A digital signature is a cryptographic mechanism that serves as a secure way to authenticate the signer of a digital message or document. It ensures integrity by confirming that the content has not been altered after signing. Digital signatures utilize public key infrastructure (PKI) for validation, where the signer’s private key generates the signature, and the corresponding public key allows others to verify it. This technology is crucial for secure online transactions, legal agreements, and maintaining the authenticity of digital records, thereby enhancing trust in electronic communications.