A Tel Aviv childhood and a love of puzzles
Adi Shamir was born on July 6, 1952, in Tel Aviv, four years after the founding of the State of Israel. He grew up in the young country’s largest Jewish city and, according to the Wolf Foundation, showed an early interest in science, taking part as a boy in the youth programmes and science summer camps run by the Weizmann Institute of Science in Rehovot. That institute would become his professional home for most of his life.
He studied mathematics at Tel Aviv University, graduating with high honours in 1973, and then moved to the Weizmann Institute for graduate work in computer science, earning a master’s degree in 1975 and a doctorate in 1977. His doctoral thesis, supervised by Zohar Manna, dealt with the mathematics of recursive definitions, a topic in the theory of programming languages. Cryptography was not yet on his horizon.
MIT and the problem of the key
After a short postdoctoral stay at the University of Warwick in England, Shamir went to the Massachusetts Institute of Technology in 1977. There he joined two young computer scientists, Ron Rivest and Leonard Adleman, who had been gripped by a paper published the year before by Whitfield Diffie and Martin Hellman of Stanford. Diffie and Hellman had proposed something that sounded impossible: public-key cryptography, in which anyone could lock a message using a key published openly, but only the intended recipient, holding a separate private key, could unlock it.
For thousands of years, secret communication had required both sides to share the same secret key in advance, which is why armies used couriers and diplomats used locked pouches. That approach could never work for millions of strangers communicating over computer networks. Diffie and Hellman described the idea and a way to agree on a shared key, but they had not found a complete practical system for public-key encryption and digital signatures. Rivest, Shamir and Adleman set out to build one.
The puzzle Rivest, Shamir and Adleman faced was to find what cryptographers call a trapdoor one-way function: an operation that anyone can carry out easily, but that cannot be undone without a piece of secret information. Many candidates looked promising until someone found a short cut that broke them. Shamir, who loved puzzles, threw himself into both proposing and attacking such schemes.
The birth of RSA
The three worked by attack and defence. Rivest and Shamir proposed schemes, and Adleman tried to break them; according to the National Inventors Hall of Fame he succeeded 42 times before the trio found one that held. The winning idea, completed in 1977, rested on a simple asymmetry in arithmetic: multiplying two very large prime numbers together is easy for a computer, but recovering those primes from their product is, as far as anyone knows, extraordinarily hard. In RSA, the product can be published as part of a public key, while the primes stay secret and make decryption possible.
The system was named RSA after the initials of its inventors and published in 1978 in the Communications of the ACM under the title A Method for Obtaining Digital Signatures and Public-Key Cryptosystems. Beyond encryption, it allowed a person to sign a digital message in a way that anyone could verify but no one could forge. In 1983 the three founded RSA Data Security to bring the method to market; the company’s annual RSA Conference became one of the world’s main gatherings of the security industry. (It was later revealed that Clifford Cocks at Britain’s secret signals intelligence agency, GCHQ, had found an equivalent scheme in 1973, but his work stayed classified until 1997.)
How RSA protects everyday life
For decades RSA has been one of the foundations of security on the internet. When a browser shows a padlock beside a web address, digital certificates, very often signed with RSA, assure the user that the site is genuine and help set up an encrypted connection. RSA signatures protect software updates, so that a phone or computer installs only code that really comes from its maker. RSA has been used in bank cards, secure email, virtual private networks and countless business systems.
The Wolf Foundation, in awarding Shamir its prize, called RSA a fundamental pillar of electronic commerce and information security. Online shopping, online banking and private messaging at global scale all depend on the idea Shamir helped make practical: that strangers can communicate securely without ever having met to exchange a secret.
RSA also changed who could do cryptography. Before the 1970s, serious work on codes and ciphers was almost entirely the business of governments and their intelligence agencies. The open publication of RSA, following Diffie and Hellman’s paper, helped turn cryptography into a public academic science, studied at universities, taught to students and tested in the open, which is a large part of why the systems that protect ordinary people today can be trusted.
Secret sharing and a lifetime of ideas
Shamir returned to the Weizmann Institute in 1980 and has taught there ever since, as professor of applied mathematics and computer science. In 1979 he published a short paper called How to Share a Secret, describing what is now known as Shamir’s secret sharing: a way to split a secret, such as a master key, into many pieces so that any agreed number of them can rebuild it, while fewer pieces reveal nothing at all. The method is used above all to protect encryption keys, in key-management systems, password managers and cryptocurrency wallets, so that no single person can steal or lose them.
With Uriel Feige and Amos Fiat he developed zero-knowledge identification schemes, and with Fiat the Fiat–Shamir method for turning interactive proofs into digital signatures, a technique now central to modern cryptographic systems including those used in blockchains. He introduced identity-based cryptography, in which a person’s public key can be derived from something like an email address, co-invented visual cryptography with Moni Naor, and with Rivest and Yael Tauman devised ring signatures, which let a member of a group sign without revealing which member. In complexity theory he proved in 1992 the celebrated result that IP equals PSPACE.
The codebreaker
Shamir is as famous for breaking codes as for making them, and that work has made everyday systems safer by exposing their flaws before criminals could exploit them. In 1982 he broke the Merkle–Hellman knapsack cryptosystem, one of the first public-key proposals. In the late 1980s, with his student Eli Biham, he developed differential cryptanalysis, a general method for attacking block ciphers that changed how ciphers are designed; it later emerged that IBM and the U.S. National Security Agency had known of it and kept it secret.
In 2000, with Alex Biryukov and David Wagner, he showed a practical attack on A5/1, the cipher then protecting GSM mobile phone calls. In 2001, with Scott Fluhrer and Itsik Mantin, he exposed weaknesses in the RC4 cipher that helped show the WEP standard for Wi-Fi networks to be insecure, speeding its replacement. In 2014, with Daniel Genkin and Eran Tromer, he demonstrated that a full RSA key could be extracted from the sound a laptop makes while decrypting. More recently he has turned to the security of machine-learning systems.
An Israeli scientist in the world
Shamir is an Israeli Jew who has spent almost his whole career in Israel, at the Weizmann Institute, while working closely with colleagues in the United States and Europe; from 2006 he was also an invited professor at the École Normale Supérieure in Paris. He has not made his private life or religious views a public topic, and sources describe him through his work.
In March 2019 he was unable to attend the RSA Conference in San Francisco, where he had long been a fixture of the annual Cryptographers’ Panel, because his application for a U.S. visa went unanswered for two months. He addressed the conference by video and suggested that the research community reconsider where it holds its scientific meetings, an episode that drew attention to the barriers facing foreign scientists.
Honours
Shamir shared the 2002 A.M. Turing Award, often called the Nobel Prize of computing, with Rivest and Adleman for the invention of RSA. His other honours include the Erdős Prize of the Israel Mathematical Society (1983), the IEEE W.R.G. Baker Award (1986), the Paris Kanellakis Theory and Practice Award (1996), the IEEE Koji Kobayashi Award (2000), the Israel Prize in computer science (2008), the Japan Prize (2017) and the Wolf Prize in Mathematics (2024), shared with Noga Alon. He is a member of the Israel Academy of Sciences and Humanities and the U.S. National Academy of Sciences and a Foreign Member of the Royal Society.
The Wolf Foundation credited him with being the leading force in turning cryptography into a scientific discipline grounded in mathematics.
Legacy
Few people have shaped the hidden machinery of modern life as much as Adi Shamir. Each time someone pays online, signs in to a bank, or receives a software update, they rely on mathematical ideas he helped invent or test. His secret-sharing scheme protects sensitive encryption keys, and his attacks have repeatedly forced industry to fix weak systems before they could do greater harm.
He showed that the best way to build trust in a security system is to try as hard as possible to break it. That habit of mind, practised with Rivest and Adleman in an MIT office in 1977, has protected billions of people who will never know his name.
Sources & further reading
Adi Shamir, Wikipedia · Adi Shamir, Wolf Prize Laureate in Mathematics 2024, Wolf Foundation · Leonard Adleman, RSA Cryptography, National Inventors Hall of Fame · Jewish Computer and Information Scientists, jinfo.org · Researched from the sources above and checked against them. Spotted an error? Tell us.
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