using blockchain to improve the security of the x3dh key exchange protocol

First and most important step to making secure end-to-end encryption is key exchange. x3dh is one of the most used protocols to do that. it uses a trusted server to exchange keys. if the key exchange is secure then we have identification, authentication, integrity, non-repudiation, and confidentiality for messages. in x3dh, if the trusted server is compromised the entire end-to-end encrypted connection will be exposed. transport layer security (tls) is used for client-server communication. therefore, the whole security is based on a certificate authority (ca) therefore there will be the single point of failure. in this paper, we proposed using blockchain as a trusted medium to exchange keys and identity authentication. the proposed method is based on the use of x3dh in instant messaging. this method improves the first step of the x3dh algorithm which includes authentication. this is the first time using blockchain directly to identify a user.