what is hash function, types of cryptography algorithm in details notes

A hash function is a mathematical function that takes an input (or "message") and returns a fixed-size string of bytes, which is typically a hash value. The output is often a digest of the input. Hash functions are commonly used in various aspects of computer science, including cryptography and data integrity verification. They are designed to be fast to compute and deterministic, meaning the same input will always produce the same output. There are several types of cryptographic algorithms, broadly categorized into: Symmetric Key Cryptography: Also known as secret-key or private-key cryptography, this type of cryptography uses the same key for both encryption and decryption. Examples include DES (Data Encryption Standard), AES (Advanced Encryption Standard), and Blowfish. Asymmetric Key Cryptography: Also known as public-key cryptography, this type uses a pair of keys: a public key and a private key. The public key is widely distributed and used for encryption, while the private key is kept secret and used for decryption. Examples include RSA (Rivest-Shamir-Adleman), ECC (Elliptic Curve Cryptography), and Diffie-Hellman key exchange. Hash Functions: These are cryptographic algorithms that produce a fixed-size hash value from input data of any size. Hash functions are used for various purposes, including data integrity verification, password storage, and digital signatures. Examples include SHA-256 (Secure Hash Algorithm 256-bit), MD5 (Message Digest Algorithm 5), and bcrypt. Digital Signatures: Digital signatures are cryptographic techniques used to verify the authenticity and integrity of digital messages or documents. They typically involve a combination of asymmetric key cryptography and hash functions.