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RSA cryptosystem

RSA is one of the initial implementations of public-private cryptography. It uses the principle of prime factorization to generate a public-private key pair, which acts as a trapdoor function. Encryption is performed using the public key, which is distributed to everyone, and decryption is performed using the secretly kept private key.

The idea of an asymmetric public-private key cryptosystem is attributed to Whitfield Diffie and Martin Hellman, who published this concept in 1976.

The public and private key pair are computed with the help of two large prime numbers. The public key is published to the user, and the private key is kept secret. The prime numbers are also kept secret. As long as the prime numbers used are large, it is infeasible to compute the private key from the public key. The whole RSA cryptosystem is based on the number theory problem of integer factorization, which ensures that the difficulty of prime factorization is proportional to the size of the prime numbers used.