Digital Signature

A digital signature is a cryptographic way of proving that a message, document or piece of software was created by a particular person or organisation and has not been changed since it was signed. It is the electronic equivalent of a handwritten signature and seal, but much harder to forge.

The signer hashes the content and encrypts the hash with their private key; anyone can check it with the signer's public key, usually confirmed by a certificate from a trusted authority. Digital signatures are used for HTTPS certificates, software updates, signed PDFs, e-filing of income tax returns and Aadhaar-based eSign in India.