Digital Signature

• Digital signatures are used to authenticate the identity of the sender. It is like signing a message in electronic form.
• A digital signature is a protocol that produces the same effect as a real signature.
• It is a mark that only the sender can make and other people can easily recognize that it belongs to the sender. A digital signature is also used to confirm agreement to a message.
• A digital signature must be unforgeable and authentic.
• In a digital signature process, the sender uses a signing algorithm to sign the message. The message and the signature are sent to the receiver. The receiver receives the message and the signature and applies the verifying algorithm to the combination.
• If the result is true, the message is accepted otherwise it is rejected.
• A conventional signature is like a private key belonging to the signer of the document. The signer uses it to sign documents. The copy of the signature on a file is like a public key so anyone can use it to verify a document to compare it to the original signature.

• In digital signature the signer uses her private key applied to a signing algorithm to sign the document. The verifier uses the public key of the signer applied to verifying algorithm to verify the sign.
• When a document is signed anyone including Bob can verify it because everyone has access to Alice’s public key. Alice must never use her public key to sign the document because anyone could forge her signature.
• Digital signatures have assumed great significance in the modern world of web-commerce. Many countries have made provisions for recognizing digital signature as a valid authorization mechanism like paper-based signatures.