Data Security Basic Concepts Quiz

Introduction to Encryption

• Encryption is a fundamental component of internet security.
• Encryption protects the confidentiality, integrity, and authenticity of data transmitted online.
• Modern communication relies heavily on the internet for various activities, including communication, shopping, banking, and business.
• The internet, a global network, facilitates seamless information exchange.
• Secure messaging apps like WhatsApp and secure online banking transactions are examples of modern communication that use encryption.

Evolution of Communication Techniques

• Communication methods have evolved from physical mail to digital communication.
• The evolution in techniques highlights the increasing need for safeguarding digital information.

Need for Network Security

• Sensitive data protection is crucial to prevent unauthorized access and copying of sensitive data, such as payroll records.
• Message integrity is essential to ensure that transmitted messages haven't been altered, preventing issues like unauthorized modifications to authorization files.
• Credential misuse can lead to attackers gaining unauthorized access and performing harmful actions on websites.
• Fraudulent transactions can result from manipulated messages, causing financial losses and disputes for customers.

Threats and Attacks

• A threat is a potential violation of security, with the capability to cause harm.
• An attack is a deliberate attempt to violate security, often associated with exploitation of vulnerabilities. Cybersecurity threats can be active or passive.
• Active attacks attempt to alter system resources or disrupt their operation.
• Passive attacks attempt to learn or make use of information without affecting system resources, often through eavesdropping.

Types of Attacks

• Passive attacks: These aim to learn or make use of information without affecting the system resources, like eavesdropping on communications.
• Active attacks: These aim to alter system resources or their operation, such as message modification or denial of service.

Internet Security and Services

• Internet security refers to measures designed to protect systems and user activities when connected to the internet.
• It includes online banking, shopping, email, and chatting applications.
• The goal is to reduce threats facing users and provide measures to prevent, detect, and recover from security incidents.
• Measures include preventing threats, detecting security incidents, and recovering from them.

Security Services

• Data integrity: Ensures that data received is identical to data sent, preventing unauthorized alterations.
• Confidentiality assures that only authorized parties can access data.
• Availability guarantees that data and systems are accessible to authorized users.

Security Mechanisms

• Encipherment: Transforming data into an unreadable format using mathematical algorithms.
• Digital Signature: Data appended to a data unit that allows a recipient to confirm the data's source and integrity.
• Authentication Exchange: A mechanism for confirming an entity's identity through information exchange.
• Traffic Padding: Inserting bits into gaps within data streams to thwart traffic analysis attempts.

Cryptography Fundamentals

• Cryptography is the study of techniques for secure communication.
• Plaintext: The original message.
• Ciphertext: The coded, unreadable message.
• Enciphering: Transforming plaintext into ciphertext.
• Deciphering: Transforming ciphertext into plaintext.
• Secret Key: A value used for both encryption and decryption.
• Cryptoanalysis: The art of deciphering a message without knowledge of encryption details.
• Cryptology: The broader study that combines cryptography and cryptoanalysis.

Categorization of Cryptography Techniques

• Symmetric Cryptography: Uses the same key for encryption and decryption.
• Asymmetric Cryptography: Uses different keys for encryption and decryption (public and private keys).

Cryptoanalysis

• Cryptoanalysis is the process of identifying the key used in encryption rather than recovering the current plaintext.
• Brute-force attack (or exhaustive search): Attempting all possible keys to decrypt a ciphertext.
• Cryptanalysis is based on the nature of the algorithm and existing knowledge about the plaintext to possibly crack it.

Encryption Schemes' Requirements

• Encryption schemes require procedures for generating keys, encryption algorithms, and decryption algorithms for security to be considered sufficient against cyber threats.
• Computationally secure algorithms are essential to safeguard against attackers, with the time required to break an encryption scheme exceeding the value of the encrypted information.

Symmetric vs Asymmetric

• Symmetric: Same key for encryption and decryption. Simple but harder to distribute securely.
• Asymmetric: Different keys, typically public and private. Facilitates secure key exchange but more computationally expensive.

Encryption Mechanisms (Classical and Modern Algorithms)

• Substitution techniques: Replacing letters or symbols with other letters or symbols using a predefined substitution rule. (Example: Caesar cipher)
• Transposition Techniques: Rearranging characters' positions without changing letters.
• Modern encryption algorithms offer stronger security compared to classical ones. (Examples: AES, DES)

Classical Encryption Techniques

• Substitution Cipher: Letters/symbols are replaced with other letters/symbols.
• Transposition Cipher: Letters positions are rearranged.

Examples of Classical Techniques (e.g., Caesar Cipher, Monoalphabetic Cipher, Playfair Cipher, Hill Cipher, Polyalphabetic Cipher, One-Time Pad)

• These are examples of substitution/transposition ciphers used in the past.

Modern Encryption Mechanisms

• Examples of modern encryption mechanisms include the AES, and various hash functions used for message integrity.

Cryptanalysis Using Known Plaintext

• Cryptographers often send messages as blocks (groups) of letters.
• The beginning and end of words are sometimes hidden within the blocks of letters.

Polyalphabetic Cipher

• Multiple alphabets are used for en/decryption.
• Each character is encrypted with a different alphabet depending on its position in the message and using a keyword.
• The Vigenère cipher is a type of polyalphabetic cipher.

Vigenère Cipher - Example

• Encrypting a message "helloy" with keyword bagbag demonstrates the Vigenère cipher process.

Vernam Cipher (One-Time Pad)

• Vernam cipher is perfectly secure as each message/key pair is different.
• The key must be as long as the message, otherwise, it will be less secure.
• The key stream is generated using a random number generator.

One-Time Pad Strength

• Reusing keys in the one-time pad eliminates perfect security.
• Applying random number generators, rather than general-purpose ones, is essential for protecting cryptographic systems' security.

Modern Encryption Algorithms

• Techniques include streams of random bits and block ciphers.
• Block ciphers treat fixed-size blocks of text and encrypt these blocks to an equal sized output.

Block Cipher Principal Operations

• Breaking down operations into smaller parts, followed by re-combination with mixing.
• This ensures a more complex process resistant to cryptanalysis.

Block Cipher - Secret Key

• The key is often used to modify the cipher process for encryption/decryption.
• XOR operations are often used for key mixing.

Feistel Structure

• Two halves of an input (left and right) are used for encryption/decryption procedures.
• F is a function that modifies one half, typically from the input half's bits that is provided with a subkey, resulting in output bits that are used to work with the second half of the input.

Feistel Cipher Design Feature

• Block sizes, key sizes, and the number of rounds used influence security strength.

Data Encryption Standard (DES)

• A symmetric block cipher.
• It has been superseded by AES.
• The key size is 56 bits initially, but 64-bit keys were used initially and the extra 8 bits were used for error check on the 64-bit keys.

Simplified DES(S-DES)

• A simplified version of DES for educational purposes.
• It uses a smaller key size (10 bits)

S-DES Example Encryption

Cryptanalysis of DES

• Weak keys, based on patterns of bits (1 or 0) in 64-bit keys.
• Brute-force attacks are possible but time-consuming, given the 2^56 possible keys.

Conclusion on encryption

• Encryption is fundamental to modern cybersecurity.
• Classical ciphers (like Caesar, Vigenère) have historical importance but are often not secure enough against modern attacks.
• Modern algorithms (like AES, RSA) offer better security.

Discussions on Encryption and Hashing

• This section covers topics like the principles of using hash functions (one-way) and the different classes of cryptographic hash functions, like SHA-256.
• Issues associated with symmetric-key algorithms and their limitations will also be addressed.
• It also mentions the importance of using robust random number generators to ensure the security of encryption schemes, along with why encryption/decryption algorithm should not be kept secret but rather considered public to be evaluated for possible errors.