Encryption has existed longer than computers have been around. In short encryption is a secure method of communication between two parties. They both must know some “secret” that allows them to share messages no one else can read. The simplest form of encryption is letter substitution, for example, shifting letters. A becomes c and z becomes b, each letter becomes three letters ahead, starting over at a when you reach z. The secret in this case would be the number three. The sender and receiver would both know that the letters were shifted three characters to the right allowing them to communicate without someone else easily reading the message.
In June 1944, Bailey Whitfield Diffie was born. Diffie was always very independent; he did not learn to read until age 10. He didn’t have any disability; he just preferred that his parents read to him. They followed his wishes and patiently waited for him to learn. In the fifth grade he started reading, above grade level. Mary Collins, his teacher at P.S. 178, spent an afternoon with Diffie explaining the basics of cryptography. He never forgot the lessons learned that day.
Diffie loved cryptography and took an interest in learning more about the topic. He learned that those with the secret keys practice decryption, and those who don’t have the secret key but try to access the secret information are practicing cryptanalysis. In order to avoid the draft, Diffie took up computer programming and went to work at the Mitre Corporation. He shifted to working with the MIT AI lab in 1966 and began the first discussions on using cryptography to protect computer software and digital information.
Diffie’s research contradicted the National Security Agency and work being done by IBM in conjunction with the National Bureau of Standards to institute the Data Encryption Standard (DES). Diffie and his Stanford colleague, Marty Hellman, regarded DES as tainted and potentially fraudulent due to the possibility of an NSA trapdoor which would allow the NSA and conceivably IBM to decrypt messages without knowing the secret. This brought about further research into the difficult problem of allowing two people or devices that had never communicated before to communicate securely. They could not exchange secret keys if they had never communicated, so how could they share these keys in a secure way? How do you create a system where all conversations could be protected with cryptography? How can you get a message from someone you never meet and ensure that they were the sender and no one else could read the message? This is the conundrum of secure computer communications.
This is where our current public key encryption infrastructure was born. Keeping keys secret was difficult; the very thing needed to eavesdrop on secure communications had to be passed unencrypted between two people, increasing the chances of compromise. Diffie came up with the idea of using a key pair instead of a single key. It took more than half a decade for him to perfect the technology, but he eventually solved the issue. Here is how it worked.
Let’s say Alice wants to send a secret message to Bob. She simply asks Bob for his public key, or looks it up in a “phone directory” of public keys. Alice then uses Bob’s public key to scramble the message; now only Bob’s private key can decrypt the message. Let’s say George intercepts the message; without Bob’s private key, George only gets a scrambled mash of data. Bob can read the message because he is the only person in the world with both halves of the key (public and private). Alice can also encrypt a small part of the message with her private key that can only be decrypted with her public key, so Bob can know for certain the message came from Alice. This is the key to all modern secure communication, including secure phone conversations, and was the result of the research of one key individual, Whit Diffie.