# Privately Generated Key Pairs for Post Quantum Cryptography in a Distributed Network
## 2 Background Information  
Current Public Key Infrastructure (PKI) for establishing secure communication and verifying an end user depends on the Certificate Authority (CA) for the authentication of a user [11]. The role of the CA is one of the most crucial parts of security in PKI. This authentication of the user can be performed by applying various methods. In the user drive certificates method (see Figure 1a), the CA provides a certificate to an end user. The user generates its public and private key pair, encrypts the certificate with the private key, and sends it back to the CA. The Registration Authority (RA) keeps the signed certificate and the public key of the user. To establish secure communication with the user, other users will verify the signed certificate and public key against the RA record. User-driven certificates give the highest privacy to the users as the private keys are never disclosed; however, they can be prone to \"Man-in-the middle\" (MIM) attacks [12]. Such a protocol is also vulnerable to bad players due to the weak authentication capabilities.  
Most commercial PKIs rely on third parties to authenticate the users and generate the public and private key pairs. The service provider communicates with both the CA and the end user to provide the key pairs. The CA provides a certificate to the user for signing with the private key and sending the signature to the CA. The RA keeps a record of the public key received from the service provider and the signature from the user. Figure 1b shows a graphical representation of the overall process. For example, a Hardware Security Module (HSM) generates the key pairs. The RA receives the user's public key from the HSM, and the private key can be stored in a device, e.g., a smart card or token, and given to the end user. During the authentication process, the CA issues a certificate for the user and the user signs the certificate utilizing the private key and sends it back to the CA. Other users can verify the user by using the signature from the CA and the public key from the RA. The described methods have their own strengths and weaknesses.  
The third-party driven certificates discussed here can generate new keys easily and are less sensitive to MIM attacks, but the key distribution is a weak link and must rely on additional protections. Temper-resistant tokens might give the user leverage against MIM attacks and a better key distribution policy, but the whole security depends on the level of confidence in the HSM. In addition to this, none of the schemes can fully guarantee confident protection against impersonation attacks. Also, the end users always must rely on a service provider or CA for the key pairs. This leads to creating a weak link in the security scheme and trust issues among the users and service providers. Most cryptocurrencies, secure mail, banking cards, and Subscriber Identity Modules (SIMs) still rely on the current PKI, and this could lead to a huge security breach as attacks by malicious groups are getting more sophisticated every day.  
An overall block diagram of the schemes proposed in this paper is shown in Figure 2. The objective is to allow users to generate their own key pairs. The Private Key Store can verify the legitimacy of users and their private keys. Such a protocol thereby combines the benefits of the user-driven protocol of Figure 1a with the third party protocol of Figure 1b without their inherent limitations.