<h3><strong>Hash Functions</strong></h3><p>A <strong>hash function</strong> is a cryptographic algorithm that transforms an input (or "message") into a fixed-size string of characters, which is typically a hash code. The output, known as a <strong>hash value</strong>, is unique to each input. Hash functions are one-way functions, meaning they cannot be reversed to retrieve the original data. They are widely used in blockchain to create unique identifiers for blocks, ensuring data integrity by making it nearly impossible to alter any part of the blockchain without changing the entire hash sequence.</p>