Question
What is the fundamental interface security problem, and how do attackers exploit it?
Answer
The whole class of injection attacks is one inequality: Dec(Enc(M)) ≠ M — the receiver decodes the data into something the sender never meant, and the attacker engineers that difference on purpose.
When the round-trip is faithful (Dec(Enc(M)) = M) the interface is safe; the moment it breaks, the attacker's data acquires a second meaning on the far side:
The problem:
Sender intends M → Enc(M) → Channel → Dec(Enc(M)) → Receiver gets M' ≠ M
How attackers exploit this — all 4 conditions must hold:
| Condition | Meaning | SQL injection example |
|---|---|---|
| M ≠ Dec(Enc(M)) | Input transforms into something different | O'Brien becomes SQL code break |
| M is valid for sender | Input passes client-side checks | Name field accepts apostrophes |
| Dec(Enc(M)) is valid for receiver | Result is executable | Database parses it as valid SQL |
| Actions differ | Sender expects data storage, receiver executes code | INSERT becomes INSERT + DROP TABLE |
Why this matters: SQL injection, XSS, command injection, and URL encoding attacks ALL exploit this same pattern — data that means one thing to the sender means something different to the receiver.
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Question
What is the role of a software architect in translating requirements into technical design?
Answer
The architect turns business needs into a high-level technical structure — and bakes in non-functional requirements like security from the start.
Bridges business needs to technical implementation by creating the high-level system structure.
Key responsibilities:
- Define component decomposition and communication patterns
- Design interfaces (internal APIs and external integrations)
- Make technology decisions (frameworks, databases, protocols)
- Establish coding guidelines and principles for the team
- Ensure non-functional requirements (security, scalability, maintainability) are addressed in design
The architect ensures security is part of the architecture — not an afterthought bolted on later.
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