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Underneath the hood SSL isn’t that simple. It’s quite complicated to implement from scratch - believe me! I have tried! Many vendors use a common implementation of SSL called openssl.
This is a bit of a security issue for the industry in that:
No one really understands all of the depths of openssl.
Yet it’s used universally in the industry in all sorts of places.
Read TLS Handshake for an overview of how TLS secures communication between a client and server.