What are the two main categories of threats in cryptography?

Unintentional errors/failures (unintelligent adversaries) and deliberate attacks by intelligent adversaries.

Category 1: Unintentional threats (unintelligent adversaries)

• Transmission noise and interference
• System failures and crashes
• Natural disasters
• Software and hardware bugs
• User errors

These are addressed through error correction, redundancy, and fault tolerance — not cryptography.

Category 2: Deliberate attacks (intelligent adversaries)

• Hackers and crackers
• Criminal organizations
• Nation-state actors and intelligence agencies
• Malicious insiders
• Tech-savvy individuals (script kiddies to advanced)

An unauthorized action by an intelligent adversary is called an attack (Angriff/Attacke).

What cryptography can NOT defend against:

• Denial of Service (DoS)
• Software vulnerabilities (e.g., in the OS)
• Hardware vulnerabilities (e.g., bugs in chips)
• Improper key handling ("you can even encrypt keys incorrectly!")

Tip: An unintelligent adversary is not necessarily a dumb person — it refers to random, non-targeted threats like noise or hardware failure, as opposed to a thinking attacker adapting their strategy.