Final Exam Review

What is Access Control

Ensures that resources are only granted to those users who are entitled to them

What is Encryption

The process of converting plaintext data into an unreadable format (ciphertext) to prevent unauthorized access.

What is Decryption

The process of converting ciphertext back into its original format (plaintext).

What is Authentication

The process of verifying the identity of a user, device or system.

What is a threat in computer security?

An action or event that might compromise security.

What are some basic problems and concerns involving cryptographic systems?

Weak encryption, improper key management, inadequate randomness, inadequate authentication.

What is Plaintext?

The original, readable message that is input into the encryption process.

What is Ciphertext?

The scrambled, unreadable message that results from the encryption process.

What is a Cipher?

The algorithm used for transforming plaintext to ciphertext.

What are the pros of classical cryptographic techniques?

Simple, can be done manually, protect plaintext f4rom casual snooping.

What are the cons of classical cryptographic technique?

Limited security, vulnerable to frequency analysis and brut-force attacks, challenging key management.

How does the Caesar Cipher work?

By shifting the letters in the plaintext message by a certain number of positions, known as the “shift” or “key”.

What is Symmetric Encryption?

A form of cryptosystem in which encryption and decryption are performed using the same key.

Compare Symmetric and Asymmetric Cryptography

Symmetric uses a single key for encryption and decryption; asymmetric uses a pair of keys (public and private).

What are Hash Functions?

Algorithms that calculate a fixed length hash value form plaintext, making it impossible to recover the contents of the plaintext.

What was the first recorded use of cryptography for correspondence?

The Spartans’ use of the scytale.

What is the Enigma machine?

A cipher device used extensively by Nazi Germany during World War II to protect communication.

What is the Hebern cipher machine?

A typewriter-like device with 26 letters that light up, scrambling the electrical signal between the letters of the keyboard and the light panel.

What can lead to a break in good encryption schemes?

Using weak algorithms, improper key management, using vulnerable algorithms, and incorrect implementation of strong algorithms.

What is divisibility in mathematics?

If a and b are integers, with a not equaling 0, a divides b if there exists an integer q such that b = a q.

What is Modular Arithmetic?

A system of arithmetic for integers, where numbers wrap around upon reaching a certain value, called the modulus.

How do you apply the Euclidean Algorithm to find the GCD?

Using repeated division: GCD (A,B) = GCD (B,R) where R is the remainder when A is divided by B.

What is a prime number?

A natural number greater than 1 that has no positive divisors other than 1 and itself.

What is Euler’s Totient Function?

The number of positive integers less than or equal to a given integer that are relatively prime to it.

What are Stream Ciphers?

They encrypt plaintext one bit or byte at a time, suitable for varying data lengths and fast encryption/decryption.

What are Block Ciphers?

They encrypt data in fixed-size blocks, allowing for secure decryption, and has similar encryption and decryption operations.

Why is a Feistel cipher superior to a full permutation block cipher?

It is guaranteed to be invertible, allowing for secure decryption, and has similar encryption and decryption operations.

What are the parts of a Feistel cipher that give it security?

Round function, invertibility, and key schedule.

How does the Data Encryption Standard (DES) work?

Through initial permutation, 16 rounds of processing, and a final permutation, incorporating substitution and transposition.

What is the Advanced Encryption Standard (AES)?

A block cipher that encrypts data in 128-bit blocks using key lengths of 128, 192, or 256 bits.

What is Electronic Code Book (ECB) mode?

A block cipher mode that directly encrypts each block of input plaintext into blocks of encrypted ciphertext.

What is Cipher Block Chaining (CBC) mode?

An advancement on ECB where the previous cipher block is XORed with the next plaintext block before encryption.

What is a meet-in-the-middle attack?

A cryptanalytic attack that divides the key space into two parts and encrypts plaintext while decrypting ciphertext to find a match.

What is the difference between TRNGs, PRNGs, and CSPRNGs?

TRNGs generate numbers from physical processes, PRNGs use deterministic algorithms, and CSPRNGs are secure PRNGs suitable for cryptography.

What is Symmetric Key Encryption?

It uses the same key for both encryption and decryption.

What is Public Key Encryption?

It uses a pair of keys, a public key and a private key, for encryption and decryption.

How does RSA encryption work?

One party generates a key pair, uses the public key for encryption, and the private key for decryption.

How does Diffie-Hellman key exchange work?

Both parties exchange public key information to arrive at a shared secret key.

What is Elliptical Curve Cryptography (ECC)?

A public-key cryptography approach based on the algebraic structure of elliptic curves over finite fields.

What are has functions used for?

To ensure data integrity, generate checksums, and create secure hash algorithms in cryptographic applications.

What is a cryptographic hash function?

A transformation that takes an input and returns a fixed-sizing string of bytes unique to each unique input.

What properties should a good cryptographic hash function have?

Preimiage resistance, second preimage resistance resistance, and collision resistance.

What is a hash function collision?

When two different inputs result in the same output.

What are some good hashing algorithms?

SHA-256 and SHA-3

What is a Message Authentication Code (MAC)?

A code used to authenticate the origin and integrity of a message.

What are Digital Signatures

Digital signatures ensure the authenticity and integrity of a message, software, or digital document.

How do you verify a digital signature?

By decrypting the signature with the sender’s public key and comparing it to the hash of the received message.

What is Public Key Infrastructure (PIK)?

A system for creation, storage, distribution, and revocation of digital certificates.

What is a Certificate Authority (CA)?

An entity that issues digital certificates for use by other parties.

How are keys managed in cryptographic systems?

Through generation, distribution, storage, and destruction, with secure protocols.

What is a Bitcoin Block?

A file where data related to transactions are permanently recorded.

What sets the limit on the size of the Bitcoin block?

Blocksize.

What is included in the Block Header of a Bitcoin block?

Version, Previous Block Hash, Merkle Root, Timestamp, Difficulty, Target, Nonce, and Transaction Counter.

What is the Previous Block Hash?

An encrypted number of previous block’s header.

What is the Merkle root?

An encrypted number of transactions in the Merkle tree of the current block.

What does the Timestamp in a Bitcoin block signify?

It places the block in the blockchain.

What is the Difficulty Target in a Bitcoin block?

The difficulty rating of the target encrypted number, signifying the difficulty in generating an encrypted number that is equal to or less than target.

What is the Nonce in a Bitcoin block?

A number that the miner increases incrementally when encrypting.

What is the Transaction Counter in a Bitcoin block?

A field that lists the number of transactions stored in the block.

What are Transactions in a Bitcoin block?

A list of all the transactions within a block.

What is Bitcoin mining?

The process by which transactions are officially entered on the blockchain.

What are the steps involved in Bitcoin mining?

Transaction Verification, Hashing, Finding the Hash, Block Addition.

What happens during Transaction Verification in Bitcoin mining?

When a transaction is made between wallets, the addresses and amount are entered into a block on the blockchain.

What is Hashing in Bitcoin mining?

The block is assigned some information, and all of the data in the block is put through cryptographic algorithm.

What is Finding the Hash in Bitcoin mining?

Miners compete to find a hash that is equal to or less than a number set by the Bitcoin network’s difficulty algorithm.

What happens during Block Addition in Bitcoin mining?

The first miner to find the solution to the problem receives bitcoins as a reward, and the process begins again.

What do miners need for Bitcoin mining?

Substantial hardware and software, such as GPU or an ASIC.