Cryptography -Manju C Nair

Welcome to this lecture on Cryptography. In this video, I covered the following subtopics:
Cryptography and Network Security
Cryptography and network security are essential components in protecting digital data and communication in today's interconnected world. They work together to ensure the confidentiality, integrity, and availability of information across networks.
Security Attacks
Security attacks are deliberate attempts to compromise the functionality, integrity, or confidentiality of information systems. They are classified into two main types:
• Passive Attacks: Involve monitoring or eavesdropping on transmissions without altering the data, such as traffic analysis and sniffing.
• Active Attacks: Involve modifying or disrupting data or services, including Denial of Service (DoS), spoofing, phishing, and man-in-the-middle attacks.
Security Goals
The main goals of network security, often referred to as the CIA Triad, include:
• Confidentiality: Ensuring that only authorized users can access sensitive data.
• Integrity: Guaranteeing that the data is not altered during transmission.
• Availability: Making sure that data and services are available to authorized users when needed.
Other important goals include authentication, non-repudiation, and access control.
Cryptography
Cryptography is the science of securing information by converting it into a form that is unreadable to unauthorized users. It ensures secure communication over insecure channels like the internet.
Basic Terms
• Plaintext: Original readable message or data.
• Ciphertext: Encrypted form of the plaintext.
• Key: A value used in the encryption and decryption process.
• Algorithm: A mathematical procedure for performing encryption or decryption.
Encryption and Decryption
• Encryption is the process of converting plaintext into ciphertext using an algorithm and a key.
• Decryption is the reverse process—converting ciphertext back into plaintext using a decryption key.
Categories of Cryptography
1. Symmetric Key Cryptography: Same key is used for encryption and decryption. Fast but requires secure key exchange.
2. Asymmetric Key Cryptography: Uses a public key for encryption and a private key for decryption. More secure for communication but slower.
3. Hash Functions: One-way encryption used for data integrity. No key is used (e.g., SHA-256).

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