPC helps in protecting the privacy of the parties involved by ensuring that sensitive information is only shared as necessary for the transaction to be completed, minimizing the risk of data leaks or breaches. Overall, MPC helps in distributing trust and control among multiple parties, thereby improving the security and privacy of Bitcoin custody solutions.