Cryptography Basics Quiz

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Questions and Answers

What is the term for the original message before encryption?

Ciphertext

Decryption

Plaintext (correct)

Encryption

What is the purpose of encryption?

To decode the data

To provide data confidentiality (correct)

To represent the data in a certain format

To convert a message into a standard alphabet

Who is the passive attacker in the simplified model of symmetric encryption?

Alice

Mallory

Eve (correct)

Bob

What is the range of possible values of the key called?

Keyspace Signup and view all the answers

What is the process of turning ciphertext back into plaintext?

Decryption Signup and view all the answers

What is the branch of applied mathematics that encompasses both cryptography and cryptanalysis?

Cryptology Signup and view all the answers

What is the term for the mathematical function used for encryption and decryption?

Algorithm Signup and view all the answers

What percentage of attendance will result in a second warning letter?

20% Signup and view all the answers

What is the purpose of cryptography?

To keep messages secure Signup and view all the answers

What is the total marks for the practical assessments?

16 Marks Signup and view all the answers

What is the recommended study routine advised?

20 minutes study round Signup and view all the answers

What is the tool used to write the code for labs?

Jupyter Notebook Signup and view all the answers

What is a security attack?

Any action that compromises the security of information owned by an organization Signup and view all the answers

What is the primary goal of passive attacks?

To learn or make use of information from the system Signup and view all the answers

What is a security mechanism according to ITU-T X.800?

A process that is designed to detect, prevent, and recover from security attacks Signup and view all the answers

What is the primary goal of access control?

To prevent the unauthorized use of a resource Signup and view all the answers

What is data confidentiality?

Protection of data from unauthorized disclosure Signup and view all the answers

What is a security service according to X.800?

A communication service that provides a specific kind of protection to system resources Signup and view all the answers

What is the goal of cryptanalysis?

To recover the plaintext or the key Signup and view all the answers

What is a brute-force attack?

A trial of every possible key on a piece of ciphertext until an intelligible translation is obtained Signup and view all the answers

What is the primary objective of a computationally secure cipher?

To make the cost of breaking the cipher exceed the value of the encrypted information Signup and view all the answers

What is linear cryptanalysis?

A linear approximation of the encryption algorithm Signup and view all the answers

What is the main characteristic of an unconditionally secure cipher?

The cipher cannot be broken no matter how much time or ciphertext is available Signup and view all the answers

What is the significance of the one-time pad (OTP) in cryptography?

It is a theoretically unconditionally secure cipher Signup and view all the answers

What is a primary difference between traditional cryptography and quantum cryptography?

Laws of physics Signup and view all the answers

What is the primary goal of steganography?

To hide the existence of a message Signup and view all the answers

In what ways can steganography be applied?

In images, audio, video, text, and network Signup and view all the answers

What is the strength of modern cryptography based on?

Mathematical and computational principles Signup and view all the answers

What is the main difference between cryptography and steganography?

Cryptography obscures content, steganography hides existence Signup and view all the answers

What is a characteristic of traditional cryptographic schemes?

Based on secrecy of protocols Signup and view all the answers

Study Notes

Aspects of Security based on ITU-T X.800

Security Attacks

Any action that compromises the security of information owned by an organization
Threat: possible danger that might exploit an attack
Types of attacks:
- Passive attacks: attempts to learn or make use of information from the system but does not affect system resources
  - Eavesdropping/Sniffing/Snooping
  - Traffic Analysis
- Active attacks

Security Mechanism

A process designed to detect, prevent, and recover from security attacks
X.800 process

Security Service

A process or communication service that provides a specific kind of protection to system resources
Uses one or more security mechanisms to provide the service
Types of security services:
- Authentication: assurance that the communicating entity is the one claimed
- Access Control: prevention of unauthorized use of a resource
- Data Confidentiality: protection of data from unauthorized disclosure
- Data Integrity: assurance that data received is as sent by an authorized entity

Introduction to Cryptology

Overview of Secret Communications using Cryptography

Cryptology: branch of applied mathematics encompassing both cryptography and cryptanalysis
Cryptography: the art and science of keeping messages secure
Cryptanalysis: the science of recovering the plaintext of a message without access to the key

Principles of Cryptography

Brute-Force Attack: trying every possible key on a piece of ciphertext until an intelligible translation into plaintext is obtained
Statistical Attack: estimating the occurrence frequency of letters in a text
Algebraic Attack: trying to find equivalent representation of the encryption algorithm to simplify it
Linear Cryptanalysis: linear approximation of the encryption algorithm
Differential Cryptanalysis: studying how the plaintexts difference propagates and affects the ciphertext difference to find unbalanced output

Dimensions of Cryptography

Non-Repudiation: protection against denial by one of the parties in a communication
Cryptosystem: combination of an algorithm, plus all possible plaintexts, ciphertexts, and keys
Types of Cipher Security:
- Unconditionally Secure: theoretically impossible to break, e.g., One-Time Pad (OTP)
- Computationally Secure: the cost of breaking the cipher exceeds the value of the encrypted information, and the time required to break the cipher exceeds the useful lifetime of the information

Basic Terminologies

Plaintext: any simple message
Encryption: the process of disguising a message to hide its contents
Ciphertext: an encrypted message
Decryption: the process of turning ciphertext back into plaintext
Cryptographic Algorithm: mathematical function used for encryption and decryption
Key: denoted by K, might be any one of a large number of values
Keyspace: range of possible values of the key

Players

Alice: sender of an encrypted message
Bob: intended receiver of encrypted message
Eve: passive attacker
Mallory: active attacker

Simplified Model of Symmetric Encryption

General approaches to cryptanalysis:
- Cryptanalytic attack: exploiting the characteristics of the algorithm to attempt to deduce a specific plaintext or to deduce the key being used
- Schemes were designed in an ad-hoc manner and then evaluated based on their perceived complexity/cleverness

Historical Perspective

Historical: based on secrecy of protocols
Modern: based on scientific foundations, used for more than just data confidentiality, can protect data integrity, enable user authentication, etc.
Quantum: field of study that utilizes the principles of quantum mechanics to develop cryptographic schemes that are theoretically impossible to break using classical computing methods

Steganography

Definition: hiding information within another medium so its existence is concealed
Difference from cryptography: cryptography obscures content, while steganography hides the very existence of the message
Common mediums: images, audio, video, text, and network

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Description

Test your understanding of basic cryptography concepts, including non-repudiation, plaintext, encryption, decryption, and ciphertext. Learn how to protect communication from denial.