SUMMARY: Digital signature methodology provides cryptographic services such as entity authentication, authenticated key transmission, and authenticated key agreement. A digital signature is used to provide authentication, non-repudiation and integrity of digital data exchanged and to validate the authorized identity of the recipient over an open network. The goal of a digital signature algorithm is to ensure the security of messages or data. Keywords: Digital signature, Authentication, Non-repudiation, IntegritySay no to plagiarism. Get a tailor-made essay on “Why Violent Video Games Should Not Be Banned”? Get the original essay INTRODUCTION The information is highly secret, which requires high security, so extensive security measures must be adopted. There are many algorithms and techniques that can be used to protect our data or information from threats. These types of technologies and algorithms are collectively known as cryptography. Cryptography system can be broadly classified into two parts: one is symmetric key cryptography (single key system) which is possessed by both sender and receiver and the other is public key system ( asymmetric key cryptography) in which the use of two keys is provided, the first is the public key which is common to the sender and the receiver and the other is the private key which is known only to the individual . DIGITAL SIGNATURE The authenticity of many legal, financial and other documents is determined by the presence or absence of an authorized handwritten signature. “Digital Signature” is the best solution for authenticity in various fields. A. The digital signature is an authentication mechanism that allows the creator of a message to attach a code that acts as a signature. The signature is formed by taking the hash of the message and encrypting the message with the creator's private key. The signature guarantees the source and integrity of the message. It must have the following properties: It must verify the author and the date and time of signing It must authenticate the content at the time of signing It must be verifiable by third parties to resolve disputes. IMPORTANCE OF DIGITAL SIGNATURE Among all cryptographic primitives, digital signature using public key cryptography is considered a very important and useful tool to ensure information security. In addition to the ability to ensure non-repudiation of the message, the digital signature also ensures message authentication and data integrity. Let us briefly see how this is achieved by digital signature - Message Authentication - When the verifier validates the digital signature using the public key of a sender, it is ensured that the signature was created only by the sender who has the corresponding secret private key and not another. Data Integrity – In case an attacker gains access to the data and modifies it, the digital signature verification at the receiver side fails. The hash of the modified data and the result provided by the verification algorithm will not match. Therefore, the recipient can safely reject the message assuming that the data integrity has been violated. Non-repudiation - Since it is assumed that only the signatory has knowledge of the signing key, he or she can only create a unique signature on a given piece of data. Thus, the recipient can present the data and the digital signature to a third party as proof in the event of a subsequent dispute. APPROACHES The digital signature algorithm (DSA) is part of the DSS (Digital Signature) approach..