What do you mean by cryptography?

 Cryptography is the practice and study of techniques for securing communication and information by transforming it into a format that is unreadable to unauthorized users. It involves the use of mathematical algorithms and protocols to ensure the confidentiality, integrity, authenticity, and non-repudiation of data.

Key concepts in cryptography include:

1. Encryption: The process of converting plaintext (readable data) into ciphertext (encoded data) using an algorithm and a key. Only those with the correct key can decrypt the ciphertext back into plaintext.

2. Decryption: The reverse process of encryption, where ciphertext is converted back into plaintext using a key.

3. Keys: A key is a piece of information used in the encryption and decryption processes. Keys can be symmetric (the same key is used for both encryption and decryption) or asymmetric (a pair of keys is used: a public key for encryption and a private key for decryption).

4. Hash Functions: These are algorithms that take an input (or message) and produce a fixed-size string of characters, which is typically a digest that represents the data. Hash functions are used to ensure data integrity, as even a small change in the input will produce a significantly different hash.

5. Digital Signatures: A cryptographic technique that allows a person to sign a document digitally, providing proof of authenticity and integrity. It uses asymmetric cryptography to create a unique signature that can be verified by others.

6. Public Key Infrastructure (PKI): A framework that manages digital certificates and public-key encryption, allowing secure data exchange and authentication over networks.

7. Symmetric and Asymmetric Cryptography:

   • Symmetric Cryptography: Uses the same key for both encryption and decryption. It is generally faster but requires secure key distribution.
   • Asymmetric Cryptography: Uses a pair of keys (public and private) for encryption and decryption. It is more secure for key exchange but typically slower than symmetric methods.

Cryptography is essential for securing communications over the internet, protecting sensitive data, ensuring privacy, and enabling secure transactions in various applications, including online banking, e-commerce, and secure messaging.