Post quantum cryptography

Public key cryptography is widely used for many applications such as signing contracts,electronic voting,encryption,securing transactions over the internet and stor- ing sensitive data. the discovery of an effcient algorithm based on quantum mechanics for factoring large integers and computing discrete logarithms by peter shor in 1994 undermined the security assumptions upon which currently used public key cryptographic algorithms are based,like rsa,el gamal and ecc. however,some cryptosystems,called post quantum cryptosystems,while not currently in widespread use are believed to be resistant to quantum computing based attacks. in this paper,we provide a survey of quantum and post quantum cryptography. we review the principle of a quatum computer as well as shor's algorithm and quantum key dis- tribution. then,we review some cryptosystems undermined by shor's algorithm as well as some post quantum cryptosystems,that are believed to resist classical and quantum computers.