Public Key Crptography (week 10) Flashcards
What principle did William Stanley Jevons illustrate with his factorisation example?
The difficulty of reversing factorisation underpins RSA security.
Who invented the RSA algorithm?
Ron Rivest, Adi Shamir, and Leonard Adleman.
What are the key components required for RSA key generation?
Two large prime numbers (p, q) and a public/private key pair.
How does public key encryption ensure confidentiality?
The sender encrypts data with the recipient’s public key; only the recipient can decrypt it using their private key.
What is non-repudiation in public key cryptography?
Proof that a message was sent by the claimed sender.
Why is encrypting the entire document often unnecessary in practice?
Encrypting a hash is faster and provides equivalent authenticity.
What are the two processes combined for confidentiality and authentication?
Encrypting with the recipient’s public key and signing with the sender’s private key.
How can Bob verify Linda’s identity using public key cryptography?
Using Linda’s public key to decrypt her signed message.
What is a Certificate Authority (CA)?
An entity that issues digital certificates to verify identities.
What role does a Registration Authority (RA) play in public key infrastructure?
It verifies user requests before certificates are issued.
What is the Web of Trust model?
A decentralized method where users vouch for each other’s keys.
Why is the Web of Trust difficult to manage in practice?
Trust chains can be complex and difficult to maintain.
What is the primary role of Pretty Good Privacy (PGP)?
Encrypting and signing emails for privacy and authentication.
How does the Estonian ID-Card model ensure public key verification?
Through government-backed digital certificates.
What are the key properties of cryptographic hash functions?
Deterministic, fast, irreversible, and collision-resistant.
Why is MD5 considered flawed for modern security purposes?
It is vulnerable to collision attacks.
What hash algorithm is recommended for modern applications?
SHA-256 or SHA-3.
How does Linux secure passwords using hashing and salts?
By combining a password with a unique salt before hashing.
What is the purpose of a Message Authentication Code (MAC)?
To ensure data integrity and authenticity.
How does a Digital Signature ensure message authenticity?
By signing the message with the sender’s private key.
What is the Diffie-Hellman key exchange?
A method for securely exchanging cryptographic keys.
Why is public key cryptography not used for real-time encryption?
It is slower than symmetric encryption methods.
What vulnerability exists in the Diffie-Hellman exchange?
Man-in-the-middle attacks if authentication isn’t applied.
How can you mitigate a man-in-the-middle (MITM) attack in Diffie-Hellman?
Use digital certificates to verify identity.
What does GSM stand for?
Global System for Mobile Communications.
What is the primary purpose of GSM encryption?
To protect voice and data transmission over mobile networks.
How does GSM encryption use XOR for secure communication?
By combining plaintext with a generated keystream.
What is the relationship between XOR and addition modulo 2?
They are mathematically identical.
Why does XOR provide better security than AND or OR in encryption?
XOR’s output reveals no direct information about the inputs.
How does GSM’s A5 stream cipher generate a key?
Using the session key (Kc) and frame number.
What is the role of the SIM card in GSM encryption?
It stores the secret key for generating Kc.
What is the significance of the session key (Kc) in GSM encryption?
It is unique for each communication session.
Why is the A5/1 cipher considered vulnerable?
It can be cracked using rainbow tables and brute force.
What encryption algorithms replaced A5/1 in later generations of mobile communication?
A5/3, Kasumi, and AES.
What are the key differences between 3G, 4G, and 5G encryption methods?
Each iteration improved encryption strength and added enhanced authentication methods.
How does AES improve security in modern mobile communication?
With stronger encryption keys and improved performance.
What is the role of a pseudo-random key stream in GSM encryption?
It ensures data appears random to attackers.
Why is XOR encryption reversible using the same XOR operation?
XORing twice with the same key cancels out the original encryption.
What property makes XOR ideal for encryption?
Its ability to easily encrypt and decrypt data by repeating the same process.
What logic gate does XOR resemble?
The exclusive OR (XOR) gate in digital logic.
