Digital Signature

A digital signature is a cryptographic technique that lets the recipient of an electronic message verify both who sent it and that its contents have not been altered since signing, doing for digital documents what a handwritten signature and a wax seal traditionally did for paper ones. The American cryptographers Whitfield Diffie and Martin Hellman first described the mathematical concept in their 1976 paper introducing public-key cryptography, proposing that a message encrypted with a sender's private key could be verified by anyone holding the corresponding public key. Ronald Rivest, Adi Shamir and Leonard Adleman turned the idea into a practical working method the following year with the RSA algorithm, published in 1977 and 1978, and digital signatures built on RSA and later algorithms now underpin the security of software updates, secure websites and electronically signed contracts worldwide.