This document discusses digital signatures. It begins by introducing digital signatures as an electronic equivalent to handwritten signatures for authenticating documents. It then explains that a digital signature is created by encrypting a document's hash value with the sender's private key. The digital signature and public key allow any recipient to verify the sender's identity and confirm the document has not been altered. The document outlines the basic requirements for digital signatures like private and public keys and digital certificates. It also describes how the technology works and some common applications as well as challenges and drawbacks of digital signatures.