Cryptography-and-Network-Security

This repository contains Cryptography programs in the Python programming language.

Cryptography:

• Definition:

  • Cryptography is the practice and study of techniques for securing communication and information from adversaries.

• Objectives:

  • Ensure confidentiality, integrity, and authenticity of information.
  • Provide secure communication in the presence of malicious third parties.

• Types of Cryptography:

  • Symmetric Key Cryptography (uses a single key for both encryption and decryption).
  • Asymmetric Key Cryptography (uses a pair of public and private keys).

• Applications:

  • Used in securing online transactions (e.g., HTTPS).
  • Protects sensitive data in storage and transmission.

• Challenges:

  • Continuous need for stronger algorithms due to advancements in computing power.
  • Balancing security and usability in real-world applications.

Caesar Cipher:

• Algorithm:

  • Substitution cipher where each letter in the plaintext is shifted a certain number of places down or up the alphabet.

• Key Concept:

  • Key represents the number of positions each letter of the alphabet is shifted.

• Weakness:

  • Vulnerable to brute-force attacks due to a limited number of possible keys (26 in the case of the English alphabet).

• Encryption Example:

  • Plain text: "HELLO"
  • Key: 3
  • Cipher text: "KHOOR"

• History:

  • Named after Julius Caesar, who is believed to have used it for military communication.

Rail Fence Cipher:

• Algorithm:

  • Transposition cipher where the plaintext is written in a zigzag pattern on a set of rails.

• Key Concept:

  • Key represents the number of rails (rows) used in the encryption process.

• Encryption Example:

  • Plain text: "HELLO"
  • Key: 3
  • Cipher text: "HOLELW"

• Decryption:

  • Reconstruct the zigzag pattern and read off the message.

• Usage:

  • Historical use in non-secure communication due to its simplicity.
  • Rarely used for serious encryption today, more of a puzzle or educational tool.