Conventional public key cryptography relies on a key pair — a public key and a private key. Email recipients can freely give anyone their public key, allowing email senders to encrypt messages using it.

The idea is that only the recipient’s private key can decrypt the messages. It’s based on clever mathematics that allows each of the encryption keys to work in one “direction” — usually, the public key encrypts and the private key decrypts.

Asymmetric encryption using a public/private key pair was first proposed in 1874, by British economist and logician William Stanley Jevons. In The Principles of Science: A Treatise on Logic and Scientific Method, Jevons discussed the possible use of one-way functions in cryptography — specifically the integer factorization problem, which lies at the heart of public key cryptography.

A workable scheme was finally invented in 1973 by a team at the Government Communications Headquarters (GCHQ), the British signals intelligence security agency — where it remained a state secret until 1997.

It was later reinvented in 1976 by U.S. academics Whitfield Diffie and Martin Hellman; then made workable at MIT in 1977 by Ron Rivest, Adi Shamir, and Leonard Adleman (which is where the abbreviation RSA comes from).

… Richi Jennings