The main purpose of a digital signature in electronic transactions is to authenticate the identity of the sender and ensure the integrity of the message being transmitted. It provides assurance that the message has not been altered during transmission and verifies the origin of the document. This process enhances security in online transactions, preventing fraud and unauthorized access. Digital signatures utilize cryptographic methods, making them reliable for personal and business communications. The widespread use of digital signatures is crucial in legal agreements, software distribution, and other scenarios where document authentication is essential.