What are the four key properties a cryptographic implementation must have?

It must be trustworthy (secure), cheap (affordable), efficient (low resource usage), and fast (performant).

The four properties:

1. Trustworthy (sicher) — the implementation must be secure and correct
2. Cheap (billig) — cost-effective in development and operation
3. Efficient (effektiv) — should not consume excessive resources (power, memory, bandwidth)
4. Fast (effizient) — operations must complete quickly enough for practical use

The critical insight: The weakest link determines the overall security. Even with strong algorithms, if any layer is weak, the system can be compromised.

A layered security hierarchy (top to bottom):

• Protocol → security partitioning, energy-security trade-off
• Algorithm → crypto algorithms, public key or secret key
• Architecture and interfaces → co-design, HW/SW, SoC
• Micro-Architecture → co-processor design, RTL, assembly code
• Circuit → techniques to combat side-channel attacks

"Security is as strong as the weakest link!"