SON5 Flashcards
What is cryptography, and why is it important?
🔹 Definition – The art & science of securing communication from unauthorized access.
🔹 Core Idea – Uses encryption to protect confidentiality, integrity, and authenticity.
🔹 Mnemonic – Think of a locked diary—only someone with the key (encryption) can read it!
How does cryptanalysis differ from cryptography?
Definition – The study of breaking codes and ciphers.
🔹 Purpose – Identifies weaknesses in cryptographic systems.
🔹 Example – Brute-force attacks and side-channel attacks.
🔹 Mnemonic – Think of a hacker cracking a secret code to reveal hidden messages!
What does cryptology include, and how is it different from cryptography?
🔹 Cryptology = Cryptography + Cryptanalysis.
🔹 Field of study – Covers both creating and breaking encryption.
🔹 Think of it as the umbrella term for everything encryption-related.
🔹 Example – A cybersecurity expert who both encrypts and tests security systems.
🔹 Visualization – A two-sided coin: one side encrypts, the other breaks encryption.
What is a cryptovariable, and why is it crucial in encryption?
🔹 Definition – Cryptographic keys, also called cryptovariables, are used for encryption & decryption.
🔹 Importance – Secure key management = stronger encryption.
🔹 Example – AES encryption relies on secret keys.
🔹 Mnemonic – The key to a treasure chest—without it, the gold (data) stays locked!
What are the four main goals of cryptography?
🔹 Confidentiality – Keeps data secret using encryption.
🔹 Integrity – Prevents unauthorized changes using hash functions.
🔹 Authentication – Verifies identity (e.g., digital certificates).
🔹 Non-repudiation – Prevents denial of actions (e.g., digital signatures).
Tip: Use the mnemonic C.I.A.N. – Confidentiality, Integrity, Authentication, Non-repudiation!
How do cryptographic keys and algorithms work together?
🔹 Keys – Unique strings of bits that encrypt/decrypt data.
🔹 Algorithms – Lock that transforms data; keys act as the unlocking tool.
🔹 Security Factor – Stronger, longer, and random keys = better encryption.
🔹 Key Management – Even strong algorithms fail with weak or exposed keys.
(Tip: Think of a padlock and key—the lock (algorithm) stays the same, but different keys (cryptographic keys) control access!)
What does Kerckhoffs’s Principle say about cryptographic security?
🔹 Definition – A cryptosystem remains secure even if its design is public, as long as the key stays secret.
🔹 Why it matters – Security should rely on key secrecy, not algorithm secrecy.
🔹 Real-world example – Modern encryption (e.g., AES) is public, but its security depends on the key.
When should you use a block cipher, and how does it work?
🔹 Encrypts data in fixed-size blocks (e.g., AES - 128-bit blocks).
🔹 Best for large data processing (e.g., file encryption).
🔹 Stronger but slower than stream ciphers.
(Tip: Think of a chessboard—each piece (block) moves in a structured way! ♟️)
What are stream ciphers used for, and why are they faster?
🔹 Encrypts data one bit/byte at a time (e.g., RC4).
🔹 Best for real-time data streams (e.g., voice calls, low-power devices).
🔹 Faster but riskier if key reuse occurs.
(Tip: Think of a waterfall—data flows continuously, and encryption happens in real time! 🌊)
How does a substitution cipher work, and what is a common example?
🔹 Replaces each letter with another letter/symbol (e.g., Caesar cipher shifts letters).
🔹 Keeps letter order the same, but changes their identity.
🔹 Easy to break with frequency analysis.
How does a transposition cipher work, and how is it different from a substitution cipher?
🔹 Rearranges the letters in plaintext without changing them.
🔹 Same letters, different order (e.g., Rail Fence Cipher).
🔹 Stronger with complex patterns, but still breakable.
How does key stretching strengthen weak passwords?
🔹 Definition – Enhances weak passwords by making them harder to brute-force.
🔹 How it works – Repeatedly hashes a password with additional data (e.g., salt).
🔹 Purpose – Increases computation time, slowing down attackers.
🔹 Examples – PBKDF2, bcrypt, Argon2.
(Tip: Think of kneading dough—the more you work it, the stronger it gets! 🍞)
Why is key sharing a challenge in symmetric encryption?
🔹 Same key for encryption & decryption – Must be shared & kept secret.
🔹 Key management is critical – Secure distribution is a challenge.
🔹 Risk – If the key is exposed, all encrypted data is compromised.
(Tip: Think of a shared house key—if someone steals it, they can unlock everything! 🔑🏠)
Why is symmetric encryption faster than asymmetric encryption?
🔹 Faster & more efficient than asymmetric encryption.
🔹 Best for large data encryption (e.g., AES for file encryption).
🔹 Uses simpler math operations, reducing processing time.
(Tip: Think of a fast zipline—quick and direct, unlike the complex routes of asymmetric encryption! 🚀)
Where is symmetric encryption commonly used?
🔹 Used for:
Secure storage (encrypted files & databases).
Data in transit (VPNs, wireless networks).
Bulk encryption (fast and efficient for large data).
🔹 Common Algorithms – AES, DES, 3DES.
(Tip: Think of a locked vault—great for storing & moving data securely! 🔒)
Why is key management a challenge in symmetric encryption?
🔹 Same key = Encryption & Decryption – Must be securely shared & stored.
🔹 Scalability issue – Hard to manage in large networks.
🔹 Risk – If the key is leaked, all data is exposed.
(Tip: Think of a single master key—if stolen, everything is compromised! 🔑⚠️)
How does key length affect the security of symmetric encryption?
🔹 Key length matters – Longer keys = Stronger encryption.
🔹 128-bit, 256-bit AES – Harder to brute-force.
🔹 Algorithm security – Must be well-tested & resistant to attacks.
(Tip: Think of a password length rule—the longer, the harder to crack! 🔐💡)
Why is key distribution a major challenge in symmetric encryption?
🔹 Same key for encryption & decryption – Must be securely shared.
🔹 Risk – If intercepted, encrypted data is compromised.
🔹 Key Exchange Problem – Needs a secure method to distribute keys (e.g., pre-shared keys or key exchange protocols).
(Tip: Think of a secret letter—if the delivery is intercepted, the message is exposed! ✉️🔑)
Why does symmetric encryption struggle with scalability?
🔹 More users = More keys – Key growth is exponential.
🔹 Formula – N(N−1)/2 unique keys for N users.
🔹 Problem – Managing many keys becomes impractical in large networks.
(Tip: Imagine a group chat where every pair needs a secret passcode—it quickly becomes overwhelming! 📲🔐)
Why is secure key storage critical in symmetric encryption?
🔹 Keys must be securely stored – If stolen, data is exposed.
🔹 More users = Harder key protection – Large systems increase risk.
🔹 Solution – Use hardware security modules (HSMs) or encrypted storage.
(Tip: Think of a bank vault for keys—if someone steals the key, they unlock everything! 🔑🏦)
Why does symmetric encryption fail to provide non-repudiation?
🔹 Same key for all users – No way to track who encrypted/decrypted data.
🔹 No proof of authorship – Cannot verify which user performed an action.
🔹 Alternative – Asymmetric encryption (digital signatures) enables non-repudiation.
(Tip: Imagine a shared PIN code—anyone can use it, but you can’t prove who did! 🔢🤷♂️)
What are the key characteristics of DES encryption?
🔹 64-bit block cipher – Encrypts data in fixed-size blocks.
🔹 56-bit effective key – (64-bit key, but 8 bits used for parity).
🔹 Uses XOR operations – For encryption transformation.
🔹 16 rounds of processing – Strengthens encryption but now considered weak.
(Tip: Think of a lock with 16 turns—each round strengthens encryption but can still be picked! 🔐)
How does 3DES improve on DES, and why is it being phased out?
🔹 Applies DES three times per block for stronger encryption.
🔹 64-bit block cipher – Same block size as DES.
🔹 Key sizes: 64-bit, 112-bit, or 168-bit (but effective strength ~111 bits).
🔹 End-of-life – No longer recommended, AES is the better replacement.
(Tip: Think of locking a box three times—stronger than one lock, but outdated! 🔐🔐🔐)
What improvements did IDEA bring over DES?
🔹 Created to replace DES – Addressed weak key length.
🔹 64-bit block cipher – Encrypts data in fixed blocks.
🔹 Key sizes: 64-bit or 128-bit, divided into 52 subkeys.
🔹 Still secure, but replaced by AES in modern systems.
(Tip: Think of a more complex lock with more keys—harder to break! 🔑🔐)
