What is Cryptography?

Cryptography is the practice and study of securing information by transforming it into a format that is unreadable to unauthorized parties. It ensures confidentiality, integrity, authenticity, and non-repudiation in communication.

Key Aspects of Cryptography

Confidentiality – Ensures that only the intended recipient can understand the message.
Integrity – Protects data from being altered or tampered with.
Authentication – Confirms the identity of the sender and receiver.
Non-repudiation – Prevents the sender from denying they sent a message.

Types of Cryptography

1. Symmetric Encryption (Secret Key Cryptography)

Uses a single key for both encryption and decryption.

Examples: AES (Advanced Encryption Standard), DES (Data Encryption Standard).

2. Asymmetric Encryption (Public Key Cryptography)

Uses a pair of keys: a public key for encryption and a private key for decryption.

Examples: RSA, ECC (Elliptic Curve Cryptography).

3. Hash Functions

Converts data into a fixed-length string that cannot be reversed (one-way encryption).

Examples: SHA-256, MD5 (though MD5 is considered insecure today).

History of Cryptography

Ancient Cryptography: Used in historical texts, such as the Caesar Cipher (shift cipher used by Julius Caesar).
Medieval Cryptography: The Atbash Cipher (simple letter substitution).
Modern Cryptography: Advanced encryption methods like AES and RSA secure online communications.

Where is Cryptography Used Today?

Online Banking & E-commerce – Encrypts transactions to prevent fraud.
Messaging Apps (e.g., WhatsApp, Signal) – Uses end-to-end encryption to secure conversations.
Cybersecurity – Protects sensitive data in databases and secure servers.
Blockchain & Cryptocurrencies – Uses cryptographic hash functions for security.

Conclusion

Cryptography is essential for modern security, protecting sensitive information from hackers, fraud, and unauthorized access. It is widely used in everyday digital interactions, ensuring secure communications and data protection.