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Hashing
What is Hashing?
Hashing is the process of taking an input (or 'message') of any length and producing a fixed-size output, called a hash. In blockchain and cryptocurrency, hashing is a fundamental operation used for various purposes, including securing the network, verifying data integrity, and mining new blocks.
Key Features
Deterministic: The same input always produces the same hash output.
Quick Computation: Hashing is designed to be a fast operation.
Pre-image Resistance: It's computationally infeasible to determine the input from its hash.
Avalanche Effect: A small change in input causes a significant change in the output.
Fixed Output Size: The hash output has a fixed length, regardless of input size.
Uses in Blockchain
Block Chaining: Each block contains the hash of the previous block, creating a chain.
Mining: Proof-of-work systems require finding a hash that meets specific criteria.
Transaction Verification: Hashing is used to verify the integrity of transactions.
Address Generation: Cryptocurrency addresses are often derived from hashed public keys.
Merkle Trees: Efficient verification of large data structures in blockchains.
Common Hashing Algorithms
SHA-256: Used in Bitcoin and many other cryptocurrencies.
Ethash: Ethereum's hashing algorithm (moving away from with Ethereum 2.0).
Scrypt: Memory-hard function used in Litecoin and other cryptocurrencies.
X11: Used in Dash, combines 11 different hash functions.
Hashing in Mining
Target Hash: Miners aim to find a hash below a certain target value.
Nonce Manipulation: Miners change the nonce to produce different hashes.
Difficulty Adjustment: The network adjusts the target to maintain consistent block times.
ASIC Resistance: Some hashing algorithms are designed to resist specialized mining hardware.
Security Aspects
Collision Resistance: It should be extremely difficult to find two inputs with the same hash.
Second Pre-image Resistance: Given an input and its hash, it should be hard to find another input with the same hash.
Avalanche Effect: Ensures that similar inputs produce very different hashes.
Limitations and Vulnerabilities
Birthday Attack: Exploits probability theory to find collisions.
Length Extension Attack: Possible with some hash functions if proper precautions aren't taken.
Quantum Computing Threat: Future quantum computers might break current hashing algorithms.
Hashing vs. Encryption
Reversibility: Hashing is one-way, encryption is reversible with a key.
Purpose: Hashing verifies integrity, encryption provides confidentiality.
Key Usage: Hashing doesn't use keys, encryption requires them.
Similar Terms
Mining: The process that often involves finding specific hash values.
Hash: A fixed-size alphanumeric string that results from running data through a cryptographic hash function.
Proof of Work: A consensus mechanism that heavily relies on hashing.
Merkle Root: A hash of all the transactions in a block, used in blockchain structures.