- Person
- Shafi Goldwasser
- Lived
- b. 1959
- Field
- Computer science, cryptography
- From
- American-Israeli
The story
In 1979 the three inventors of RSA encryption proposed a way to play poker over the telephone, dealing from an encrypted deck so that no trusted dealer was needed. A Berkeley professor, Richard Lipton, spotted a problem: partial information about the encrypted cards could leak, and a player could use it to cheat. Two Berkeley graduate students, Shafi Goldwasser and Silvio Micali, both studying with Manuel Blum, took up the challenge of hiding every bit of information about the cards, not just most of it.
Their answer, published in 1982 in a paper called Probabilistic Encryption, overturned the way codes had been built for centuries. They showed that secure encryption must be randomized: each message has to have many possible encrypted forms, all equally likely, and the sender picks one at random each time it is sent. If the same message always turns into the same scrambled text, an eavesdropper who sees it twice has already learned something.
They also gave the first rigorous definition of what secure encryption means, called semantic security: someone who sees the encrypted text learns nothing about the message that they could not have guessed without it. And they introduced a way to prove that a system meets this standard, by showing that anything an attacker could gather from watching it, the attacker could have produced alone. MIT News described these definitions as the gold standard for security to this day.
According to MIT Technology Review, the work exposed a weakness in any system, including early versions of RSA, that always encrypted a message the same way, and it led to cryptographic standards that require randomized methods. The magazine adds that randomized public-key cryptography became the key to commercializing the internet, since it was the only way to send credit card numbers online securely.
The work was a central reason Goldwasser and Micali received the 2012 A.M. Turing Award, which the Association for Computing Machinery gave them for laying the mathematical foundations of modern cryptography.
Why it matters
Online shopping, banking and private messaging all rely on randomized encryption judged by the security standard Goldwasser and Micali defined.
About Shafi Goldwasser
Computer scientist who co-invented probabilistic encryption and zero-knowledge proofs, giving the mathematical foundations for secure online life. Turing Award 2012.
More about Shafi Goldwasser
Sources
- Shafi Goldwasser: The number theory expert who helped revolutionize cryptography MIT Technology Review
- Goldwasser and Micali win Turing Award MIT News
- Shafi Goldwasser, A.M. Turing Award Laureates ACM
Another act of tikkun olam. This is part of tikkun olam, the Jewish idea of repairing the world, and every one of us can add to it.