- Cryptography:
- Cryptography is the study and practice of securing information through mathematical techniques.
- It encompasses a broad range of techniques, including encryption, hashing, digital signatures, and authentication protocols.
- Cryptography aims to achieve security goals like confidentiality, integrity, authentication, and non-repudiation.
- Encryption:
- Encryption is a subset of cryptography.
- It refers specifically to the process of converting plaintext into ciphertext to protect the confidentiality of information.
- Encryption requires a key and an algorithm to transform data.
Analogy: If cryptography is a toolkit, encryption is one of the tools in that kit.
Cryptography as a Discipline in Computer Security
Cryptography is a fundamental field within computer security, focusing on the theoretical and practical aspects of protecting information. Below are the major terms and concepts to understand cryptography:
1. Goals of Cryptography
Cryptography aims to achieve the following core security objectives:
- Confidentiality: Ensuring that information is accessible only to authorized parties (achieved using encryption).
- Integrity: Guaranteeing that information is not altered during transmission or storage (achieved using cryptographic hashing and Message Authentication Codes).
- Authentication: Verifying the identity of parties involved in communication (achieved using digital signatures and certificates).
- Non-Repudiation: Preventing denial of actions or communications (achieved using digital signatures).
2. Cryptographic Techniques
Cryptography involves a variety of techniques, each serving specific purposes:
- Encryption:
- Symmetric Encryption (e.g., AES, DES): Uses one key for encryption and decryption.
- Asymmetric Encryption (e.g., RSA, ECC): Uses a pair of keys (public and private) for encryption and decryption.
- Hashing:
- One-way transformations of data to fixed-size outputs.
- Used for data integrity and password storage (e.g., SHA-256, MD5).
- Digital Signatures:
- Ensures message authenticity and integrity using asymmetric cryptography (e.g., RSA signatures, ECDSA).
- Key Exchange:
- Securely exchanging cryptographic keys over insecure channels (e.g., Diffie-Hellman, ECDH).
- Authentication Protocols:
- Systems for verifying identities (e.g., Kerberos, OAuth).
3. Branches of Cryptography
Cryptography is divided into several specialized areas:
- Classical Cryptography:
- Historical techniques, such as Caesar cipher and Vigenère cipher.
- Relies on substitution and transposition of characters.
- Modern Cryptography:
- Built on mathematical foundations.
- Includes symmetric, asymmetric, and hashing algorithms.
- Post-Quantum Cryptography:
- Focuses on algorithms resistant to quantum computer attacks (e.g., lattice-based cryptography).
- Cryptanalysis:
- The study of breaking cryptographic algorithms or systems.
- Explores vulnerabilities and methods to defeat encryption.
- Steganography:
- The practice of hiding information in other media (e.g., images, audio).
- Quantum Cryptography:
- Uses principles of quantum mechanics to secure communication (e.g., Quantum Key Distribution).
4. Key Cryptographic Terms
- Plaintext: The original, readable message or data.
- Ciphertext: The encrypted version of the plaintext.
- Key: A secret value used in cryptographic algorithms to encrypt or decrypt data.
- Algorithm: The mathematical process or set of rules used for encryption or decryption (e.g., AES, RSA).
- Key Management: Techniques for securely generating, storing, distributing, and destroying cryptographic keys.
- Initialization Vector (IV): A random or pseudo-random value used to ensure encryption produces unique ciphertexts even for identical plaintexts.
5. Cryptographic Protocols
Protocols combine cryptographic techniques to provide secure communication and data protection. Examples include:
- TLS/SSL: Secures communication over the internet.
- IPsec: Protects data in VPNs.
- PGP/GPG: Provides email encryption and digital signing.
- Blockchain: Uses cryptography for secure distributed ledgers.
The Study of Cryptography
The study of cryptography involves understanding the following:
- Mathematical Foundations:
- Number theory, finite fields, elliptic curves, and modular arithmetic.
- Essential for designing secure algorithms.
- Algorithm Design and Analysis:
- Developing cryptographic algorithms.
- Evaluating their efficiency, security, and resistance to attacks.
- Cryptanalysis:
- Techniques for testing cryptographic systems against potential vulnerabilities.
- Includes brute force, side-channel attacks, and advanced mathematical techniques.
- Applications:
- Cryptography is applied in fields like secure communication (e.g., HTTPS), digital rights management, cryptocurrencies (e.g., Bitcoin), and secure storage.
Summary of Cryptography in Computer Security
Cryptography is a comprehensive discipline encompassing tools, techniques, and protocols to ensure the secure exchange, storage, and validation of information. Its principles underpin nearly every aspect of modern cybersecurity, from internet communications to secure storage and identity management. It bridges mathematics, computer science, and information theory to address the challenges of securing data in an increasingly connected world.