Public Key Infrastructure (PKI) is used in blockchain technology to authenticate entities and ensure the integrity of the blockchain. The overall security of a wallet depends on how anyone secures their private key, and the most critical data stored in a wallet is the user's private key, which is also the only identifier of ownership of encrypted digital assets. We often see cases of lost or stolen wallet private keys or even hacked cases in the domestic and international news, which makes people pay more attention to the issue of wallet private key management. Since there are some problems with traditional key management, such as cold and hot wallets and exchanges, it is no longer possible to fully guarantee the security of key management. All key management protocols have some weaknesses; if these weaknesses are not considered, the designed encryption tools are still insecure. For example, DH cannot protect against MITM (man-in-the-middle) and DoS (denial-of-service) attacks, and cryptosystems cannot be developed without proper protection against these attacks. To solve these challenges, we will propose research topics to improve the mechanism through smart contracts, which can achieve a more efficient approach. These research topics will result in a blockchain key management system with privacy, cross-trainability, and efficiency.