<h3><strong>Digital Signatures and Public Key Infrastructure (PKI)</strong></h3><h4><strong>Digital Signatures</strong></h4><p>A <strong>digital signature</strong> is a cryptographic mechanism used to verify the authenticity and integrity of data. It works by using a <strong>private key</strong> to create the signature and a <strong>public key</strong> to validate it. Digital signatures ensure that a message or transaction has not been altered and that it comes from a trusted source. Commonly used in blockchain, digital signatures help verify transactions and protect against fraud.</p><h4><strong>Public Key Infrastructure (PKI)</strong></h4><p><strong>PKI</strong> is a system of managing digital keys and certificates that enable secure communication over networks. PKI involves:</p><ul><li><strong>Public keys</strong> (used for encryption),</li><li><strong>Private keys</strong> (used for decryption),</li><li><strong>Digital certificates</strong> (used to authenticate the identity of the sender),</li><li><strong>Certificate Authorities (CAs)</strong> (trusted entities that issue certificates).</li></ul><p>Together, PKI ensures secure communication, data integrity, and identity verification in digital transactions, including in blockchain systems.</p>