Question

Recall that TCP has no security. If an application author wants to pass his messages to another process that can encrypt them, at what layer will that encryption (like TLS or SSL) be found?

Answer 1

If an application author wants to pass his messages to another process that can encrypt them, then the encryption performed in Transport Layer. Transport Layer Security was designed to operate on top of reliable transport protocol such as TCP. However, It has also been adapted to run over datagrams protocols such as UDP. The TLS protocol is designed to provide three essential services to all applications running above it, and these three services are :-

Encryption: A mechanism to obfuscate what is sent from one host to another.

Authentication: A mechanism to verify the validity of provided identification material.

Integrity: A mechanism to detect message tampering and forgery.  

In order to establish a cryptographycally secure data channel, the connection peers must agree on which ciphersuites will be used and the key used to encrypt the data. The TLS protocol specifies a well defined handshake sequence to perform this exchange is called TLS Handshake. As part of the TLS handshake, the protocol also allows both peers to authenticate their identity. when used in the browser, this authentication mechanism allows the client to verify that the server is who it claims to be and not someone simply pretending to be the destination by spoofing its name or IP address. finally with encryption and authentication in place the TLS protocols also provides its own message authentication cod (MAC).