Computer Security and Cryptography Basics
Protecting systems and data
Security goals
Security aims to preserve confidentiality, integrity, and availability. Threats include phishing, malware, insecure passwords, software vulnerabilities, and misconfigured systems. Defensive thinking starts by assuming systems can fail and then designing layers of protection.
Core security concepts
Cryptography basics
Cryptography uses mathematical techniques to protect data. Symmetric encryption uses one shared key for encryption and decryption, while public-key cryptography uses a key pair. Hash functions map data to fixed-length digests and are useful for integrity checks and password storage when combined with salt and other safeguards.
Which security goal is about preventing unauthorized reading of data?
Confidentiality protects data from unauthorized disclosure.
Correct answer: Confidentiality
What is the difference between authentication and authorization?
They are related but distinct security checks.
Correct answer: Authentication verifies who you are, while authorization determines what you are allowed to do.
Password warning
A strong password is helpful, but secure systems also rely on multi-factor authentication, rate limiting, and breach-resistant storage.
What is a hash function commonly used for?
Hashes are useful for fingerprints of data and password verification workflows.
Correct answer: Checking integrity and storing password verifiers
Why should passwords not be stored in plain text?
Storing plain text passwords is a major security risk.
Correct answer: Because anyone who accesses the database could immediately read and reuse them.
A basic security checklist
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Step 1: Identify the data and actions that need protection.
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Step 2: Apply least privilege to users and services.
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Step 3: Use secure authentication and encryption where needed.
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Step 4: Patch vulnerabilities and validate input.
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Step 5: Monitor logs and incident indicators regularly.