I am reading design documents of an internal Whats-app like chat application.
Developers are planning to use asymmetric encryption to encrypt all messages.
Every user will have a public/private key pair and for every new chat a chat-public and a chat-private key will be generated. Keys will be delivered to relevant parties via a central server.
When a user sends a message, the message will be encrypted with user private and chat public keys. Receiver will decrypt the message using sender's public and chat's private key.
This looks fine but most popular chat apps are using PKI to exchange a shared key and continue with symmetric encryption.
Is there a reason I should argue against asymmetric method and offer using a symmetric encryption algorithm?