Certificate pinning is a technique that embeds one or more trusted certificates or public keys inside an application, and verifies that any certificate presented by a server matches one of those certificates or public keys. Certificate pinning can prevent on-path attacks, such as man-in-the-middle (MITM) attacks, which intercept and modify the communication between a client and a server.
Configuring certificate pinning inside the application would allow the mobile application developer to create a global, highly scalable, secure chat application that is not susceptible to on-path attacks while the user is traveling in potentially hostile regions, because it would:
Ensure that only trusted servers can communicate with the application, by rejecting any server certificate that does not match one of the pinned certificates or public keys.
Protect the confidentiality, integrity, and authenticity of the chat messages, by preventing any attacker from intercepting, modifying, or impersonating them.
Enhance the security of the application by reducing its reliance on external factors, such as certificate authorities (CAs), certificate revocation lists (CRLs), or online certificate status protocol (OCSP).