app.py

# app.py
from fastapi import FastAPI

app = FastAPI()

@app.get("/")
def read_root():
    return {"message": "Hello, secure world!"}


'''
OpenSSL is a widely used, open-source software library and toolkit that 
implements the Secure Sockets Layer (SSL) and Transport Layer Security (TLS) protocols.

Steps to set up HTTPS:

1) openssl req -x509 -newkey rsa:4096 -keyout key.pem -out cert.pem -days 365 -nodes

2) uvicorn app:app \
--host 0.0.0.0 \
--port 8443 \
--ssl-keyfile=key.pem \
--ssl-certfile=cert.pem: 

Which starts API on:

https://localhost:8443

3) Real Production Flow (Important)

In production -x509 is not used.
Instead:
Server → Generate CSR (Certificate Signing Request)
CSR → Sent to Certificate Authority
CA → Issues trusted certificate

Example CA:
1)Let's Encrypt
2)Cloudflare
3)DigiCert

Then command used as:  openssl req -new -key key.pem -out mycsr.csr

CSR contains:
 - Public key
 - Domain name
 - Organization info

Send CSR to CA.

The CA verifies:
- You control the domain
- Your organization info (for extended validation)

CA issues a certificate 
- Signed by the CA
- Trusted by browsers

It can be installed on server and Browser trusts this certificate automatically.

'''