What is a digital signature? What does its authentication mean? Give various salient built-in features of a digital signature. (UPSC 2013)

A digital signature is a cryptographic method used to sign an electronic record and confirm the signer’s identity. It uses a private key to create a unique code, which can be checked with a public key, much like a secure electronic seal.

• Authentication: it verifies that the signer is genuine and the document has not been changed.
• Integrity: even one alteration in the file makes verification fail.
• Non-repudiation: the signer cannot easily deny the signature later.
• Confidentiality support: it may work with encryption for secure transmission.
• Time-stamping: it records when the signature was made.

Thus, digital signatures provide trust, legal validity and security in electronic communication.