The ACM Turing Award is considered the highest honour in the field of Computer Science – some have called it the “Nobel Prize” of the Computer Science world. The award for 2015 has been awarded to Whitfield Diffie and Martin Hellman for their invention of public key encryption and digital signatures.
Whittled Diffie is former Chief Security Officer of Sun Microsystems and Martin Hellman is Professor Emeritus of Electrical Engineering at Stanford University. Their 1976 paper titled “New Directions in Cryptography” first discussed public key encryption and digital signatures – the basis for the most widely used encryption and security protocols on the Internet.
The basic principle behind public key encryption is that each user has a private key (or pass phrase) and a public key (or pass phrase). Imagine a user called Bob wants to send an encrypted document to Alice. Bob would have a copy of Alice’s public key on his computer. He would use this key and encrypt the document using an encryption programme. Then the encrypted document would be emailed to Alice. Alice will be able to decrypt the document using her private key. The document can ONLY be decrypted using Alice’s private key, since it was encrypted using her public key, thus guaranteeing privacy.
Digital signatures guarantee the integrity of a document, though not necessarily privacy. Bob can encrypt a document using his private key. He can then email this document to Alice along with his public key. If the document has not been tampered with in anyway, then Alice will be able to decrypt it using Bob’s public key. If it has been tampered with, Bob’s public key will no longer work. This guarantees integrity and the recipient can be sure that the document is exactly what the sender had sent.
Above examples are simplifications, and in reality the implementations can be more sophisticated. But we have to thank Whitfield Diffie and Martin Hellman for giving us access to this amazing technology that is fuelling growth of digital initiatives world wide today. Their work has made encryption accessible to individuals and companies – rather than just governments.