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 digital data integrity in exchanged data and to validate the authorized identity of the recipient over an open network. The goal of a digital signature algorithm is to provide security for messages or data. Keywords: Digital signature, Authentication, Non-repudiation, Integrity Say no to plagiarism. Get a tailor-made essay on "Why Violent Video Games Shouldn't Be Banned"? Get an Original Essay INTRODUCTION Information is highly secret and requires great security, therefore extensive security measures must be taken. Many algorithms and techniques can be used to protect our data or information from threats. These types of technologies and algorithms are collectively known as encryption. The cryptography system can be broadly classified into two parts: the first is the symmetric key cryptography (single key system) owned by both the sender and the recipient and the other is the public key system (asymmetric key cryptography) in which are given the uses of two keys, the first is the public key which is common to both the sender and the recipient and the other is the private key known only to the individual. DIGITAL SIGNATURE The authenticity of many legal, financial and other documents is guaranteed by the presence or absence of an authorized handwritten signature. “Digital Signature” is the best solution for authenticity in various fields. A. A digital signature is an authentication mechanism that allows the author 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 origin and integrity of the message. It must have the following properties: It must verify the author, date and time of the signature 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 to be a very important and useful tool to achieve information security. In addition to the ability to ensure message non-repudiation, the digital signature also provides message authentication and data integrity. Let's see briefly how this is achieved with the digital signature − Message authentication − When the verifier validates the digital signature using the public key of a sender, he is certain that the signature was created only by the sender who possesses the corresponding secret private key and not another. Data integrity: In case an attacker has access to the data and modifies it, the verification of the digital signature by the recipient fails. The hash of the modified data and the output provided by the verification algorithm will not match. Therefore, the recipient can safely deny the message assuming that the data integrity has been violated. Non-repudiation − Since only the signer is assumed to know the signature key, he can create a unique signature only on a given piece of data. In this way the recipient can present the data and digital signature to third parties as evidence in the event of a future dispute. APPROACHES The digital signature algorithm (DSA) is part of the DSS (Digital Signature Standard) approach, developed by the National Security Agency (NSA) of the United States. DSA is a federal information processing standard for digital signatures. In August 1991 DSA was developed by the National Institute of Standards..