Approximately 2 to 5 questions appears in CISA exam on ‘Digital Signature’ concept .The objective of this e-book is to ensure that CISA candidate get adequate knowledge of digital signature and related concepts. Question Answer and Explanation (QAE) on digital signature are designed in accordance with CISA exam pattern. This small e-book will help CISA candidate to attempt questions on concept of digital signature more confidently and correctly.