# public key cryptography

The basic idea behind public key cryptography, is that a user can publish (for instance on the internet) all the information needed to send them an encypted message, but for this information to be insufficient to decrypt the message in *reasonable time*. In general, this time requirement is taken to that, if the public key has length $n$ (over a particular alphabet), then the message cannot be decrypted in time $\le p(n)$ for any polynomial $p$.

The information published to all users is called the *public key*, and the additional information needed to decrypt a message is a users *private key*.

Public key cryptography was first conceived by James Ellis in 1969, and a workable scheme was developed in 1973. This was kept secret however, and it was not until 1978 that two schemes were announced publicly. These were the *Merkle-Hellman* scheme, and the *RSA* scheme.

Title | public key cryptography |
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Canonical name | PublicKeyCryptography |

Date of creation | 2013-03-22 15:12:38 |

Last modified on | 2013-03-22 15:12:38 |

Owner | aoh45 (5079) |

Last modified by | aoh45 (5079) |

Numerical id | 4 |

Author | aoh45 (5079) |

Entry type | Definition |

Classification | msc 94A60 |