Supervisor: Klaus Mølmer

Title: Quantum Cryptography: Fighting eavesdroppers in outer space

The art of writing in secrecy is dated back to ancient Egypt, almost four millennials ago, when scholars practiced simple substitution ciphers on hieroglyphs. Since then, variable codes and ciphers have kept diaries and political propaganda safe from surveillance. When keys are broken, military plans and coup d’état are revealed, and so has cryptography printed itself into our history. Today, cryptography plays an integral part of our digital society. Every credit card payment, cell phone conversation or software update relies on cryptography. However, RSA and elliptic encryption are based on conjectures. The security is unproven. Furthermore, Shors algorithm already proves that a quantum computer will be able to break these keys. Finishing dates for such computers are debatable, but attention to quantum cryptography is necessary. I will present protocols for key distribution, the challenges of long distances and state of the art technologic solutions using satellites and quantum repeaters.