Only two persons know about password for decryption, you and your oponent.
SECURITY: No private/public keys, only AES256 data encrypted with password triple hashed by SHA512.
LOGIC: Password is not sent over internet, so it cant be stealed.
PROVEN: Only approved encryption are used, like: TLS -> SHA512(triple) -> AES256
PRIVATE: All information is fully encrypted and can by decrypted only with your password.
Finally you can be safe from any intruders.