Introduction to Encryption and Security

Introduction to Encryption

• Encryption is a crucial part of internet security, ensuring data confidentiality, integrity, and authenticity.
• Digital communication, online transactions, and business activities rely heavily on encryption.
• Modern communication methods like WhatsApp and online banking use encryption for security.
• The Internet is a global network that enables the smooth transfer of information.

Evolution of Communication Techniques

• Communication methods have evolved significantly, from snail mail to digital platforms.
• The internet provides a global platform for rapid and seamless communication.
• Security is a significant concern in this global networked world.

Need for Network Security

• Unauthorized users can intercept and copy sensitive data, like payroll records.
• Intruders can modify messages, potentially altering authorization files with false information.
• Stolen credentials can be exploited for unauthorized activities on websites.
• Attackers can manipulate financial transactions for unauthorized gains.

Threats and Attacks

• A threat is a potential security violation, arising from capabilities, situations, or actions that can cause harm.
• Attacks are deliberate attempts to breach security systems and exploit vulnerabilities.
• Threats and attacks endanger the security of systems and services.
• Denial of Service (DoS) attacks prevent the normal use of a facility or overwhelm a network.

Types of Attacks

• Passive attacks aim to learn or use information without altering the system.
• Examples include eavesdropping on messages and analyzing communication patterns.
• Passive attacks are often hard to detect effectively.
• Active attacks try to alter system resources or operation.
• Examples include masquerading, modifying messages, and Denial-of-Service attacks.
• Active attacks are often more detectable than passive attacks and are harder to prevent.

Internet Security and Services

• Internet security focuses on protecting connected systems and user activities.
• It addresses web browsers, banking, shopping, and emails.
• Implementing measures to prevent, detect, and recover from threats is part of internet security.
• Measures are important in reducing risks to users.
• Security services include protecting data integrity, ensuring confidentiality, and maintaining system availability.

Security Services

• Data Integrity: ensuring what is sent equals what is received.
• Confidentiality: limiting access of information to authorized parties only.
• Availability: ensuring the system is operational and accessible

Security Mechanisms

• Encryption: converting data into an unreadable format using mathematical algorithms.
• Digital Signature: adding data to a unit to verify its source and integrity.
• Authentication Exchange: validating the identity of an entity through an exchange of information.
• Traffic Padding: adding bits to gaps in a data stream to mask its analysis.

Cryptography Fundamentals

• Cryptography is the study of techniques to secure communications.
• Techniques used for secure communication.
• Processes of converting data into intelligible forms and back; encryption and decryption.
• Cryptoanalysis is the art of deciphering a message without knowing the enciphering process.

Some Encipherment Terminologies

• Plaintext: original message; Ciphertext: coded message.
• Encryption: converting plaintext to ciphertext; Decryption: converting ciphertext back to plaintext.
• Secret key: a secret value that is independent of plaintext for encryption/decryption.
• Cryptography: the study of different communication schemes and techniques.

Common Cryptography Techniques

• Symmetric encryption uses the same key for encryption and decryption (e.g., AES).
• Asymmetric encryption uses different keys for encryption and decryption (e.g., RSA).
• Categorized by operations, keys used, and proceeding/plaintext methods: block (one block at time), or stream cipher (process data continuously).

Cryptography

• Method of transforming understandable messages into unintelligible ones, and back again for secure communication.
• Used in conjunction with algorithms for encryption and decryption.
• The process uses secret values, called cryptographic keys for encoding and decoding tasks.

Model of Conventional Cryptosystem

• Describes the process of encryption and decryption using algorithms.
• Data is encrypted by the encryption algorithm using a key and transmitted via secure channel.
• The decrypted data is received and decrypted by destination using the decryption algorithm in the receiver’s end.

Cryptoanalysis

• Identifying encryption keys by exploiting algorithm vulnerabilities.
• Uses various methods including brute-force searches and cryptanalytic techniques.
• Approaches include strategies based on the nature of algorithms and insights about plaintext or ciphertext pairs.

Types of Cryptanalytic Attacks

• Ciphertext-only attack where attacker has encrypted data, trying to decrypt the data using the cipher algorithm.
• Known-plaintext attack - attacker has some knowledge of the plaintext and corresponding ciphertext.
• Chosen-plaintext attack - attacker can choose plaintexts for decryption.
• Chosen-ciphertext attack - attacker can choose ciphertexts to decrypt.

Encryption on Schemes' Requirements

• Encryption schemes must be computationally secure to prevent attackers from breaking the cipher.
• Schemes should meet the needs for generating keys/algorithms for encryption and decryption.
• Schemes should consider the required time for an attacker to break a scheme. Unconditionally secure schemes cannot be broken even with unlimited computational power or resources.

Symmetric vs Asymmetric Encryption

• Symmetric: uses a single key for encryption and decryption.
• Asymmetric: uses different public and private keys for encryption and decryption.

Classical Encryption Techniques

• Substitution ciphers substitute letters with other characters or symbols.
• Examples: Caesar cipher, monoalphabetic cipher, Playfair cipher.
• Transposition ciphers change characters' positions.

Modern Encryption Algorithms

• Examples include Block Ciphers and Stream Ciphers.

Block Cipher

• Encrypt and Decrypt a fixed-size blocks of plaintext (and ciphertext).
• Examples include DES, AES.
• Main Property: A block cipher must behave like a random permutation; minor changes in plaintext will change the ciphertext dramatically.

Feistel Structure

• Feistel cipher: a common design for symmetric block ciphers.
• The Feistel network operates in rounds, where a round function mixes a sub-key to the data.
• This involves substitution and permutation operations in each round to improve security.

Simplified DES (S-DES)

• Educational version of DES.
• A simplified version of DES used in education.
• Has a smaller key and block size compared to a full DES.

Cryptanalysis of DES

• DES has weak keys that create consistent patterns in the key schedule.
• Brute-force attack is possible for a 64-bit key, and that’s why DES is no longer in use.

Conclusion

• Encryption is essential for internet security, ensuring confidentiality, integrity, and authenticity.
• Modern ciphers like AES and RSA offer advanced security over classical ciphers.

References

• Include references if possible.

Discussions

• Security depends on the secrecy of the key, not the algorithm.
• Practical concerns/limitations of one-time pads and other techniques should be discussed.
• Important aspects in designing algorithms to be difficult to break.

Hash Functions & Modern Security

• Hash functions provide integrity checks without revealing information.
• Hash functions are one-way, making it difficult or impossible to reverse the process.
• Examples include SHA-256 and TLS/SSL.