Quantum key distribution does this by encoding the information in the polarisation states of individual photons, the particles of light, which are sent from Alice to Bob over an optical fibre.

ECONOMIST: Secure cryptography is only as safe as its weakest link

"I light candles in church when I say a prayer, " said Alice Ajak, a mother, who lost two children during the long years of war.

BBC: South Sudanese celebrate their divorce