Prove who you're talking to, then encrypt everything.
In this interactive Infrastructure lesson from Stencel Academy you don't just read — you type real commands like openssl s_client -connect api.stencel.ai:443, curl https://203.0.113.10/ and watch the machine respond on a live, animated map. It is part of the free How Infrastructure Works course.
Builds on: TCP: The Reliable Pipe.
echo | openssl s_client -connect api.stencel.ai:443 2>/dev/null | openssl x509 -noout -dates — Certificates expire — Let's Encrypt gives you 90 days.curl -k https://203.0.113.10/health — -k skips verification: encrypted, but to whom?ls /etc/ssl/certs | head -4 — The roots your machine trusts unconditionally.curl -v https://api.stencel.ai/health 2>&1 | grep -E 'subject|issuer' — curl verifies the same chain on every request.