01Overview
In 1994 Netscape began designing SSL for its browser and shipped SSL 2.0 in 1995. In 1999 the IETF took it over and renamed it TLS 1.0. In 2014 Heartbleed exposed implementation risk in OpenSSL; in 2018 TLS 1.3 simplified the handshake, removed weak algorithms and made forward secrecy the default.
TLS rests on a chain of certificates: browsers ship root certificates and servers present one signed by a CA. This PKI is imperfect — a CA can be compromised and certificates can be misissued — yet it carries e-commerce, APIs and nearly all secure communication. Today Let’s Encrypt has made certificates free, and HTTPS is the default.
02History
- 1995
SSL 2.0
Netscape's security layer.
- 1999
TLS 1.0
Standardised by the IETF.
- 2014
Heartbleed
A memory leak in OpenSSL.
- 2015
Let's Encrypt
Free certificates make HTTPS universal.
- 2018
TLS 1.3
Faster handshakes and stronger defaults.
03Core concepts
Handshake
Negotiate version and algorithms, establish keys, verify identity.
Certificate chain
Trust handed down from a root certificate to the server’s.
Forward secrecy
Past sessions stay safe even if the long-term key leaks.
04Hands-on
Do it once — it beats reading it ten times
Run openssl s_client against a site, dump the certificate chain and explain each hop of trust
05Self-check
Say it in your own words first, then open the answer. Whatever you cannot explain is what to review next.
Can you explain "Handshake"?
Negotiate version and algorithms, establish keys, verify identity.
Can you explain "Certificate chain"?
Trust handed down from a root certificate to the server’s.
Can you explain "Forward secrecy"?
Past sessions stay safe even if the long-term key leaks.
What problem did it solve, and why was there nothing better at the time?
Go back to the history section: how was this done before, and what did it cost?
If you had to build it today, how would you break it down?
Use the hands-on task above: write a plan of at most three steps before you start.
06Key people
Taher Elgamal
1955 –
One of the designers of SSL.
Paul Kocher
1973 –
SSL 3.0 and a pioneer of differential power analysis.
07Further reading
- SSL and TLS: Designing and Building Secure Systems
- RFC 8446: TLS 1.3