He spent the rest of the night formalizing his idea, and he had much of the paper ready by daybreak. Rivest, unable to sleep, lay on the couch with a math textbook and started thinking about their one-way function. In April 1977, they spent Passover at the house of a student and drank a good deal of wine before returning to their homes at around midnight. For a time, they thought what they wanted to achieve was impossible due to contradictory requirements. They tried many approaches, including ' knapsack-based' and 'permutation polynomials'.

Rivest and Shamir, as computer scientists, proposed many potential functions, while Adleman, as a mathematician, was responsible for finding their weaknesses. Ron Rivest, Adi Shamir, and Leonard Adleman at the Massachusetts Institute of Technology made several attempts over the course of a year to create a function that was hard to invert. However, they left open the problem of realizing a one-way function, possibly because the difficulty of factoring was not well-studied at the time. Their formulation used a shared-secret-key created from exponentiation of some number, modulo a prime number. They also introduced digital signatures and attempted to apply number theory. The idea of an asymmetric public-private key cryptosystem is attributed to Whitfield Diffie and Martin Hellman, who published this concept in 1976. History Adi Shamir, co-inventor of RSA (the others are Ron Rivest and Leonard Adleman) More often, RSA is used to transmit shared keys for symmetric-key cryptography, which are then used for bulk encryption–decryption. Because of this, it is not commonly used to directly encrypt user data. There are no published methods to defeat the system if a large enough key is used. Whether it is as difficult as the factoring problem is an open question. Breaking RSA encryption is known as the RSA problem. The security of RSA relies on the practical difficulty of factoring the product of two large prime numbers, the ' factoring problem'. Messages can be encrypted by anyone, via the public key, but can only be decoded by someone who knows the prime numbers. In a public-key cryptosystem, the encryption key is public and distinct from the decryption key, which is kept secret (private).Īn RSA user creates and publishes a public key based on two large prime numbers, along with an auxiliary value. An equivalent system was developed secretly in 1973 at Government Communications Headquarters (GCHQ), the British signals intelligence agency, by the English mathematician Clifford Cocks. The initialism 'RSA' comes from the surnames of Ron Rivest, Adi Shamir and Leonard Adleman, who publicly described the algorithm in 1977. RSA ( Rivest–Shamir–Adleman) is a public-key cryptosystem, one of the oldest that is widely used for secure data transmission. General number field sieve for classical computers Ron Rivest, Adi Shamir, and Leonard Adleman

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