1. Introduction:-
Traditionally signature with a message is used to give evidence of identity and intention with regard to that message. For years people have been using various types of signature to associate their identity and intention to the messages. Wax imprint, seal, and handwritten signature are the common examples. But when someone need to sign a digital message, things turn different. In case of signing a digital document one cannot use any classical approach of signing, because it can be forged easily. Forger just need to cut the signature and paste it with any other message. For signing a digital document one uses digital signature [1][2][3].
Therefore, digital signature are required not to be separated from the message and attached to another. That is a digital signature is required to be both message and signer dependent. For validating the signature anyone can verify the signature, so digital signature are suppose to be verified easily.
A digital signature scheme typically consist of three distinct steps:
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Key generation:- User compute their public key and corresponding private key.
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Signing:- In this step user sign a given message with his/her private key.
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Verification:- In this step user verify a signature for given message and public key.
So the functionality provided by digital signature can be stated as follows:
Authentication:- Digital signature provides authentication of the source of the messages as a message is signed by the private key of the sender which is only known to him/her. Authentication is highly desirable in many applications.
Integrity:- Digital signature provides integrity as digital signature uniquely associate with corresponding message. i.e. After signing a message a message cannot be altered if someone do it will invalidate the signature. There is no efficient method to change message and its signature to produce a new message and valid signature without having private key. So both sender and receiver don’t have to worry about in transit alteration.
Non- repudiation:- For a valid signature sender of message cannot deny having signed it.
In this report we are going to discuss different variation of digital signature. First we will describe RSA digital signature scheme and Elgamal signature scheme, along with their elliptic curve version. After covering above signature scheme we will talk about digital signature standards, and then we will cover proxy signature scheme, blind signature scheme and then we will finally talk about short signature scheme.