What are the two main goals for secure interface design?

Two goals: (1) secure input validation — accept only valid input and read it the same way every time; (2) identical interpretation — sender and receiver must agree exactly on what the data means.

These are two halves of one promise: validation stops bad data getting in, while identical interpretation stops good data being read wrongly on the far side. You need both, because an attacker can win either by sending malicious input OR by exploiting a meaning-mismatch between the two ends.

Goal 1 — Secure Input Validation:

• Accept ONLY valid input
• Interpret input always in the same way
• No unforeseen reactions on ANY input

Goal 2 - Identical Interpretation:

• Sender's language = Receiver's language
• Design contracts must be defined explicitly
• Contracts must be followed provably

Tip: "Say what you mean, mean what you say" — both sides must agree on the meaning of all data.