ELI5

Architecture and strategy, explained simply

Security architecture is the plan for how all the locks, guards and alarms fit together, and the plan has changed a lot over the years.

The big idea

Imagine looking after a castle. At first you just hope nobody bothers you. Then you build a big wall with one gate, and you guard the gate. That is the perimeter: strong outside, trusting inside.

Then you notice that once someone gets over the wall, they can go anywhere. So you add more layers: locked towers, guards inside, alarms on the treasure room. That is defence in depth.

Later, people start working outside the castle and visitors come and go all day, so the wall stops meaning much. Now every door checks everyone, every time, wherever they come from. That is zero trust: nobody is trusted just because they are inside.

The newest stages join all those checks up so they share what they see, and then let the castle notice trouble and react by itself, sometimes with the help of AI.

Here is the useful part: no castle ever knocks down its old wall. Real organisations use several of these stages at once, in different parts of the estate. The job of a security architect is to decide which part needs which, and how to get there.

Words you will meet

• Security architecture: the overall design of how an organisation's protections fit together.
• Perimeter: a strong boundary, like a castle wall or a company network, with trust inside it.
• Defence in depth: several layers of protection, so one failure is not the end.
• Zero trust: check every request, every time; being inside the network earns no trust by itself.
• Pub-sub: short for publish and subscribe. Things announce what they know on a shared channel, and anything interested listens.
• Cryptography: the maths that locks data so only the right people can read it.
• Post-quantum: new kinds of lock designed to stay safe even against the powerful quantum computers of the future.

The field notes, in plain words

• Post-quantum migration starts with a cryptography inventory

  Future computers may break today's locks, so first find every lock you have, which is much harder than it sounds.

• Security runs on pub-sub: the mesh, the logs and the monitoring

  Lots of security works like a noticeboard: some things pin up what they saw, others read the board and act, and neither has to know the other.

• Where security architecture stands, and why most organisations run several at once

  Security has grown up in stages, from a locked front door to guards who check everyone everywhere, and most places still use a mix of old and new.

Ready for more? Architecture and strategy: where things stand

Personal work and my own view, not my employer's. Sources are public.