Introduction to Cryptography

[PRE-ASSESSMENT] What role does modular arithmetic play in cryptographic algorithms?

Performing calculations within a finite set of numbers. | Concept: modular arithmetic.

[PRE-ASSESSMENT] How is lattice-based cryptography applied in modern encryption techniques?

Using geometric structures for cryptographic algorithms. | Concept: lattice-based cryptography.

[PRE-ASSESSMENT] What is encryption?

The process of encoding data so that it is protected from unauthorized access. | Concept: encryption converts plaintext to ciphertext using an algorithm and key.

[PRE-ASSESSMENT] What role do large prime numbers play in cryptographic algorithms?

They ensure the security and strength of encryption. | Concept: large primes are important in public-key cryptography such as RSA.

[PRE-ASSESSMENT] What is a cryptosystem?

A combination of cryptographic algorithms and protocols. | Concept: a cryptosystem is broader than a single algorithm.

[PRE-ASSESSMENT] How are digital signatures used in cryptographic protocols?

They verify the authenticity and integrity of data. | Concept: signing uses a private key: verification uses the public key.

[PRE-ASSESSMENT] What is nonrepudiation?

The ability to prevent a sender from denying that they sent a message or performed an action. | Concept: digital signatures provide nonrepudiation.

[PRE-ASSESSMENT] Which encryption method is associated with symmetric encryption?

Advanced Encryption Standard (AES). | Concept: symmetric encryption uses the same shared key for encryption and decryption.

[PRE-ASSESSMENT] Which of the following is an example of asymmetric encryption?

Rivest-Shamir-Adleman (RSA). | Concept: RSA uses a public/private key pair.

[PRE-ASSESSMENT] What are hash functions used for?

Message integrity. | Concept: hashing is a one-way function commonly used to detect changes.

[PRE-ASSESSMENT] Which is a type of homomorphic encryption?

Full homomorphic encryption (FHE). | Concept: the study guide identifies AHE and SHE and and FHE as types: the pre-assessment's correct option is FHE.

[PRE-ASSESSMENT] What is a characteristic of stream ciphers in a cryptographic system?

They generate a continuous stream of key material. | Concept: stream ciphers process data bit-by-bit or byte-by-byte using a keystream.

[PRE-ASSESSMENT] What is ciphertext in a cryptographic system?

The encrypted form of the plaintext message. | Concept: plaintext is readable: ciphertext is the encrypted result.

[PRE-ASSESSMENT] What distinguishes cipher block chaining (CBC) mode in a cryptographic system?

CBC uses an initialization vector (IV) and XORs each plaintext block with the previous ciphertext block. | Concept: the study guide identifies CBC as using an IV and having error propagation.

[PRE-ASSESSMENT] Which term refers to the blocks in a blockchain containing cryptographic proof of work?

Proof-of-work. | Concept: proof-of-work is the computational mechanism associated with adding blocks in a proof-of-work blockchain.

[PRE-ASSESSMENT] How is cryptography utilized in cryptocurrencies?

To secure transactions and protect the integrity of the blockchain. | Concept: cryptography supports transaction security and blockchain integrity.

[PRE-ASSESSMENT] What is blockchain?

A chain of blocks linked by cryptographic hashes. | Concept: the links help protect the integrity of the ledger.

[PRE-ASSESSMENT] What was the purpose of NIST's selection of Ascon for lightweight cryptography?

To secure data on IoT and small devices with limited resources. | Concept: lightweight cryptography targets constrained devices.

[PRE-ASSESSMENT] Why is lightweight cryptography designed for modern systems?

To provide efficient and secure encryption solutions for devices with limited resources. | Concept: the goal is security with reduced resource requirements.

[PRE-ASSESSMENT] In a company that successfully aligned its cryptographic practices and what was likely a contributing factor?

A dedicated security team that regularly communicates with all departments. | Concept: organizational alignment requires coordination across departments.

[PRE-ASSESSMENT] Why should cryptographic controls be monitored continuously?

To verify compliance with industry regulations. | Concept: continuous monitoring helps confirm that controls remain effective and aligned with requirements.

[PRE-ASSESSMENT] Which statement is true regarding NIST standards?

NIST provides guidelines for cryptographic standards and their implementation. | Concept: NIST publishes guidance and standards: the pre-assessment does not state that all NIST standards are mandatory for every organization.

[PRE-ASSESSMENT] In what way can cryptography support data integrity?

By ensuring that data cannot be altered without detection. | Concept: hashes and HMACs and and digital signatures can support integrity.

[PRE-ASSESSMENT] What is the primary purpose of aligning cryptography frameworks with organizational policies?

To maximize the effectiveness of data protection measures. | Concept: cryptography should support organizational security objectives rather than operate in isolation.

[PRE-ASSESSMENT] What is a purpose of ISO/IEC 27001?

To establish guidelines for implementing an Information Security Management System (ISMS). | Concept: ISO/IEC 27001 addresses information security management.

[PRE-ASSESSMENT] What does GDPR say about data encryption?

It should be used as a measure to safeguard personal data. | Concept: encryption is a security measure for protecting personal data.

[PRE-ASSESSMENT] In which area is lightweight cryptography most useful?

Internet of Things (IoT) devices. | Concept: constrained devices benefit from efficient cryptographic protection.

[PRE-ASSESSMENT] What is the first step in developing a cryptographic policy for an organization?

Assessing the organization's security objective. | Concept: policy development begins with understanding security needs and objectives.

[PRE-ASSESSMENT] What is a potential ethical dilemma when using cryptography in an organization?

Ensuring employee privacy while using monitoring tools. | Concept: security monitoring can conflict with privacy expectations.

[PRE-ASSESSMENT] What does Nobody But Us (NOBUS) refer to?

The idea that a cryptographic capability or access method should be usable only by its intended holder rather than becoming broadly usable by others. | Concept: NOBUS concerns exclusive access to a capability.

[HIGH-YIELD] What is plaintext?

The original readable message.

[HIGH-YIELD] What is ciphertext?

The encrypted and unreadable form of plaintext.

[HIGH-YIELD] What is a cryptographic key?

A secret value that controls encryption or decryption.

[HIGH-YIELD] What is confidentiality?

Keeping data secret from unauthorized parties.

[HIGH-YIELD] What is integrity?

Ensuring data has not been altered without detection.

[HIGH-YIELD] What is authentication?

Verifying identity.

[HIGH-YIELD] What is availability?

Keeping data accessible when needed.

[HIGH-YIELD] What is the key difference between symmetric and asymmetric cryptography?

Symmetric cryptography uses the same shared key for encryption and decryption: asymmetric cryptography uses a public/private key pair.

[HIGH-YIELD] What is hashing?

A one-way mathematical function used for purposes such as integrity verification.

[HIGH-YIELD] What is keyspace?

The complete set of possible cryptographic keys. A larger keyspace generally makes exhaustive search harder.

[HIGH-YIELD] What is entropy?

A measure of randomness.

[HIGH-YIELD] What is an initialization vector (IV)?

Random or varying data used to add randomness to encryption modes such as CBC.

[HIGH-YIELD] What is a salt?

Random data added to a password before hashing.

[HIGH-YIELD] What is the difference between substitution and transposition ciphers?

Substitution replaces characters according to a pattern: transposition rearranges characters.

[HIGH-YIELD] What is a Caesar cipher?

A simple substitution cipher that shifts letters by a fixed amount.

[HIGH-YIELD] Why is the Caesar cipher weak?

Its keyspace is small and letter-frequency patterns remain predictable.

[HIGH-YIELD] What is the Vigenère cipher?

A polyalphabetic substitution cipher using a keyword.

[HIGH-YIELD] What is a one-time pad?

A cipher using a random key equal in length to the message and used only once.

[HIGH-YIELD] When is a one-time pad provably secure?

When the key is random and secret and equal in length to the message and and used only once.

[HIGH-YIELD] What is confusion?

A property where changes in the key cause large changes in ciphertext and hiding the relationship between key and ciphertext.

[HIGH-YIELD] What is diffusion?

A property where changes in plaintext cause large changes in ciphertext and hiding plaintext structure.

[HIGH-YIELD] What is Kerckhoffs's Principle?

Security should depend on keeping the key secret and not keeping the algorithm secret.

[HIGH-YIELD] What is a stream cipher?

A cipher that encrypts data bit-by-bit or byte-by-byte using a keystream.

[HIGH-YIELD] What is a major stream-cipher weakness?

Reusing a key or keystream can create severe vulnerabilities.

[HIGH-YIELD] What is a block cipher?

A cipher that processes fixed-size blocks of data.

[HIGH-YIELD] Why can block ciphers require padding?

Padding is needed when plaintext is not an exact multiple of the block size.

[HIGH-YIELD] What is ECB mode's major weakness?

Identical plaintext blocks produce identical ciphertext blocks and revealing patterns.

[HIGH-YIELD] What is CBC mode's key characteristic?

Each plaintext block is XORed with the previous ciphertext block and and CBC uses an IV.

[HIGH-YIELD] What is CFB mode?

A block cipher mode that behaves like a stream cipher by XORing with previous ciphertext.

[HIGH-YIELD] What is OFB mode?

A mode that generates a keystream independently of ciphertext and so transmission errors do not propagate.

[HIGH-YIELD] What is CTR mode?

A mode that combines a counter and nonce to generate a keystream: it is parallelizable.

[HIGH-YIELD] What are DES's block and key sizes?

64-bit block size and 56-bit key size.

[HIGH-YIELD] Why is DES vulnerable to brute force?

Its 56-bit key size is too small against modern computing resources.

[HIGH-YIELD] How does 3DES work?

It applies DES three times and was used to extend DES's useful life.

[HIGH-YIELD] What are AES-128 and AES-192 and and AES-256's block sizes?

All use a 128-bit block size.

[HIGH-YIELD] How many rounds does AES-128 use?

10 rounds.

[HIGH-YIELD] How many rounds does AES-192 use?

12 rounds.

[HIGH-YIELD] How many rounds does AES-256 use?

14 rounds.

[HIGH-YIELD] What is RSA based on?

The difficulty of factoring large prime-related numbers.

[HIGH-YIELD] What is Diffie-Hellman primarily used for?

Secure key exchange and not encryption.

[HIGH-YIELD] What is ECC's major advantage?

It provides strong security with smaller keys and is useful in mobile and IoT environments.

[HIGH-YIELD] What is the public key used for in asymmetric encryption?

Encrypting data for the key owner or verifying a digital signature.

[HIGH-YIELD] What is the private key used for?

Decrypting data encrypted to the owner or creating a digital signature.

[HIGH-YIELD] What is PKI?

A framework for managing digital certificates and public keys.

[HIGH-YIELD] What does a Certificate Authority (CA) do?

Issues and revokes and and distributes certificates.

[HIGH-YIELD] What does a Registration Authority (RA) do?

Verifies an applicant's identity for certificate issuance.

[HIGH-YIELD] What is a CRL?

A Certificate Revocation List containing revoked certificates.

[HIGH-YIELD] What does a KMS do?

Automates key generation and distribution and rotation and and revocation.

[HIGH-YIELD] What is SRTP used for?

Securing voice and video over IP.

[HIGH-YIELD] What port does SRTP use according to the study guide?

UDP 5004.

[HIGH-YIELD] What port does LDAPS use?

TCP 636.

[HIGH-YIELD] What port does HTTPS use?

TCP 443.

[HIGH-YIELD] What port does POPS use?

TCP 995.

[HIGH-YIELD] What port does IMAPS use?

TCP 993.

[HIGH-YIELD] What port does SSH use?

TCP 22.

[HIGH-YIELD] What is S/MIME used for?

Securing email through encryption and digital signatures.

[HIGH-YIELD] What security services does S/MIME provide?

Authentication and integrity and non-repudiation and and confidentiality.

[HIGH-YIELD] What is a nonce?

A number used once to provide freshness and help resist replay attacks.

[HIGH-YIELD] What is challenge-response authentication?

An authentication method where a random challenge is sent and the claimant returns a response based on the challenge and secret.

[HIGH-YIELD] What is mutual authentication?

Both parties verify each other's identities.

[HIGH-YIELD] What is a session key?

A temporary symmetric key established for protecting a communication session.

[HIGH-YIELD] What is SSH used for?

Secure remote login and tunneling of insecure traffic.

[HIGH-YIELD] What does IPsec protect?

IP packets using encryption and authentication: it is commonly used for VPNs and secure tunneling.

[HIGH-YIELD] What does ESP provide in IPsec?

Encryption and integrity.

[HIGH-YIELD] What does AH provide in IPsec?

Integrity only and not encryption.

[HIGH-YIELD] What is a brute-force attack?

Trying possible keys until the correct key is found.

[HIGH-YIELD] What is a dictionary attack?

Trying known words or common patterns to guess passwords.

[HIGH-YIELD] What is a rainbow table attack?

Using precomputed hash values to help recover passwords from stolen password hashes.

[HIGH-YIELD] What is a birthday attack?

An attack that targets hash collisions and where two different inputs produce the same hash.

[HIGH-YIELD] What is a side-channel attack?

An attack that uses physical or observable behavior such as timing or power consumption.