The purpose of a digital signature in electronic communications is to authenticate and ensure the integrity of digital messages or documents. By using cryptographic techniques, a digital signature verifies the sender's identity and indicates that the message has not been altered during transmission. This process enhances trust in electronic communications, making it vital for various applications, such as legal documents and financial transactions. Digital signatures comply with regulations like the Electronic Signatures in Global and National Commerce (ESIGN) Act, providing a legal equivalent to handwritten signatures.