The most secure way to enhance the security of a blockchain system is by implementing multi-signature wallets. These wallets require multiple private keys from different users and devices to authorize a transaction. This means that even when a hacker can access a private key, he still needs to access other keys to execute a transaction. I have personally implemented this technique for myself and my clients. So far, it has been useful in storing large amounts of cryptocurrencies, especially in environments that have multiple parties involved.